SRP-9001 Benefits Duchenne Patients Originally Given Placebo in Trial

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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SRP-9001 | Muscular Dystrophy News | illustration of clinical trial results

Children with Duchenne muscular dystrophy (DMD) who had been given a placebo in a clinical trial experienced a marked improvement in motor abilities after being treated with Sarepta Therapeutics‘ experimental gene therapy SRP-9001, new top-line data show.

“We are delighted to report positive results for Part 2 of our blinded, placebo-controlled Study 102 in Duchenne, where the 48-week functional benefits of SRP-9001 in patients dosed at cross-over were statistically significant when compared to pre-specified matched external controls,” Doug Ingram, Sarepta’s president and CEO, said in a press release.

DMD is caused by mutations that impair the production of a protein called dystrophin. SRP-9001 (delandistrogene moxeparvovec) uses a harmless viral vector, called adeno-associated virus (AAV), to deliver to muscle cells a gene encoding a shortened but functional version of the protein called micro-dystrophin.

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Sarepta is sponsoring a Phase 2 trial, called Study 102 (NCT03769116), that enrolled 41 boys with DMD, ages 4 to 7 at enrollment.

In the first part of the study, participants were randomly assigned to a single infusion of SRP-9001 or a placebo and were followed for 48 weeks (just under a year). Results, reported in fall, showed that patients given the gene therapy scored significantly higher on the North Star Ambulatory Assessment (NSAA) — a measure of functional motor abilities in DMD patients able to walk, with higher scores reflecting better function.

In the study’s second part, the children who had originally gotten a placebo (now ages 5 to 8) were treated with an infusion of SRP-9001. Their NSAA scores were compared with those of an external group of patients, matched for variables including age, steroid usage, and functional tests.

After 48 weeks, SRP-9001-treated patients scored a mean 2 points higher than the external controls, a statistically significant difference. Specifically, in the external group, NSAA scores decreased by 0.7 points, while the mean score in the SRP-9001 group increased by 1.3 points.

There were no novel safety-related findings from this portion of the trial. The most common side effect associated with the treatment was vomiting. Trial participants will continue to be monitored for five years total after treatment.

“The safety profile of SRP-9001 remains consistent with the wealth of previous clinical data,” Ingram said, adding that the results “add to the totality of evidence for SRP-9001 generated thus far — with promising results across multiple clinical trials and more than 80 patients dosed, encompassing a wide range of phenotypes [observable characteristics] as well as the oldest and heaviest Duchenne patients to be dosed with a full body AAV gene therapy infusion to date.”

Sarepta is currently running a Phase 3 clinical trial called EMBARK (NCT05096221) to further test the safety and efficacy of SRP-9001.

Participants in the trial will be given a single infusion of the gene therapy or placebo and be monitored for 52 weeks (about a year). Then, participants originally given SRP-9001 will get an infusion of placebo, and vice versa, followed by another year of monitoring. The study’s main goal is to measure changes in NSAA scores.

EMBARK is currently recruiting males with DMD ages 4 to 7 at several locations in the U.S.

“The totality of results that we have seen across our multiple trials bolsters our confidence in the potential disease-modifying benefits of this therapy and reinforces our conviction in the probability of success of EMBARK, our large, phase 3 placebo-controlled global study presently underway and dosing,” Ingram said.

“We will continue to move as quickly as possible to bring SRP-9001 to patients in the United States and around the world,” Ingram added.