Free Writing Prospectus (Form FWP)

Filed Pursuant to Rule 433

Registration No. 333-291384

Issuer Free Writing Prospectus, dated November 11, 2025

PRICING TERM SHEET

November 11, 2025

Cogent Biosciences, Inc.

Offerings of

9,677,420 Shares of Common Stock

$200.0 Million Aggregate Principal Amount of 1.625% Convertible Senior Notes due 2031

The information in this pricing term sheet supplements (i) Cogent Biosciences, Inc.'s ("Cogent") preliminary prospectus supplement, dated November 10, 2025 (the "Common Stock Preliminary Prospectus Supplement"), relating to an offering of Common Stock (the "Common Stock Offering"), and (ii) Cogent's preliminary prospectus supplement, dated November 10, 2025 (the "Convertible Notes Preliminary Prospectus Supplement"), relating to an offering of convertible senior notes (the "Convertible Notes Offering"), and, in each case, the accompanying prospectus, dated November 7, 2025, each filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended (the "Securities Act"). This pricing term sheet supersedes the information in the Common Stock Preliminary Prospectus Supplement and the Convertible Notes Preliminary Prospectus Supplement to the extent inconsistent with the information in the Common Stock Preliminary Prospectus Supplement and Convertible Notes Preliminary Prospectus Supplement, respectively. Terms used, but not defined, in this pricing term sheet have the respective meanings set forth in the Common Stock Preliminary Prospectus Supplement and the Convertible Notes Preliminary Prospectus Supplement. As used in this pricing term sheet, "we," "our" and "us" refer to Cogent and "Common Stock" refers to the common stock, par value $0.001 per share, of Cogent. Cogent has increased the size of the Common Stock Offering from $200.0 million to $300.0 million (or, if the underwriters of the Common Stock Offering fully exercise their option to purchase additional shares of Common Stock, $345.0 million). The final prospectus supplement relating to the Common Stock Offering will reflect conforming changes relating to such increase in the size of the Common Stock Offering.

Increase in Conversion Rate in Connection with a Make-Whole Fundamental Change

If a make-whole fundamental change occurs and the conversion date for the conversion of a Note occurs during the related make-whole fundamental change conversion period, then, subject to the provisions described in the Convertible Notes Preliminary Prospectus Supplement under the caption "Description of Notes-Conversion Rights-Increase in Conversion Rate in Connection with a Make-Whole Fundamental Change," the conversion rate applicable to such conversion will be increased by a number of shares of Common Stock (the "Additional Shares") set forth in the table below corresponding (after interpolation as described below) to the make-whole fundamental change effective date and the stock price of such make-whole fundamental change:

If such make-whole fundamental change effective date or stock price is not set forth in the table above, then:

Notwithstanding anything to the contrary, in no event will the conversion rate be increased to an amount that exceeds 32.2580 shares of our Common Stock per $1,000 principal amount of notes, which amount is subject to adjustment in the same manner as, and at the same time and for the same events for which, the conversion rate is required to be adjusted pursuant to the provisions described in the Convertible Notes Preliminary Prospectus Supplement under the caption "Description of Notes-Conversion Rights-Conversion Rate Adjustments-Generally."

We have filed a registration statement (including a prospectus), the Common Stock Preliminary Prospectus Supplement and the Convertible Notes Preliminary Prospectus Supplement with the SEC for the offerings to which this communication relates. Before you invest, you should read the Common Stock Preliminary Prospectus Supplement or the Convertible Notes Preliminary Prospectus Supplement, as applicable, and the prospectus in that registration statement and other documents we have filed with the SEC for more complete information about us and these offerings. You may get these documents free by visiting EDGAR on the SEC website at www.sec.gov. Alternatively, we, any underwriter or any dealer participating in the applicable offering will arrange to send you the Common Stock Preliminary Prospectus Supplement or the Convertible Notes Preliminary Prospectus Supplement, as applicable (or, when available, the applicable final prospectus supplement) and the accompanying prospectus upon request to: Jefferies LLC, Attention: Equity Syndicate Prospectus Department, 520 Madison Avenue, New York, NY 10022, by telephone at (877) 821-7388 or by email at [email protected]; J.P. Morgan Securities LLC, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717, or by email at [email protected] and [email protected]; Leerink Partners LLC, Attention: Syndicate Department, 53 State Street, 40th Floor, Boston, MA 02109, by telephone at (800) 808-7525, ext. 6105, or by email at [email protected]; or Guggenheim Securities, LLC, Attention: Equity Syndicate Department, 330 Madison Ave., New York, NY 10017, or by telephone at (212) 518-9544, or by email at [email protected].

The information in this pricing term sheet is not a complete description of the Common Stock, the Common Stock Offering, the Notes or the Convertible Notes Offering. You should rely only on the information contained or incorporated by reference in the Common Stock Preliminary Prospectus Supplement and the Convertible Notes Preliminary Prospectus Supplement and the accompanying prospectus, as supplemented by this pricing term sheet, in making an investment decision with respect to the Common Stock or the Notes.

ANY DISCLAIMERS OR OTHER NOTICES THAT MAY APPEAR BELOW ARE NOT APPLICABLE TO THIS COMMUNICATION AND SHOULD BE DISREGARDED. SUCH DISCLAIMERS OR OTHER NOTICES WERE AUTOMATICALLY GENERATED AS A RESULT OF THIS COMMUNICATION BEING SENT VIA BLOOMBERG OR ANOTHER EMAIL SYSTEM.