FDA Does Not Approve Immune Disorder Gene Therapy

Rocket Pharmaceuticals said on Friday the U.S. health regulator declined to approve its gene therapy to treat a rare and severe pediatric disorder that causes the immune system to malfunction, sending its shares down more than 12% in early trading.

The Food and Drug Administration, through a so-called complete response letter, has sought limited additional information related to certain processes for the gene therapy, called Kresladi, to complete its review.

The company was seeking its first approval from the agency to use the therapy to treat patients with severe Leukocyte Adhesion Deficiency-I (LAD-I), a disorder Rocket estimates impacts roughly 800 to 1,000 individuals in the U.S. and Europe.

In these patients, the white blood cells cannot stick properly to blood vessel walls of an infection site due to a mutation in the protein-encoding ITGB2 gene. This could lead to severe immune system deficiencies and recurrent infections.

The New Jersey-based company said it had met with the FDA to discuss the sought information for a quick approval.

The company's marketing approval application was based on data from an early-to-mid-stage trial where all nine patients survived for at least 12 months post-infusion.

In February, the FDA had extended its timeline to decide on approval to review similar data related to certain processes for the gene therapy.

Analysts at TD Cowen had then said the delay seemed to be an FDA bandwidth-related issue and not an issue at the company's end.

Kresladi is a small opportunity for Rocket, but success here will validate the company's lentiviral platform that is being used for other therapies in its pipeline with larger patient populations, TD Cowen analyst Tyler Van Buren said.

The only curative treatment currently for the condition is a type of bone marrow transplant, which is often not readily available and carries substantial risk.