Sarepta Therapeutics Inc (NASDAQ:SRPT) shares surged almost 26% to about $22 after the biotechnology company shared early clinical results from two of its investigational siRNA therapies for neuromuscular diseases, showing dose-dependent muscle exposure and favorable tolerability.
Phase 1/2 studies of SRP-1001 for facioscapulohumeral muscular dystrophy type 1 (FSHD1) and SRP-1003 for myotonic dystrophy type 1 (DM1) demonstrated that the αvβ6 integrin-targeted delivery platform achieved high concentrations in muscle tissue without dose-limiting toxicity.
The studies also generated proof-of-concept evidence that a single dose of each therapy can reduce target protein or mRNA levels. Most adverse events were reported as mild to moderate and were not dose dependent.
RNA-targeted therapies like SRP-1001 and SRP-1003 aim to address rare genetic diseases caused by overexpression of mutant proteins or toxic mRNA, though such approaches have historically faced challenges with drug delivery to target cells. Sarepta’s investigational treatments combine optimized siRNA chemistry with a proprietary αvβ6 integrin-targeted ligand to facilitate muscle penetration.
“These preliminary clinical data show consistent dose-dependent increases in plasma and muscle drug exposures across clinical and nonclinical studies and suggest that the αvβ6 integrin-targeting ligand mediates robust siRNA muscle delivery,” said Louise Rodino-Klapac, Ph.D., Sarepta’s President of Research & Development and Technical Operations.
She added that the findings support the potential of the platform to enable higher dosing and may ultimately translate into clinical efficacy for patients with FSHD1 and DM1.
Jefferies analysts highlighted the early data as positive, noting that Phase 1/2 biomarker signals and favorable safety profiles in these rare diseases could support stock upside of 15% to 30%.
The analysts believe the results “partially de-risk the broader siRNA platform” and may help Sarepta diversify beyond Duchenne muscular dystrophy (DMD) and gene therapy approaches.
They also noted that single ascending dose data from SRP-1001 showed strong DUX4 reductions in FSHD1, while SRP-1003 showed a 50% knockdown of DMPK in DM1, with no drug-related serious adverse events.
Jefferies expects more data from multiple ascending dose studies in the second half of 2026.