Sarepta gains credibility, but confirmation is still three years away

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With Sarepta already running a confirmatory trial of its third exon-skipping Duchenne muscular dystrophy therapy, its US accelerated approval last night perhaps lacked the drama of earlier green lights. Moreover, though the label of the drug now branded Amondys 45 is backed by a surrogate endpoint, dystrophin expression, there is a placebo comparator. In this regard Sarepta is gaining credibility: its first two DMD exon skippers, Exondys 51 and Vyondys 53, got accelerated approvals based on small, uncontrolled studies. The former’s confirmatory trial did not even start for another four years, and the latter had to contend with a complete response letter. The Essence study will seek to confirm the approvals of Vyondys and Amondys alike, and Amondys’s conditional green light is backed by early data from this same trial. If Sarepta dragged its feet it was not alone: US data show that, of 23 accelerated approvals granted in 2010-20 to non-oncology drugs, only four had converted to full approvals through clinical confirmation as at the end of 2020, taking an average of 3.5 years to do so. And as-yet unconverted accelerated approvals for Makena, Ferriprox and Sirturo date back to 2011-12.

Sarepta's accelerated approvals
        Confirmatory trial
Drug 2026e sales ($m) Accelerated approval basis Approval Name & start Data?
Exondys 51 442 6min walk test in 2 trials (n=12), vs external controls, & dystrophin expression Sep 2016 MIS51ON, mid-2020 2026
Vyondys 53 243 Dystrophin expression in 1 trial (n=25) Dec 2019 Essence, mid-2016 2024
Amondys 45 202 Dystrophin expression in Essence trial (n=27), vs placebo Feb 2021 Essence, mid-2016 2024
Source: EvaluatePharma & clinicaltrials.gov.

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