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. The amendment, dated March 17, 2026, reports on transactions and ownership of SOLID BIOSCIENCES INC. common stock. RA Capital Management, L.P., along with Peter Kolchinsky, Rajeev Shah, and RA Capital Healthcare Fund, L.P., are the reporting persons. The filing details recent purchases of SOLID BIOSCIENCES INC. common stock by the Fund between March 11 and March 17, 2026, totaling approximately $23.7 million. These purchases were funded by the Fund's working capital. The reporting persons collectively hold a significant percentage of the company's outstanding shares, with RA Capital Management, L.P. holding 9,313,756 shares, representing 9.9% ownership.