SCHEDULE 13D/A

SOLID BIOSCIENCES INC COM NEW

Common Stock, $0.001 par value per share · CUSIP: 83422E105

Event date: 2026-03-06

Reporting persons may disclose overlapping interests. Their amounts are shown individually and are not added into a filing total.

Filing-level shares

Unavailable

Percent of class

Unavailable

• BCLS SB Investco, LPReported CIK 0001728056

  Shares: 0 · Class: 0%

• Bain Capital Life Sciences Fund II, L.P.Reported CIK 0001773187

  Shares: 267,257 · Class: 0.3%

• BCLS II Investco, LPReported CIK 0001818893

  Shares: 8,604,852 · Class: 8.8%

• BCIP Life Sciences Associates, LPReported CIK 0001702921

  Shares: 32,550 · Class: 0.1%

• BCLS II Equity Opportunities, LPReported CIK 0001814474

  Shares: 904,160 · Class: 1.0%

• Bain Capital Life Sciences Opportunities IV, L.P.Reported CIK 0002015553

  Shares: 5,302,897 · Class: 5.4%

Amounts are as disclosed in this filing. Schedule type alone does not establish investment intent.