Astellas Pharmaceuticals have announced today that the first patient has been dosed in VALOR, their gene therapy trial for x-linked myotubular myopathy. Please read the letter to the patient community here (PDF). Astellas Pharmaceuticals XLMTM Community Letter-27 APRIL 2026 or below:

“Dear XLMTM Community,

As requested, we are writing to share an update on our XLMTM research program and to continue our commitment to keeping you informed as our work progresses. We’re excited to share some progress in our XLMTM clinical research program and provide information around other corporate developments related to our XLMTM program.

Update on the VALOR program (ASP2957)

We are pleased to share that the first patient has been dosed in the VALOR clinical trial. The VALOR trial is a phase 1/2 trial evaluating the safety and efficacy of ASP2957, an investigational gene therapy for boys under three years of age, living with XLMTM.

This milestone reflects that the VALOR study has moved into its next stage following extensive laboratory research and review by health authorities. We are eager to learn more about ASP2957, and how the investigational gene therapy behaves in the body, as the VALOR trial progresses.

Of course, patient safety remains our highest priority. The trial is being conducted with careful medical oversight and participants will be closely monitored throughout the study.

Update on AT132 (resamirigene bilparvovec)

We also want to share an update regarding AT132, our first investigational gene therapy that was evaluated in the ASPIRO study.

As previously communicated, the AT132 program remains on clinical hold. Astellas recently completed an internal review of the AT132 program and its associated research investment. As a result of this review, the company has recorded an impairment loss related to AT132 in its financial reporting. This is a financial business decision that has been made so that we can prioritise ASP2957 moving forward. This decision is not related to a new scientific or safety finding.

We want to reassure you that this does not change our ongoing commitment to the families and boys who participated in the ASPIRO study. Children who received AT132 will continue to be followed long term, as planned, to help us understand important safety and long-term outcomes. We look forward to sharing further data, including 5-year follow-up data, from the ASPIRO clinical trial in the future.

Most importantly, this step does not diminish the value of the contributions made by the boys and families who took part in the AT132 program. Their involvement has profoundly shaped our understanding of XLMTM and has directly inspired and informed our current and future research efforts.

Looking ahead

We know that progress in rare disease research can bring hope alongside uncertainty, caution, and complex emotions. We want you to know that we continue to carry the lessons of the past with us as we move forward, and we remain deeply committed to working alongside the XLMTM community with transparency, respect, and care.

We will continue to listen, to engage with community representatives, and to communicate openly as our XLMTM research efforts evolve.

Thank you, as always, for your partnership, and for your continued willingness to engage with us on this journey. We look forward to sharing more information as our research progresses.

With very best wishes,

”