noodls browser compatibility check

The security settings of your browser are blocking the execution of scripts.

To use noodls, javascript support must be enabled. Please change your browser's security settings to enable javascript.

If you have changed your browser's security settings, you can click here.

related announcements

News

Willkie Farr & Gallagher LLP

Willkie Advises Novacap and InVita Healthcare Technologies on[...]
Upay Inc.

Quarterly Report for Quarter Ending May 31, 2026 (Form 10-Q)
Celcuity Inc.

Celcuity Announces FDA Approval of REVTORPYK™ (gedatolisib) for the[...]

Crescent Biopharma Inc.

07/14/2026 | Press release | Distributed by Public on 07/14/2026 14:01

Supplemental Prospectus (Form 424B5)

Filed Pursuant to Rule 424(b)(5)
Registration No. 333-297199

The information in this preliminary prospectus supplement and the accompanying prospectus is not complete and may be changed. A registration statement relating to the securities has been declared effective by the Securities and Exchange Commission. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting offers to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED JULY 14, 2026

PRELIMINARY PROSPECTUS SUPPLEMENT

(To Prospectus Dated July 10, 2026)

Ordinary Shares

Pre-Funded Warrants to Purchase Ordinary Shares

We are offering ordinary shares. We are also offering, in lieu of ordinary shares to investors that so choose, pre-funded warrants to purchase ordinary shares. The purchase price of each pre-funded warrant will equal the price per share at which our ordinary shares are being sold to the public in this offering, minus $0.001, which is the exercise price of each pre-funded warrant. Each pre-funded warrant will be exercisable at any time after the date of issuance of such pre-funded warrant, subject to an ownership limitation. This prospectus supplement also relates to the offering of the ordinary shares issuable upon the exercise of such pre-funded warrants.

Our ordinary shares are traded on The Nasdaq Capital Market under the symbol "CBIO." On July 13, 2026, the last reported sale price for our ordinary shares was $15.69 per share. There is no established public trading market for the pre-funded warrants, and we do not expect a market to develop. We do not intend to list the pre-funded warrants on The Nasdaq Capital Market or any other national securities exchange or nationally recognized trading system.

We are a "smaller reporting company" as defined under the U.S. federal securities laws and, as such, have elected to comply with certain reduced public company reporting requirements. See "Prospectus Supplement Summary - Implications of Being a Smaller Reporting Company."

Investing in our securities involves a high degree of risk. See "Risk Factors" beginning on page S-4 of this prospectus supplement, on page 6 of the accompanying prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

PER SHARE

PER PRE-FUNDED WARRANT

TOTAL

Public Offering Price……………………………

Underwriting Discounts and Commissions(1)……

Proceeds, before expenses, to Crescent Biopharma, Inc.……………………………....


(1)						See "Underwriting" for additional information regarding underwriting compensation.

Delivery of the securities is expected to be made on or about , 2026. We have granted the underwriters an option for a period of 30 days to purchase up to an additional ordinary shares. If the underwriters exercise the option in full, the total underwriting discounts and commissions payable by us will be $ and the total proceeds to us, before expenses, will be $ .


Joint Book-Running Managers
Jefferies	TD Cowen	Guggenheim Securities	Cantor
Book-Running Manager
LifeSci Capital

Prospectus Supplement dated July , 2026.

TABLE OF CONTENTS

Page

Prospectus Supplement


ABOUT THIS PROSPECTUS SUPPLEMENT			S-ii
PROSPECTUS SUPPLEMENT SUMMARY			S-1
THE COMPANY			S-1
THE OFFERING			S-3
RISK FACTORS			S-5
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS			S-7
USE OF PROCEEDS			S-8
DILUTION			S-9
DESCRIPTION OF PRE-FUNDED WARRANTS			S-11
MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS			S-13
CERTAIN CAYMAN ISLANDS TAX CONSIDERATIONS			S-19
UNDERWRITING			S-20
LEGAL MATTERS			S-28
EXPERTS			S-28
WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE			S-29

Prospectus


ABOUT THIS PROSPECTUS			1
CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS			2
WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE			3
THE COMPANY			5
RISK FACTORS			6
USE OF PROCEEDS			7
DIVIDEND POLICY			8
DESCRIPTION OF SHARE CAPITAL			9
DESCRIPTION OF DEBT SECURITIES			17
DESCRIPTION OF WARRANTS			24
DESCRIPTION OF UNITS			25
PLAN OF DISTRIBUTION			26
LEGAL MATTERS			28
EXPERTS			28

Neither we nor any of the underwriters have authorized anyone to provide information different from that contained in this prospectus supplement. When you make a decision about whether to invest in our securities, you should not rely upon any information other than the information in this prospectus supplement. Neither the delivery of this prospectus supplement nor the sale of our securities means that information contained in this prospectus supplement is correct after the date of this prospectus supplement. This prospectus supplement is not an offer to sell or solicitation of an offer to buy our securities in any circumstances under which the offer or solicitation is unlawful.

S-i

ABOUT THIS PROSPECTUS SUPPLEMENT

This prospectus supplement and the accompanying prospectus dated July 10, 2026, are part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission (the "SEC"), utilizing a "shelf" registration process. This prospectus supplement and the accompanying prospectus relate to the offer by us of our ordinary shares and pre-funded warrants to certain investors. We provide information to you about this offering of our ordinary shares and pre-funded warrants in two separate documents that are bound together: (1) this prospectus supplement, which describes the specific details regarding this offering; and (2) the accompanying prospectus, which provides general information, some of which may not apply to this offering. Generally, when we refer to this "prospectus," we are referring to both documents combined. If information in this prospectus supplement is inconsistent with the accompanying prospectus, you should rely on this prospectus supplement. However, if any statement in one of these documents is inconsistent with a statement in another document having a later date-for example, a document incorporated by reference in this prospectus supplement or the accompanying prospectus-the statement in the document having the later date modifies or supersedes the earlier statement as our business, financial condition, results of operations and prospects may have changed since the earlier dates. You should read this prospectus supplement, the accompanying prospectus, the documents and information incorporated by reference in this prospectus supplement and the accompanying prospectus, and any free writing prospectus that we have authorized for use in connection with this offering when making your investment decision. You should also read and consider the information in the documents we have referred you to under the headings "Where you can find more information; incorporation by reference."

You should rely only on information contained in or incorporated by reference into this prospectus supplement and the accompanying prospectus or any free writing prospectus prepared by or on behalf of us or to which we have referred you. We have not, and the underwriters have not, authorized anyone to provide you with information that is different. We are offering to sell and seeking offers to buy our ordinary shares and pre-funded warrants only in jurisdictions where offers and sales are permitted. The information contained in this prospectus supplement, the accompanying prospectus, the documents and information incorporated by reference in this prospectus supplement and the accompanying prospectus, and any free writing prospectus that we have authorized for use in connection with this offering are accurate only as of their respective dates, regardless of the time of delivery of this prospectus supplement or of any sale of our ordinary shares or pre-funded warrants.

When we refer to "Crescent," "we," "our," "us" and the "Company" in this prospectus supplement, we mean Crescent Biopharma, Inc. and our subsidiaries, unless otherwise specified. When we refer to "you," we mean the holders of the applicable series of securities.

We use our trademarks and service marks in this prospectus supplement, as well as trademarks, tradenames and service marks that are the property of other organizations. Solely for convenience, trademarks and tradenames referred to in this prospectus supplement appear without the ® and ™ symbols, but those references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights or that the applicable owner will not assert its rights, to these trademarks and tradenames.

S-ii

PROSPECTUS SUPPLEMENT SUMMARY

The items in the following summary are described in more detail later in, or incorporated by reference into, this prospectus supplement and in the accompanying prospectus. This summary provides an overview of selected information and does not contain all the information you should consider before investing in our ordinary shares and pre-funded warrants. Therefore, you should read the entire prospectus supplement, the accompanying prospectus and any free writing prospectus that we have authorized for use in connection with this offering carefully, including the "Risk Factors" section, and other documents or information included or incorporated by reference in this prospectus supplement and the accompanying prospectus before making any investment decision.

THE COMPANY

Overview

We are a clinical-stage biotechnology company focused on delivering the next wave of transformative therapies to bring a brighter future for people living with cancer. We have a bold vision to build the next leading biotechnology oncology company. We are executing across two distinct strategies to build our portfolio to achieve this vision. First, we are developing our lead product candidate, CR-001, which we refer to as a PD-1 x VEGF bispecific antibody because it is designed to bind both the PD-1 immune checkpoint and Vascular Endothelial Growth Factor, which has potential to replace pembrolizumab, marketed by Merck as Keytruda®, as the foundational immuno-oncology backbone; second, we are building a robust portfolio of potentially best-in-class antibody drug conjugates ("ADCs"). Importantly, as we execute on these two strategies, we intend to combine CR-001 and ADC therapies to create what we believe will be best-in-class synergistic combinations to transform care for multiple types of cancer.

We initiated a global Phase 1/2 trial of CR-001 in February 2026, and a Phase 1/2 trial of CR-003 (also referred to as SKB105), an integrin beta-6 ("ITGB6")-directed ADC, as a monotherapy in the first quarter of 2026 in China through our partner, Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. ("Kelun"). In addition, we anticipate initiation of a monotherapy clinical trial of CR-002, a PD-L1-directed ADC with a topoisomerase payload, as well as the first ADC combination trial with CR-001 and a Kelun ADC in 2026.

Preliminary Financial Update

As of June 30, 2026, we estimate that our cash and cash equivalents were approximately $171.6 million.

The cash and cash equivalents information above is based on preliminary unaudited information and management estimates for the quarter ended June 30, 2026, is not a comprehensive statement of our financial results as of and for the quarter ended June 30, 2026, and is subject to completion of our financial closing procedures. Our actual cash and cash equivalents as of June 30, 2026 will be included in our Quarterly Report on Form 10-Q for the quarter ended June 30, 2026 and may differ from this amount after we complete our comprehensive accounting procedures for the quarter ended June 30, 2026. Our financial statements for the quarter ended June 30, 2026 will not be available until after this offering is completed, and consequently will not be available to you prior to investing in this offering. See the sections entitled "Risk Factors" and "Special Note Regarding Forward-Looking Statements" in this prospectus supplement and the documents incorporated by reference herein, for a discussion of certain factors that could result in differences between these preliminary unaudited estimates and the actual results.

The preliminary financial data included in this prospectus supplement has been prepared by, and is the responsibility of, our management. PricewaterhouseCoopers LLP has not audited, reviewed, examined, compiled, nor applied agreed-upon procedures with respect to the preliminary financial data. Accordingly, PricewaterhouseCoopers LLP does not express an opinion or any other form of assurance with respect thereto.

Corporate Information

S-1

transaction, Pre-Merger Crescent was established and incorporated under the laws of the State of Delaware on September 19, 2024. Pre-Merger Crescent was founded to research and develop cancer therapy candidates.

On June 16, 2025, in connection with the reverse recapitalization transaction with Pre-Merger Crescent, we changed our jurisdiction of incorporation from the State of Delaware to the Cayman Islands pursuant to a plan of conversion.

Our principal executive offices are located at 300 Fifth Avenue, Waltham, MA 02451, and our telephone number is (617) 430-5595.

Implications of Being a Smaller Reporting Company

We are a "smaller reporting company," as defined in the Exchange Act. We will continue to be a smaller reporting company as long as (i) the market value of our ordinary shares held by non-affiliates is less than $250.0 million or (ii) our annual revenue is less than $100.0 million during the most recently completed fiscal year and the market value of our ordinary shares held by non-affiliates is less than $700.0 million. As a smaller reporting company, we may choose to present only the two most recent fiscal years of audited financial statements in our Annual Report on Form 10-K, and smaller reporting companies have reduced disclosure obligations regarding executive compensation.

S-2

THE OFFERING


Ordinary shares offered by us			ordinary shares.
Pre-funded warrants offered by us			We are also offering, in lieu of our ordinary shares to investors that so choose, pre-funded warrants to purchase ordinary shares. The purchase price of each pre-funded warrant equals the price per share at which the ordinary shares are being sold to the public in this offering, minus $0.001, which is the exercise price of each pre-funded warrant. Each pre-funded warrant will be exercisable at any time after the date of issuance until the date the pre-funded warrant is exercised in full, subject to an ownership limitation. See "Description of Pre-Funded Warrants." This prospectus supplement also relates to the offering of our ordinary shares issuable upon exercise of such pre-funded warrants.
Option to purchase additional ordinary shares			We have granted the underwriters an option exercisable for a period of 30 days after the date of this prospectus supplement to purchase up to additional ordinary shares at the public offering price, less underwriting discounts and commissions.
Ordinary shares to be outstanding immediately after this offering			ordinary shares (or ordinary shares if the underwriters exercise in full their option to purchase additional shares), assuming no exercise of any pre-funded warrants offered and sold by us in this offering.
Use of proceeds			We intend to use the net proceeds from this offering, together with our existing cash and cash equivalents to fund the clinical development of CR-001, CR-002 and CR-003, the advancement of chemistry, manufacturing and controls activities, continued research and development for our preclinical programs, and for working capital and other general corporate purposes. See the section titled "Use of Proceeds."
Risk factors			You should read the "Risk Factors" section of this prospectus supplement and in the documents incorporated by reference in this prospectus supplement for a discussion of factors to consider before deciding to invest in our securities.
Nasdaq Capital Market trading symbol			"CBIO" There is no established public trading market for the pre-funded warrants, and we do not expect a market to develop. We do not intend to list the pre-funded warrants on the Nasdaq Capital Market or any other national securities exchange or nationally recognized trading system. Without an active trading market, the liquidity of the pre-funded warrants will be limited. See "Description of Pre-Funded Warrants."

The number of our ordinary shares to be outstanding immediately after this offering is based on 27,571,935 ordinary shares outstanding as of March 31, 2026. The number of shares outstanding as of March 31, 2026 excludes:

S-3

•2,890,000 ordinary shares issuable upon conversion of our Series A non-voting convertible preferred shares outstanding as of March 31, 2026;

•2,898,556 ordinary shares issuable upon exercise of our pre-funded warrants outstanding as of March 31, 2026, with an exercise price of $0.001 per share (including the 131,434 ordinary shares issuable upon exercise of the pre-funded warrants issued pursuant to that certain Securities Purchase Agreement for a private placement, dated December 4, 2025 (the "Private Placement Pre-Funded Warrants") and 1,636,706 ordinary shares issuable upon exercise of the pre-funded warrants issued to Fairmount Funds Management LLC (the "Fairmount Pre-Funded Warrants"));

•437,297 ordinary shares issuable upon exercise of warrants outstanding as of March 31, 2026, including 402,731 warrants issued on December 31, 2025 with an exercise price of $11.86 and 34,566 warrants issued on January 31, 2026 with an exercise price of $13.50, under the ADC Discovery and Option Agreement (as amended and restated on April 28, 2025, the "ADC Paragon Option Agreement") with Parascent Holding LLC;

•1,885,194 ordinary shares issuable upon the exercise of options outstanding as of March 31, 2026 under our 2025 Stock Incentive Plan (the "2025 Plan"), at a weighted-average exercise price of $13.18 per share;

•278,332 ordinary shares issuable upon the vesting of restricted share units outstanding as of March 31, 2026 under our 2025 Plan;

•3,683,519 ordinary shares issuable upon the exercise of options outstanding as of March 31, 2026 under our 2024 Equity Incentive Plan (the "2024 Plan"), at a weighted-average exercise price of $7.90 per share;

•328,789 ordinary shares issuable upon the vesting of restricted share units outstanding as of March 31, 2026 under our 2024 Plan;

•732,776 ordinary shares issuable upon the exercise of options outstanding as of March 31, 2026 under our 2025 Employment Inducement Incentive Award Plan (the "2025 Inducement Plan"), at a weighted-average exercise price of $12.39 per share;

•1,831,145 ordinary shares reserved for future issuance under the 2025 Plan as of March 31, 2026, as well as any automatic increase in the number of ordinary shares reserved for future issuance under our 2025 Plan;

•517,224 ordinary shares reserved for future issuance under the 2025 Inducement Plan as of March 31, 2026; and

•528,950 ordinary shares reserved for future issuance under our 2025 Employee Stock Purchase Plan (the "ESPP") as of March 31, 2026, as well as any automatic increase in the number of ordinary shares reserved for future issuance under the ESPP.

Except as otherwise indicated, all information in this prospectus supplement assumes no exercise of outstanding options or warrants, no conversion of outstanding Series A non-voting convertible preferred shares, no vesting of restricted share units or restricted ordinary shares after March 31, 2026, no exercise of the pre-funded warrants offered herein and no exercise by the underwriters of their option to purchase up to additional ordinary shares.

In addition, the number of our ordinary shares to be outstanding immediately after this offering as shown above does not include the $200 million of ordinary shares that remain available for sale under that certain Open Market Sale AgreementSM (the "Sales Agreement"), with Jefferies LLC, dated July 1, 2026. We have agreed not to make any sales under the Sales Agreement until the earlier of (i) the exercise in full by the underwriters of their option to purchase additional ordinary shares and (ii) 30 calendar days after the date of this prospectus supplement. For more information, see the section titled "Underwriting."

S-4

RISK FACTORS

You should consider carefully the risks described below and discussed under the section captioned "Risk Factors" contained in our Annual Report on Form 10-K for the year ended December 31, 2025 and our Quarterly Report on Form 10-Q for the quarter ended March 31, 2026 as updated by our subsequent filings under the Securities Exchange Act of 1934, as amended (the Exchange Act), which are incorporated by reference in this prospectus supplement and the accompanying prospectus in their entirety, together with other information in this prospectus supplement, the accompanying prospectus and the information and documents incorporated by reference in this prospectus supplement and the accompanying prospectus, and any free writing prospectus that we have authorized for use in connection with this offering before you make a decision to invest in our ordinary shares and pre-funded warrants. If any of the following events actually occur, our business, operating results, prospects or financial condition could be materially and adversely affected. This could cause the trading price of our ordinary shares to decline, and you may lose all or part of your investment. The risks described below are not the only ones that we face. Additional risks not presently known to us or that we currently deem immaterial may also affect our business operations.

Risks Relating to this Offering

If you purchase ordinary shares or pre-funded warrants sold in this offering, you will experience immediate and substantial dilution in the net tangible book value of your shares. In addition, we may issue additional equity or convertible debt securities in the future, which may result in additional dilution to investors.

Purchasers of ordinary shares (or pre-funded warrants in lieu thereof) in this offering will experience immediate dilution of approximately $ per ordinary share, based on an assumed public offering price of $ per ordinary share and assuming no sale of any pre-funded warrants in this offering. In the past, we issued options to acquire ordinary shares at prices significantly below the public offering price. To the extent these outstanding options, or warrants, including those issued in this offering, are ultimately exercised, investors purchasing ordinary shares (or pre-funded warrants in lieu thereof) in this offering will sustain further dilution. For a further description of the dilution that you will experience immediately after this offering, see the section titled "Dilution." In addition, to the extent we need to raise additional capital in the future and we issue additional ordinary shares or securities convertible or exchangeable for our ordinary shares, our then existing shareholders may experience dilution and the new securities may have rights senior to those of our ordinary shares offered in this offering.

In addition, pursuant to the Sales Agreement, we may issue and sell from time to time through Jefferies LLC, our ordinary shares, in an aggregate amount not to exceed $200 million. As of the date of this prospectus supplement, $200 million of ordinary shares remains available for sale under the Sales Agreement. To the extent that we sell additional ordinary shares pursuant to the Sales Agreement subsequent to this offering, investors purchasing securities in this offering could experience further dilution.

We may allocate the net proceeds from this offering in ways that you and other shareholders may not approve.

Our management will have broad discretion in the application of the net proceeds from this offering, including for any of the purposes described in the section titled "Use of Proceeds." Because of the number and variability of factors that will determine our use of the net proceeds from this offering, their ultimate use may vary substantially from their currently intended use. Our management might not apply our net proceeds in ways that ultimately increase the value of your investment, and the failure by our management to apply these funds effectively could harm our business. Pending their use, we may invest the net proceeds from this offering in short-and intermediate term, interest-bearing obligations, investment-grade instruments, certificates of deposit or direct or guaranteed obligations of the U.S. government. These investments may not yield a favorable return to our shareholders. If we do not invest or apply the net proceeds from this offering in ways that enhance shareholder value, we may fail to achieve expected results, which could cause our stock price to decline.

There is no public market for the pre-funded warrants being offered in this offering.

There is no existing trading market for the pre-funded warrants and there can be no assurance that a liquid market will develop or be maintained for the pre-funded warrants, or that you will be able to sell any of the pre-funded

S-5

warrants at a particular time (if at all). In addition, we do not intend to apply for listing of the pre-funded warrants on The Nasdaq Capital Market or any other securities exchange or nationally recognized trading system. Without an active trading market, the liquidity of the pre-funded warrants will be limited. See the section titled "Description of Pre-Funded Warrants."

We will not receive a significant amount of additional funds upon the exercise of the pre-funded warrants.

Each pre-funded warrant will be exercisable for $0.001 per ordinary share underlying such warrant, which may be paid by way of a cashless exercise, in which the holder would receive upon such exercise the net number of ordinary shares determined according to the formula set forth in the pre-funded warrant. Accordingly, we will not receive a significant amount of additional funds upon the exercise of the pre-funded warrants.

Holders of the pre-funded warrants will have no rights as shareholders until such holders exercise their pre-funded warrants and acquire ordinary shares.

Until holders of the pre-funded warrants exercise their pre-funded warrants and acquire ordinary shares, such holders will have no rights with respect to the ordinary shares underlying such pre-funded warrants. Upon exercise of the pre-funded warrants, the holders will be entitled to exercise the rights of a holder of ordinary shares, provided, however, that if a holder exercises its pre-funded warrants after the record date for a meeting of shareholders, such holder will not be entitled to vote at such meeting with respect to the ordinary shares issued upon such exercise.

If we do not maintain a current and effective registration statement relating to the ordinary shares issuable upon exercise of the pre-funded warrants, holders will only be able to exercise such pre-funded warrants on a "cashless basis."

If we do not maintain a current and effective registration statement relating to the ordinary shares issuable upon exercise of the pre-funded warrants at the time that holders wish to exercise such pre-funded warrants, they will only be able to exercise them on a "cashless basis" provided that an exemption from registration is available. As a result, the number of ordinary shares that holders will receive upon exercise of the pre-funded warrants will be fewer than it would have been had such holder exercised his or her warrant for cash, and holders may be limited in their ability to immediately sell shares upon exercise subject to volume or other securities law limitations. Further, if an exemption from registration is not available, holders would not be able to exercise on a cashless basis and would only be able to exercise their pre-funded warrants for cash if a current and effective registration statement relating to the ordinary shares issuable upon exercise of the pre-funded warrants is available.

Significant holders or beneficial owners of our ordinary shares may not be permitted to exercise the pre-funded warrants that they hold.

A holder of the pre-funded warrants will not be entitled to exercise any portion of any pre-funded warrant that, upon giving effect to such exercise, would cause the aggregate number of ordinary shares beneficially owned by such holder (together with its affiliates) to exceed 19.99% or such other specified percentage of the number of ordinary shares outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the pre-funded warrants and subject to such holder's rights under the pre-funded warrants to increase or decrease such percentage to any other percentage not in excess of 19.99% upon at least 61 days' prior notice from the holder to us. As a result, you may not be able to exercise your pre-funded warrants for ordinary shares at a time when it would be financially beneficial for you to do so. In such a circumstance, you could seek to sell your pre-funded warrants to realize value, but you may be unable to do so in the absence of an established trading market.

S-6

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement and the accompanying prospectus, including the documents incorporated by reference herein and therein, and any free writing prospectus that we have authorized for use in connection with this offering contain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the "Securities Act"), and Section 21E of the Exchange Act.

All statements other than statements of historical facts contained in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein are forward-looking statements, including statements regarding our future results of operations and financial position, business strategy, the length of time that we believe our existing cash resources will fund our operations, the use of proceeds from this offering, our market size, our competition, our potential growth opportunities, our preclinical and future clinical development activities, the efficacy and safety profile of our product candidates, the potential therapeutic benefits and economic value of our product candidates, the timing and results of preclinical studies and clinical trials, the expected impact of macroeconomic conditions, including inflation, increasing interest rates and volatile market conditions, as well as global events, including military conflicts and geopolitical tensions on our operations, and the receipt and timing of potential regulatory designations, approvals and commercialization of product candidates, are forward-looking statements.

These statements involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements. This prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein also contain estimates and other statistical data made by independent parties and by us relating to market size and growth and other data about our industry. This data involves a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. In addition, projections, assumptions and estimates of our future performance and the future performance of the markets in which we operate are necessarily subject to a high degree of uncertainty and risk.

In some cases, you can identify forward-looking statements by terms such as "may," "will," "should," "expect," "plan," "anticipate," "could," "intend," "target," "project," "contemplates," "believes," "estimates," "predicts," "potential" or "continue" or the negative of these terms or other similar expressions. The forward-looking statements in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein are only predictions. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our business, financial condition and results of operations. These forward-looking statements speak only as of the date of this prospectus supplement and are subject to a number of risks, uncertainties and assumptions, which we discuss in greater detail in the documents incorporated by reference herein, including under the heading "Risk Factors" and elsewhere in this prospectus supplement. The events and circumstances reflected in our forward-looking statements may not be achieved or occur and actual results could differ materially from those projected in the forward-looking statements. Moreover, we operate in an evolving environment. New risk factors and uncertainties may emerge from time to time, and it is not possible for management to predict all risk factors and uncertainties. Given these risks and uncertainties, you should not place undue reliance on these forward-looking statements. Except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained in this prospectus supplement, the accompanying prospectus or the documents incorporated by reference herein and therein, whether as a result of any new information, future events, changed circumstances or otherwise. For all forward-looking statements, we claim the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995.

In addition, statements that "we believe" and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date when made, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete. Our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely upon these statements.

S-7

USE OF PROCEEDS

We estimate that the net proceeds to us from our issuance and sale of ordinary shares and pre-funded warrants in this offering will be approximately $ million, after deducting the underwriting discounts and commissions and estimated offering expenses payable by us. If the underwriters exercise their option to purchase additional ordinary shares in full, we estimate that our net proceeds will be approximately $ million, after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

We will only receive nominal additional proceeds, if any, from any exercise of pre-funded warrants.

We currently intend to use the net proceeds from this offering, together with our existing cash and cash equivalents, to fund the clinical development of CR-001, CR-002 and CR-003, the advancement of chemistry, manufacturing and controls activities, continued research and development for our preclinical programs, and for working capital and other general corporate purposes.

We estimate that our current cash and cash equivalents, prior to the receipt of proceeds from this offering, will fund operations into 2028. Based on our planned use of the net proceeds of this offering and our existing cash and cash equivalents, we estimate that such funds will be sufficient to enable us to fund our projected operating expenses, working capital and capital expenditure needs into . We have based this estimate on assumptions that may prove to be incorrect, and we could use our available capital resources sooner than we currently expect. We may satisfy our future cash needs through the sale of equity securities, debt financings, working capital lines of credit, corporate collaborations or license agreements, grant funding, interest income earned on invested cash balances or a combination of one or more of these sources.

This expected use of the net proceeds from this offering and our existing cash and cash equivalents represents our intentions based upon our current plans and business conditions, which could change in the future as our plans and business conditions evolve. We may also use a portion of the net proceeds or our existing cash and cash equivalents to in-license, acquire, or invest in additional businesses, technologies, products or assets, although currently we have no specific agreements, commitments or understandings in this regard. We cannot predict with certainty all of the particular uses of capital or the amounts that we will actually spend on the uses set forth above. Predicting the cost necessary to develop product candidates can be difficult and we anticipate that we will need additional funds to complete the development of our product candidates. The amounts and timing of our actual expenditures and the extent of clinical development may vary significantly depending on numerous factors, including the progress of our development efforts, the status of and results from preclinical studies and clinical trials, as well as any unforeseen cash needs. As a result, our management will retain broad discretion over the allocation of the net proceeds from this offering.

Pending our use of the net proceeds from this offering, we intend to invest the net proceeds in a variety of capital preservation investments, including short-term and intermediate-term, investment-grade, interest-bearing instruments and U.S. government securities.

S-8

DILUTION

If you invest in our securities in this offering, your interest will be diluted to the extent of the difference between the public offering price per ordinary share or pre-funded warrants and the as adjusted net tangible book value per ordinary share after this offering.

As of March 31, 2026, we had a historical net tangible book value of $183.8 million, or $6.67 per ordinary share, based on 27,571,935 ordinary shares outstanding. Our net tangible book value per share represents the amount of our total tangible assets reduced by the amount of our total liabilities, divided by the total number of ordinary shares outstanding as of March 31, 2026.

After giving effect to the issuance and sale in this offering by us of ordinary shares and pre-funded warrants at a public offering price of $ per share and $ per pre-funded warrant and after deducting underwriting discounts and commissions and estimated offering expenses payable by us, our as adjusted net tangible book value as of March 31, 2026 would have been $ million, or $ per share. This represents an immediate increase of net tangible book value of $ per share to our existing shareholders and an immediate dilution of $ per share to new investors participating in this offering. The following table illustrates this per share dilution:


Public offering price per share		$
Historical net tangible book value per share as of March 31, 2026	$6.67
Increase in net tangible book value per share attributable to this offering
As adjusted net tangible book value per share after this offering
Dilution per share to new investors in this offering		$

The dilution information discussed above assumes no exercise of the pre-funded warrants sold in this offering and is illustrative only. Investors who receive our ordinary shares upon the exercise of the pre-funded warrants offered hereby may experience additional dilution depending on our net tangible book value at the time of exercise.

If the underwriters exercise their option to purchase additional ordinary shares in full, the as adjusted net tangible book value per share after this offering would be $ , the increase in net tangible book value per share would be $ and the dilution to new investors would be $ per share, in each case based on a public offering price of $ per share and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

•2,890,000 ordinary shares issuable upon conversion of our Series A non-voting convertible preferred shares outstanding as of March 31, 2026;

•2,898,556 ordinary shares issuable upon exercise of our pre-funded warrants outstanding as of March 31, 2026, with an exercise price of $0.001 per share (including the 131,434 ordinary shares issuable upon exercise of the Private Placement Pre-Funded Warrants and 1,636,706 ordinary shares issuable upon exercise of the Fairmount Pre-Funded Warrants);

•437,297 ordinary shares issuable upon exercise of warrants outstanding as of March 31, 2026, including 402,731 warrants issued on December 31, 2025 with an exercise price of $11.86 and 34,566 warrants issued on January 31, 2026 with an exercise price of $13.50, under the ADC Paragon Option Agreement with Parascent Holding LLC;

•1,885,194 ordinary shares issuable upon the exercise of options outstanding as of March 31, 2026 under our 2025 Plan, at a weighted-average exercise price of $13.18 per share;

S-9

•278,332 ordinary shares issuable upon the vesting of restricted share units outstanding as of March 31, 2026 under our 2025 Plan;

•3,683,519 ordinary shares issuable upon the exercise of options outstanding as of March 31, 2026 under our 2024 Plan, at a weighted-average exercise price of $7.90 per share;

•328,789 ordinary shares issuable upon the vesting of restricted share units outstanding as of March 31, 2026 under our 2024 Plan;

•732,776 ordinary shares issuable upon the exercise of options outstanding as of March 31, 2026 under our 2025 Inducement Plan, at a weighted-average exercise price of $12.39 per share;

•517,224 ordinary shares reserved for future issuance under the 2025 Inducement Plan as of March 31, 2026; and

•528,950 ordinary shares reserved for future issuance under our ESPP as of March 31, 2026, as well as any automatic increase in the number of ordinary shares reserved for future issuance under the ESPP.

To the extent that any options or warrants are exercised, Series A non-voting convertible preferred shares convert, any restricted share units or restricted ordinary shares vest, any new awards are issued under our equity incentive plans, or we otherwise issue additional ordinary shares or securities convertible into ordinary shares in the future, there will be further dilution to new investors. In addition, the number of our ordinary shares to be outstanding immediately after this offering as shown above does not include the $200 million of ordinary shares that remain available for sale under the Sales Agreement.

S-10

DESCRIPTION OF PRE-FUNDED WARRANTS

The following is a brief summary of certain terms and conditions of the pre-funded warrants. The following description is subject to and qualified in its entirety by the form of pre-funded warrant.

Form

The pre-funded warrants will be issued as individual warrant agreements to the purchasers in certificated form only. The form of pre-funded warrant will be filed as an exhibit to a Current Report on Form 8-K that we will file with the SEC.

Term

The pre-funded warrants will not expire until they are fully exercised.

Exercisability

The pre-funded warrants will be exercisable at any time until they are fully exercised. The exercise price of each pre-funded warrant will be $0.001. The pre-funded warrants will be exercisable, at the option of each holder, in whole or in part, by delivering to us a duly executed exercise notice and payment of the exercise price. No fractional ordinary shares will be issued in connection with the exercise of a pre-funded warrant. In lieu of fractional shares, we will pay the holder an amount in cash equal to the fractional amount multiplied by the fair market value of our ordinary shares on the exercise date. The holder of the pre-funded warrants may also satisfy its obligation to pay the exercise price through a "cashless exercise," in which the holder receives the net value of the pre-funded warrant in ordinary shares determined according to the formula set forth in the pre-funded warrant.

Exercise Limitations

We may not effect the exercise of any pre-funded warrant, and a holder will not be entitled to exercise any portion of any pre-funded warrant that, upon giving effect to such exercise, would cause the aggregate number of ordinary shares beneficially owned by such holder (together with its affiliates) to exceed 4.99%, 9.99% or 19.99% (or such other percentage that was elected by each holder prior to the issuance of the pre-funded warrants) of the number of ordinary shares outstanding immediately after giving effect to the exercise, as such percentage ownership is set forth in accordance with the terms of the pre-funded warrants. However, any holder of a pre-funded warrant may increase or decrease such percentage upon at least 61 days' prior written notice from the holder to us, provided that such percentage may not be in excess of 19.99%.

Certain Adjustments

The exercise price of the pre-funded warrants for ordinary shares to be issued upon the exercise of the pre-funded warrants is $0.001 per share. The exercise price of the pre-funded warrants and the number of ordinary shares issuable upon exercise of the pre-funded warrants is subject to appropriate adjustment in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting our ordinary shares, as well as upon any distribution of assets, including cash, stock or other property, to our shareholders.

Transferability

Subject to applicable laws, the pre-funded warrants may be offered for sale, sold, transferred or assigned without our consent.

Exchange Listing

We do not intend to list the pre-funded warrants on The Nasdaq Capital Market, any other national securities exchange or any other nationally recognized trading system.

S-11

Warrant Agent

We will initially serve as the warrant agent under the pre-funded warrants.

Fundamental Transactions

Upon the consummation of a fundamental transaction (as described in the pre-funded warrants), the holders of the pre-funded warrants will be entitled to receive, upon exercise of the pre-funded warrants, the kind and amount of securities, cash, or other property that such holders would have received had they exercised the pre-funded warrants immediately prior to such fundamental transaction, without regard to any limitations on exercise contained in the pre-funded warrants.

No Rights as a Shareholder

Except as otherwise set forth in the form of pre-funded warrant or by virtue of such holder's ownership of our ordinary shares, the holder of a pre-funded warrant does not have the rights or privileges of a holder of our ordinary shares, including any voting rights, until such holder exercises the pre-funded warrant.

S-12

MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS

The following discussion is a summary of the material U.S. federal income tax considerations of the purchase, ownership and disposition of the ordinary shares and pre-funded warrants, which we refer to collectively as the "Securities," issued pursuant to this offering, but does not purport to be a complete analysis of all potential tax effects. The effects of other U.S. federal tax laws, such as estate and gift tax laws, and any applicable state, local or foreign tax laws are not discussed. This discussion is based on the Internal Revenue Code of 1986, as amended (the "Code"), Treasury Regulations promulgated thereunder, judicial decisions, and published rulings and administrative pronouncements of the U.S. Internal Revenue Service (the "IRS") in effect as of the date of this offering. These authorities may change or be subject to differing interpretations. Any such change or differing interpretation may be applied retroactively in a manner that could adversely affect a holder of the Securities. We have not sought and will not seek any rulings from the IRS regarding the matters discussed below. There can be no assurance the IRS or a court will not take a contrary position regarding the tax consequences of the purchase, ownership and disposition of the Securities.

This discussion is limited to holders that hold the Securities as a "capital asset" within the meaning of Section 1221 of the Code (generally, property held for investment). This discussion does not address all U.S. federal income tax consequences relevant to a holder's particular circumstances, including the impact of the alternative minimum tax or the unearned income Medicare contribution tax. In addition, it does not address consequences relevant to holders subject to particular rules, including, without limitation:

•U.S. expatriates and certain former citizens or long-term residents of the United States;

•persons holding the Securities as part of a hedge, straddle or other risk reduction strategy or as part of a conversion transaction or other integrated investment;

•banks, insurance companies and other financial institutions;

•brokers, dealers or traders in securities;

•"controlled foreign corporations," "foreign controlled foreign corporations," "passive foreign investment companies" and corporations that accumulate earnings to avoid U.S. federal income tax;

•partnerships or other entities or arrangements treated as partnerships for U.S. federal income tax purposes (and investors therein);

•tax-exempt organizations or governmental organizations;

•persons deemed to sell the Securities under the constructive sale provisions of the Code;

•persons who hold or receive the Securities pursuant to the exercise of any employee stock option or otherwise as compensation;

•real estate investment trusts or regulated investment companies;

•persons subject to special tax accounting rules as a result of any item of gross income with respect to the Securities being taken into account in an "applicable financial statement" (as defined in the Code);

•"qualified foreign pension funds" as defined in Section 897(l)(2) of the Code and entities all of the interests of which are held by qualified foreign pension funds; and

•tax-qualified retirement plans.

If an entity treated as a partnership for U.S. federal income tax purposes holds the Securities, the tax treatment of a partner in the partnership will depend on the status of the partner, the activities of the partnership and certain determinations made at the partner level. Accordingly, partnerships holding the Securities and the partners in such partnerships should consult their tax advisors regarding the U.S. federal income tax consequences to them.

THIS DISCUSSION IS FOR INFORMATIONAL PURPOSES ONLY AND IS NOT TAX ADVICE. INVESTORS SHOULD CONSULT THEIR TAX ADVISORS WITH RESPECT TO THE APPLICATION

S-13

OF THE U.S. FEDERAL INCOME TAX LAWS TO THEIR PARTICULAR SITUATIONS AS WELL AS ANY TAX CONSEQUENCES OF THE PURCHASE, OWNERSHIP AND DISPOSITION OF THE SECURITIES ARISING UNDER THE U.S. FEDERAL ESTATE OR GIFT TAX LAWS OR UNDER THE LAWS OF ANY STATE, LOCAL OR NON-U.S. TAXING JURISDICTION OR UNDER ANY APPLICABLE INCOME TAX TREATY.

Tax Classification of the Company as a U.S. Corporation

For U.S. federal income tax purposes, a corporation generally is considered to be a tax resident in the jurisdiction of its organization or incorporation. Accordingly, under the generally applicable U.S. federal income tax rules, the Company, which is incorporated under the laws of the Cayman Islands, would be classified as a non-U.S. corporation (and, therefore, not a U.S. tax resident) for U.S. federal income tax purposes. However, Section 7874 of the Code provides an exception to this general rule, under which a non-U.S. incorporated entity may, in certain circumstances, be treated as a U.S. corporation for U.S. federal income tax purposes. These rules are complex and there is limited guidance regarding their application. A number of significant and complicated U.S. federal income tax consequences may result from such classification, and this summary does not attempt to describe all such U.S. federal income tax consequences. Section 7874 of the Code and the Treasury Regulations promulgated thereunder do not address all the possible tax consequences that arise from the Company being treated as a U.S. corporation for U.S. federal income tax purposes. Accordingly, there may be additional or unforeseen U.S. federal income tax consequences to the Company that are not discussed in this summary.

Under such rules, even though the Company is organized as a Cayman Islands corporation, it is treated as a U.S. corporation for U.S. federal income tax purposes as a result of the Redomestication and application of the so-called "inversion" rules under Section 7874 of the Code. As such, the Company is subject to U.S. federal income tax as if it were organized under the laws of the United States, any state thereof or the District of Columbia, and its dividends are treated as dividends from a U.S. corporation. In addition, the Company is required to file a U.S. federal income tax return annually with the IRS. It is anticipated that such U.S. federal income tax treatment will continue indefinitely and that our securities will be treated indefinitely as securities of a U.S. corporation for U.S. federal income tax purposes. The Company's status as a U.S. corporation for U.S. federal income tax purposes has implications for all holders of the Securities.

This discussion assumes that the Company will be treated as a U.S. corporation for U.S. federal income tax purposes.

Treatment of Pre-Funded Warrants

Although not free from doubt, a pre-funded warrant should be treated as an ordinary share for U.S. federal income tax purposes, and a holder of pre-funded warrants should generally be taxed in the same manner as a holder of ordinary shares, as described below. Accordingly, no gain or loss should be recognized (other than with respect to cash paid in lieu of a fractional share) upon the exercise of a pre-funded warrant (except in the case of a cashless exercise, the treatment of which for U.S. federal income tax purposes is not clear) and, upon exercise, the holding period of a pre-funded warrant should carry over to the ordinary share received. Similarly, the tax basis of the pre-funded warrant should carry over to the ordinary share received upon exercise, increased by the exercise price of $0.001. The discussion below assumes the characterization described above is respected for U.S. federal income tax purposes. Holders should consult their tax advisors regarding the risks associated with the acquisition of pre-funded warrants pursuant to this offering (including alternative characterizations).

Tax Considerations Applicable to U.S. Holders

Definition of a U.S. Holder

For purposes of this discussion, a "U.S. holder" is any beneficial owner of the Securities that, for U.S. federal income tax purposes, is or is treated as any of the following:

•an individual who is a citizen or resident of the United States;

S-14

•a corporation created or organized under the laws of the United States, any state thereof or the District of Columbia;

•an estate, the income of which is subject to U.S. federal income tax regardless of its source; or

•a trust that (1) is subject to the primary supervision of a U.S. court and all substantial decisions of which are subject to the control of one or more United States persons (within the meaning of Section 7701(a)(30) of the Code), or (2) has a valid election in effect to be treated as a United States person for U.S. federal income tax purposes.

Distributions

We do not intend to pay cash dividends on our ordinary shares in the foreseeable future. However, if we do make distributions on our ordinary shares, such distributions of cash or property on our ordinary shares will constitute dividends to the extent paid out of our current or accumulated earnings and profits, as determined for U.S. federal income tax purposes. Dividends received by a corporate U.S. holder may be eligible for a dividends received deduction, subject to applicable limitations. Dividends received by certain non-corporate U.S. holders, including individuals, are generally taxed at the lower applicable capital gains rate provided certain holding period and other requirements are satisfied. Distributions in excess of our current and accumulated earnings and profits will constitute a return of capital and first be applied against and reduce a U.S. holder's adjusted tax basis in its ordinary shares, but not below zero. Any excess will be treated as capital gain and will be treated as described below in the section titled "-Sale or Other Taxable Disposition of the Securities."

Sale or Other Taxable Disposition of the Securities

Upon the sale, exchange or other taxable disposition of the Securities, a U.S. holder generally will recognize capital gain or loss equal to the difference between (1) the amount of cash and the fair market value of any property received upon the sale, exchange or other taxable disposition and (2) such U.S. holder's adjusted tax basis in the ordinary share or pre-funded warrant. Such capital gain or loss will be long-term capital gain or loss if the U.S. holder's holding period in such ordinary share or pre-funded warrant is more than one year at the time of the sale, exchange or other taxable disposition. Long-term capital gains recognized by certain non-corporate U.S. holders, including individuals, generally will be subject to reduced rates of U.S. federal income tax. The deductibility of capital losses is subject to certain limitations.

Constructive Dividends on Pre-Funded Warrants

A U.S. holder of a pre-funded warrant may, in some circumstances, be deemed to have received a distribution subject to U.S. federal income tax as a result of an adjustment or the non-occurrence of an adjustment to the exercise price or number of ordinary shares issuable upon exercise of the pre-funded warrant. U.S. holders should consult their tax advisors regarding the proper treatment of any adjustments (or the non-occurrence of any adjustments) to the pre-funded warrants.

Information Reporting and Backup Withholding

A U.S. holder may be subject to information reporting and backup withholding when such holder receives payments on the Securities (including constructive dividends) or receives proceeds from the sale or other taxable disposition of the Securities. Certain U.S. holders are exempt from backup withholding, including corporations and certain tax-exempt organizations. A U.S. holder will be subject to backup withholding if such holder is not otherwise exempt and such holder:

(a)fails to furnish the holder's taxpayer identification number, which for an individual is ordinarily his or her social security number;

(b)furnishes an incorrect taxpayer identification number; or

(c)is notified by the IRS that the holder previously failed to properly report payments of interest or dividends, or fails to certify under penalties of perjury that the holder has furnished a correct taxpayer identification number and that the IRS has not notified the holder that the holder is subject to backup withholding.

S-15

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against a U.S. holder's U.S. federal income tax liability, provided the required information is timely furnished to the IRS. U.S. holders should consult their tax advisors regarding their qualification for an exemption from backup withholding and the procedures for obtaining such an exemption.

Tax Considerations Applicable to Non-U.S. Holders

For purposes of this discussion, a "non-U.S. holder" is a beneficial owner of the Securities that is neither a U.S. holder nor an entity treated as a partnership for U.S. federal income tax purposes.

Distributions

We do not intend to pay cash dividends on our ordinary shares for the foreseeable future. However, if we do make distributions on our ordinary shares, such distributions of cash or property on our ordinary shares will constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. Amounts not treated as dividends for U.S. federal income tax purposes will constitute a return of capital and first be applied against and reduce a non-U.S. holder's adjusted tax basis in its ordinary shares, but not below zero. Any excess will be treated as capital gain and will be treated as described below in the section titled "-Sale or Other Taxable Disposition of the Securities." Because we may not know the extent to which a distribution is a dividend for U.S. federal income tax purposes at the time it is made, for purposes of the withholding rules discussed below we or the applicable withholding agent may treat the entire distribution as a dividend.

Dividends paid to a non-U.S. holder that are not effectively connected with the non-U.S. holder's conduct of a trade or business within the United States will be subject to U.S. federal withholding tax at a rate of 30% of the gross amount of the dividends (or such lower rate specified by an applicable income tax treaty).

Non-U.S. holders will be entitled to a reduction in or an exemption from withholding on dividends as a result of either (a) an applicable income tax treaty or (b) the non-U.S. holder holding our ordinary shares in connection with the conduct of a trade or business within the United States and dividends being effectively connected with that trade or business. To claim such a reduction in or exemption from withholding, the non-U.S. holder must provide the applicable withholding agent with a properly executed (a) IRS Form W-8BEN or W-8BEN-E (or other applicable documentation) claiming an exemption from or reduction of the withholding tax under the benefit of an income tax treaty between the United States and the country in which the non-U.S. holder resides or is established, or (b) IRS Form W-8ECI stating that the dividends are not subject to withholding tax because they are effectively connected with the conduct by the non-U.S. holder of a trade or business within the United States, as may be applicable. These certifications must be provided to the applicable withholding agent prior to the payment of dividends. Non-U.S. holders that do not timely provide the applicable withholding agent with the required certification, but that qualify for a reduced rate under an applicable income tax treaty, may obtain a refund of any excess amounts withheld by timely filing an appropriate claim for refund with the IRS.

If dividends paid to a non-U.S. holder are effectively connected with the non-U.S. holder's conduct of a trade or business within the United States (and, if required by an applicable income tax treaty, the non-U.S. holder maintains a permanent establishment in the United States to which such dividends are attributable), then, although exempt from U.S. federal withholding tax (provided the non-U.S. holder provides appropriate certification, as described above), the non-U.S. holder will be subject to U.S. federal income tax on such dividends on a net income basis at the regular rates applicable to United States persons. In addition, a non-U.S. holder that is a corporation may be subject to a branch profits tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on its effectively connected earnings and profits for the taxable year that are attributable to such dividends, as adjusted for certain items. Non-U.S. holders should consult their tax advisors regarding their entitlement to benefits under any applicable income tax treaty.

Sale or Other Taxable Disposition of the Securities

A non-U.S. holder will not be subject to U.S. federal income tax on any gain realized upon the sale or other taxable disposition of the Securities unless:

S-16

•the gain is effectively connected with the non-U.S. holder's conduct of a trade or business within the United States (and, if required by an applicable income tax treaty, the non-U.S. holder maintains a permanent establishment in the United States to which such gain is attributable);

•the non-U.S. holder is a nonresident alien individual present in the United States for 183 days or more during the taxable year of the disposition and certain other requirements are met; or

•the Securities constitute U.S. real property interests ("USRPIs") by reason of our status as a U.S. real property holding corporation ("USRPHC") for U.S. federal income tax purposes.

Gain described in the first bullet point above will generally be subject to U.S. federal income tax on a net income basis at the regular rates applicable to United States persons. A non-U.S. holder that is a corporation also may be subject to a branch profits tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on such effectively connected gain, as adjusted for certain items.

A non-U.S. holder described in the second bullet point above will be subject to U.S. federal income tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on any gain realized upon the sale or other taxable disposition of the Securities, which may be offset by certain U.S. source capital losses of the non-U.S. holder (even though the individual is not considered a resident of the United States) provided the non-U.S. holder has timely filed U.S. federal income tax returns with respect to such losses.

With respect to the third bullet point above, we believe we are not currently and do not anticipate becoming a USRPHC. Because the determination of whether we are a USRPHC depends on the fair market value of our USRPIs relative to the fair market value of our other business assets and our non-U.S. real property interests, however, there can be no assurance that we are not a USRPHC or will not become one in the future.

Non-U.S. holders should consult their tax advisors regarding potentially applicable income tax treaties that may provide for different rules.

Constructive Dividends on Pre-Funded Warrants

A non-U.S. holder of pre-funded warrants can be treated as receiving deemed payment of a taxable dividend under certain circumstances as a result of an adjustment or the non-occurrence of an adjustment to the exercise price or number of ordinary shares issuable upon exercise of the pre-funded warrant. Any resulting withholding tax attributable to deemed dividends may be collected from other amounts payable or distributable to the non-U.S. holder. Non-U.S. holders should consult their tax advisors regarding the proper treatment of any adjustments (or the non-occurrence of any adjustments) to the pre-funded warrants.

Information Reporting and Backup Withholding

A non-U.S. holder will not be subject to backup withholding with respect to distributions on the Securities (including constructive dividends), provided the applicable withholding agent does not have actual knowledge or reason to know such holder is a United States person and the holder certifies its non-U.S. status, such as by providing a valid IRS Form W-8BEN, W-8BEN-E or W-8ECI, or other applicable certification. However, information returns generally will be filed with the IRS in connection with any distributions (including deemed distributions) made on the Securities to the non-U.S. holder, regardless of whether any tax was actually withheld. Copies of these information returns may also be made available under the provisions of a specific treaty or agreement to the tax authorities of the country in which the non-U.S. holder resides or is established.

Information reporting and backup withholding may apply to the proceeds of a sale or other taxable disposition of the Securities within the United States, and information reporting may (although backup withholding generally will not) apply to the proceeds of a sale or other taxable disposition of the Securities outside the United States conducted through certain U.S.-related financial intermediaries, in each case, unless the beneficial owner certifies under penalty of perjury that it is a non-U.S. holder on IRS Form W-8BEN or W-8BEN-E, or other applicable form (and the payor does not have actual knowledge or reason to know that the beneficial owner is a United States person) or such owner otherwise establishes an exemption. Proceeds of a disposition of the Securities conducted through a non-U.S. office of a non-U.S. broker generally will not be subject to backup withholding or information reporting.

S-17

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against a non-U.S. holder's U.S. federal income tax liability, provided the required information is timely furnished to the IRS.

Additional Withholding Tax on Payments Made to Foreign Accounts

Withholding taxes may be imposed under Sections 1471 to 1474 of the Code (such Sections commonly referred to as the Foreign Account Tax Compliance Act ("FATCA")) on certain types of payments made to non-U.S. financial institutions and certain other non-U.S. entities. Specifically, a 30% withholding tax may be imposed on dividends (including deemed dividends) paid on the Securities, or (subject to the proposed Treasury Regulations discussed below) gross proceeds from the sale or other disposition of the Securities paid to a "foreign financial institution" or a "non-financial foreign entity" (each as defined in the Code), unless (1) the foreign financial institution undertakes certain diligence and reporting obligations, (2) the non-financial foreign entity either certifies it does not have any "substantial United States owners" (as defined in the Code) or furnishes identifying information regarding each substantial United States owner, or (3) the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from these rules. If the payee is a foreign financial institution and is subject to the diligence and reporting requirements in (1) above, it must enter into an agreement with the U.S. Department of the Treasury requiring, among other things, that it undertake to identify accounts held by certain "specified United States persons" or "United States-owned foreign entities" (each as defined in the Code), annually report certain information about such accounts, and withhold 30% on certain payments to non-compliant foreign financial institutions and certain other account holders. Foreign financial institutions located in jurisdictions that have an intergovernmental agreement with the United States governing FATCA may be subject to different rules.

Under applicable Treasury Regulations and administrative guidance, withholding under FATCA generally applies to payments of dividends (including deemed dividends). Because we may not know the extent to which a distribution (including deemed distributions) is a dividend for U.S. federal income tax purposes at the time it is made, for purposes of these withholding rules we or the applicable withholding agent may treat the entire distribution as a dividend. While withholding under FATCA would have applied also to payments of gross proceeds from the sale or other disposition of the Securities, beginning on January 1, 2019, proposed Treasury Regulations eliminate FATCA withholding on payments of gross proceeds entirely. Taxpayers generally may rely on these proposed Treasury Regulations until final Treasury Regulations are issued.

Prospective investors should consult their tax advisors regarding the potential application of withholding under FATCA to their investment in the Securities.

S-18

CERTAIN CAYMAN ISLANDS TAX CONSIDERATIONS

It is the responsibility of all persons interested in purchasing Securities to inform themselves as to any tax consequences from their investing in us and our operations or management, as well as any foreign exchange or other fiscal or legal restrictions, which are relevant to their particular circumstances in connection with the acquisition, holding or disposition of Securities. Holders should therefore seek their own separate tax advice in relation to their holding of Securities and accordingly we do not accept any responsibility for the taxation consequences of any investment in us by a holder.

There is, at present, no direct taxation in the Cayman Islands and interest, dividends and gains payable to us will be received free of all Cayman Islands taxes. We are registered as an "exempted company" pursuant to the Companies Act (as amended). We have received an undertaking from the Government of the Cayman Islands to the effect that, for a period of 30 years from the date of the undertaking, no law that thereafter is enacted in the Cayman Islands imposing any tax or duty to be levied on profits, income or on gains or appreciation, or any tax in the nature of estate duty or inheritance tax, will apply to any property comprised in or any income arising under us, or to our holders, in respect of any such property or income.

S-19

UNDERWRITING

Subject to the terms and conditions set forth in the underwriting agreement, dated , 2026, among us and Jefferies LLC and TD Securities (USA) LLC, as the representatives of the underwriters named below and the lead joint book-running managers of this offering, we have agreed to sell to the underwriters, and each of the underwriters has agreed, severally and not jointly, to purchase from us, the respective number of ordinary shares and pre-funded warrants shown opposite its name below:


UNDERWRITER	NUMBER OF SHARES	NUMBER OF PRE-FUNDED WARRANTS
Jefferies LLC
TD Securities (USA) LLC
Guggenheim Securities, LLC
Cantor Fitzgerald & Co.
LifeSci Capital LLC
Total

The underwriting agreement provides that the obligations of the several underwriters are subject to certain conditions precedent such as the receipt by the underwriters of officers' certificates and legal opinions and approval of certain legal matters by their counsel. The underwriting agreement provides that the underwriters will purchase all of the ordinary shares and pre-funded warrants if any of them are purchased. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the non-defaulting underwriters may be increased or the underwriting agreement may be terminated. We have agreed to indemnify the underwriters and certain of their controlling persons against certain liabilities, including liabilities under the Securities Act, and to contribute to payments that the underwriters may be required to make in respect of those liabilities.

The underwriters have advised us that, following the completion of this offering, they currently intend to make a market in the ordinary shares as permitted by applicable laws and regulations. However, the underwriters are not obligated to do so, and the underwriters may discontinue any market-making activities at any time without notice in their sole discretion. Accordingly, no assurance can be given as to the liquidity of the trading market for the ordinary shares, that you will be able to sell any of the ordinary shares held by you at a particular time or that the prices that you receive when you sell will be favorable.

The underwriters are offering the ordinary shares and pre-funded warrants subject to their acceptance of the ordinary shares and pre-funded warrants from us and subject to prior sale. The underwriters reserve the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part. The underwriters have not been engaged to act as warrant agent for the pre-funded warrants or to act as underwriter or agent or otherwise participate in the issuance of the ordinary shares upon the exercise of the pre-funded warrants.

Commission and Expenses

The underwriters have advised us that they propose to offer the ordinary shares and pre-funded warrants to the public at the initial public offering price set forth on the cover page of this prospectus supplement and to certain dealers, which may include the underwriters, at that price less a concession not in excess of $ per ordinary share or $ per pre-funded warrant. After the offering, the initial public offering price, concession and reallowance to dealers may be reduced by the representatives. No such reduction will change the amount of proceeds to be received by us as set forth on the cover page of this prospectus supplement.

The following table shows the public offering price, the underwriting discounts and commissions that we are to pay the underwriters and the proceeds, before expenses, to us in connection with this offering. Such amounts are shown assuming both no exercise and full exercise of the underwriters' option to purchase additional shares.

S-20

PER SHARE

TOTAL

WITHOUT OPTION TO PURCHASE ADDITIONAL SHARES

WITH OPTION TO PURCHASE ADDITIONAL SHARES

PER PRE-FUNDED WARRANT

WITHOUT OPTION TO PURCHASE ADDITIONAL SHARES

WITH OPTION TO PURCHASE ADDITIONAL SHARES

Public offering price

Underwriting discounts and commissions paid by us

Proceeds to us, before expenses

We estimate expenses payable by us in connection with this offering, other than the underwriting discounts and commissions referred to above, will be approximately $ . We have also agreed to reimburse the underwriters for their Financial Industry Regulatory Authority, Inc. (FINRA) counsel fee in an amount up to $40,000. In accordance with FINRA Rule 5110, this reimbursed fee is deemed underwriting compensation for this offering.

We have entered into an agreement with Piper Sandler & Co. for financial advisory services in connection with this offering.

Listing

Our ordinary shares are listed on The Nasdaq Capital Market under the trading symbol "CBIO." There is no established trading market for the pre-funded warrants, and we do not expect a trading market to develop. We do not intend to list the pre-funded warrants on any securities exchange or nationally recognized trading system, including The Nasdaq Capital Market. Without a trading market, the liquidity of the pre-funded warrants will be limited.

Option to Purchase Additional Ordinary Shares

We have granted to the underwriters an option, exercisable for 30 days from the date of this prospectus supplement, to purchase, from time to time, in whole or in part, up to an aggregate of ordinary shares from us at the public offering price set forth on the cover page of this prospectus supplement, less underwriting discounts and commissions. If the underwriters exercise this option, each underwriter will be obligated, subject to specified conditions, to purchase a number of additional ordinary shares proportionate to that underwriter's initial purchase commitment as indicated in the table above. This option may be exercised only if the underwriters sell more ordinary shares than the total number set forth on the cover page of this prospectus.

No Sales of Similar Securities

We, our executive officers and directors and certain stockholders have agreed, subject to specified exceptions, not to directly or indirectly:

•sell, offer, contract or grant any option to sell (including any short sale), pledge, transfer, establish an open "put equivalent position" within the meaning of Rule 16a-l(h) under the Exchange Act, or

•otherwise dispose of any ordinary shares, options or warrants to acquire ordinary shares, or securities exchangeable or exercisable for or convertible into ordinary shares currently or hereafter owned either of record or beneficially, or

•enter into any swap, hedge or similar arrangement or agreement that transfers, in whole or in part, the economic risk of ownership of our ordinary shares, or of options or warrants to purchase ordinary shares, or securities or rights exchangeable or exercisable for or convertible into ordinary shares, or publicly announce an intention to do any of the foregoing for a period of 60 days after the date of this prospectus without the prior written consent of the representatives. This restriction terminates after the close of trading of our ordinary shares on and including the 60th day after the date of this prospectus supplement.

S-21

The representatives may, in their sole discretion and at any time or from time to time before the termination of the 60-day period, release all or any portion of the securities subject to lock-up agreements. Except for customary lock-up exceptions, including with respect to our Sales Agreement with Jefferies LLC (until the earlier of (i) the exercise in full by the underwriters of their option to purchase additional ordinary shares and (ii) 30 calendar days after the date of this prospectus supplement), there are no existing agreements between the underwriters and any of our shareholders who executed a lock-up agreement, providing consent to the sale of ordinary shares prior to the expiration of the lock-up period.

Stabilization

The underwriters have advised us that, pursuant to Regulation M under the Exchange Act, certain persons participating in the offering may engage in short sale transactions, stabilizing transactions, syndicate covering transactions or the imposition of penalty bids in connection with this offering. These activities may have the effect of stabilizing or maintaining the market price of our ordinary shares at a level above that which might otherwise prevail in the open market. Establishing short sales positions may involve either "covered" short sales or "naked" short sales.

"Covered" short sales are sales made in an amount not greater than the underwriters' option to purchase additional ordinary shares in this offering. The underwriters may close out any covered short position by either exercising their option to purchase additional ordinary shares or purchasing ordinary shares in the open market. In determining the source of ordinary shares to close out the covered short position, the underwriters will consider, among other things, the price of ordinary shares available for purchase in the open market as compared to the price at which they may purchase shares through the option to purchase additional ordinary shares.

"Naked" short sales are sales in excess of the option to purchase additional ordinary shares. The underwriters must close out any naked short position by purchasing shares in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the ordinary shares in the open market after pricing that could adversely affect investors who purchase in this offering.

A stabilizing bid is a bid for the purchase of ordinary shares on behalf of the underwriters for the purpose of fixing or maintaining the price of our ordinary shares. A syndicate covering transaction is the bid for or the purchase of ordinary shares on behalf of the underwriters to reduce a short position incurred by the underwriters in connection with the offering. Similar to other purchase transactions, the underwriter's purchases to cover the syndicate short sales may have the effect of raising or maintaining the market price of our ordinary shares or preventing or retarding a decline in the market price of our ordinary shares. As a result, the price of our ordinary shares may be higher than the price that might otherwise exist in the open market. A penalty bid is an arrangement permitting the underwriters to reclaim the selling concession otherwise accruing to a syndicate member in connection with the offering if the ordinary shares originally sold by such syndicate member are purchased in a syndicate covering transaction and therefore have not been effectively placed by such syndicate member.

Neither we, nor any of the underwriters make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of our ordinary shares. The underwriters are not obligated to engage in these activities and, if commenced, any of the activities may be discontinued at any time.

The underwriters may also engage in passive market making transactions in our ordinary shares on The Nasdaq Capital Market in accordance with Rule 103 of Regulation M during a period before the commencement of offers or sales of ordinary shares in this offering and extending through the completion of distribution. A passive market maker must display its bid at a price not in excess of the highest independent bid of that security. However, if all independent bids are lowered below the passive market maker's bid, that bid must then be lowered when specified purchase limits are exceeded.

Electronic Distribution

A prospectus supplement in electronic format may be made available by e-mail or on the web sites or through online services maintained by one or more of the underwriters or their respective affiliates. In those cases, prospective investors may view offering terms online and may be allowed to place orders online. The underwriters may agree

S-22

with us to allocate a specific number of ordinary shares for sale to online brokerage account holders. Any such allocation for online distributions will be made by the underwriters on the same basis as other allocations. Other than this prospectus supplement and the accompanying prospectus in electronic format, the information on the underwriters' web sites and any information contained in any other web site maintained by any of the underwriters is not part of this prospectus supplement or the accompanying prospectus, has not been approved and/or endorsed by us or the underwriters and should not be relied upon by investors.

Other Activities and Relationships

The underwriters and certain of their respective affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. The underwriters and certain of their respective affiliates have, from time to time, performed, and may in the future perform, various commercial and investment banking and financial advisory services for us and our affiliates, for which they received or will receive customary fees and expenses. For example, on July 1, 2026, we entered into the Sales Agreement with Jefferies LLC pursuant to which we may offer and sell our ordinary shares from time to time through Jefferies LLC acting as our sales agent.

In the ordinary course of their various business activities, the underwriters and certain of their respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers, and such investment and securities activities may involve securities and/or instruments issued by us and our affiliates. If the underwriters or their respective affiliates have a lending relationship with us, they routinely hedge their credit exposure to us consistent with their customary risk management policies. The underwriters and their respective affiliates may hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities or the securities of our affiliates, including potentially the securities offered hereby. Any such short positions could adversely affect future trading prices of the securities offered hereby. The underwriters and certain of their respective affiliates may also communicate independent investment recommendations, market color or trading ideas and/or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

Disclaimers About Non-U.S. Jurisdictions

European Economic Area

In relation to each Member State of the European Economic Area (each a Relevant State), no securities have been offered or will be offered pursuant to the offering to the public in that Relevant State prior to the publication of a prospectus in relation to the securities which has been approved by the competent authority in that Relevant State or, where appropriate, approved in another Relevant State and notified to the competent authority in that Relevant State, all in accordance with the Prospectus Regulation, except that the securities may be offered to the public in that Relevant State at any time:

(i)to any legal entity which is a qualified investor as defined under Article 2 of the Prospectus Regulation;

(ii)to fewer than 150 natural or legal persons (other than qualified investors as defined under Article 2 of the Prospectus Regulation), subject to obtaining the prior consent of the representative for any such offer; or

(iii)in any other circumstances falling within Article 1(4) of the Prospectus Regulation,

provided that no such offer of the securities shall require us or the representative to publish a prospectus pursuant to Article 3 of the Prospectus Regulation or supplement a prospectus pursuant to Article 23 of the Prospectus Regulation.

S-23

For the purposes of this provision, the expression an "offer to the public" in relation to the securities in any Relevant State means the communication in any form and by any means of sufficient information on the terms of the offer and any securities to be offered so as to enable an investor to decide to purchase or subscribe for any securities, and the expression "Prospectus Regulation" means Regulation (EU) 2017/1129.

United Kingdom

No securities have been offered or will be offered pursuant to the offering to the public in the United Kingdom except that the securities may be offered to the public in the United Kingdom at any time:

(a)where (i) the offer is conditional on the admission of the securities to trading on the London Stock Exchange plc's main market (in reliance on the exception in paragraph 6(a) of Schedule 1 of the POATR) or (ii) the securities being offered are at the time of the offer already admitted to trading on London Stock Exchange plc's main market (in reliance on the exception in paragraph 6(b) of Schedule 1 of the POATR);

(b)to any "qualified investor" as defined in paragraph 15 of Schedule 1 of the POATR;

(c)to fewer than 150 persons (other than qualified investors as defined in paragraph 15 of Schedule 1 of the POATR), subject to obtaining the prior consent of the underwriters for any such offer; or

(d)in any other circumstances falling within Part 1 of Schedule 1 of the POATR.

For the purposes of this provision, the expression an "offer to the public" in relation to the securities in the United Kingdom means the communication to any person which presents sufficient information on: (a) the securities to be offered; and (b) the terms on which they are to be offered, to enable an investor to decide to buy or subscribe for the securities and the expression "POATR" means the Public Offers and Admissions to Trading Regulations 2024.

This prospectus supplement is only being distributed to and is only directed at: (A) persons who are outside the United Kingdom, or (B) qualified investors who are also (i) investment professionals falling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (the Order), or (ii) high-net-worth companies, and other persons to whom it may lawfully be communicated, falling within Article 49(2)(a) to (d) of the Order (all such persons falling within (1) - (3) together being referred to as "relevant persons"). The securities are only available to, and any invitation, offer or agreement to subscribe, purchase or otherwise acquire the securities will be engaged in only with, relevant persons. Any person who is not a relevant person should not act or rely on this prospectus supplement or any of its contents.

Canada

(A) Resale Restrictions

The distribution of securities in Canada is being made only in the provinces of Ontario, Quebec, Alberta, British Columbia, Manitoba, New Brunswick and Nova Scotia on a private placement basis exempt from the requirement that we prepare and file a prospectus with the securities regulatory authorities in each province where trades of these securities are made. Any resale of the securities in Canada must be made under applicable securities laws which may vary depending on the relevant jurisdiction, and which may require resales to be made under available statutory exemptions or under a discretionary exemption granted by the applicable Canadian securities regulatory authority. Purchasers are advised to seek legal advice prior to any resale of the securities.

(B) Representations of Canadian Purchasers

By purchasing securities in Canada and accepting delivery of a purchase confirmation, a purchaser is representing to us and the dealer from whom the purchase confirmation is received that:

•the purchaser is entitled under applicable provincial securities laws to purchase the securities without the benefit of a prospectus qualified under those securities laws as it is an "accredited investor" as defined under National Instrument 45-106 - Prospectus Exemptions or Section 73.3(1) of the Securities Act (Ontario), as applicable,

S-24

•the purchaser is a "permitted client" as defined in National Instrument 31-103 - Registration Requirements, Exemptions and Ongoing Registrant Obligations,

•where required by law, the purchaser is purchasing as principal and not as agent, and

•the purchaser has reviewed the text above under Resale Restrictions.

Canadian purchasers are hereby notified that certain of the underwriters are relying on the exemption set out in section 3A.3 or 3A.4, if applicable, of National Instrument 33-105 - Underwriting Conflicts from having to provide certain conflict of interest disclosure in this prospectus supplement.

(D) Statutory Rights of Action

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if the prospectus (including any amendment thereto) such as this prospectus supplement contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser's province or territory. The purchaser of these securities in Canada should refer to any applicable provisions of the securities legislation of the purchaser's province or territory for particulars of these rights or consult with a legal advisor.

(E) Enforcement of Legal Rights

All of our directors and officers as well as the experts named herein may be located outside of Canada and, as a result, it may not be possible for Canadian purchasers to effect service of process within Canada upon us or those persons. All or a substantial portion of our assets and the assets of those persons may be located outside of Canada and, as a result, it may not be possible to satisfy a judgment against us or those persons in Canada or to enforce a judgment obtained in Canadian courts against us or those persons outside of Canada.

(F) Taxation and Eligibility for Investment

Canadian purchasers of securities should consult their own legal and tax advisors with respect to the tax consequences of an investment in the securities in their particular circumstances and about the eligibility of the securities for investment by the purchaser under relevant Canadian legislation.

(G) Language of Documents

The purchaser confirms its express wish and that it has requested that this document, all documents evidencing or relating to the sale of the securities described herein and all other related documents be drawn up exclusively in the English language. L'acquéreur confirme sa volonté expresse et qu'il a demandé que le présent document, tous les documents attestant de la vente des titres décrits dans le présent document ou s'y rapportant ainsi que tous les autres documents s'y rattachant soient rédigés exclusivement en langue anglaise.

Australia

This prospectus supplement is not a disclosure document for the purposes of Australia's Corporations Act 2001 (Cth) of Australia (the Corporations Act) has not been lodged with the Australian Securities & Investments Commission and is only directed to the categories of exempt persons set out below. Accordingly, if you receive this prospectus supplement in Australia:

You confirm and warrant that you are either:

•a "sophisticated investor" under section 708(8)(a) or (b) of the Corporations Act;

S-25

•a "sophisticated investor" under section 708(8)(c) or (d) of the Corporations Act and that you have provided an accountant's certificate to us which complies with the requirements of section 708(8)(c)(i) or (ii) of the Corporations Act and related regulations before the offer has been made;

•a person associated with us under Section 708(12) of the Corporations Act; or

•a "professional investor" within the meaning of section 708(11)(a) or (b) of the Corporations Act.

To the extent that you are unable to confirm or warrant that you are an exempt sophisticated investor, associated person or professional investor under the Corporations Act any offer made to you under this prospectus supplement is void and incapable of acceptance.

You warrant and agree that you will not offer any of the securities issued to you pursuant to this prospectus supplement for resale in Australia within 12 months of those securities being issued unless any such resale offer is exempt from the requirement to issue a disclosure document under section 708 of the Corporations Act.

Hong Kong

No securities have been offered or sold, and no securities may be offered or sold, in Hong Kong, by means of any document, other than to persons whose ordinary business is to buy or sell shares or debentures, whether as principal or agent; or to "professional investors" as defined in the Securities and Futures Ordinance (Cap. 571) of Hong Kong (SFO) and any rules made under that Ordinance; or in other circumstances which do not result in the document being a "prospectus" as defined in the Companies Ordinance (Cap. 32) of Hong Kong (CO) or which do not constitute an offer or invitation to the public for the purpose of the CO or the SFO. No document, invitation or advertisement relating to the securities has been issued or may be issued or may be in the possession of any person for the purpose of issue (in each case whether in Hong Kong or elsewhere), which is directed at, or the contents of which are likely to be accessed or read by, the public of Hong Kong (except if permitted under the securities laws of Hong Kong) other than with respect to securities which are or are intended to be disposed of only to persons outside Hong Kong or only to "professional investors" as defined in the SFO and any rules made under that Ordinance.

This prospectus supplement has not been registered with the Registrar of Companies in Hong Kong. Accordingly, this prospectus supplement may not be issued, circulated or distributed in Hong Kong, and the securities may not be offered for subscription to members of the public in Hong Kong. Each person acquiring the securities will be required, and is deemed by the acquisition of the securities, to confirm that he is aware of the restriction on offers of the securities described in this prospectus supplement and the relevant offering documents and that he is not acquiring, and has not been offered any securities in circumstances that contravene any such restrictions.

Israel

This prospectus supplement does not constitute a prospectus under the Israeli Securities Law, 5728-1968 (the Securities Law) and has not been filed with or approved by the Israel Securities Authority. In Israel, this prospectus supplement is being distributed only to, and is directed only at, and any offer of the securities is directed only at, (i) a limited number of persons in accordance with the Israeli Securities Law and (ii) investors listed in the first addendum (the Israel Addendum) to the Israeli Securities Law, consisting primarily of joint investment in trust funds, provident funds, insurance companies, banks, portfolio managers, investment advisors, members of the Tel Aviv Stock Exchange, underwriters, venture capital funds, entities with equity in excess of NIS 50 million and "qualified individuals," each as defined in the Israel Addendum (as it may be amended from time to time), collectively referred to as qualified investors (in each case, purchasing for their own account or, where permitted under the Israel Addendum, for the accounts of their clients who are investors listed in the Israel Addendum). Qualified investors are required to submit written confirmation that they fall within the scope of the Israel Addendum, are aware of the meaning of same and agree to it.

Japan

The offering has not been and will not be registered under the Financial Instruments and Exchange Law of Japan (Law No. 25 of 1948 of Japan, as amended) (FIEL) and the underwriters will not offer or sell any securities, directly or indirectly, in Japan or to, or for the benefit of, any resident of Japan (which term as used herein means any person

S-26

resident in Japan, including any corporation or other entity organized under the laws of Japan), or to others for re-offering or resale, directly or indirectly, in Japan or to, or for the benefit of, any resident of Japan, except pursuant to an exemption from the registration requirements of, and otherwise in compliance with, the FIEL and any other applicable laws, regulations and ministerial guidelines of Japan.

Singapore

This prospectus supplement has not been and will not be lodged or registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus supplement and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the securities may not be circulated or distributed, nor may the securities be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (SFA) (ii) to a relevant person pursuant to Section 275(1), or any person pursuant to Section 275(1A), and in accordance with the conditions specified in Section 275, of the SFA, or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA.

Where the securities are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

•a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or

•a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary of the trust is an individual who is an accredited investor,

securities (as defined in Section 239(1) of the SFA) of that corporation or the beneficiaries' rights and interest (howsoever described) in that trust shall not be transferred within six months after that corporation or that trust has acquired the securities pursuant to an offer made under Section 275 of the SFA except:

•to an institutional investor or to a relevant person defined in Section 275(2) of the SFA, or to any person arising from an offer referred to in Section 275(1A) or Section 276(4)(i)(B) of the SFA;

•where no consideration is or will be given for the transfer;

•where the transfer is by operation of law;

•as specified in Section 276(7) of the SFA; or

•as specified in Regulation 32 of the Securities and Futures (Offers of Investments) (Shares and Debentures) Regulations 2005 of Singapore.

Switzerland

The securities may not be publicly offered in Switzerland and will not be listed on the SIX Swiss Exchange, or SIX, or on any other stock exchange or regulated trading facility in Switzerland. This prospectus supplement has been prepared without regard to the disclosure standards for issuance prospectuses under art. 652a or art. 1156 of the Swiss Code of Obligations or the disclosure standards for listing prospectuses under art. 27 ff. of the SIX Listing Rules or the listing rules of any other stock exchange or regulated trading facility in Switzerland. Neither this prospectus supplement nor any other offering or marketing material relating to the securities or the offering may be publicly distributed or otherwise made publicly available in Switzerland.

Neither this prospectus supplement nor any other offering or marketing material relating to the offering, us or the securities have been or will be filed with or approved by any Swiss regulatory authority. In particular, this prospectus supplement will not be filed with, and the offer of the securities will not be supervised by, the Swiss Financial Market Supervisory Authority (FINMA), and the offer of the securities has not been and will not be authorized under the Swiss Federal Act on Collective Investment Schemes (CISA). The investor protection afforded to acquirers of interests in collective investment schemes under the CISA does not extend to acquirers of securities.

S-27

LEGAL MATTERS

The validity of the ordinary shares offered by this prospectus supplement will be passed upon for us by Walkers (Cayman) LLP. The validity of the pre-funded warrants offered by this prospectus supplement will be passed upon for us by Latham & Watkins LLP. Cooley LLP, New York, New York, is acting as counsel for the underwriters in connection with this offering.

EXPERTS

The financial statements incorporated in this prospectus supplement by reference to the Annual Report on Form 10-K for the year ended December 31, 2025 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

S-28

WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE

Available Information

We have filed with the SEC a registration statement on Form S-3 under the Securities Act, of which this prospectus supplement forms a part. The rules and regulations of the SEC allow us to omit from this prospectus supplement and the accompanying prospectus certain information included in the registration statement. For further information about us and the securities we are offering under this prospectus supplement, you should refer to the registration statement and the exhibits and schedules filed with the registration statement. With respect to the statements contained in this prospectus supplement and the accompanying prospectus regarding the contents of any agreement or any other document, in each instance, the statement is qualified in all respects by the complete text of the agreement or document, a copy of which has been filed as an exhibit to the registration statement.

We file reports, proxy statements and other information with the SEC. The SEC maintains a website that contains reports, proxy and information statements and other information about issuers, such as us, who file electronically with the SEC. The address of that website is http://www.sec.gov.

Our website address is www.crescentbiopharma.com. The information on, or accessible through, our website is not part of, and is not incorporated into, this prospectus supplement or the accompanying prospectus and should not be considered part of this prospectus supplement or the accompanying prospectus.

Incorporation by Reference

The SEC's rules allow us to "incorporate by reference" information into this prospectus supplement, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus supplement and the accompanying prospectus, and subsequent information that we file with the SEC will automatically update and supersede that information. Any statement contained in this prospectus supplement or a previously filed document incorporated by reference will be deemed to be modified or superseded for purposes of this prospectus supplement and the accompanying prospectus to the extent that a statement contained in this prospectus supplement, the accompanying prospectus, or a subsequently filed document incorporated by reference modifies or replaces that statement.

This prospectus supplement and the accompanying prospectus incorporate by reference the documents set forth below that have previously been filed with the SEC (except for information in these documents or filings that is deemed "furnished" and not "filed" in accordance with the SEC rules, including pursuant to Item 2.02 or 7.01 of Form 8-K, or corresponding information furnished under Item 9.01 as an exhibit, and no such information shall be deemed specifically incorporated by reference herein or in any accompanying prospectus supplement):

•our Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on February 26, 2026;

•our Quarterly Report on Form 1 0-Q for the quarter ended March 31, 2026, filed with the SEC on April 29, 2026, as amended by A mendment No. 1 to our Quarterly Report on Form 10-Q, filed with the SEC on June 22, 2026;

•the information specifically incorporated by reference into our Annual Report on Form 10-K from our Definitive Proxy Statement on Schedule 14A, filed with the SEC on April 21, 2026;

•our Current Report on Form 8-K, filed with the SEC on June 3, 2026; and

•the description of our securities contained in our registration statement on Form 8A12B/A, filed with the SEC on November 6, 2025, including any amendment or report filed with the SEC for the purpose of updating the description, including Exhibit 4.3 to our Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on February 26, 2026.

S-29

All reports and other documents we subsequently file pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the termination of this offering, excluding any information furnished to, rather than filed with, the SEC, will also be incorporated by reference into this prospectus supplement and the accompanying prospectus and deemed to be part of this prospectus supplement and the accompanying prospectus from the date of the filing of such reports and documents.

You may request a free copy of any of the documents incorporated by reference in this prospectus supplement and the accompanying prospectus (other than exhibits, unless they are specifically incorporated by reference in the documents) by writing or telephoning us at the following address:

Crescent Biopharma, Inc.

Attention: Corporate Secretary

300 Fifth Avenue

Waltham, MA 02451

(617) 430-5595

Exhibits to the filings will not be sent, however, unless those exhibits have specifically been incorporated by reference in this prospectus supplement or the accompanying prospectus.

S-30

PROSPECTUS

$500,000,000

Ordinary Shares

Preferred Shares

Debt Securities

Warrants

Units

We may offer and sell up to $500 million in the aggregate of the securities identified above from time to time in one or more offerings. This prospectus provides you with a general description of the securities.

Each time we offer and sell securities, we will provide a supplement to this prospectus that contains specific information about the offering and the amounts, prices and terms of the securities. The supplement may also add, update or change information contained in this prospectus with respect to that offering. You should carefully read this prospectus and the applicable prospectus supplement, together with the documents we incorporate by reference, before you invest in any of our securities.

We may offer and sell the securities described in this prospectus and any prospectus supplement to or through one or more underwriters, dealers and agents, or directly to purchasers, or through a combination of these methods. If any underwriters, dealers or agents are involved in the sale of any of the securities, their names and any applicable purchase price, fee, commission or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement. See the sections of this prospectus entitled "About this Prospectus" and "Plan of Distribution" for more information. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such securities.

INVESTING IN OUR SECURITIES INVOLVES RISKS. SEE THE "RISK FACTORS" ON PAGE 6 OF THIS PROSPECTUS AND ANY SIMILAR SECTION CONTAINED IN THE APPLICABLE PROSPECTUS SUPPLEMENT CONCERNING FACTORS YOU SHOULD CONSIDER BEFORE INVESTING IN OUR SECURITIES.

Our ordinary shares are listed on the Nasdaq Capital Market under the symbol "CBIO." On June 30, 2026, the last reported sale price of our ordinary shares on the Nasdaq Capital Market was $18.00 per share.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is July 10, 2026.

TABLE OF CONTENTS



ABOUT THIS PROSPECTUS						1
CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS						2
WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE						3
THE COMPANY						5
RISK FACTORS						6
USE OF PROCEEDS						7
DIVIDEND POLICY						8
DESCRIPTION OF SHARE CAPITAL						9
DESCRIPTION OF DEBT SECURITIES						17
DESCRIPTION OF WARRANTS						24
DESCRIPTION OF UNITS						25
PLAN OF DISTRIBUTION						26
LEGAL MATTERS						28
EXPERTS						28

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the U.S. Securities and Exchange Commission (the "SEC"), using a "shelf" registration process. By using a shelf registration statement, we may sell securities from time to time and in one or more offerings up to a total dollar amount of $500 million as described in this prospectus. Each time that we offer and sell securities, we will provide a prospectus supplement to this prospectus that contains specific information about the securities being offered and sold and the specific terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. The prospectus supplement or free writing prospectus may also add, update or change information contained in this prospectus with respect to that offering. If there is any inconsistency between the information in this prospectus and the applicable prospectus supplement or free writing prospectus, you should rely on the prospectus supplement or free writing prospectus, as applicable. Before purchasing any securities, you should carefully read both this prospectus and the applicable prospectus supplement (and any applicable free writing prospectuses), together with the additional information described under the heading "Where You Can Find More Information; Incorporation by Reference."

We have not authorized anyone to provide you with any information or to make any representations other than those contained in this prospectus, any applicable prospectus supplement or any free writing prospectuses prepared by or on behalf of us or to which we have referred you. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We will not make an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus and the applicable prospectus supplement to this prospectus is accurate only as of the date on its respective cover, that the information appearing in any applicable free writing prospectus is accurate only as of the date of that free writing prospectus, and that any information incorporated by reference is accurate only as of the date of the document incorporated by reference, unless we indicate otherwise. Our business, financial condition, results of operations and prospects may have changed since those dates. This prospectus incorporates by reference, and any prospectus supplement or free writing prospectus may contain and incorporate by reference, market data and industry statistics and forecasts that are based on independent industry publications and other publicly available information. Although we believe these sources are reliable, we do not guarantee the accuracy or completeness of this information and we have not independently verified this information. In addition, the market and industry data and forecasts that may be included or incorporated by reference in this prospectus, any prospectus supplement or any applicable free writing prospectus, may involve estimates, assumptions, and other risks and uncertainties and are subject to change based on various factors, including those discussed under the heading "Risk Factors" contained in this prospectus, the applicable prospectus supplement and any applicable free writing prospectus, and under similar headings in other documents that are incorporated by reference into this prospectus. Accordingly, investors should not place undue reliance on this information.

When we refer to "Crescent," "we," "our," "us" and the "Company" in this prospectus, we mean Crescent Biopharma, Inc. and our subsidiaries, unless otherwise specified. When we refer to "you," we mean the potential holders of the applicable series of securities.

We use our trademarks and service marks in this prospectus, as well as trademarks, tradenames and service marks that are the property of other organizations. Solely for convenience, trademarks and tradenames referred to in this prospectus appear without the ® and ™ symbols, but those references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights or that the applicable owner will not assert its rights, to these trademarks and tradenames.

CAUTIONARY STATEMENT CONCERNING FORWARD-LOOKING STATEMENTS

This prospectus contains "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933, as amended (the "Securities Act"), and Section 21E of the Securities Exchange Act of 1934, as amended (the "Exchange Act"). These forward-looking statements involve a number of risks and uncertainties. We caution readers that any forward-looking statement is not a guarantee of future performance and that actual results could differ materially from those contained in the forward-looking statement. These statements are based on current expectations of future events.

All statements, other than statements of historical facts contained in this prospectus, including, without limitation, statements regarding our future results of operations and financial position, business strategy, the length of time that we believe our existing cash resources will fund our operations, our market size, our potential growth opportunities, our preclinical and future clinical development activities, the efficacy and safety profile of our product candidates, the potential therapeutic benefits and economic value of our product candidates, the timing and results of preclinical studies and clinical trials, the expected impact of macroeconomic conditions, including inflation, increasing interest rates and volatile market conditions, as well as global events, including military conflicts and geopolitical tensions on our operations, and the receipt and timing of potential regulatory designations, approvals and commercialization of product candidates, are forward-looking statements. Forward-looking statements generally relate to future events or our future financial or operating performance. The words "believe," "may," "will," "potentially," "estimate," "continue," "anticipate," "predict," "target," "intend," "could," "would," "should," "project," "plan," "expect," and similar expressions that convey uncertainty of future events or outcomes are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.

These forward-looking statements are subject to a number of risks, uncertainties and assumptions. Moreover, we operate in a very competitive and rapidly changing environment, and new risks emerge from time to time. It is not possible for our management to predict all risks, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements we may make. Factors that might cause such a difference are disclosed in the sections titled "Risk Factors" in this prospectus and in the documents incorporated by reference in this prospectus and any applicable prospectus supplement. You should evaluate all forward-looking statements made in this prospectus in the context of these risks and uncertainties. We caution you that the risks, uncertainties and other factors referred to in this prospectus may not contain all of the risks, uncertainties and other factors that may affect our future results and operations.

In addition, statements that "we believe" and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based on information available to us as of the date of this prospectus. While we believe that such information provides a reasonable basis for these statements, such information may be limited or incomplete. Our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all relevant information. These statements are inherently uncertain, and investors are cautioned not to unduly rely on these statements.

This prospectus contains or incorporates by reference estimates, projections and other information concerning our industry, our business and the potential markets for our product candidates, including data regarding the estimated size of such markets and the incidence of certain medical conditions. We obtained the industry, market and competitive position data set forth in this prospectus from our own internal estimates and research, as well as from academic and industry publications, research, surveys and studies conducted by third parties. Internal estimates are derived from publicly available information released by industry analysts and third-party sources, our internal research and our industry experience, and are based on assumptions made by us based on such data and our knowledge of the industry and market, which we believe to be reasonable. In some cases, we do not expressly refer to the sources from which this data is derived. We believe that the third-party data set forth in this prospectus is reliable and based on reasonable assumptions. This information, to the extent it contains estimates or projections involves a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates or projections. The industry in which we operate is subject to risks and uncertainties and is subject to change based on various factors, including those set forth under the section titled "Risk Factors" included in this prospectus. These and other factors

could cause results to differ materially from those expressed in the estimates made by the independent parties and by us.

All subsequent written or oral forward-looking statements attributable to us or any person acting on our behalf are expressly qualified in their entirety by the cautionary statements contained or referred to in this section. We do not undertake any obligation to release publicly any revisions to these forward-looking statements to reflect events or circumstances after the date of this prospectus or to reflect the occurrence of unanticipated events, except as may be required under applicable U.S. securities laws. If we do update one or more forward-looking statements, no inference should be drawn that we will make additional updates with respect to those or other forward-looking statements.

WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE

Available Information

Our website address is www.crescentbiopharma.com. The information on our website, however, is not, and should not be deemed to be, a part of this prospectus.

This prospectus and any prospectus supplement are part of a registration statement that we filed with the SEC and do not contain all of the information in the registration statement. The full registration statement may be obtained from the SEC or us, as provided below. Forms of the indenture and other documents establishing the terms of the offered securities are or may be filed as exhibits to the registration statement or documents incorporated by reference in the registration statement. Statements in this prospectus or any prospectus supplement about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the actual documents for a more complete description of the relevant matters. You may inspect a copy of the registration statement through the SEC's website, as provided above.

Incorporation by Reference

The SEC's rules allow us to "incorporate by reference" information into this prospectus, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, and subsequent information that we file with the SEC will automatically update and supersede that information. Any statement contained in this prospectus or a previously filed document incorporated by reference will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus or a subsequently filed document incorporated by reference modifies or replaces that statement.

This prospectus and any accompanying prospectus supplement incorporate by reference the documents set forth below that have previously been filed with the SEC (except for information in these documents or filings that is deemed "furnished" and not "filed" in accordance with the SEC rules, including pursuant to Item 2.02 or 7.01 of Form 8-K, or corresponding information furnished under Item 9.01 as an exhibit, and no such information shall be deemed specifically incorporated by reference herein or in any accompanying prospectus supplement):

•our Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on February 26, 2026;

•our Quarterly Report on Form 10-Q for the quarter ended March 31, 2026, filed with the SEC on April 29, 2026, as amended by Amendment No. 1 to our Quarterly Report on Form 10-Q, filed with the SEC on June 22, 2026;

•the information specifically incorporated by reference into our Annual Report on Form 10-K from our Definitive Proxy Statement on Schedule 14A, filed with the SEC on April 21, 2026;

•our Current Report on Form 8-K, filed with the SEC on June 3, 2026; and

All reports and other documents we subsequently file pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the termination of this offering, including all such documents we may file with the SEC after the date of the initial registration statement and prior to the effectiveness of the registration statement, but excluding any information furnished to, rather than filed with, the SEC, will also be incorporated by reference into this prospectus and deemed to be part of this prospectus from the date of the filing of such reports and documents.

You may request a free copy of any of the documents incorporated by reference in this prospectus by writing or telephoning us at the following address:

Crescent Biopharma, Inc.

Attention: Corporate Secretary

300 Fifth Avenue

Waltham, MA 02451

(617) 430-5595

Exhibits to the filings will not be sent, however, unless those exhibits have specifically been incorporated by reference in this prospectus or any accompanying prospectus supplement.

THE COMPANY

Overview

Corporate Information

We were initially incorporated under the laws of the State of Delaware in 2003. Our company, formerly known as GlycoMimetics, Inc., is a biotechnology company that is the result of a reverse recapitalization transaction with a private company named Crescent Biopharma, Inc. ("Pre-Merger Crescent"). Prior to the reverse recapitalization transaction, Pre-Merger Crescent was established and incorporated under the laws of the State of Delaware on September 19, 2024. Pre-Merger Crescent was founded to research and develop cancer therapy candidates.

Our principal executive offices are located at 300 Fifth Avenue, Waltham, MA 02451, and our telephone number is (617) 430-5595.

RISK FACTORS

Investment in any securities offered pursuant to this prospectus and the applicable prospectus supplement involves risks. You should carefully consider the risk factors incorporated by reference herein from our most recent Annual Report on Form 10-K and any subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K, including those we file after the date of this prospectus, and all other information contained in or incorporated by reference into this prospectus, as updated by our subsequent filings under the Exchange Act, and the risk factors and other information contained in the applicable prospectus supplement and any applicable free writing prospectus before acquiring any of such securities. The occurrence of any of these risks might cause you to lose all or part of your investment in the offered securities. There may be other unknown or unpredictable economic, business, competitive, regulatory or other factors that could have material adverse effects on our future results. Past financial performance may not be a reliable indicator of future performance, and historical trends should not be used to anticipate results or trends in future periods. If any of these risks actually occurs, our business, financial condition, results of operations or cash flow could be seriously harmed. This could cause the trading price of our securities to decline, resulting in a loss of all or part of your investment.

For more information, please see "Where You Can Find More Information; Incorporation by Reference."

USE OF PROCEEDS

We will retain broad discretion over the use of the net proceeds from the sale of the securities offered by this prospectus. We intend to use the net proceeds from the sale of the securities as set forth in the applicable prospectus supplement.

DIVIDEND POLICY

We have never declared or paid any cash dividends on our ordinary shares. We currently intend to retain all available funds and any future earnings to support our operations and finance the growth and development of our business. We do not intend to pay cash dividends on our ordinary shares for the foreseeable future.

DESCRIPTION OF SHARE CAPITAL

The following is a description of certain terms and provisions of our ordinary shares. The following summary does not purport to be complete, and is subject to, and qualified in its entirety by, the Company's memorandum and articles of association (the "Articles of Association"), the Company's Certificate of Designation of Preferences, Rights and Limitations of Series A Non-Voting Convertible Preferred Shares (the "Series A Certificate of Designation"), and the Companies Act (as amended) of the Cayman Islands (the "Companies Act"). Copies of the Articles of Association and the Series A Certificate of Designation have been filed as exhibits to our most recent Annual Report on Form 10-K and are incorporated by reference herein.

General

The authorized share capital of the Company under the Articles of Association is US$180,000 divided into 175,000,000 "ordinary shares," having a par value of US$0.001 per share; and 5,000,000 "preferred shares," having a par value of US$0.001 per share. Subject to the rights and restrictions of holders of any series of Series A Preferred Shares (as defined below) specified by the Articles of Association or the Series A Certificate of Designation, the Company may increase its authorized share capital through an ordinary resolution (the affirmative vote of a simple majority of the votes cast at a general meeting). See "Preferred Shares" below for further information.

As of June 30, 2026, there were approximately 53 holders of record of our ordinary shares. The actual number of holders of our ordinary shares is greater than this number of record holders and includes shareholders who are beneficial owners, but whose shares are held in "street name" by brokers or held by other "nominees." The number of holders of record also does not include shareholders whose shares may be held in trust by other entities.

Ordinary Shares

Voting Rights

Each holder of ordinary shares carries the right to receive notice of, to attend and to vote one vote per ordinary share at any Company general meeting.

Structure of Board of Directors

The board of directors of the Company (the "Board") is divided into three classes: Class I, Class II and Class III. The Board is authorized to assign members of the directors already in office to such classes in accordance with a resolution or resolutions adopted by the Board. At each annual general meeting of shareholders, directors shall be elected for a full term of three years to succeed the directors of the particular class whose terms expire at such annual general meeting. Notwithstanding the foregoing provisions of this section, each director shall serve until his or her successor is duly elected and qualified or until his or her earlier death, resignation or removal. The Class I directors' terms expire at the 2028 annual meeting of shareholders, Class II directors' terms expire at the 2029 annual meeting of shareholders and Class III directors' terms expire at the 2027 annual meeting of shareholders.

Thereafter, at each succeeding annual general meeting of shareholders, directors will be elected for a full three-year term to succeed the directors of the class whose terms expire at such meeting. Any decrease in the number of directors constituting the Board will not shorten the term of any incumbent director.

At all times when at least 30% of the originally issued Series A Preferred Shares (as defined below) remains issued and outstanding: (i) the holders of record of the Series A Preferred Shares, exclusively and voting together as a separate class on an as-converted to ordinary shares basis, shall be entitled to elect two directors ("Preferred Directors"); and (ii) the holders of the ordinary shares and of any other class or series of voting shares (including the Series A Preferred Shares), exclusively and voting together as a single class on an as-converted to ordinary shares basis, shall be entitled to elect the balance of the total number of directors of the Company. Each Preferred Director shall be entitled to three votes on each matter presented to the Board.

Preemptive Rights

Company shareholders do not have preemptive rights. Thus, if additional ordinary shares are issued, the current holders of ordinary shares own a proportionately smaller interest in a larger number of outstanding ordinary shares to the extent that they do not participate in the additional issuance.

Distributions to Shareholders

Subject to the Companies Act, the Articles of Association and any certificate of designation, and except as otherwise provided by the rights attached to any shares, the directors may resolve to declare dividends (including interim dividends) and other distributions on shares in issue and authorize payment of the dividends or other distributions out of the funds of the Company lawfully available therefor. All dividends shall be declared and paid according to the amounts paid up on the ordinary shares, but if and for so long as nothing is paid up on any of the ordinary shares, dividends may be declared and paid according to the par value of the ordinary shares. Dividends may be paid in cash, in property, or in shares.

Other Matters

All outstanding ordinary shares are fully paid and nonassessable. The ordinary shares are not subject to redemption or sinking fund provisions.

Preferred Shares

The Articles of Association provide that, whenever the capital of the Company is divided into different classes (and as otherwise determined by the Board) the rights attached to any such class may, subject to any rights or restrictions for the time being attached to any class, only be materially adversely varied or abrogated with the consent required under the terms of any certificate of designation (if applicable) or, where there is no certificate of designation or the certificate of designation does not provide for a consent threshold, the consent in writing of the holders of simple majority of the issued ordinary or preferred shares of the relevant class, or with the sanction of a resolution passed at a separate meeting of the holders of the ordinary or preferred shares of such class by a simple majority of the votes cast at such a meeting. The Board may vary the rights attaching to any class without the consent or approval of shareholders; provided that the rights may not, in the determination of the directors, be materially adversely varied or abrogated by such action.

The Articles of Association also provide that the rights conferred upon the holders of the ordinary or preferred shares of any class shall not, unless otherwise expressly provided by the terms of issue of the relevant class, be deemed to be materially adversely varied or abrogated by the creation, allotment or issue of ordinary or preferred shares ranking pari passu with them, subsequent to them, with preferred rights (including enhanced voting rights) or the redemption or purchase of any of the relevant class by the Company.

The Board has designated a series of preferred shares through the Series A Certificate of Designation: Series A Non-Voting Convertible Preferred Shares (the "Series A Preferred Shares"). Except as otherwise provided for in the Articles of Association, the Series A Certificate of Designation or at law, a holder of Series A Preferred Shares does not have voting rights. The Series A Certificate of Designation provides for certain voting rights in relation to the election of directors as discussed under "Ordinary Shares- Structure of Board of Directors". In addition, as long as any Series A Preferred Shares are issued and outstanding, the Company does not, without the affirmative vote of the Preferred Directors, acting together, or the holders of a simple majority of the then issued and outstanding Series A Preferred Shares: (i) alter or change adversely the powers, preferences or rights given to the Series A Preferred Shares or alter or amend the Series A Certificate of Designation, amend the Articles of Association, or file any articles of amendment, certificate of designations, preferences, limitations and relative rights of any series of Company preferred shares, in each case if such action would adversely alter or change the preferences, rights, privileges or powers of, or restrictions provided for the benefit of the Series A Preferred Shares, regardless of whether any of the foregoing actions are by means of amendment to the Articles of Association or by merger, consolidation, recapitalization, reclassification, conversion or otherwise, (ii) issue further Series A Preferred Shares or increase or decrease (other than

by conversion) the number of authorized Series A Preferred Shares, (iii) at any time while at least 30% of the originally issued Series A Preferred Shares remains issued and outstanding, consummate either: (A) any Fundamental Transaction (as defined in the Series A Certificate of Designation) or (B) any merger or consolidation of the Company or other business combination in which the shareholders of the Company immediately before such transaction do not hold at least a simple majority on an as-converted-to-ordinary shares basis of the share capital of the Company immediately after such transaction, (iv) increase the authorized number of directors constituting the Board or change the number of votes entitled to be cast by any director or directors on any matter or (v) enter into any agreement with respect to any of the foregoing that does not explicitly require the approval contemplated to consummate such transaction.

Anti-Takeover Provisions

Certain provisions of Cayman Islands law and the Articles of Association, which are summarized below, may have the effect of delaying, deferring, or discouraging another person from acquiring control of the Company. They are also designed, in part, to encourage persons seeking to acquire control of the Company to negotiate first with the Board.

Removal of Directors

Subject to the rights and restrictions of holders of any series of preferred shares to remove directors specified by the Articles of Association or any certificate of designation, any individual director or the Board may only be removed with cause by a special resolution passed by the affirmative vote of not less than two-thirds of the votes cast at a general meeting.

At all times when at least 30% of the originally issued Series A Preferred Shares remains issued and outstanding, any Preferred Director may be removed without cause only by the affirmative vote of the holders of a simple majority of the Series A Preferred Shares.

Vacancies on the Board of Directors

Subject to the rights of the holders of any series of preferred shares, including pursuant to any certificate of designation, any vacancies on the Board resulting from death, resignation, disqualification, removal or other causes, and any newly created directorships resulting from any increase in the number of directors, shall, unless the Board determines by resolution that any such vacancies or newly created directorships shall be filled by the shareholders as permitted in accordance with the Articles of Association and any certificate of designation, be filled only by the affirmative vote of a simple majority of the voting power of the directors then in office, or by unanimous written consent of all directors, or by a sole remaining director and not by the shareholders. Any director elected in accordance with the preceding sentence shall hold office for the remainder of the full term of the director for which the vacancy was created or occurred and until such director's successor shall have been elected and qualified.

At all times when at least 30% of the originally issued Series A Preferred Shares remains issued and outstanding, any vacancies of a Preferred Director directorship resulting from death, resignation, disqualification, removal or other causes shall be filled by the affirmative vote of the holders of a simple majority of the Series A Preferred Shares.

Shareholder Action by Written Consent

A resolution in writing signed by all the shareholders entitled to receive notice of and to attend and vote at general meetings of the Company (or being corporations by their duly authorized representatives) shall be as valid and effective as if the same had been passed at a general meeting of the Company duly convened and held.

Special Meetings of Shareholders

Under Cayman Islands law, there is no statutory right for shareholders to call a general meeting where the articles of association provide for the calling of meetings. Where the articles of association provide for calling of meetings, the ability to convene such a meeting is governed by the company's articles of association.

General meetings of the Company shareholders may be called, for any purpose as is a proper matter for shareholder action under Cayman Islands law, by (i) the chairman of the Board, (ii) the chief executive officer, or (iii) the Board pursuant to a resolution adopted by a simple majority of the voting power of the directors present at a meeting of directors or by unanimous written consent of all directors.

The Board shall determine the date, time and place (including any electronic facility), if any, of such general meeting. Upon determination of the date, time and place (including any electronic facility), if any, of the meeting, the Board or secretary shall cause a notice of general meeting to be given to the Company shareholders entitled to vote, in accordance with the Articles of Association. No business may be transacted at such special meeting otherwise than specified in the notice of general meeting.

Shareholder Vote for Mergers and Other Corporate Reorganizations

Under Cayman Islands law, a company may merge with another company (wherever incorporated, provided that such merger is not prohibited by the laws of the jurisdiction of incorporation of that company) pursuant to the Companies Act. A merger under Cayman Islands law requires the approval by a special resolution, which in the context of a general meeting of the Company requires (i) not less than a two-thirds majority of the votes cast by such shareholders attending and voting in person or, where proxies are allowed, by proxy at a quorate general meeting of the Company or (ii) the written resolution of all shareholders entitled to vote at such general meeting.

No shareholder resolution is required for a merger between a parent company (i.e., a company that holds issued shares that together represent 90% of the votes at a general meeting of the subsidiary company) and its subsidiary company, provided the parent company is the surviving entity and a copy of the plan of merger (including the memorandum and articles of association of the company) is given to every member of each subsidiary company to be merged unless that member agrees otherwise.

Under Cayman Islands law, a Cayman Islands exempted company may be acquired through a tender offer by a third party. Where the holders of 90% or more in value of a class of the Company's shares (excluding any shares already beneficially owned by the offeror) have within four months of the making of an offer accepted an offer for their shares in the Company, the remaining shareholders in that class may be statutorily required to also transfer their shares by notice given at any time within two months of the expiry of the four month period, unless, within one month, the non-tendering shareholders can obtain a Cayman court order otherwise providing. If the offeror has acquired acceptances of 90% of all the Company's shares but does not exercise its "squeeze out" right, then the non-accepting shareholders have no statutory right to require the offeror to acquire their shares on the same terms as the original offer.

A Cayman Islands exempted company may also be acquired by way of a Cayman Islands court-approved scheme of arrangement under the Companies Act. A scheme of arrangement is a compromise or arrangement which may be entered into between a company and one or more classes of shareholders. In order to become binding and effective in accordance with its terms, the scheme of arrangement requires the approval of shareholders representing 75% or more by value of the shares of each class comprised in the scheme, in each case at the relevant meeting or meetings, and an order of the Grand Court of the Cayman Islands sanctioning the scheme of arrangement. A scheme of arrangement, if approved by the requisite statutory majorities and sanctioned by the Grand Court of the Cayman Islands, is binding on all of the shareholders of each class, including any dissenting shareholders. There is currently no cross class cramdown available under Cayman Islands law. Shares held by the acquiring party are likely to be considered to belong to a separate class for the purposes of approving the scheme.

Advance Notice Requirements for Shareholder Proposals and Director Nominations

Nominations of persons for election to the Board and the proposal of business to be considered by the shareholders may be made at an annual general meeting of shareholders: (i) pursuant to the Company's notice of meeting of shareholders (with respect to business other than nominations); (ii) brought specifically by or at the direction of the Board; or (iii) by any shareholder of the Company who was a shareholder of record at the time of giving the shareholders' notice provided for in the Articles of Association below, who is entitled to vote at the meeting and who complied with the notice procedures set forth in Articles of Association. Such notice must be received by the Company not later than the close of business on the ninetieth day and no earlier than the close of business on the one hundred twentieth day prior to the first anniversary of the preceding year's annual meeting, in the case of an annual meeting nomination, and not later than the close of business on the later of the ninetieth day prior to such meeting or the tenth day following the day on which public announcement is first made of the date of the general meeting and of the nominees proposed by the Board to be elected at such meeting, in the case of a general meeting nomination.

No Cumulative Voting

The Companies Act does not provide for cumulative voting as a mechanism for electing directors and if a Cayman Islands exempted company wants to allow cumulative voting, it must explicitly set out in its articles of association. The Articles of Association do not provide for cumulative voting.

Amendment of Articles of Association

Subject to the Companies Act and the rights attaching to the various classes, including pursuant to any certificate of designation, the Company may at any time and from time to time by special resolution passed by the affirmative vote of not less than two-thirds of the votes cast at a general meeting alter or amend the memorandum of association forming a part of the Articles of Association in whole or in part.

Other Shareholder Rights

Certain other provisions of Cayman Islands law and the Articles of Association summarized below also have important effects on the rights of shareholders of the Company.

Shareholder Inspection Rights

Under Cayman Islands law, shareholders generally do not have any rights to inspect or obtain copies of the register of shareholders or other corporate records of a company, though directors may from time to time determine whether and to what extent and at what times and places and under what conditions or regulations the accounts and books of a Cayman Islands exempted company or any of them may be open to the inspection of shareholders not being directors.

Appraisal or Dissenter's Rights

Generally, under Cayman Islands law, shareholders of a Cayman Islands exempted company do not have statutory appraisal rights; provided that in the event of a statutory merger under the Companies Act a shareholder shall be entitled to receive the fair value of their shares upon dissenting from such merger. Rights of a dissenting shareholder are not available in certain circumstances, for example, to dissenters holding shares of any class in respect of which an open market exists on a recognized stock exchange or recognized interdealer quotation system at the relevant date and where the consideration for such shares to be contributed are shares of any company listed on a national securities exchange or shares of the surviving or consolidated company.

Exclusive Forum

The Articles of Association provide that, unless the Company consents in writing to the selection of an alternative forum, the courts of the Cayman Islands shall have exclusive jurisdiction over any claim or dispute arising out of or in connection with the Articles of Association or otherwise related in any way to each member's shareholding in the Company, including but not limited to: (a) any derivative action or proceeding brought on behalf of the

Company; (b) any action asserting a claim of breach of any fiduciary or other duty owed by any current or former director, officer or other employee of the Company to the Company or the members; (c) any action asserting a claim arising pursuant to any provision of the Companies Act, the Articles of Association; or (d) any action asserting a claim against the Company concerning its internal affairs and that each shareholder irrevocably submits to the exclusive jurisdiction of the courts of the Cayman Islands over all such claims or disputes. This exclusive forum provision would not apply to suits brought to enforce any liability or duty created by the Securities Act or the Exchange Act or any other claim for which the federal courts have exclusive jurisdiction. To the extent that any such claims may be based upon federal law claims, Section 27 of the Exchange Act creates exclusive federal jurisdiction over all suits brought to enforce any duty or liability created by the Exchange Act or the rules and regulations thereunder. Furthermore, Section 22 of the Securities Act creates concurrent jurisdiction for federal and state courts over all suits brought to enforce any duty or liability created by the Securities Act or the rules and regulations thereunder. Although our Articles of Association contains the choice of forum provision described above, it is possible that a court could rule that such a provision is inapplicable for a particular claim or action or that such provision is unenforceable.

Business Opportunities

Cayman Islands law does not have a codified corporate opportunity doctrine and a director's obligations in relation to business opportunities are governed by general fiduciary duties which include the duty to act in good faith and in the best interests of the company, the duty to avoid conflicts of interests and a duty to exercise independent judgement and avoid self-dealing. A Cayman Islands director may engage in business activities outside a Cayman Islands exempted company, provided that they have disclosed any personal interest in the opportunity. If the director properly declares their interest at a board meeting, Cayman Islands law generally permits the company to approve the transaction. A director may also vote on resolutions related to such a contract provided the interest has been disclosed.

Shareholders' Derivative Actions

In most cases, under Cayman Islands law, the Company is the proper plaintiff in any claim based on a breach of duty owed to it, and a claim against (for example) the Company's directors or officers usually may not be brought by a shareholder: in principle, a shareholder does not have a direct right of action against directors of the Company. However, based on Cayman Islands authorities and English authorities (which will be of persuasive authority in the Cayman Islands), there are exceptions to the foregoing principle such that a shareholder may be entitled to bring a derivative action on behalf of the Company, but only in limited circumstances, including but not limited to: the Company acts or proposes to act illegally or ultra vires; the act complained of (although not ultra vires) could be affected if duly authorized by a special resolution that has not been obtained; and those who control the Company are perpetuating a "fraud on the minority". A shareholder may have a direct right of action against the Company where the individual rights of that shareholder have been or will be infringed. Derivative actions have been brought in the Cayman Islands courts, and whilst the Cayman Islands courts have confirmed the availability for such actions, they are less common relative to similar claims brought in Delaware pursuant to the Delaware law. In addition, Cayman Islands law does not specifically restrict a Cayman Islands exempted company from exculpating its directors or officers from liability for negligence or a breach of duty, except to the extent any such provision may be held by the Cayman Islands courts to be contrary to public policy, such as to limit liability against willful default, willful neglect, actual fraud or the consequences of committing a crime.

Limitation on Director and Officer Liability

The Companies Act does not restrict the authority of a Cayman exempted company to indemnify its directors, officers, employees or agents.

The Articles of Association provide that no Indemnified Person (as defined below) shall be liable: (a) for the acts, receipts, neglects, defaults or omissions of any other director or officer or agent of the Company; or (b) for any loss on account of defect of title to any property of the Company; or (c) on account of the insufficiency of any security in or upon which any money of the Company shall be invested; or (d) for any loss incurred through any bank, broker or other similar person; or (e) for any loss occasioned by any negligence, default, breach of duty, breach of trust, error of judgement or oversight on such Indemnified Person's part; or (f) for any loss, damage or misfortune whatsoever

which may happen in or arise from the execution of discharge of the duties, powers, authorities, or discretions of such Indemnified Person's office or in relation thereto; unless the same shall happen through such Indemnified Person's own actual fraud, willful default or willful neglect as determined by a court of competent jurisdiction.

Indemnification

The Articles of Association provide that, to the fullest extent permitted by law, every director (including any alternate director appointed pursuant to the provisions of the Articles of Association), secretary, assistant secretary, or other officer (but not including the Company's auditors) and the personal representatives of the same (each an "Indemnified Person") shall be indemnified and secured harmless out of the assets and funds of the Company against all actions or proceedings whether threatened, pending or completed, costs, charges, expenses, losses, damages or liabilities incurred or sustained by such Indemnified Person, other than by reason of such Indemnified Person's own actual fraud, willful default or willful neglect as determined by a court of competent jurisdiction, (i) in or about the conduct of the Company's business or affairs (including as a result of any mistake of judgment), (ii) in the execution or discharge of his or her duties, powers, authorities or discretions, or (iii) in respect of any actions or activities undertaken by an Indemnified Person provided for and in accordance with the provisions set out above (inclusive) including without prejudice to the generality of the foregoing, any costs, expenses, losses or liabilities incurred by such Indemnified Person in defending or otherwise being involved in, (whether successfully or otherwise) any civil proceedings concerning the Company or its affairs in any court whether in the Cayman Islands or elsewhere.

Each shareholder waives any claim or right of action they might have, whether individually or by or in the right of the Company, against any director or officer on account of any action taken by such director or officer, or the failure of such director or officer to take any action in the performance of his or her duties with or for the Company; provided that such waiver shall not extend to any matter in respect of any actual fraud, willful default or willful neglect which may attach to such director or officer.

The Company will pay the expenses (including attorneys' fees) incurred by an Indemnified Person in defending any proceeding in advance of its final disposition; provided, however, that, to the extent required by applicable law, such payment of expenses in advance of the final disposition of the proceeding shall be made only upon receipt of an undertaking by the Indemnified Person to repay all amounts advanced if it should be ultimately determined that the Indemnified Person is not entitled to be indemnified under the Articles of Association or otherwise.

The rights to indemnification and advancement of expenses conferred on any Indemnified Person as set out above are not exclusive of any other rights that any Indemnified Person may have or hereafter acquire pursuant to an agreement with the Company or otherwise.

Enforcement of Civil Liabilities

The Cayman Islands has a different body of securities laws as compared to the United States and may provide less protection to investors. Additionally, Cayman Islands companies may not have standing to sue before the Federal courts of the United States.

There is uncertainty as to whether the courts of the Cayman Islands will recognize and enforce against us, our directors and/or executive officers in the United States judgments obtained in the United States courts predicated upon the civil liability provisions of the securities laws of the United States. The courts of the Cayman Islands may be unlikely (i) to recognize or enforce against us judgments of courts of the United States predicated upon the civil liability provisions of the federal securities laws of the United States or any state; and (ii) in original actions brought in the Cayman Islands, to impose liabilities against us predicated upon the civil liability provisions of the federal securities laws of the United States or any state, so far as the liabilities imposed by those provisions are penal in nature.

In those circumstances, although there is no statutory enforcement in the Cayman Islands of judgments obtained in the United States (and the Cayman Islands are not a party to any treaties for the reciprocal enforcement or recognition of such judgments with the United States), the courts of the Cayman Islands may, by an action commenced on the judgment obtained in the United States in the courts of the Cayman islands, recognize and enforce, without

retrial of the merits at common law, a foreign money judgment of a foreign court of competent jurisdiction provided certain conditions are met. For a foreign judgment to be enforced in the Cayman Islands, the court must have had proper jurisdiction over the parties subject to such judgment as a matter of Cayman Islands conflict of law rules, and such judgment must be: final and conclusive and for a liquidated sum, and must not be in respect of multiple damages, taxes or a fine or penalty, or other charges of a like natures, inconsistent with a Cayman Islands judgment in respect of the same matter, impeachable on the grounds of fraud or obtained in a manner, and or be of a kind the enforcement of which is, contrary to natural justice or the public policy of the Cayman Islands (awards of punitive or multiple damages may well be held to be contrary to public policy), no new admissible evidence relevant to the action is submitted prior to the rendering of the judgment by the courts of the Cayman Islands; and there is due compliance with the correct procedures under the laws of the Cayman Islands. A Cayman Islands Court may stay enforcement proceedings if concurrent proceedings are being brought elsewhere.

Transfer Agent and Registrar

Computershare Trust Company N.A. serves as the transfer agent and registrar for the Company's ordinary shares.

Listing

The Company's ordinary shares are listed on The Nasdaq Capital Market under the symbol "CBIO." The CUSIP assigned to the Company's ordinary shares is G2545C104.

DESCRIPTION OF DEBT SECURITIES

The following description, together with the additional information we include in any applicable prospectus supplement or free writing prospectus, summarizes certain general terms and provisions of the debt securities that we may offer under this prospectus. When we offer to sell a particular series of debt securities, we will describe the specific terms of the series in a supplement to this prospectus. We will also indicate in the supplement to what extent the general terms and provisions described in this prospectus apply to a particular series of debt securities.

We may issue debt securities either separately, or together with, or upon the conversion or exercise of or in exchange for, other securities described in this prospectus. Debt securities may be our senior, senior subordinated or subordinated obligations and, unless otherwise specified in a supplement to this prospectus, the debt securities will be our direct, unsecured obligations and may be issued in one or more series.

The debt securities will be issued under an indenture between us and a trustee named in the prospectus supplement. We have summarized select portions of the indenture below. The summary is not complete. The form of the indenture has been filed as an exhibit to the registration statement and you should read the indenture for provisions that may be important to you. Capitalized terms used in the summary and not defined herein have the meanings specified in the indenture.

As used in this section only, "Crescent," "we," "our" or "us" refer to Crescent Biopharma, Inc., excluding our subsidiaries, unless expressly stated or the context otherwise requires.

General

The terms of each series of debt securities will be established by or pursuant to a resolution of our board of directors and set forth or determined in the manner provided in a resolution of our board of directors, in an officer's certificate or by a supplemental indenture (as applicable). The particular terms of each series of debt securities will be described in a prospectus supplement relating to such series (including any pricing supplement or term sheet).

We can issue an unlimited amount of debt securities under the indenture that may be in one or more series with the same or various maturities, at par, at a premium, or at a discount. We will set forth in a prospectus supplement (including any pricing supplement or term sheet) relating to any series of debt securities being offered, the aggregate principal amount and the following terms of the debt securities, if applicable:

•the title and ranking of the debt securities (including the terms of any subordination provisions);

•the price or prices (expressed as a percentage of the principal amount) at which we will sell the debt securities;

•any limit on the aggregate principal amount of the debt securities;

•the date or dates on which the principal of the securities of the series is payable;

•the rate or rates (which may be fixed or variable) per annum or the method used to determine the rate or rates (including any commodity, commodity index, stock exchange index or financial index) at which the debt securities will bear interest, the date or dates from which interest will accrue, the date or dates on which interest will commence and be payable and any regular record date for the interest payable on any interest payment date;

•the place or places where principal of, and interest, if any, on the debt securities will be payable (and the method of such payment), where the debt securities of such series may be surrendered for registration of transfer or exchange, and where notices and demands to us in respect of the debt securities may be delivered;

•the period or periods within which, the price or prices at which and the terms and conditions upon which we may redeem the debt securities;

•any obligation we have to redeem or purchase the debt securities pursuant to any sinking fund or analogous provisions or at the option of a holder of debt securities and the period or periods within which, the price or prices at which and the terms and conditions upon which the debt securities of a particular series shall be redeemed or purchased, in whole or in part, pursuant to such obligation;

•the dates on which and the price or prices at which we will repurchase debt securities at the option of the holders of debt securities and other detailed terms and provisions of these repurchase obligations;

•the denominations in which the debt securities will be issued, if other than denominations of $1,000 and any integral multiple thereof;

•whether the debt securities will be issued in the form of certificated debt securities or global debt securities;

•the portion of principal amount of the debt securities payable upon declaration of acceleration of the maturity date, if other than the principal amount;

•the currency of denomination of the debt securities, which may be U.S. dollars or any foreign currency, and if such currency of denomination is a composite currency, the agency or organization, if any, responsible for overseeing such composite currency;

•the designation of the currency, currencies or currency units in which payment of principal of, and premium and interest on, the debt securities will be made;

•if payments of principal of, or premium or interest on, the debt securities will be made in one or more currencies or currency units other than that or those in which the debt securities are denominated, the manner in which the exchange rate with respect to these payments will be determined;

•the manner in which the amounts of payment of principal of, and premium, if any, and interest on, the debt securities will be determined, if these amounts may be determined by reference to an index based on a currency or currencies or by reference to a commodity, commodity index, stock exchange index or financial index;

•any provisions relating to any security provided for the debt securities;

•any addition to, deletion of or change in the Events of Default described in this prospectus or in the indenture with respect to the debt securities and any change in the acceleration provisions described in this prospectus or in the indenture with respect to the debt securities;

•any addition to, deletion of or change in the covenants described in this prospectus or in the indenture with respect to the debt securities;

•any depositaries, interest rate calculation agents, exchange rate calculation agents or other agents with respect to the debt securities;

•the provisions, if any, relating to conversion or exchange of any debt securities of such series, including if applicable, the conversion or exchange price and period, provisions as to whether conversion or exchange will be mandatory, the events requiring an adjustment of the conversion or exchange price and provisions affecting conversion or exchange;

•any other terms of the debt securities, which may supplement, modify or delete any provision of the indenture as it applies to that series, including any terms that may be required under applicable law or regulations or advisable in connection with the marketing of the securities; and

•whether any of our direct or indirect subsidiaries will guarantee the debt securities of that series, including the terms of subordination, if any, of such guarantees.

We may issue debt securities that provide for an amount less than their stated principal amount to be due and payable upon declaration of acceleration of their maturity pursuant to the terms of the indenture. We will provide you with information on the federal income tax considerations and other special considerations applicable to any of these debt securities in the applicable prospectus supplement.

If we denominate the purchase price of any of the debt securities in a foreign currency or currencies or a foreign currency unit or units, or if the principal of, and premium, if any, and interest on, any series of debt securities is payable in a foreign currency or currencies or a foreign currency unit or units, we will provide you with information on the restrictions, elections, general tax considerations, specific terms and other information with respect to that issue of debt securities and such foreign currency or currencies or foreign currency unit or units in the applicable prospectus supplement.

Transfer and Exchange

Each debt security will be represented by either one or more global securities registered in the name of The Depository Trust Company ("DTC" or the "Depositary") or a nominee of the Depositary (we will refer to any debt

security represented by a global debt security as a "book-entry debt security"), or a certificate issued in definitive registered form (we will refer to any debt security represented by a certificated security as a "certificated debt security") as set forth in the applicable prospectus supplement. Except as set forth under the heading "Global Debt Securities and Book-Entry System" below, book-entry debt securities will not be issuable in certificated form.

Certificated Debt Securities. You may transfer or exchange certificated debt securities at any office we maintain for this purpose in accordance with the terms of the indenture. No service charge will be made for any transfer or exchange of certificated debt securities, but we may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection with a transfer or exchange.

You may effect the transfer of certificated debt securities and the right to receive the principal of, premium and interest on certificated debt securities only by surrendering the certificate representing those certificated debt securities and either reissuance by us or the trustee of the certificate to the new holder or the issuance by us or the trustee of a new certificate to the new holder.

Global Debt Securities and Book-Entry System. Each global debt security representing book-entry debt securities will be deposited with, or on behalf of, the Depositary, and registered in the name of the Depositary or a nominee of the Depositary.

Covenants

We will set forth in the applicable prospectus supplement any restrictive covenants applicable to any issue of debt securities.

No Protection in the Event of a Change of Control

Unless we state otherwise in the applicable prospectus supplement, the debt securities will not contain any provisions which may afford holders of the debt securities protection in the event we have a change in control or in the event of a highly leveraged transaction (whether or not such transaction results in a change in control) which could adversely affect holders of debt securities.

Consolidation, Merger and Sale of Assets

We may not consolidate with or merge with or into, or convey, transfer or lease all or substantially all of our properties and assets to, any person (a "successor person") unless:

•we are the surviving entity or the successor person (if other than Crescent) is a corporation, partnership, trust or other entity organized and validly existing under the laws of any U.S. domestic jurisdiction and expressly assumes our obligations on the debt securities and under the indenture; and

•immediately after giving effect to the transaction, no Default or Event of Default, shall have occurred and be continuing.

Notwithstanding the above, any of our subsidiaries may consolidate with, merge into or transfer all or part of its properties to us.

Events of Default

"Event of Default" means with respect to any series of debt securities, any of the following:

•default in the payment of any interest upon any debt security of that series when it becomes due and payable, and continuance of such default for a period of 30 days (unless the entire amount of the payment is deposited by us with the trustee or with a paying agent prior to the expiration of the 30-day period);

•default in the payment of principal of any debt security of that series at its maturity;

•default in the performance or breach of any other covenant or warranty by us in the indenture or any debt security (other than a covenant or warranty that has been included in the indenture solely for the benefit

of a series of debt securities other than that series), which default continues uncured for a period of 60 days after we receive written notice from the trustee or Crescent and the trustee receive written notice from the holders of not less than 25% in principal amount of the outstanding debt securities of that series as provided in the indenture;

•certain voluntary or involuntary events of bankruptcy, insolvency or reorganization of Crescent; or

•any other Event of Default provided with respect to debt securities of that series that is described in the applicable prospectus supplement.

No Event of Default with respect to a particular series of debt securities (except as to certain events of bankruptcy, insolvency or reorganization) necessarily constitutes an Event of Default with respect to any other series of debt securities. The occurrence of certain Events of Default or an acceleration under the indenture may constitute an event of default under certain indebtedness of ours or our subsidiaries outstanding from time to time.

We will provide the trustee written notice of any Default or Event of Default within 30 days of becoming aware of the occurrence of such Default or Event of Default, which notice will describe in reasonable detail the status of such Default or Event of Default and what action we are taking or propose to take in respect thereof.

If an Event of Default with respect to debt securities of any series at the time outstanding occurs and is continuing, then the trustee or the holders of not less than 25% in principal amount of the outstanding debt securities of that series may, by a notice in writing to us (and to the trustee if given by the holders), declare to be due and payable immediately the principal of (or, if the debt securities of that series are discount securities, that portion of the principal amount as may be specified in the terms of that series) and accrued and unpaid interest, if any, on all debt securities of that series. In the case of an Event of Default resulting from certain events of bankruptcy, insolvency or reorganization, the principal (or such specified amount) of and accrued and unpaid interest, if any, on all outstanding debt securities will become and be immediately due and payable without any declaration or other act on the part of the trustee or any holder of outstanding debt securities. At any time after a declaration of acceleration with respect to debt securities of any series has been made, but before a judgment or decree for payment of the money due has been obtained by the trustee, the holders of a majority in principal amount of the outstanding debt securities of that series may rescind and annul the acceleration if all Events of Default, other than the non-payment of accelerated principal and interest, if any, with respect to debt securities of that series, have been cured or waived as provided in the indenture. We refer you to the prospectus supplement relating to any series of debt securities that are discount securities for the particular provisions relating to acceleration of a portion of the principal amount of such discount securities upon the occurrence of an Event of Default.

The indenture provides that the trustee may refuse to perform any duty or exercise any of its rights or powers under the indenture, unless the trustee receives indemnity satisfactory to it against any cost, liability or expense which might be incurred by it in performing such duty or exercising such right or power. Subject to certain rights of the trustee, the holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee or exercising any trust or power conferred on the trustee with respect to the debt securities of that series.

No holder of any debt security of any series will have any right to institute any proceeding, judicial or otherwise, with respect to the indenture or for the appointment of a receiver or trustee, or for any remedy under the indenture, unless:

•that holder has previously given to the trustee written notice of a continuing Event of Default with respect to debt securities of that series; and

•the holders of not less than 25% in principal amount of the outstanding debt securities of that series have made written request, and offered indemnity or security satisfactory to the trustee, to the trustee to institute the proceeding as trustee, and the trustee has not received from the holders of not less than a majority in principal amount of the outstanding debt securities of that series a direction inconsistent with that request and has failed to institute the proceeding within 60 days.

Notwithstanding any other provision in the indenture, the holder of any debt security will have an absolute and unconditional right to receive payment of the principal of, and premium and any interest on, that debt security on or after the due dates expressed in that debt security and to institute suit for the enforcement of payment.

The indenture requires us, within 120 days after the end of our fiscal year, to furnish to the trustee a statement as to compliance with the indenture. If a Default or Event of Default occurs and is continuing with respect to the securities of any series and if it is known to a responsible officer of the trustee, the trustee shall mail to each holder of the securities of that series notice of a Default or Event of Default within 90 days after it occurs or, if later, after a responsible officer of the trustee has knowledge of such Default or Event of Default. The indenture provides that the trustee may withhold notice to the holders of debt securities of any series of any Default or Event of Default (except in payment on any debt securities of that series) with respect to debt securities of that series if the trustee determines in good faith that withholding notice is in the interest of the holders of those debt securities.

Modification and Waiver

We and the trustee may modify, amend or supplement the indenture or the debt securities of any series without the consent of any holder of any debt security:

•to cure any ambiguity, defect or inconsistency;

•to comply with covenants in the indenture described above under the heading "Consolidation, Merger and Sale of Assets;"

•to provide for uncertificated securities in addition to or in place of certificated securities;

•to add guarantees with respect to debt securities of any series or secure debt securities of any series;

•to surrender any of our rights or powers under the indenture;

•to add covenants or Events of Default for the benefit of the holders of debt securities of any series;

•to comply with the applicable procedures of the applicable depositary;

•to make any change that does not adversely affect the rights of any holder of debt securities;

•to provide for the issuance of and establish the form and terms and conditions of debt securities of any series as permitted by the indenture;

•to effect the appointment of a successor trustee with respect to the debt securities of any series and to add to or change any of the provisions of the indenture to provide for or facilitate administration by more than one trustee; or

•to comply with requirements of the SEC in order to effect or maintain the qualification of the indenture under the Trust Indenture Act.

We may also modify and amend the indenture with the consent of the holders of at least a majority in principal amount of the outstanding debt securities of each series affected by the modifications or amendments. We may not make any modification or amendment without the consent of the holders of each affected debt security then outstanding if that amendment will:

•reduce the amount of debt securities whose holders must consent to an amendment, supplement or waiver;

•reduce the rate of or extend the time for payment of interest (including default interest) on any debt security;

•reduce the principal of or premium on or change the fixed maturity of any debt security or reduce the amount of, or postpone the date fixed for, the payment of any sinking fund or analogous obligation with respect to any series of debt securities;

•reduce the principal amount of discount securities payable upon acceleration of maturity;

•waive a Default or Event of Default in the payment of the principal of, or premium or interest on, any debt security (except a rescission of acceleration of the debt securities of any series by the holders of at least a majority in aggregate principal amount of the then outstanding debt securities of that series and a waiver of the payment default that resulted from such acceleration);

•make the principal of, or premium or interest on, any debt security payable in currency other than that stated in the debt security;

•make any change to certain provisions of the indenture relating to, among other things, the right of holders of debt securities to receive payment of the principal of, and premium and interest on, those debt securities and to institute suit for the enforcement of any such payment and to waivers or amendments; or

•waive a redemption payment with respect to any debt security.

Except for certain specified provisions, the holders of at least a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all debt securities of that series waive our compliance with provisions of the indenture. The holders of a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all the debt securities of such series waive any past default under the indenture with respect to that series and its consequences, except a default in the payment of the principal of, premium or any interest on, any debt security of that series; provided, however, that the holders of a majority in principal amount of the outstanding debt securities of any series may rescind an acceleration and its consequences, including any related payment default that resulted from the acceleration.

Defeasance of Debt Securities and Certain Covenants in Certain Circumstances

Legal Defeasance. The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, we may be discharged from any and all obligations in respect of the debt securities of any series (subject to certain exceptions). We will be so discharged upon the irrevocable deposit with the trustee, in trust, of money and/or U.S. government obligations or, in the case of debt securities denominated in a single currency other than U.S. Dollars, government obligations of the government that issued or caused to be issued such currency, that, through the payment of interest and principal in accordance with their terms, will provide money or U.S. government obligations in an amount sufficient in the opinion of a nationally recognized firm of independent public accountants or investment bank to pay and discharge each installment of principal of, premium and interest on, and any mandatory sinking fund payments in respect of, the debt securities of that series on the stated maturity of those payments in accordance with the terms of the indenture and those debt securities.

This discharge may occur only if, among other things, we have delivered to the trustee an opinion of counsel stating that we have received from, or there has been published by, the U.S. Internal Revenue Service a ruling or, since the date of execution of the indenture, there has been a change in the applicable U.S. federal income tax law, in either case to the effect that, and based thereon such opinion shall confirm that, the holders of the debt securities of that series will not recognize income, gain or loss for U.S. federal income tax purposes as a result of the deposit, defeasance and discharge and will be subject to U.S. federal income tax on the same amounts and in the same manner and at the same times as would have been the case if the deposit, defeasance and discharge had not occurred.

Defeasance of Certain Covenants. The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, upon compliance with certain conditions:

•we may omit to comply with the covenant described under the heading "Consolidation, Merger and Sale of Assets" and certain other covenants set forth in the indenture, as well as any additional covenants which may be set forth in the applicable prospectus supplement; and

•any omission to comply with those covenants will not constitute a Default or an Event of Default with respect to the debt securities of that series ("covenant defeasance").

The conditions include:

•depositing with the trustee money and/or U.S. government obligations or, in the case of debt securities denominated in a single currency other than U.S. dollars, government obligations of the government that issued or caused to be issued such currency, that, through the payment of interest and principal in accordance with their terms, will provide money in an amount sufficient in the opinion of a nationally recognized firm of independent public accountants or investment bank to pay and discharge each installment of principal of, premium and interest on, and any mandatory sinking fund payments in respect of, the debt securities of that series on the stated maturity of those payments in accordance with the terms of the indenture and those debt securities; and

•delivering to the trustee an opinion of counsel to the effect that the holders of the debt securities of that series will not recognize income, gain or loss for U.S. federal income tax purposes as a result of the deposit and related covenant defeasance and will be subject to U.S. federal income tax on the same amounts and in the same manner and at the same times as would have been the case if the deposit and related covenant defeasance had not occurred.

No Personal Liability of Directors, Officers, Employees or Securityholders

None of our past, present or future directors, officers, employees or securityholders, as such, will have any liability for any of our obligations under the debt securities or the indenture or for any claim based on, or in respect or by reason of, such obligations or their creation. By accepting a debt security, each holder waives and releases all such liability. This waiver and release is part of the consideration for the issue of the debt securities. However, this waiver and release may not be effective to waive liabilities under U.S. federal securities laws, and it is the view of the SEC that such a waiver is against public policy.

Governing Law

The indenture and the debt securities, including any claim or controversy arising out of or relating to the indenture or the debt securities, will be governed by the laws of the State of New York.

The indenture will provide that we, the trustee and the holders of the debt securities (by their acceptance of the debt securities) irrevocably waive, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to the indenture, the debt securities or the transactions contemplated thereby.

The indenture will provide that any legal suit, action or proceeding arising out of or based upon the indenture or the transactions contemplated thereby may be instituted in the federal courts of the United States of America located in the City of New York or the courts of the State of New York in each case located in the City of New York, and we, the trustee and the holder of the debt securities (by their acceptance of the debt securities) irrevocably submit to the non-exclusive jurisdiction of such courts in any such suit, action or proceeding. The indenture will further provide that service of any process, summons, notice or document by mail (to the extent allowed under any applicable statute or rule of court) to such party's address set forth in the indenture will be effective service of process for any suit, action or other proceeding brought in any such court. The indenture will further provide that we, the trustee and the holders of the debt securities (by their acceptance of the debt securities) irrevocably and unconditionally waive any objection to the laying of venue of any suit, action or other proceeding in the courts specified above and irrevocably and unconditionally waive and agree not to plead or claim any such suit, action or other proceeding has been brought in an inconvenient forum.

DESCRIPTION OF WARRANTS

We may issue warrants for the purchase of our ordinary shares or preferred shares or of debt securities. We may issue warrants independently or together with other securities, and the warrants may be attached to or separate from any offered securities. Each series of warrants will be issued under a separate warrant agreement to be entered into between us and the investors or a warrant agent. The following summary of material provisions of the warrants and warrant agreements is subject to, and qualified in its entirety by reference to, all the provisions of the warrant agreement and warrant certificate applicable to a particular series of warrants. The terms of any warrants offered under a prospectus supplement may differ from the terms described below. We urge you to read the applicable prospectus supplement and any related free writing prospectus, as well as the complete warrant agreements and warrant certificates that contain the terms of the warrants.

The particular terms of any issue of warrants will be described in the prospectus supplement relating to the issue. Those terms may include:

•the number of ordinary shares or preferred shares purchasable upon the exercise of warrants to purchase such shares and the price at which such number of shares may be purchased upon such exercise;

•the designation, stated value and terms (including, without limitation, liquidation, dividend, conversion and voting rights) of the series of preferred shares purchasable upon exercise of warrants to purchase preferred shares;

•the principal amount of debt securities that may be purchased upon exercise of a debt warrant and the exercise price for the warrants, which may be payable in cash, securities or other property;

•the date, if any, on and after which the warrants and the related debt securities, preferred shares or ordinary shares will be separately transferable;

•the terms of any rights to redeem or call the warrants;

•the date on which the right to exercise the warrants will commence and the date on which the right will expire;

•U.S. federal income tax consequences applicable to the warrants; and

•any additional terms of the warrants, including terms, procedures, and limitations relating to the exchange, exercise and settlement of the warrants.

Holders of equity warrants will not be entitled to:

•vote, consent or receive dividends;

•receive notice as shareholders with respect to any meeting of shareholders for the election of our directors or any other matter; or

•exercise any rights as shareholders of Crescent.

Each warrant will entitle its holder to purchase the principal amount of debt securities or the number preferred shares or ordinary shares at the exercise price set forth in, or calculable as set forth in, the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to the specified time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

A holder of warrant certificates may exchange them for new warrant certificates of different denominations, present them for registration of transfer and exercise them at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement. Until any warrants to purchase debt securities are exercised, the holder of the warrants will not have any rights of holders of the debt securities that can be purchased upon exercise, including any rights to receive payments of principal, premium or interest on the underlying debt securities or to enforce covenants in the applicable indenture. Until any warrants to purchase ordinary shares or preferred shares are exercised, the holders of the warrants will not have any rights of holders of the underlying ordinary shares or preferred shares, including any rights to receive dividends or payments upon any liquidation, dissolution or winding up on the ordinary shares or preferred shares, if any.

DESCRIPTION OF UNITS

We may issue units consisting of any combination of the other types of securities offered under this prospectus in one or more series. We may evidence each series of units by unit certificates that we will issue under a separate agreement. We may enter into unit agreements with a unit agent. Each unit agent will be a bank or trust company that we select. We will indicate the name and address of the unit agent in the applicable prospectus supplement relating to a particular series of units.

The following description, together with the additional information included in any applicable prospectus supplement, summarizes the general features of the units that we may offer under this prospectus. You should read any prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the series of units being offered, as well as the complete unit agreements that contain the terms of the units. Specific unit agreements will contain additional important terms and provisions and we will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from another report that we file with the SEC, the form of each unit agreement relating to units offered under this prospectus.

If we offer any units, certain terms of that series of units will be described in the applicable prospectus supplement, including, without limitation, the following, as applicable:

•the title of the series of units;

•identification and description of the separate constituent securities comprising the units;

•the price or prices at which the units will be issued;

•the date, if any, on and after which the constituent securities comprising the units will be separately transferable;

•a discussion of certain U.S. federal income tax considerations applicable to the units; and

•any other terms of the units and their constituent securities.

PLAN OF DISTRIBUTION

We may sell the securities from time to time pursuant to underwritten public offerings, negotiated transactions, block trades or a combination of these methods or through underwriters or dealers, through agents and/or directly to one or more purchasers. The securities may be distributed from time to time in one or more transactions:

•at a fixed price or prices, which may be changed;

•at market prices prevailing at the time of sale;

•at prices related to such prevailing market prices; or

•at negotiated prices.

Each time that we sell securities covered by this prospectus, we will provide a prospectus supplement or supplements that will describe the method of distribution and set forth the terms and conditions of the offering of such securities, including the offering price of the securities and the proceeds to us, if applicable.

Offers to purchase the securities being offered by this prospectus may be solicited directly. Agents may also be designated to solicit offers to purchase the securities from time to time. Any agent involved in the offer or sale of our securities will be identified in a prospectus supplement.

If a dealer is utilized in the sale of the securities being offered by this prospectus, the securities will be sold to the dealer, as principal. The dealer may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale.

If an underwriter is utilized in the sale of the securities being offered by this prospectus, an underwriting agreement will be executed with the underwriter at the time of sale and the name of any underwriter will be provided in the prospectus supplement that the underwriter will use to make resales of the securities to the public. In connection with the sale of the securities, we or the purchasers of securities for whom the underwriter may act as agent, may compensate the underwriter in the form of underwriting discounts or commissions. The underwriter may sell the securities to or through dealers, and those dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions from the purchasers for which they may act as agent. Unless otherwise indicated in a prospectus supplement, an agent will be acting on a best efforts basis and a dealer will purchase securities as a principal, and may then resell the securities at varying prices to be determined by the dealer.

Any compensation paid to underwriters, dealers or agents in connection with the offering of the securities, and any discounts, concessions or commissions allowed by underwriters to participating dealers will be provided in the applicable prospectus supplement. Underwriters, dealers and agents participating in the distribution of the securities may be deemed to be underwriters within the meaning of the Securities Act, and any discounts and commissions received by them and any profit realized by them on resale of the securities may be deemed to be underwriting discounts and commissions. We may enter into agreements to indemnify underwriters, dealers and agents against civil liabilities, including liabilities under the Securities Act, or to contribute to payments they may be required to make in respect thereof and to reimburse those persons for certain expenses.

Any ordinary shares will be listed on the Nasdaq Capital Market, but any other securities may or may not be listed on a national securities exchange. To facilitate the offering of securities, certain persons participating in the offering may engage in transactions that stabilize, maintain or otherwise affect the price of the securities. This may include over-allotments or short sales of the securities, which involve the sale by persons participating in the offering of more securities than were sold to them. In these circumstances, these persons would cover such over-allotments or short positions by making purchases in the open market or by exercising their over-allotment option, if any. In addition, these persons may stabilize or maintain the price of the securities by bidding for or purchasing securities in the open market or by imposing penalty bids, whereby selling concessions allowed to dealers participating in the offering may be reclaimed if securities sold by them are repurchased in connection with stabilization transactions. The effect of these transactions may be to stabilize or maintain the market price of the securities at a level above that which might otherwise prevail in the open market. These transactions may be discontinued at any time.

We may engage in at the market offerings into an existing trading market in accordance with Rule 415(a)(4) under the Securities Act. In addition, we may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement so indicates, in connection with those derivatives, the third parties may sell securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third party may use securities pledged by us or borrowed from us or others to settle those sales or to close out any related open borrowings of stock, and may use securities received from us in settlement of those derivatives to close out any related open borrowings of stock. The third party in such sale transactions will be an underwriter and, if not identified in this prospectus, will be named in the applicable prospectus supplement (or a post-effective amendment). In addition, we may otherwise loan or pledge securities to a financial institution or other third party that in turn may sell the securities short using this prospectus and an applicable prospectus supplement. Such financial institution or other third party may transfer its economic short position to investors in our securities or in connection with a concurrent offering of other securities.

The specific terms of any lock-up provisions in respect of any given offering will be described in the applicable prospectus supplement.

The underwriters, dealers and agents may engage in transactions with us, or perform services for us, in the ordinary course of business for which they receive compensation.

LEGAL MATTERS

Certain matters with respect to U.S. federal and New York State law will be passed upon for us by Latham & Watkins LLP. Walkers (Cayman) LLP will pass upon the validity of the securities offered in this prospectus with respect to the Ordinary Shares and matters of Cayman Islands law. Additional legal matters may be passed upon for us, or any underwriters, dealers or agents, by counsel that we will name in the applicable prospectus supplement.

EXPERTS

The financial statements incorporated in this Prospectus by reference to the Annual Report on Form 10-K for the year ended December 31, 2025 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

Ordinary Shares

Pre-Funded Warrants to Purchase Ordinary Shares

PROSPECTUS SUPPLEMENT


Jefferies
TD Cowen
Guggenheim Securities
Cantor
LifeSci Capital

, 2026

Crescent Biopharma Inc. published this content on July 14, 2026, and is solely responsible for the information contained herein. Distributed via EDGAR on July 14, 2026 at 20:02 UTC. If you believe the information included in the content is inaccurate or outdated and requires editing or removal, please contact us at [email protected]

related announcements

News

Healthcare

Crescent Biopharma Inc.

Supplemental Prospectus (Form 424B5)