Dive Brief:

• The Food and Drug Administration has rejected a gene therapy developed by Rocket Pharmaceuticals for a rare type of inherited immunodeficiency, the biotechnology company disclosed Friday.
• According to Rocket, the FDA asked for “limited additional” information on what’s known as chemistry, manufacturing and controls — the data detailing the quality and consistency of the final drug product. The company said it has met with the agency to “align” on the scope of that request so it can move quickly to secure an eventual approval. 
• “It is reassuring to have the FDA as a close collaborator who understands the high unmet medical need, clear clinical benefit and importance of timely patient access,” Rocket CEO Gaurav Shah said in the company’s statement.

Dive Insight:

The FDA doesn’t release complete response letters, meaning descriptions of the agency’s feedback come only from the company involved. Still, Wall Street analysts who spoke with Rocket are convinced the rejection is a speed bump, rather than a dead-end for the drugmaker’s gene therapy, called Kresladi. 

“We strongly suspect that Kresladi’s eventual approval is really just a matter of when — not if,” wrote Dae Gon Ha, an analyst at Stifel, in an investor note.

The FDA had already postponed its decision on Kresladi by three months due to a change in the reviewer overseeing Rocket’s application, meaning the agency couldn’t extend its evaluation of the application further. The complete response letter “strikes us as a reluctant last option for the FDA rather than a reflection of any significant deficiencies with the submission package,” Ha wrote. 

Analysts at William Blair and at Chardan outlined similar views in notes to clients Friday. “We ultimately view the CRL as more related to FDA staffing constraints than Kresladi’s critical quality attributes,” wrote William Blair’s Sami Corwin.

Kresladi is built from a patient’s own stem cells, which Rocket genetically modifies to deliver a functional copy of the gene that’s mutated in the condition the therapy treats. Known as severe leukocyte adhesion deficiency-I, the disease weakens the body’s ability to fight infections. Infants born with it often experience bacterial and fungal infections that require hospitalizations and survival beyond childhood is uncommon without a successful bone marrow transplant. 

All nine patients treated in Rocket’s small study of Kresladi have survived through the duration of the trial’s follow-up, now between 18 to 42 months. Data showed declines in the incidence of significant infections follow treatment, as well as signs of resolution of disease-related skin lesions, per Rocket. 

Even if the FDA’s issues with Rocket’s applications are easily resolved, the rejection is another setback for a field that’s faced notable clinical, regulatory and business hurdles. Manufacturing remains a challenging area for developers, as experienced by Abeona Therapeutics, which saw its skin disease cell therapy rejected by the FDA in April.

Biotechnology companies aren’t the only ones running into issues. Both Daiichi Sankyo and AbbVie have recently received manufacturing-related complete response letters from the FDA for drugs they submitted for approval.