FDA and Rocket agree on a path to finish the Danon trial

Danon disease is caused by a defect in the LAMP2 gene; the heart muscle thickens and fails, and boys with it often need a transplant before adulthood. RP-A501 is an AAV gene therapy meant to put a working copy of LAMP2 back into cardiac cells.

Rocket Pharmaceuticals announced on 15 September 2026, from Cranbury, New Jersey, that it had reached agreement with the FDA on how the pivotal Phase 2 trial will be completed. The study continues under a modified protocol at a recalibrated dose of 3.8 × 10¹³ genome copies per kilogram, using commercial-grade product. The pivotal population is 12 male patients at that dose; the first three already count toward it, leaving nine to enrol.

The co-primary endpoints are assessed at 12 months: expression of LAMP2 protein in myocardium, and a 10 percent reduction from baseline in left ventricular mass index. Both are measures of the mechanism rather than of how patients feel, and the company intends them to support accelerated approval.

On safety, the three patients treated under the modified protocol each completed at least four weeks of follow-up with no clinical or laboratory evidence of thrombotic microangiopathy or capillary leak syndrome. Rocket expects to finish dosing the remaining nine by mid-2027, with the 12-month reads following after that.