FDA Approves First LVV-based Gene Therapy for Wiskott-Aldrich Syndrome

WASHINGTON D.C. — December 10, 2025—

The U.S. Food and Drug Administration (FDA) has granted its stamp of approval to Waskyra, a novel, cell-based gene therapy for the treatment of Wiskott-Aldrich syndrome (WAS). The approval marks the first therapy of its kind for the rare disease and signals a historic first for the nonprofit sector, as Italy’s Fondazione Telethon becomes the first nonprofit organization globally to successfully bring an ex vivo gene therapy across the regulatory finish line in the U.S.

Waskyra is specifically indicated for children aged 6 months and older, as well as adults who carry a mutation in the WAS gene. To be eligible for the treatment, patients must lack an available human leukocyte antigen-matched related stem cell donor and be deemed cleared for hematopoietic stem cell transplantation, the FDA said in its announcement.

The LVV-Based Mechanism

The drug was developed through decades of research at the San Raffaele Telethon Institute for Gene Therapy in Milan. Waskyra utilizes a patient’s own hematopoietic blood stem cells, which are extracted and genetically modified using a Lentiviral Vector (LVV) system to include functional copies of the WAS gene. The corrected cells are then reinfused intravenously back into the patient following chemotherapy.

“Today’s approval is a transformative milestone for patients with Wiskott-Aldrich syndrome, offering the first FDA-approved gene therapy that uses the patient’s own genetically corrected hematopoietic stem cells to treat the disease,” stated Dr. Vinay Prasad, director of the FDA’s Center for Biologics Evaluation and Research (CBER).

Clinical Efficacy and Regulatory Flexibility

WAS is a severe, X-linked disease—primarily affecting males—that causes recurring infections, severe bleeding, and heightened risk of autoimmune disease and lymphoma. The only current curative option is hematopoietic stem cell transplantation with a matched donor.

Data submitted to the FDA, derived from two open-label studies and an expanded access program, demonstrated significant clinical benefits:

• The rate of severe infections shrank by 93% in the six to 18 months post-treatment period compared to the year before treatment.

• Moderate and severe bleeding events were reduced by 60% in the first year following treatment, with “most” patients not reporting such bleeding four years post-treatment.

In approving Waskyra, Dr. Prasad noted that the FDA “continues to exercise flexibility in the regulatory approach for rare diseases.” This flexibility included allowing the use of relevant manufacturing and quality data from a “similar” approved product in Waskyra’s application.

Ilaria Villa, CEO of Fondazione Telethon, hailed the decision, calling it “an extraordinary achievement for the global rare disease community,” confirming the value of a patient-centered research model. The European Union granted regulatory approval for the treatment last month.