Shares of Rocket Pharmaceuticals rose 10% in Friday's pre-market trading following the U.S. Food and Drug Administration's (FDA) approval of its gene therapy for a rare and often fatal immunodeficiency disorder in children. This marks the first regulatory approval of a treatment for this condition.

The FDA-approved drug, named Kresladi, is intended for the treatment of severe Leukocyte Adhesion Deficiency-I (LAD-I). Individuals with this disease have white blood cells that cannot properly travel to sites of infection, making them highly susceptible to serious infections.

Previously, there were no FDA-approved treatments specifically for this disease. Without a stem cell transplant, approximately 75% of untreated patients die before the age of two.

Kresladi is a one-time therapy. The treatment involves collecting a patient's own hematopoietic stem cells, genetically correcting the defective gene, and then infusing the modified cells back into the patient.

The FDA granted the drug accelerated approval based on a surrogate endpoint that measured the improvement of immune cell function.

The approval decision was led by the FDA's biologics chief, Vinay Prasad, who is set to leave his position at the end of April and has previously expressed skepticism about surrogate endpoints.

However, Prasad stated on Thursday that the FDA "consistently applies significant regulatory flexibility" when reviewing therapies for rare diseases.

Jefferies analyst Andrew Tsai said the approval of Kresladi "de-risks the entire gene therapy platform."

He noted that while Kresladi's commercial potential is limited, the approval is strategically significant, and Rocket Pharmaceuticals is expected to pursue only a "minimally viable launch strategy."

The approval was supported by data from an early-to-mid-stage clinical trial. The trial showed a 100% survival rate at 12 months post-infusion, no treatment-related serious adverse events, and a significant reduction in the incidence of serious infections.