FDA's rare disease framework faces its first real test in Capricor’s DMD drug

News FDA Opinion: FDA’s rare disease framework faces its first real test in Capricor’s DMD drug November 10, 2026 | 4 min read | Elijah Stacy Twitter LinkedIn Facebook Email Print Last month, the FDA committed to designing a “fit-for-purpose” framework for regulating rare disease therapies based on patient need and realistically attainable evidence. With the upcoming decision for Capricor’s Duchenne muscular dystrophy cell therapy deramiocel, this paradigm faces its first key test. In Duchenne muscular dystrophy, losing the ability to walk isn’t the end of the disease.

It’s the start of a new fight to keep the use of your arms and hands. I’m 25; I stopped walking years ago, and I’ve recently started developing sores because I can no longer reposition myself in bed.I’m not a clinician, and I don’t design trials. But I’ve spent my career in biotech evaluating them and I’ve spent my life being measured by them.

When a scale like the Performance of the Upper Limb 2.0 (PUL 2.0) records a lost point, I know what that point used to be.My unique perspective is what the FDA says it wants. On October 14, the agency launched its Rare Disease Framework Initiative and asked for public input on “fit-for-purpose” review based on realistically attainable evidence. The agency’s comment docket is open until Dec.

11. The clearest test of what fit for purpose means arrives first: On Nov. 22, the FDA will decide whether to approve deramiocel, a cell therapy developed by Capricor Therapeutics—for whom I am a consultant—for upper limb function in Duchenne.

Capricor’s Phase 3 HOPE-3 trial randomized 106 patients with Duchenne, most of them non-ambulatory, to receive deramiocel or placebo for 12 months. Under the analysis published in The Lancet in August, deramiocel slowed upper limb decline on PUL 2.0 by 54% compared with placebo, meeting the study’s primary endpoint.That result is contested, and anyone following this story knows it. The FDA in briefing documents published in July ahead of an advisory committee meeting said the trial did not meet its pre-specified primary and secondary efficacy endpoints.

The published result relies on a revised statistical analysis plan, and reviewers and advisory committee members questioned whether it holds up under alternative assumptions about missing data. FDA UPDATE: FDA disputes Capricor’s claims of Phase 3 success for DMD cell therapy In briefing documents published Monday ahead of an advisory committee meeting for deramiocel, the FDA disagreed with Capricor’s assertion that a Phase 3 trial met its primary outcome measures. July 27, 2026 · 3 min read · Heather McKenzie Read more These are fair questions.

Changes to an analysis plan should draw scrutiny; that’s how the system guards against wishful thinking. But in rare disease, the question can’t stop at whether or not the plan changed. It also has to consider why, and when.

In a 106-patient trial of a progressive, heterogeneous disease, missing data and modeling assumptions can swing results in either direction. A revision made for sound statistical reasons before unblinding is a correction. One made after seeing the results is a rescue.

A fit-for-purpose framework should require the FDA to say plainly which it believes this is, and why.How the FDA responds matters well beyond this one drug. When expectations for analysis plans, endpoints or confirmatory evidence shift late in review, investment capital moves to easier diseases, and patients pay for it. For deramiocel, the longer-term data also point to efficacy on HOPE-3’s primary endpoint.

In the 24-month open-label extension study, patients in the trial who received placebo for a year and then switched to deramiocel saw their rate of upper-limb decline slow by 76% compared with their own preceding year. That analysis wasn’t powered or alpha-controlled, and it can’t substitute for a randomized comparison. But consistency across datasets matters when every patient is precious and a second large trial would take years.The July 29 advisory committee vote should also be read precisely.

Panelists voted 9-3 that the evidence presented by Capricor did not establish deramiocel’s effectiveness for Duchenne cardiomyopathy, the indication the biotech had originally sought. The advisors were not asked to vote on the upper limb endpoint but they did touch on it at the meeting, and their discussion was encouraging. Capricor has since refined the indication to upper limb function and submitted a year of data from the OLE study.

FDA FDA advisers vote against approval of Capricor’s DMD therapy in chaotic adcomm meeting During a perplexing advisory committee meeting in which FDA reviewers focused largely on the Phase 3 HOPE-3 trial’s secondary endpoint of cardiac function, experts pointed to “very fragile” data. The committee voted 9-3 against approval of deramiocel. July 29, 2026 · 8 min read · Heather McKenzie Read more That endpoint deserves more weight than it often gets.

In Duchenne patients who are non-ambulatory, upper limb function isn’t a surrogate. It is a measurement of whether a patient can feed himself, drive a power chair, use a phone or hold a job. Once those abilities are lost, they don’t come back.

In a progressive disease, slowing decline isn’t a consolation prize. It’s what allows patients to hold on to their last bits of independence for longer.That changes the cost of delay. Requiring another multi-year randomized trial in a population this small means one cohort of patients will lose function they won’t get back while waiting for the result to arrive.

None of this is an argument for the FDA to lower its standards. It is an argument for standards that are explicit and predictable. Rare disease sponsors invest years in small populations, and they need to know the rules before they place those bets.A fit-for-purpose framework should commit the FDA to three promises:Agree on analysis plans and approaches to address potential missing data with sponsors early and hold both sides to them.Explain clearly how the agency will weigh a contested primary analysis against the totality of evidence.Treat slowing the loss of function as a meaningful outcome in progressive diseases.The deramiocel decision will illustrate whether the new framework changes how the FDA weighs evidence, or only how it describes it.I know what it takes to develop these treatments because I work in this industry.

I know what’s lost when they don’t arrive because I live with Duchenne. A therapy that slows progression won’t make headlines as a cure. But for me, it could mean more years with the use of my hands, allowing me to feed myself when I go out to eat with my friends—and more easily continue writing advocacy pieces like this one.

FDA FDA’s new rare disease framework aims to leverage patient voices for better innovation Inclusion of the patient perspective is currently an “optional” part of the rare disease drug development process, CBER Director Karim Mikhail told BioSpace. Mikhail, along with his CDER counterpart Michael Davis and other agency rare disease leaders, is trying to change that. November 9, 2026 · 7 min read · Heather McKenzie Read more Twitter LinkedIn Facebook Email Print Opinion Duchenne muscular dystrophy Cell therapy Rare diseases Regulatory Capricor Therapeutics Elijah Stacy Elijah Stacy is a biotech consultant and the founder of Destroy Duchenne.

He lives with Duchenne muscular dystrophy. He is a consultant to Capricor Therapeutics and a shareholder; he writes here as a patient, and the views expressed are his own.