Rocket Pharmaceuticals says FDA aligns on Danon disease pivotal trial path

Rocket Pharmaceuticals said on September 15, 2026 that it reached alignment with the FDA on how to finish its global pivotal Phase 2 trial of RP-A501 for Danon disease. The alignment covers continued enrollment and dosing under a modified protocol, a recalibrated dose, a 12-patient pivotal population, and established 12-month co-primary endpoints.¹

The agency's review drew on data from the first three patients dosed under the revised protocol. All three had completed at least four weeks of follow-up and had been discharged after the protocol-specified observation period.¹ No clinical or laboratory signs of thrombotic microangiopathy or capillary leak syndrome were reported in these patients.¹ Based on this safety data, the FDA agreed that enrollment and dosing under the modified protocol, at the recalibrated dose, could continue.¹

The pivotal population will consist of 12 male patients dosed with RP-A501 at a recalibrated level of 3.8 × 10¹³ genome copies per kilogram, using commercial-grade material.¹ The three patients already treated at this dose count toward that total, leaving nine more to be enrolled.¹ The company said it anticipates finishing dosing of these remaining patients around the middle of 2027.¹

Efficacy will be assessed a year after dosing. The trial's co-primary endpoints, myocardial LAMP2 protein expression and a 10% drop from baseline in left ventricular mass index, measured at 12 months, are meant to support a possible accelerated approval route, according to the company.¹

The modified protocol pairs the recalibrated dose with an adjusted immune-suppressing regimen using rituximab, sirolimus, and corticosteroids, alongside tighter eligibility, monitoring, and risk-management steps.¹ Rocket said the new dose level was chosen using analytical data on the Phase 2 commercial-grade product, including full-particle content, and is backed by nonclinical bridging studies.¹ In a Danon disease mouse model, the Phase 2 material dosed at 3.8 × 10¹³ GC/kg produced cardiac LAMP2B expression similar to a higher dose, with comparable vector distribution in tissue.¹

Rocket plans an investor webinar on the Danon disease program on October 6, 2026, at 4:30 p.m. ET.¹