Sarepta Therapeutics said that SRP-5051 (vesleteplirsen) has increased dystrophin expression and exon skipping in Part B of the Phase 2 MOMENTUM study of patients with Duchenne muscular dystrophy (DMD) who are amenable to exon 51 skipping.

SRP-5051 is engineered to selectively bind to exon 51 of dystrophin pre-mRNA. The purpose of this investigational agent is to exclude the exon during mRNA processing specifically in patients with genetic mutations conducive to skipping of exon 51.

It has been developed using Sarepta Therapeutics’ peptide phosphorodiamidate morpholino oligomer (PPMO) chemistry and exon-skipping technology.

The global, multi-ascending dose MOMENTUM trial enrolled 40 volunteers for its Part B, both ambulant and non-ambulant, between the ages of eight and 21.

SRP-5051, at the higher, target dose of around 30mg/kg, resulted in mean dystrophin expression of 5.17%, and mean exon skipping of 11.11% at 28 weeks.

In addition, consistent dystrophin expression was observed in ambulatory and non-ambulatory participants at 28 weeks.

In MOMENTUM Part B, seven treatment-emergent adverse events were considered significant, along with four hypomagnesemia occurrences, and three hypokalaemia cases.

In previous clinical studies, hypomagnesemia was observed in patients taking SRP-5051. It was managed and monitored through prophylactic magnesium supplementation as part of the trial protocol.

Sarepta Therapeutics research and development head, chief scientific officer, and executive vice president Louise Rodino-Klapac said: “SRP-5051 dosed every four weeks is showing substantially higher increases in dystrophin and exon skipping compared to eteplirsen dosed weekly.

“The data suggest a favourable 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.”

The MOMENTUM study is designed to measure the levels of dystrophin protein in skeletal muscle tissue after SRP-5051 treatment. SRP-5051 will be administered every four weeks.

In June last year, Sarepta Therapeutics secured the US Food and Drug Administration (FDA) accelerated approval for Elevidys for the treatment of DMD.