By Reuters

(Reuters) - Rocket Pharmaceuticals shares jumped 10% on Friday before the bell after the U.S. Food and Drug Administration ‌approved its gene therapy for a rare and often fatal ‌immune disorder in children, marking the first regulatory green light for a treatment of ​the condition.

The agency approved the drug, Kresladi, for the treatment of severe Leukocyte Adhesion Deficiency-I, a disorder in which a person’s white blood cells can’t reach infection sites properly, making them extremely vulnerable to serious ‌infections.

There had previously been ⁠no FDA-approved treatment specifically for the disease. About 75% of untreated patients die before the age of two ⁠unless they receive a stem cell transplant.

Kresladi works by collecting a patient’s own blood stem cells, genetically correcting the faulty gene, and then infusing ​the modified ​cells back into the patient ​as a one-time treatment.

The FDA ‌granted accelerated approval based on a surrogate endpoint measuring improved immune cell function.

The decision comes under Vinay Prasad, the FDA’s head of biologics who is set to leave the agency at the end of April, and has previously expressed skepticism toward surrogate endpoints.

But Prasad said on ‌Thursday that the FDA "continues to exercise ​significant regulatory flexibilities" during the review of ​rare-disease therapies.

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

He said that although Kresladi’s commercial ​potential is limited, ​the approval is strategically important, with Rocket expected to pursue only a “minimum viable launch strategy.”

The approval was supported by an early-to-mid-stage ​trial showing 100% survival ‌at 12 months after infusion, causing no treatment-related serious side ​effects, and sharply reducing serious infections.

(Reporting by Kamal Choudhury ​in Bengaluru; Editing by Sahal Muhammed)

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