Sarepta Therapeutics Announces Positive Data from Part B of MOMENTUM, a Phase 2 Study of SRP-5051 in Patients with Duchenne Muscular Dystrophy Amenable to Skipping Exon 51

Sarepta Therapeutics, Inc. (NASDAQ:SRPT), the leader in precision genetic medicine for rare diseases, today announced positive data from Part B of the MOMENTUM study (Study SRP-5051-201), a global, Phase 2, multi-ascending dose clinical trial of SRP-5051 (vesleteplirsen) that enrolled patients aged 8 to 21 years. SRP-5051 is a next-generation peptide phosphorodiamidate morpholino oligomer (PPMO) treatment for patients with Duchenne muscular dystrophy who are amenable to exon 51 skipping.

Data from Part B of MOMENTUM found that at the higher, target dose, approximately 30 mg/kg dosed every four weeks, SRP-5051 resulted in mean dystrophin expression of 5.17%, and mean exon skipping of 11.11% at 28 weeks (n=20). Consistent dystrophin expression was seen in ambulatory (4.76%, n=11) and non-ambulatory (5.67%, n=9) participants at 28 weeks. Hypomagnesemia has previously been identified in patients taking SRP-5051 and was managed and monitored through prophylactic magnesium supplementation as part of the study protocol.

“SRP-5051 dosed every four weeks is showing substantially higher increases in dystrophin and exon skipping compared to eteplirsen dosed weekly,” said Louise Rodino-Klapac, Ph.D., executive vice president, chief scientific officer and head of research and development, Sarepta Therapeutics. “The data suggest a favorable benefit-risk profile for SRP-5051 and we look forward to discussing the results and next steps with FDA. As the leader in Duchenne, Sarepta is committed to advancing meaningful treatments for those with Duchenne and other rare diseases where there is unmet need.”

High dose results at 28 weeks (~30 mg/kg, dosed every four weeks, n=20):

• 5.17% mean dystrophin expression as measured by western blot
• 4.53% mean change from baseline, P < 0.0001
• Mean exon skipping of 11.11%, as measured by digital drop polymerase chain reaction (ddPCR), and a mean change from baseline in exon skipping of 10.07%
• The changes from baseline represent a 12.2-fold increase in dystrophin expression and a 24.6-fold increase in exon skipping compared to a weekly 30 mg/kg dose of eteplirsen at 24 weeks (mean dystrophin expression of 0.82%, mean exon skipping of 0.59%, n=16).

Low dose results at 28 weeks (~20 mg/kg, dosed every four weeks, n=20):