Warren, New Jersey, August 12, 2026
PTC Therapeutics announced that it was selected as the winning bidder to acquire ST-920 (isaralgagene civaparvovec), a BLA-stage, one-time AAV gene therapy for Fabry disease, from Sangamo Therapeutics following a competitive bankruptcy auction. The proposed transaction includes $111 million in upfront consideration and up to $100 million in contingent milestone payments tied to certain regulatory approvals. PTC expects the acquisition to strengthen its rare disease portfolio while leveraging its existing regulatory and commercial infrastructure for potential future development and commercialization of ST-920.
ST-920 Targets the Underlying Cause of Fabry Disease
ST-920 is designed as a one-time administered AAV gene therapy intended to address the enzyme deficiency associated with Fabry disease. Fabry disease is a rare inherited lysosomal storage disorder caused by mutations in the GLA gene, resulting in insufficient activity of the alpha-galactosidase A (α-Gal A) enzyme. The deficiency leads to accumulation of globotriaosylceramide (Gb3) in cells and can damage vital organs, including the kidneys, heart, nerves, eyes, gastrointestinal system and skin. Patients can experience a broad range of symptoms, including neuropathic pain, kidney disease, cardiac complications, gastrointestinal disturbances and reduced or absent sweating. ST-920 is intended to enable long-term production of the deficient α-Gal A enzyme following a single infusion. The program has demonstrated sustained increases in α-Gal A activity and reductions in Gb3 levels, with the earliest treated participant maintaining increased enzyme activity for up to 4.5 years. The therapy is also designed to reduce the treatment burden associated with chronic enzyme replacement therapy (ERT). ST-920 has received FDA Orphan Drug, Fast Track and Regenerative Medicine Advanced Therapy (RMAT) designations, supporting its development as a potential treatment for this rare genetic disease.
Phase 1/2 STAAR Data Support BLA Submission
The proposed acquisition is supported by clinical data from the Phase 1/2 STAAR study, a global, open-label, single-dose, dose-ranging study evaluating ST-920 in patients with Fabry disease. According to PTC, the study demonstrated a positive mean annualized estimated glomerular filtration rate (eGFR) slope at Week 52, along with evidence of favorable effects on cardiac function and quality of life. Participants who were receiving ERT at the beginning of the study were withdrawn from ERT, while ST-920 demonstrated sustained enzyme activity and evidence of maintained renal benefits across the study population. The program also showed an encouraging safety and tolerability profile, with no routine prophylactic or post-infusion systemic immunosuppression required. PTC expects to complete a rolling Biologics License Application (BLA) submission to the U.S. FDA in the fourth quarter of 2026, seeking accelerated approval based on the intermediate clinical endpoint of annualized eGFR at Week 52. The company plans to use 104-week STAAR results as confirmatory evidence toward traditional approval. The nonclinical and clinical portions of the BLA have already been submitted through the rolling process, while the CMC package is expected in Q4 2026. PTC also intends to pursue regulatory approvals outside the United States using its established rare disease regulatory and commercial infrastructure.
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PTC Expands Rare Disease Gene Therapy Strategy
The acquisition represents a strategic expansion of PTC Therapeutics’ rare disease portfolio and adds a late-stage gene therapy program with potential commercial opportunities. PTC expects to leverage its existing infrastructure and experience in rare disease commercialization to accelerate ST-920’s potential path toward market availability. The transaction remains subject to definitive documentation, bankruptcy court approval, antitrust review and other customary closing conditions, with completion expected in late Q3 or early Q4 2026. If completed and subsequent regulatory milestones are achieved, ST-920 could provide a potential one-time gene therapy approach for patients with Fabry disease, addressing the underlying enzyme deficiency rather than requiring lifelong enzyme replacement. The program therefore represents an important development in rare disease gene therapy, advanced biopharmaceutical development and targeted genetic medicine, while the proposed acquisition highlights continued investment in late-stage rare disease assets with established clinical and regulatory foundations.
Source: PTC Therapeutics press release
