Form SC 13D/A Solid Biosciences Inc. Filed by: PERCEPTIVE ADVISORS LLC

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D/A

Under the Securities Exchange Act of 1934

(Amendment No. 4)*

Solid Biosciences Inc.

(Name of Issuer)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

83422E 105

(CUSIP Number)

Alexander Rakitin

Perceptive Advisors LLC

51 Astor Place, 10^th Floor

New York, NY 10003

(646) 205-5340

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

December 2, 2022

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.  ☐

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Section 240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934, as amended (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. 83422E 105

CUSIP No. 83422E 105

CUSIP No. 83422E 105

CUSIP No. 83422E 105

Item 1 is amended and supplemented as follows:

This Amendment No. 4 amends and supplements the statement on Schedule 13D originally filed with the Securities and Exchange Commission (the “SEC”) on Feburary 8, 2018, as amended by Amendment No. 1 filed on December 17, 2020, Amendment No. 2 filed on March 23, 2021 and Amendment No. 3 filed on September 2, 2022, and relates to the shares of common stock, par value $0.001 per share (“Common Stock”), of Solid Biosciences Inc., a Delaware corporation (the “Issuer”), which has its principal executive offices at 500 Rutherford Avenue, Charlestown, Massachusetts 02129.

Item 2 is amended and supplemented as follows:

Item 3 is amended and supplemented as follows:

AavantiBio Merger Agreement

On September 29, 2022, the Issuer entered into an Agreement and Plan of Merger (the “Merger Agreement”) by and among the Issuer, Greenland Merger Sub LLC, a wholly owned subsidiary of the Issuer (“Transitory Subsidiary”), AavantiBio, Inc. (“AavantiBio”), and, solely in his capacity as equityholder representative, Doug Swirsky. The Merger Agreement provides for the acquisition of AavantiBio by the Issuer through the merger of Transitory Subsidiary into AavantiBio, with AavantiBio surviving as a wholly owned subsidiary of the Issuer (the “Merger”).

On December 2, 2022, pursuant to the Merger Agreement, the Issuer acquired AavantiBio through the merger of Transitory Subsidiary into AavantiBio, with AavantiBio surviving as a wholly owned subsidiary of the Issuer. In connection with the Merger, the Master Fund received 365,536 shares of Common Stock in exchange for its 5,483,040 shares of preferred stock of AavantiBio and Perceptive Xontogeny received 73,107 shares of Common Stock in exchange for its 1,096,605 shares of preferredstock of AavantiBio.

References to and the description of the Merger Agreement set forth above in this Item 3 do not purport to be complete and are qualified in their entirety by reference to the full text of the Merger Agreement, which is attached hereto as Exhibit 6 and incorporated by reference herein.

Securities Purchase Agreement

On September 29, 2022, the Issuer entered into securities purchase agreements (the “Securities Purchase Agreement”) with several accredited investors (the “PIPE Investors”), pursuant to which the Issuer agreed to issue and sell to the PIPE Investors in a private placement an aggregate of 10,638,290 (as adjusted for the Issuer’s reverse stock split completed on October 27, 2022) shares of the Issuer’s Common Stock (the “PIPE Shares”), for aggregate gross proceeds of approximately $75.0 million (the “Private Placement”). The Private Placement closed immediately following the closing of the Merger on December 2, 2022. The Master Fund purchased 2,163,120 shares of the Issuer’s Common Stock in the Private Placement, for total consideration of $15,249,999.

References to and the description of the Securities Purchase Agreement set forth above in this Item 3 do not purport to be complete and are qualified in their entirety by reference to the full text of the Securities Purchase Agreement, which is attached hereto as Exhibit 7 and incorporated by reference herein.

Item 4 is amended and supplemented as follows:

The information set forth in Item 6 below is incorporated by reference into this Item 4.

Item 5 is amended and supplemented as follows:

Item 6 is amended and supplemented as follows:

Support Agreements

On September 29, 2022, the Master Fund entered into a support agreement with the Issuer and AavantiBio (the “Issuer Support Agreement”) pursuant to which it agreed to vote all shares of the Issuer’s Common Stock held by it in favor of the Merger and the Private Placement and against any alternative acquisition proposals.

On September 29, 2022, the Master Fund and Perceptive Xontogeny entered into a support agreement with the Issuer and AavantiBio (the “AavantiBio Support Agreement”) pursuant to which they agreed to vote all of their shares of AavantiBio preferred stock in favor of the adoption of the Merger Agreement and against any alternative acquisition proposals.

References to and the descriptions of the Issuer Support Agreement and the AavantiBio Support Agreement set forth above in this Item 6 do not purport to be complete and are qualified in their entirety by reference to the full text of the Issuer Support Agreement and the AavantiBio Support Agreement, which are attached hereto as Exhibit 8 and Exhibit 9, respectively, and incorporated by reference herein.

Registration Rights Agreement

On September 29, 2022, the Issuer entered into a registration rights agreement (the “Registration Rights Agreement”) with the PIPE Investors, including the Master Fund, pursuant to which the Issuer agreed to register for resale the PIPE Shares and the stock consideration held by the PIPE Investors. Under the Registration Rights Agreement, the Issuer has agreed to file a registration statement covering the resale of the PIPE Shares and any stock consideration within 60 days following the closing of the Private Placement (the “Filing Date”). The Issuer has agreed to use commercially reasonable efforts to cause such registration statement to become effective as soon as practicable and to keep such registration statement effective until the date the PIPE Shares and any stock consideration covered by such registration statement have been sold or cease to be registrable securities under the Registration Rights Agreement.

If (i) the registration statement has not been filed by the Filing Date, (ii) the registration statement has not been declared effective by the SEC prior to the earlier of (A) five business days after the date on which the Issuer is notified by 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) 90 days following the closing of the Merger (or, in the event the SEC reviews and has written comments to the registration statement, 120 days following the closing of the Merger) 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 (including by reason of a stop order or the Issuer’s failure to update such registration statement), subject to certain limited exceptions, then the Issuer has agreed to make pro rata payments to each holder of registrable securities as liquidated damages in an amount equal to 1% of the aggregate amount invested by each such holder in the registrable securities for the initial day of failure and for each subsequent 30-day period (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 Issuer has granted the PIPE Investors customary indemnification rights in connection with the registration statement. The PIPE Investors have also granted the Issuer customary indemnification rights in connection with the registration statement.

On or prior to the closing of the Merger, each AavantiBio shareholder receiving stock consideration in the Merger may elect to become party to the Registration Rights Agreement. Percptive Xontogeny joined the Registration Rights Agreement with respect to its stock consideration pursuant to the foregoing election prior to the closing of the Merger.

References to and the description of the Registration Rights Agreement set forth above in this Item 6 do not purport to be complete and are qualified in their entirety by reference to the full text of the Registration Rights Agreement, which is attached hereto as Exhibit 10 and incorporated by reference herein.

Item 7 is amended and restated as follows:

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: December 6, 2022

PERCEPTIVE ADVISORS LLC

PERCEPTIVE LIFE SCIENCES MASTER FUND, LTD.

PERCEPTIVE XONTOGENY VENTURE FUND, L.P.