March 10, 2026-
Astellas is advancing its genetic medicine pipeline with the launch of the Phase 1/2 VALOR clinical trial, evaluating ASP2957, an investigational AAV-based gene therapy designed to treat infants with X-linked myotubular myopathy (XLMTM). The trial is sponsored by Astellas Gene Therapies, a division of Astellas Pharma focused on developing genetic medicines for rare diseases.
ASP2957 (MyoAAV3.8-MHCK7-hMTM1) uses an adeno-associated virus (AAV) vector to deliver a functional copy of the MTM1 gene, aiming to restore production of the myotubularin protein that is missing in patients with XLMTM. The disease is a rare congenital neuromuscular disorder that primarily affects male infants and causes profound muscle weakness, respiratory failure, and dependence on ventilatory support early in life.
The VALOR study, the first human trial of ASP2957, will enroll up to nine boys aged three years or younger who require invasive ventilatory support for at least 20 hours per day. Participants will receive a single intravenous infusion of the AAV gene therapy through a dose-escalation strategy evaluating two dose levels—1.0 × 10¹² and 2.0 × 10¹² vector genomes per kilogram—followed by a dose-expansion phase once safety is confirmed.
To reduce risks associated with systemic AAV delivery, the trial incorporates sentinel dosing, with participants treated sequentially and separated by an eight-week monitoring interval. Patients will also receive prophylactic immunosuppressive therapy to mitigate potential immune responses against the viral vector.
The primary objective of the trial is to evaluate safety and tolerability, including monitoring for adverse events and assessing liver, cardiac, hematologic, and muscle biomarkers. Secondary and exploratory endpoints will examine potential clinical effects such as changes in ventilatory requirements, neuromuscular development, and caregiver-reported outcomes.
Gene replacement therapy has long been considered a promising approach for XLMTM because the disease results from loss of functional MTM1 protein. Earlier research, including the ASPIRO trial, showed encouraging signs of improved respiratory and motor function in some patients treated with AAV-based gene therapies, though safety concerns highlighted the need for careful dose selection and monitoring.
By combining an engineered muscle-tropic AAV capsid with a targeted gene replacement strategy, Astellas hopes ASP2957 will provide a safer and more effective therapeutic option for children affected by this devastating genetic disorder.
