Amendment to Schedule 13D Filing for SOLID BIOSCIENCES INC.

This filing is an amendment to a Schedule 13D originally filed on February 9, 2018, by RA Capital Management, L.P. and related entities, collectively referred to as the "Reporting Persons." The amendment supplements information regarding their beneficial ownership of SOLID BIOSCIENCES INC. common stock. The Reporting Persons acquired 4,456,327 pre-funded warrants in a private placement on March 6, 2026, for $24,995,538, funded by working capital. These warrants are subject to a beneficial ownership blocker, limiting exercise to 9.99% of outstanding shares. Additionally, on February 6, 2026, the Fund purchased 354,936 shares for $2,304,350.99. The filing also details a registration rights agreement for the shares and warrants issued in the March 2026 private placement. RA Capital Management, L.P. now holds 9.9% of the outstanding shares, amounting to 9,663,926 shares.