FDA approves Waskyra as first gene therapy for Wiskott-Aldrich syndrome

On December 9, 2025, the FDA approved Waskyra (etuvetidigene autotemcel; Fondazione Telethon), marking the first cell-based gene therapy authorized in the United States for the treatment of Wiskott-Aldrich syndrome (WAS). The therapy is indicated for pediatric patients 6 months and older, as well as adults who have a confirmed mutation in the WAS gene, are eligible for hematopoietic stem cell transplantation (HSCT), and lack a suitable HLA-matched related donor.^1,2

“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,” said Vinay Prasad, MD, MPH, chief medical and scientific officer and director of the FDA’s Center for Biologics Evaluation and Research. “The FDA continues to exercise flexibility in the regulatory approach for rare diseases by considering all available data sources, including as appropriate data from expanded access programs, to facilitate the advancement of life-changing treatments while ensuring scientific requirements are satisfied.”¹

WAS is a rare, life-threatening immunodeficiency caused by mutations in the WAS gene. The disorder affects blood cells and immune cells, leading to bleeding episodes, eczema, recurrent infections, and increased risk of autoimmunity and lymphoreticular malignancies. It occurs almost exclusively in males and has an estimated incidence of 1 in 250,000 live male births. Prior to the approval, treatment options were limited to supportive care or allogeneic HSCT, the only potentially curative option—yet one dependent on the availability of a compatible donor.

Developed through decades of research at the San Raffaele Telethon Institute for Gene Therapy (SR-Tiget) in Milan, Waskyra is manufactured from a patient’s own CD34+ hematopoietic stem and progenitor cells, which are genetically modified using a lentiviral vector encoding the functional WAS gene. After undergoing reduced-intensity conditioning, the corrected cells are infused intravenously, allowing for the restoration of functional WAS protein expression.

The clinical evaluation of Waskyra included 2 open-label, single-arm, multinational studies and an expanded access program involving 27 patients with severe WAS. According to the FDA, data demonstrated “substantial and sustained clinical benefit,” including a 93% reduction in severe infections during the six to 18 months following treatment compared with the 12 months prior. Moderate and severe bleeding events declined by 60% in the first year post-treatment, and most patients reported no moderate to severe bleeding four years after therapy.

“[This] approval addresses the urgent need in the WAS community, where patients have described living ‘a life of terrifying worry and fear’ without any approved therapies available,” said Vijay Kumar, MD, acting director of the FDA’s Office of Therapeutic Products. “This action marks significant progress in the development of much-needed treatment options for patients affected by this debilitating and life-threatening disease, enabling them to engage in everyday activities such as going to school or participating in sports.”

Fondazione Telethon, which pioneered the research and development pathway for this therapy, emphasized the broader significance of the FDA’s decision. “The FDA's approval of Waskyra is an extraordinary achievement – not only for Italian research and for Fondazione Telethon, but for the global rare disease community,” said Ilaria Villa, CEO of Fondazione Telethon. “It confirms the value of a patient-centered model that turns research into real treatments, especially where the market fails to act.”

Alessandro Aiuti of SR-Tiget added, “The approval of this gene therapy represents a decisive step forward and a tangible response to the needs of patients. Seeing years of scientific research and dedication translate into real therapeutic opportunities for people gives profound meaning to our work.”

The most common adverse events associated with Waskyra include rash, respiratory tract infection, febrile neutropenia, catheter-related infection, vomiting, diarrhea, liver injury, and petechiae.

References:

1. FDA. FDA Approves First Gene Therapy Treatment for Wiskott-Aldrich Syndrome. FDA. December 9, 2025. Accessed December 10, 2025. .https://www.fda.gov/news-events/press-announcements/fda-approves-first-gene-therapy-treatment-wiskott-aldrich-syndrome
2. Fondazione Telethon. Fondazione Telethon Announces FDA approval of Waskyra™ (etuvetidigene autotemcel), a Gene Therapy for the Treatment of Wiskott-Aldrich Syndrome. PR Newswire. December 9, 2025. Accessed December 10, 2025. https://www.prnewswire.com/news-releases/fondazione-telethon-announces-fda-approval-of-waskyra-etuvetidigene-autotemcel-a-gene-therapy-for-the-treatment-of-wiskott-aldrich-syndrome