Aug 12, 2026 —
PTC Therapeutics announced that it was selected as the winning bidder to acquire ST-920, also known as isaralgagene civaparvovec, a BLA-stage one-time AAV gene therapy for Fabry disease, from Sangamo Therapeutics through a competitive bankruptcy auction.
The proposed transaction includes $111 million upfront and up to $100 million in contingent milestone payments based on certain regulatory approvals. The acquisition remains subject to definitive documentation, bankruptcy court approval, antitrust review, and other customary closing conditions, with closing expected in late third quarter or early fourth quarter of 2026.
ST-920 is designed as a one-time administered AAV gene therapy that enables long-term production of alpha-galactosidase A, or α-Gal A, the enzyme deficient in Fabry disease. The therapy aims to reduce globotriaosylceramide, or Gb3, accumulation and potentially reduce the treatment burden associated with chronic enzyme replacement therapy.
A rolling Biologics License Application, or BLA, submission to the U.S. Food and Drug Administration for accelerated approval is expected to be completed in the fourth quarter of 2026. PTC said the submission is based on evidence of favorable clinical effects on renal function, along with safety and tolerability data over 52 weeks from the Phase 1/2 STAAR study.
Fabry disease is a rare inherited lysosomal storage disorder caused by mutations in the GLA gene, resulting in deficient α-Gal A enzyme activity. Gb3 accumulation can damage multiple organs, including the kidney, heart, nerves, eyes, gut, and skin. Symptoms may include kidney disease, heart failure, neuropathic pain, gastrointestinal symptoms, heat intolerance, angiokeratomas, and reduced or absent sweat production.
In the STAAR study, ST-920 demonstrated a positive mean annualized estimated glomerular filtration rate, or eGFR, slope at Week 52, as well as evidence of favorable effects on cardiac function and quality of life. PTC noted that all study participants who were receiving enzyme replacement therapy at study entry were withdrawn from ERT.
Durability has been observed with sustained increased α-Gal A activity maintained for up to 4.5 years in the earliest treated participant, along with evidence of maintained renal function improvements across the study population.
ST-920 has demonstrated an encouraging safety and tolerability profile, with no requirement for routine prophylactic or post-infusion systemic immunosuppressive agents. The therapy has received RMAT, Orphan Drug, and Fast Track designations from the FDA, as well as Orphan Medicinal Product designation and PRIME eligibility from the European Medicines Agency.
The BLA submission for accelerated approval is based on annualized eGFR at Week 52 as an intermediate clinical endpoint aligned with FDA. PTC said 104-week results from STAAR are planned to provide confirmatory evidence to support traditional approval.
PTC said the acquisition leverages its existing rare disease regulatory and commercial infrastructure, as well as leadership experience in Fabry therapy commercialization. The company plans to pursue regulatory approval outside the United States while using its global rare disease infrastructure.
The planned acquisition could add a near-term commercial opportunity to PTC’s rare disease portfolio, with potential commercial launch in 2027 if ST-920 is approved.
