A once-and-done gene therapy candidate that could halt the progression of a lethal muscle-wasting disorder took an important step on the path toward approval Monday. Results of a clinical trial published by the Journal of the American Medical Association strongly suggest that Sarepta Therapeutics' (NASDAQ:SRPT) SRP-9001 will become a safe treatment option for boys born with Duchenne muscular dystrophy (DMD). 

Positive clinical trial results 

Back in 2017, Sarepta began a safety study with four boys born with DMD, a rare inherited disorder caused by a mutated dystrophin gene. Without functional dystrophin to protect their muscles, DMD patients inflict muscle damage on themselves with every movement, breath, and heartbeat. SRP-9001 is a non-replicating adenovirus that delivers a portion of the working dystrophin gene to muscle cells. So far, none of the four participants have reported adverse events serious enough to require hospitalization.

Scientist reading a report.

Image source: Getty Images.

About SRP-9001's efficacy

That lack of serious adverse events means the safety study was a success, and it looks like future outcome assessments will hit the mark as well. Investigators took muscle tissue samples 12 weeks after patients received SRP-9001 and found proof of micro-dystrophin generation in 82% of fibers sampled.

Creatine kinase (CK) leaks from damaged muscles into the bloodstream, but one year after treatment with SRP-9001, patients' CK levels were much lower than expected, with the exception of one who was probably a little too active just ahead of his 52-week assessment. Since the average age of these patients was less than 5 years old, getting them to sit still is much easier said than done.