Sarepta Therapeutics' Next-Gen Duchenne Muscular Therapy Shows Efficacy At Less Frequent Dosing

Sarepta Therapeutics Inc SRPT announced data from Part B of the MOMENTUM study (Study SRP-5051-201) Phase 2, multi-ascending dose trial of SRP-5051 (vesleteplirsen) that enrolled Duchenne muscular dystrophy (DMD) patients aged 8 to 21 years. 

SRP-5051 is a next-generation peptide phosphorodiamidate morpholino oligomer (PPMO) treatment for patients with DMD amenable to exon 51 skipping.

SRP-5051 is designed to work similarly to Exondys 51 (eteplirsen), an older Exon 51-skipping therapy developed by Sarepta

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 (who can walk) (4.76%, n=11) and non-ambulatory (cannot walk without assistance) (5.67%, n=9) participants at 28 weeks. 
• Hypomagnesemia (magnesium deficiency) was previously identified in patients taking SRP-5051 and was managed and monitored through prophylactic magnesium supplementation as part of the study protocol.
• The changes from baseline represent a 12.2-fold increase in dystrophin expression, and a 24.6-fold increase in exon skipping was observed compared to a weekly 30 mg/kg dose of Sarepta’s EXONDYS 51 (eteplirsen) at 24 weeks (mean dystrophin expression of 0.82%, mean exon skipping of 0.59%, n=16).

Also Read: Uphill Battle Ahead For Gene Therapy Player Sarepta, Analysts Lower Price Targets Following Duchenne Trial Miss.

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

• 2.81% mean dystrophin expression as measured by western blot
• 1.60% mean change from baseline, P= 0.0012
• Mean exon skipping of 2.47%, as measured by ddPCR, and a mean change from baseline in exon skipping of 2.00%
• The changes from baseline represent a 4.3-fold increase in dystrophin expression and a 4.9-fold increase in exon skipping compared to a weekly 30 mg/kg dose of eteplirsen at 24 weeks.

There were seven serious, treatment-emergent adverse events in MOMENTUM Part B, four severe hypomagnesemia events, and three serious cases of hypokalemia (Low potassium). 

Price Action: SRPT shares are up 3.43% at $122.80 on the last check Monday.