Sarepta Reports Early siRNA Data Showing Muscle Delivery as Shares Surge

Overview

• Sarepta, which presented Phase 1/2 readouts Wednesday, reported that SRP-1001 for FSHD1 and SRP-1003 for DM1 reached high levels in muscle and hit their genetic targets after single doses.
• Most side effects were mild to moderate with no dose‑limiting toxicities, though investigators noted serious events in the SRP‑1003 study, including a cardiac arrhythmia death they judged unrelated to treatment.
• Following Wednesday’s data release, shares rose roughly 20% to 35% and Morgan Stanley raised its price target, while analysts called the results encouraging but still early.
• Both drugs use an αvβ6 integrin‑targeted ligand to ferry siRNA into muscle, addressing a long‑standing delivery hurdle; SRP‑1001 showed strong suppression of DUX4‑related genes linked to FSHD1.
• Sarepta plans fuller updates later in 2026 and aims to start pivotal trials in 2027, advancing programs licensed from Arrowhead in 2024 that target rare muscle diseases with few treatment options.