Securities Purchase Agreement

On March 6, 2026, Solid Biosciences Inc., a Delaware corporation (the "Company"), entered into a securities purchase agreement (the "Securities Purchase Agreement") with certain institutional accredited investors (the "Investors"), pursuant to which the Company agreed to issue and sell to the Investors in a private placement an aggregate of 14,973,257 shares of the Company's common stock, par value $0.001 per share (the "Shares"), at a price of $5.61 per share, and, to investors who so choose in lieu of Shares, pre-fundedwarrants to purchase 27,807,482 shares of the Company's common stock (the "Pre-FundedWarrants"), at a price of $5.609 per Pre-FundedWarrant (the "Private Placement").

The Private Placement is expected to close on or about March 9, 2026, subject to the satisfaction of certain customary closing conditions. The Company expects to receive aggregate gross proceeds from the Private Placement of approximately $240.0 million, before deducting placement agent fees and offering expenses, and aggregate net proceeds from the Private Placement of approximately $226.8 million, after deducting placement agent fees.

Leerink Partners LLC and Citigroup Global Markets Inc. acted as joint lead placement agents for the Private Placement. Cantor Fitzgerald & Co. acted as co-leadplacement agent for the Private Placement. H.C. Wainwright & Co. LLC and Truist Securities Inc. acted as co-placementagents for the Private Placement.

The Company has granted the Investors indemnification rights with respect to its representations, warranties, covenants and agreements under the Securities Purchase Agreement.

The Private Placement includes new and existing investors, including Perceptive Advisors, Bain Capital Life Sciences, RA Capital Management, Invus, Vestal Point Capital, Janus Henderson Investors, and Deep Track Capital, among others. Each Investor has agreed that it will not trade in the Company's securities until after March 11, 2026.

Pre-FundedWarrants

Each Pre-FundedWarrant to be issued in the Private Placement will have an exercise price of $0.001 per share, will be exercisable immediately and will be exercisable until the Pre-FundedWarrant is exercised in full.

Under the terms of the Pre-FundedWarrants, the Company may not effect the exercise of any such warrant, and a holder will not be entitled to exercise any portion of any such warrant, if, upon giving effect to such exercise, the aggregate number of shares of common stock beneficially owned by the holder (together with its affiliates, any other persons acting as a group together with the holder or any of the holder's affiliates, and any other persons whose beneficial ownership of common stock would or could be aggregated with the holder's for purposes of Section 13(d) or Section 16 of the Securities Exchange Act of 1934, as amended (the "Exchange Act")) would exceed 4.99% or 9.99%, as elected by the holder, of the number of shares of common stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of such warrant, which percentage may be increased or decreased at the holder's election upon 61 days' notice to the Company subject to the terms of such warrants, provided that such percentage may in no event exceed 19.99%.

Registration Rights Agreement

Also on March 6, 2026, the Company entered into a registration rights agreement (the "Registration Rights Agreement") with the Investors, pursuant to which the Company agreed to register for resale the Shares and the shares of the Company's common stock issuable upon exercise of the Pre-FundedWarrants (the "Pre-FundedWarrant Shares" and, together with the Shares, the "Registrable Securities"). Under the Registration Rights Agreement, the Company has agreed to file a registration statement covering the resale by the Investors of their Registrable Securities no later than 30 days following the closing of the Private Placement (the "Filing Date"). The Company has agreed to use reasonable best efforts to cause such registration statement to be declared effective as soon as reasonably practicable and to keep such registration statement effective until the date that all Registrable Securities covered by such registration statement have been sold or can be sold without restriction pursuant to Rule 144

and without the requirement to be in compliance with Rule 144(c)(1) (or any successor thereof) promulgated under the Securities Act of 1933, as amended (the "Securities Act"). The Company has agreed to be responsible for all fees and expenses incurred in connection with the registration of the Registrable Securities.

In the event (i) the registration statement has not been filed by the Filing Date, (ii) the registration statement is not declared effective prior to the earlier of (a) five business days after the date on which the Company is notified by the Securities and Exchange Commission (the "SEC") that the registration statement will not be reviewed by the SEC staff or is not subject to further comment by the SEC staff or (b) the 75^th day after the Filing Date, or (iii) after the registration statement has been declared effective by the SEC, sales cannot be made pursuant to the registration statement for any reason, subject to certain limited exceptions, then the Company has agreed to make pro rata payments to each Investor then holding Registrable Securities as liquidated damages and not as a penalty in an amount equal to one percent (1.0%) of the aggregate amount invested by such Investor for the Registrable Securities per 30-dayperiod or pro rata for any portion thereof for each such month during which such event continues, subject to certain caps set forth in the Registration Rights Agreement.

The Company has granted the Investors customary indemnification rights in connection with the registration statement. The Investors have also granted the Company customary indemnification rights in connection with the registration statement.

The foregoing descriptions of the Securities Purchase Agreement, the Pre-FundedWarrants and the Registration Rights Agreement do not purport to be complete and are qualified in their entirety by reference to the full text of the forms of Securities Purchase Agreement, Pre-FundedWarrant and Registration Rights Agreement, copies of which are filed as Exhibits 10.1, 4.1 and 10.2 to this Current Report on Form 8-K,respectively, and incorporated by reference herein.

The representations, warranties and covenants contained in the Securities Purchase Agreement and the Registration Rights Agreement were made solely for the benefit of the parties thereto and the placement agents expressly named as third-party beneficiaries thereto and may be subject to limitations agreed upon by the contracting parties. Accordingly, the Securities Purchase Agreement and the Registration Rights Agreement are incorporated herein by reference only to provide investors with information regarding the terms thereof and not to provide investors with any other factual information regarding the Company or its business, and should be read in conjunction with the disclosures in the Company's periodic reports and other filings with the SEC.

Although the Company has not finalized its full financial results for the fourth quarter and fiscal year ended December 31, 2025, the Company expects to report cash, cash equivalents and available-for-salesecurities of approximately $187.9 million as of December 31, 2025.

The estimated cash, cash equivalents and available-for-salesecurities figure is preliminary and unaudited, represents management's estimate as of the date of this report, is subject to completion of the Company's financial closing procedures for the fourth quarter and fiscal year ended December 31, 2025, and does not present all necessary information for a complete understanding of the Company's financial condition as of December 31, 2025, or the Company's results of operations for the year ended December 31, 2025. The actual financial results may differ materially from the preliminary estimated financial information.

The information provided under Item 2.02 of this Current Report on Form 8-Kshall not be deemed "filed" for purposes of Section 18 of the Exchange Act or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act or the Exchange Act, except as expressly set forth by specific reference in such a filing.

The information contained above in Item 1.01 is hereby incorporated by reference into this Item 3.02. Based in part upon the representations of the Investors in the Securities Purchase Agreement, the offering and sale of the Shares and the Pre-FundedWarrants will be exempt from registration under Section 4(a)(2) of the Securities Act. The

Shares and Pre-FundedWarrants have not been registered under the Securities Act or any state securities laws, and the Shares and Pre-FundedWarrants may not be offered or sold in the United States absent registration with the SEC or an applicable exemption from the registration requirements. The sale of the securities will not involve a public offering and will be made without general solicitation or general advertising. The Investors represented that they are institutional "accredited investors" as defined in Rule 501(a)(1), (2), (3) or (7) under the Securities Act or "qualified institutional buyers" within the meaning of Rule 144A under the Securities Act, and that they are acquiring the Shares and Pre-FundedWarrants for investment purposes only and not with a view to any resale, distribution or other disposition of the Shares and Pre-FundedWarrants in violation of the United States federal securities laws.