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Rocket Pharma Solidifies Danon Disease Gene Therapy Study Design, Prices Public Stock Offering

NEW YORK – Rocket Pharmaceuticals on Wednesday said it has reached an agreement with the US Food and Drug Administration over the design of a pivotal study, which if successful, will allow it to seek accelerated approval for the gene therapy RP-A501 in Danon disease.

Danon disease is an X-linked inherited cardiovascular condition caused by mutations in the LAMP2 gene. Because of these mutations, patients accumulate autophagosomes and glycogen in cardiac muscle, which can lead to heart failure and death in adolescent and young adult males. A heart transplant is the only treatment option, but it can cause many complications and may not be curative.

Rocket's RP-A501 uses a recombinant adeno-associated serotype 9 capsid to deliver a full-length, wild-type version of the human LAMP2B transgene to patients' heart cells via intravenous infusion. The company hopes to demonstrate that a single dose of RP-A501 will improve patients' cardiac structure and function. 

Rocket has been in discussions with the FDA about the design of a pivotal study for this gene therapy and has agreed to conduct a 12-patient, single-arm, open label trial. The company said it can seek accelerated approval for RP-A501 based on its ability to change patients' LAMP2 protein expression and reduce left ventricular mass from baseline at 12 months.

Researchers will check the safety of the gene therapy in two pediatric patients first before enrolling the rest of the cohort and conduct a natural history study to compare RP-A501's benefit against how Danon disease patients fare without any interventions. Investigators will also track changes in troponin, natriuretic peptides, event-free survival at 24 months, and treatment emergent safety events. The investigators will also administer the Kansas City Cardiomyopathy Questionnaire and assess New York Heart Association class.

Cranbury, New Jersey-based Rocket said it has in-house manufacturing capacity to produce enough drug for the Phase II trial and that it has developed and qualified the necessary potency assays for the study in line with the FDA's guidance. 

The company's discussion with the FDA on the RP-A501 program "marks the first-ever regulatory pathway to approval for a genetic treatment for heart disease," Rocket CEO Gaurav Shah said in a statement. "We believe this milestone sets us on the most efficient and rapid path to delivering this potentially transformative therapy to Danon disease patients who would otherwise progress to heart transplantation or death." 

Rocket on Wednesday also announced it is selling 7,812,500 shares of its common stock at a public offering price of $16.00 per share and selling pre-funded warrants to certain investors to purchase 3,126,955 shares of common stock at $15.99 per warrant. It expects the underwritten public stock and warrant offering to bring in $175 million in gross proceeds.

The firm is also granting underwriters a 30-day option to purchase an additional 1,640,918 shares of its common stock. JP Morgan, Morgan Stanley, Leerink Partners, and TD Cowen are joint bookrunning managers in the offering slated to close around Sept. 15. LifeSci Capital is acting as lead manager in the offering.