Sarepta Therapeutics reported this week that it had submitted a written response to the US Food and Drug Administration (FDA) for its DMD treatment after the regulator had requested it use a new potency assay, a test for whether the gene therapy can access cells and trigger production of the crucial protein Duchenne patients lack.
SRP-9001 is intended to deliver the micro-dystrophin-encoding gene to muscle tissue for the targeted production of the micro-dystrophin protein.
As of now, it is not evident the impact the FDA request may have on the Cambridge, Massachusetts company’s plans to begin a large study of the DMD therapy by the end of the year.
Bernstein analyst, Vincent Chen, in a note to investors yesterday, rang an optimistic note: "Our sense is Sarepta has plenty of options for potential potency release assays; it's just a matter of aligning with the FDA and validating the assays."
Additional dialogue with the FDA is required to determine the acceptability of the potency assay approach said Sarepta, with CEO, Doug Ingram, saying the company would look to obtain clarity on the timing of its planned study.
The company has a broad pipeline of gene therapies, including three for DMD and six for Limb-girdle muscular dystrophy (LGMD), all of which are at the preclinical or clinical stage.
Sarepta is responsible for global development and manufacturing of SRP-9001 and it is planning to commercialize the therapy in the US. At the end of last year, it signed a $1bn deal with Roche for the development of that gene therapy, granting the Swiss company the rights to commercialize the DMD treatment outside the US.
As a result of that deal, Sarepta was able to invest in manufacturing capacity and infrastructure to support a potential wider commercialization effort.
Sarepta, Pfizer and Solid Biosciences are current competitors in the gene therapy space for DMD.
In November last year, Solid Biosciences announced that its gene therapy for DMD was on clinical hold after a patient experienced a serious adverse event. The company is still engaging with the FDA to get the clinical hold lifted.
Pfizer announced in August 2019 that it would be ramping up the manufacture of its own DMD gene therapy ahead of the beginning of Phase 3 trials.
The pharma giant is going ahead on the late stage study despite safety concerns noted in an earlier trial. Pfizer reported in May this year that all three patients who had serious adverse events in a phase 1b clinical study had recovered within two weeks. The company confirmed then that the safety profile of its DMD therapy warrants a P3 trial, which it has slated for the second half of this year
Sarepta also experienced a clinical hold, however, the issues for the company were not patient-related but were related to the manufacturing process for plasmids used in its therapy.