FDA briefing casts doubt on Capricor's deramiocel ahead of DMD advisory committee

San Diego-based Capricor Therapeutics (Nasdaq: CAPR) faces a critical regulatory test on Tuesday when the US FDA's Cellular, Tissue, and Gene Therapies Advisory Committee convenes to vote on whether deramiocel — an allogeneic cardiosphere-derived cell therapy — has demonstrated substantial evidence of effectiveness for cardiomyopathy in Duchenne muscular dystrophy (DMD). The agency's CBER briefing document for BLA 125842, released ahead of the July 29 meeting, presents a comprehensively negative efficacy assessment and concludes that the benefit-risk profile appears unfavorable, signaling a high bar for the committee to clear.

The meeting marks Capricor's second attempt at approval. The original BLA, based on Phase II data from Studies HOPE-2 and HOPE-2-OLE, received a Complete Response Letter in July 2025 due to lack of substantial evidence of effectiveness. The resubmission rests on the pivotal Phase III HOPE-3 study, but the FDA briefing document indicates that study also failed to meet its pre-specified endpoints — and that subsequent statistical modifications by the applicant have further undermined the data's credibility.

HOPE-3 was a 12-month, randomized, double-blind, placebo-controlled trial enrolling 106 males with DMD, predominantly non-ambulatory, with a mean left ventricular ejection fraction (LVEF) of 57% at baseline. The study was designed to detect a 1.5-point difference in the change from baseline to Month 12 in PUL 2.0 total score, a measure of upper limb skeletal muscle function, with LVEF change as the key secondary endpoint. Under the pre-specified analysis in statistical analysis plan (SAP) version 1.1, the least-squares mean difference in PUL 2.0 total score was 0.66 points (95% CI: −0.45, 1.77; p=0.24) — not statistically significant. On LVEF, the between-group difference was −0.041 percentage points (95% CI: −2.58%, 2.49%; p=0.97), indicating no treatment effect.

The applicant subsequently generated at least two additional SAP versions after study completion. The final SAP (version 3.0), dated November 24, 2025, was not submitted to FDA prior to BLA resubmission and was not agreed upon by the agency. Key modifications included changing the primary endpoint from absolute change to percent change in PUL 2.0 total score, and converting the LVEF analysis from a mixed-model repeated measures approach to an analysis of covariance on ranked change — a metric FDA describes as clinically uninterpretable and not standard in cardiac disease assessment. Under the applicant's SAP 3.0 analyses, the PUL 2.0 result reached nominal significance (p=0.029) and the LVEF ranked change difference yielded p=0.041. FDA concluded that the nominally significant findings produced under the applicant's revised SAP were not robust, with statistical significance disappearing under alternative missing-data assumptions affecting as few as two placebo patients.

FDA identified an additional structural concern: a distinctive adverse event profile between treatment arms created conditions for potential functional unblinding. Hypersensitivity reactions occurred in 41.5% of deramiocel-treated subjects versus 15.4% of placebo subjects. Eleven placebo subjects who had not experienced hypersensitivity reactions during the blinded phase subsequently developed them upon receiving open-label deramiocel in the extension period, providing a mechanism by which blinded-phase treatment assignment could be retrospectively inferred. The agency concluded that SAP modifications made after data collection under these conditions carry a high risk of being data-driven, regardless of formal blinding status.

Deramiocel consists of cardiosphere-derived cells (CDCs) derived from cadaveric donor hearts, administered by peripheral IV infusion at 150 million cells per dose every three months. The proposed mechanism — anti-fibrotic, anti-inflammatory, immunomodulatory, and pro-angiogenic effects mediated via exosome and growth factor secretion — is described by FDA as not sufficiently targeted or biologically plausible as a disease-modifying therapy in DMD, noting that prior nonclinical studies showed cardiac retention below 1% following IV administration.

No approved therapy has been shown to slow cardiac function decline in DMD. Cardiomyopathy is the primary cause of mortality in DMD through dilated cardiomyopathy, heart failure, and arrhythmia. Existing approved DMD therapies — including exon-skipping agents and dystrophin-modulating treatments — have not been systematically studied for cardiac effects, leaving the cardiomyopathy indication without a targeted treatment option. The FDA notice repeatedly acknowledges the severe unmet need in DMD cardiomyopathy and notes that regulatory flexibility is appropriate in rare diseases, but concludes that flexibility cannot substitute for persuasive evidence of effectiveness.

The advisory committee's sole voting question asks whether HOPE-3 provides substantial evidence of effectiveness for deramiocel in DMD cardiomyopathy. As previously reported, the meeting was scheduled in June 2026. The FDA has stated it will not issue a final determination on the BLA resubmission until advisory committee input has been considered and all reviews finalized. Given the agency's pre-meeting position — which found no convincing evidence of effectiveness across pre-specified or sensitivity analyses in either of the two randomized trials conducted in DMD — a second Complete Response Letter would appear to be a credible regulatory outcome.

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