Sarepta shines spotlight on next-gen muscular dystrophy drug

Controversy over data quality took the shine off Sarepta’s U.S. approval of Duchenne muscular dystrophy drug Exondys51 last year. Now the company is hoping to avoid that issue with its next-generation drug golodirsen.

The biotech released top-line results from the phase 1/2 muscle biopsy study last month but provided much more detail in a presentation at the Annual Congress of the World Muscle Society in France over the weekend. In it, Sarepta showed not only that the drug boosted overall production of dystrophin—which is deficient in DMD—but also that the increase was seen in the area of muscle (the sarcolemma) necessary to have a clinical effect.

For good measure, the trial also showed that golodirsen's (SRP-4053) exon 53-skipping activity was evident in all 25 subjects enrolled in the trial, giving a 100% response rate to the new drug, and the data “validate Sarepta’s exon-skipping platform for the treatment of DMD,” according to the biotech.

The new drug shares the same phosphorodiamidate morpholino oligomer structure as Exondys51 (eteplirsen), which was given an FDA green light last year and—despite claims the approval was based on lackluster evidence of efficacy—has been steadily growing.

Sarepta recently increased its forecasts for Exondys51, saying it expects to make $125 million to $130 million from it this year, having previously predicted around $95 million. Hitting that target will depend, however, on getting approval for the drug in Europe.

One of the concerns about Exondys51 was a tiny effect on dystrophin levels, and from the data it seems golodirsen is doing better on that score, although the numbers are still small. It achieved a statistically significant increase in dystrophin levels from 0.095% of normal at baseline to 1.019%, a 10-fold increase, which compares to a 3.5-fold increase (from 0.16% to 0.44%) in eteplirsen’s pivotal study.

The company said recently it hopes to hold a meeting with the FDA on to discuss golodirsen in the first quarter of 2018, according to analysts at Leerink. It has also been trying to capitalize on its lead in DMD by licensing other potential therapies for the disease, snapping up candidates from Genethon and Summit Therapeutics in the last 12 months.