Rocket Pharmaceuticals’ Danon Disease Trial Placed On FDA Hold Following Patient Death

Rocket Pharmaceuticals, a biotech firm, has announced a significant development in its Phase 2 trial for RP-A501, an investigational gene therapy targeting Danon disease. A patient experienced a Serious Adverse Event (SAE) related to capillary leak syndrome after receiving a new immune suppression agent added to the pre-treatment protocol. The company voluntarily paused the trial, and as of May 23, 2025, the FDA has placed the study on clinical hold. Sadly, the affected patient later passed away due to an acute systemic infection.

“We are heartbroken by this loss and are fully committed to our mission to develop gene therapies that address the underlying cause of devastating diseases like Danon. We are immensely grateful for the patients and families participating in this important research,” said Gaurav Shah, M.D., Chief Executive Officer of Rocket Pharmaceuticals.

Rocket is now conducting a comprehensive root cause analysis in collaboration with the FDA, the trial's Data Safety Monitoring Committee, and other stakeholders. The immune suppressant involved was unique to the AAV9-based Danon disease program and aimed to address complement activation, a known immune complication. The company emphasised its ongoing commitment to patient safety and is working diligently to resume the trial when appropriate.

Financially, Rocket reported $318.2 million in cash and equivalents as of March 31, 2025. The company will prioritise its AAV gene therapy platform to reduce overall cash spending while supporting its core programs. Rocket also mentioned the potential monetisation of Priority Review Vouchers from its haematology pipeline, which could extend funding further into 2027.