IPM Take
IPM Take
Accelerated approval is meant to buy time for patients. It is not meant to erase the need to prove clinical benefit.
FDA’s acceptance of Sarepta’s applications for traditional approval of AMONDYS 45 and VYONDYS 53 does not settle the central question. It puts that question formally on the table: when a confirmatory trial misses its primary endpoint, how much weight should biomarkers, post-hoc analyses and real-world evidence be allowed to carry?
That is not a technical footnote. It is one of the defining regulatory fights in rare disease.
Executive Summary
FDA has accepted for review Sarepta’s supplemental New Drug Applications seeking to convert the accelerated approvals of AMONDYS 45, casimersen, and VYONDYS 53, golodirsen, into traditional approvals for people with Duchenne muscular dystrophy whose mutations are amenable to exon 45 or exon 53 skipping.
The agency has set a target action date of 28 February 2027. The applications draw on the Phase 3 ESSENCE confirmatory study, published real-world evidence and long-term safety data.
The central evidence problem is already public. ESSENCE did not meet its primary endpoint, four-step ascend velocity at week 96. Sarepta reported a numerical treatment difference of 0.06 steps per second, which did not reach statistical significance, with p=0.309. The company has also presented post-hoc analyses excluding participants whose baseline assessments were affected by COVID-era disruption.
FDA has accepted the applications for review. It has not decided whether the evidence is sufficient for traditional approval.
Why it matters
- Patients / advocates: The medicines remain available under accelerated approval, but families deserve clarity about whether the evidence has moved from a plausible surrogate signal to confirmed clinical benefit.
- Clinicians: The question is not whether exon skipping has biological activity. It is whether the available evidence establishes a reliable, patient-relevant effect on disease progression.
- Regulators: Rare-disease flexibility has to remain credible. That means being transparent about when real-world evidence strengthens a conclusion and when it cannot repair uncertainty left by a missed primary endpoint.
Duchenne is exactly the kind of disease that made accelerated approval necessary.
Muscle damage accumulates. Function declines over years. Mutation-defined populations can be extremely small. Families cannot simply be told to wait indefinitely for a conventional evidence package that may be structurally difficult to generate.
But accelerated approval was never supposed to mean accelerated certainty.
AMONDYS 45 and VYONDYS 53 were initially approved on the basis of increased dystrophin production, a surrogate endpoint considered reasonably likely to predict clinical benefit. ESSENCE was meant to address the next question: did that biological change translate into a measurable difference in function?
On the prespecified primary analysis, it did not.
Sarepta argues that the picture is more complicated. The company points to numerical trends favouring treatment, post-hoc analyses excluding some COVID-era baseline assessments, long-term safety data and real-world evidence. Those arguments may be relevant. They are not self-validating.
That is why the FDA review matters.
This is not a choice between being pro-patient and being pro-evidence. Patients are not served by false certainty, shifting standards or regulatory language that becomes too flexible to explain. They are served by a system that can recognise the realities of ultra-rare disease while still drawing a clear line between a promising treatment, an available treatment and a treatment with confirmed clinical benefit.
By February 2027, FDA will need to show where that line sits.
