FDA pauses Rocket’s Phase II trial of RP-A501 for Danon disease

US late-stage biotech Rocket Pharmaceuticals (Nasdaq: RCKT) saw its shares plummet as much as 64% to $2.25 in pre-market activity today, after it announced an update related to a trial of RP-A501, its investigational gene therapy for Danon disease, which resulted in a patient death.

Rocket revealed that a patient participating in the Phase II pivotal study of RP-A501 experienced an unexpected serious adverse event (SAE). The SAE involved clinical complications related to a capillary leak syndrome.

Rocket is conducting a comprehensive root cause analysis and remains in active dialogue with the US Food and Drug Administration (FDA) and other key stakeholders, with the current focus being on the recent introduction of a novel immune suppression agent to the pre-treatment regimen that had been implemented to mitigate complement activation observed in some patients. This novel agent was specific to the AAV9-Danon program.