PTC Therapeutics to Acquire BLA-Stage Fabry Gene Therapy from Sangamo

Rare Daily Staff

PTC Therapeutics has agreed to acquire ST-920, Sangamo Therapeutics’ BLA-stage gene therapy candidate for Fabry disease, in a transaction that could further extend PTC’s rare-disease franchise without requiring a major new commercial buildout.

Under the proposed agreement, PTC will pay $111 million upfront and could pay up to an additional $100 million upon achievement of regulatory milestones. The company expects the acquisition to close in late third quarter or early fourth quarter of 2026, subject to execution of definitive agreements, bankruptcy court approval, and customary closing conditions.

Fabry disease is a genetic lysosomal storage disorder caused by mutations in the GLA gene. It can lead to progressive kidney, cardiac, neurologic, gastrointestinal, and dermatologic complications.

ST-920, also known as isaralgagene civaparvovec, is a one-time intravenous adeno-associated virus gene therapy designed to enable ongoing production of alpha-galactosidase A, the enzyme deficient in Fabry disease. ST-920 has received FDA Regenerative Medicine Advanced Therapy, Fast Track, and Orphan Drug designations. It also holds European orphan-drug and PRIME designations, as well as the U.K.’s Innovative Licensing and Access Pathway designation.

PTC said it expects to complete a rolling BLA submission seeking accelerated approval in the fourth quarter of 2026. If approved, the therapy could launch commercially in 2027.

“This transaction advances our strategy of leveraging our accomplished existing rare disease global commercial infrastructure to accelerate short- and intermediate-term revenue growth,” PTC CEO Matthew Klein said. “This was a unique opportunity with the potential for significant return on investment without the need for any development or commercial build and without impacting our objective of reaching cashflow break even in 2026.”

The planned accelerated-approval filing is based on data from the Phase 1/2 STAAR trial, a global, open-label, single-dose, dose-ranging study. PTC said the program has shown favorable renal-function outcomes.

The company also cited evidence of benefit in cardiac function and quality of life, along with sustained alpha-galactosidase A activity for up to 4.5 years in the earliest-treated participant. According to PTC, patients receiving enzyme replacement therapy at the start of the study were withdrawn from ERT after treatment with ST-920.

PTC emphasized that ST-920 has demonstrated an encouraging safety and tolerability profile, without a requirement for routine prophylactic or post-infusion systemic immunosuppression. That feature could distinguish it from some gene-therapy approaches whose administration depends on more intensive immunomodulatory regimens.

In Fabry disease, conventional enzyme replacement therapies require chronic administration and can impose a significant treatment burden. A durable gene therapy that reduces or eliminates the need for ERT could therefore offer a differentiated option, although the program’s ultimate value will depend on regulatory review, longer-term follow-up, and real-world durability.

PTC said the nonclinical and clinical portions of the BLA have already been submitted on a rolling basis, while the chemistry, manufacturing, and controls package is expected in the fourth quarter.

PTC expects to pursue approvals beyond the United States using its established global rare-disease regulatory and commercial infrastructure.

The acquisition adds to PTC’s effort to build revenue from marketed and near-market rare-disease therapies. Management characterized ST-920 as an asset its customer-facing teams can commercialize using existing capabilities, rather than one requiring a new launch organization.

Photo: Matthew Klein, CEO of PTC Therapeutics.