According to a new announcement, PTC Therapeutics has been selected as the winning bidder to acquire isaralgagene civaparvovec (ST-920), a Biologics License Application-stage adeno-associated virus vector-based gene therapy for Fabry disease, from Sangamo Therapeutics in a court-supervised bankruptcy auction.
PTC will pay $111 million in cash at closing, plus up to $100 million in contingent milestone payments, $80 million upon accelerated approval and $20 million upon full or traditional approval. PTC outbid Astellas, the original stalking horse bidder, and backup bidder TerSera Therapeutics over a 2-day auction process.
"We really believe that we have the capability to really just set this in with the existing infrastructure," Matthew Klein, MD, MS, chief executive officer of PTC Therapeutics, said on a conference call with investors. Klein noted the auction took place over two days, calling it an indication of how competitive the process was and how much interest the asset attracted.
Auction terms and ST-920's accelerated approval pathway
The proposed sale requires final approval from the U.S. Bankruptcy Court for the District of Delaware and remains subject to Hart-Scott-Rodino antitrust review. Eli Lilly separately acquired Sangamo's capsid delivery, zinc finger, and modular integrase platform technologies, along with the company's prion disease program, ST-506, for $50 million in the same auction process. Combined, the auction yielded approximately $163.55 million in cash consideration at closing for Sangamo's bankruptcy estate.
Sangamo initiated the Section 363 asset sale process under Chapter 11 bankruptcy protection to maximize value for stakeholders while continuing to seek buyers for its remaining pipeline assets. Sale hearings before the Delaware bankruptcy court are expected in the third quarter of 2026, with the Lilly transaction anticipated to close on or about September 4, 2026.
ST-920 requires a single intravenous infusion without lymphodepleting preconditioning. In detailed data from the registrational phase 1/2 STAAR study (NCT04046224) presented at the WORLDSymposium in February 2026, a positive mean annualized estimated glomerular filtration rate (eGFR) slope of 1.965 mL/min/1.73m² per year (95% CI, -0.153 to 4.083) was observed at 52 weeks across all dosed patients.
The FDA agreed, in a Type B interaction, to accept the 52-week eGFR slope across all STAAR patients as the primary basis for approval under the Accelerated Approval pathway, avoiding the need for an additional registrational study. Improvements in kidney function were observed regardless of sex, prior enzyme replacement therapy use, Fabry disease type, or baseline kidney impairment.
Frequently Asked Questions
What did PTC Therapeutics acquire from Sangamo?
PTC acquired ST-920 (isaralgagene civaparvovec), a BLA-stage AAV gene therapy for Fabry disease, for $111 million at closing plus up to $100 million in milestone payments, in a bankruptcy auction.
What clinical data support ST-920's accelerated approval pathway?
The Phase 1/2 STAAR study showed a positive mean annualized eGFR slope of 1.965 mL/min/1.73m² per year (95% CI, -0.153 to 4.083) at 52 weeks, which the FDA agreed can serve as the primary basis for Accelerated Approval.
What other assets did Sangamo sell in the auction?
Eli Lilly acquired Sangamo's capsid delivery, zinc finger, and modular integrase platform technologies along with its prion disease program, ST-506, for $50 million in the same auction.
Safety profile and PTC's rare disease portfolio rationale
Across the STAAR study, ST-920 was generally well tolerated. Most adverse events were grade 1 or grade 2 in severity, no adverse events led to study withdrawal, and no deaths occurred on study. No patients required steroid treatment for liver enzyme elevations following gene transfer.
PTC's rolling BLA submission for ST-920 under the Accelerated Approval pathway is expected to be completed in the fourth quarter of 2026. The therapy has also received Orphan Drug, Fast Track, and RMAT designations from the FDA, along with Orphan Medicinal Product designation and PRIME eligibility in the European Union.
"Reaching the conclusion of this first competitive auction represents an important milestone in Sangamo's reorganization," Sandy Macrae, PhD, chief executive officer of Sangamo Therapeutics, said in a statement. "Our priority has been to seek value-maximizing transactions for all stakeholders, and we are pleased that our platform technologies, Fabry disease and prion programs attracted strong interest from parties who have the scale to continue their development for patients in need."
Fabry disease is a rare, X-linked lysosomal storage disorder caused by deficient alpha-galactosidase A activity, leading to progressive renal, cardiac, and neurologic complications. Current standard of care relies on chronic enzyme replacement therapy or oral chaperone therapy, and ST-920 is designed as a one-time treatment intended to provide durable alpha-galactosidase A expression. The transaction reflects continued consolidation in the gene therapy sector, as financially distressed developers sell late-stage assets to larger, better-capitalized companies capable of completing regulatory review and commercialization.
References
Sangamo Therapeutics Selects Successful Bidders Following Competitive Asset Auction for $163.55 Million in Cash Consideration at Closing and Up to $100 Million in Potential Milestones. News release. Sangamo Therapeutics. August 12, 2026. https://www.streetinsider.com/Globe+Newswire/Sangamo+Therapeutics+Selects+Successful+Bidders+Following+Competitive+Asset+Auction+for+$163.55+Million+in+Cash+Consideration+at+Closing+and+Up+to+$100+Million+in+Potential+Milestones/26912549.html
PTC to Expand Rare Disease Portfolio with Acquisition of BLA-Stage ST-920 Fabry Disease Program. News release. PTC Therapeutics. August 12, 2026. https://www.prnewswire.com/news-releases/ptc-to-expand-rare-disease-portfolio-with-acquisition-of-bla-stage-st-920-fabry-disease-program-302850091.html
Sangamo Therapeutics Presents Detailed Data from Registrational STAAR Study in Fabry Disease at WORLDSymposium 2026. News release. Sangamo Therapeutics. February 3, 2026. https://investor.sangamo.com/news-releases/news-release-details/sangamo-therapeutics-presents-detailed-data-registrational-0
PTC's $211M bid wins Sangamo auction, teeing up 'special opportunity' to enter Fabry market. Fierce Biotech. August 2026. https://www.fiercebiotech.com/biotech/ptcs-211m-bid-wins-sangamo-auction-teeing-special-opportunity-enter-fabry-market
