Rocket aligns with FDA on path to complete phase 2 Danon disease trial

Rocket Pharmaceuticals says it has aligned with the FDA on key elements of the global pivotal phase 2 trial of gene therapy RP-A501 for the treatment of Danon disease, including the recalibrated dose, 12-patient pivotal population and established 12-month co-primary endpoints.

Rocket had paused dosing in the trial at the request of the FDA back in May 2025, after a patient experienced clinical complications related to a capillary leak syndrome. The patient then passed away after an acute systemic infection. In August 2025, the agency lifted the hold, and authorized the pivotal study to resume with a recalibrated dose of 3.8 x 10¹³ GC/kg of RP-A501 in three patients, treated sequentially with a minimum four-week interval between each treatment.

The clinical data recently reviewed by FDA included results from the first three patients treated under the modified protocol. No clinical or laboratory evidence of thrombotic microangiopathy or capillary leak syndrome had been observed. Following its review of the available safety data, the FDA confirmed continued enrollment and dosing under the modified protocol at the recalibrated dose.

The FDA also confirmed that the pivotal study population will include 12 male patients treated at the recalibrated dose and that the first three patients treated at the recalibrated dose count toward the 12-patient pivotal population, leaving nine additional patients to be enrolled and treated. Rocket expects to complete dosing of the remaining patients by mid-2027

RP-A501 is a single dose treatment administered as an intravenous infusion for the treatment of Danon disease, a rare, serious cardiac and skeletal myopathy caused by mutations in the LAMP2 gene. RP-A501 consists of a recombinant adeno-associated serotype 9 (AAV9) capsid containing a full-length, wild-type version of the human LAMP2B transgene (AAV9.LAMP2B) which, when inserted into heart cells harboring mutations in the endogenous LAMP2 gene, has the potential to fully restore cardiac function at its root.