PTC Therapeutics has been selected as the winning bidder to acquire Sangamo Therapeutics’ ST-920 Fabry disease gene therapy program in a bankruptcy auction for $111 million upfront and up to $100 million in additional regulatory milestone payments. The acquisition could have a total value of up to $211 million.
ST-920, also known as isaralgagene civaparvovec, is a BLA-stage one-time administered AAV gene therapy being developed for Fabry disease.
PTC expects the rolling Biologics License Application submission to the FDA for accelerated approval to be completed during the fourth quarter of 2026.
If approved on the anticipated timeline, PTC sees the potential for a commercial launch in 2027.
The transaction gives PTC another late-stage rare disease program that can potentially use the company’s existing regulatory and commercial infrastructure rather than requiring the creation of a new commercial organization.
PTC said the acquisition is not expected to affect its goal of reaching cash flow breakeven in 2026.
Fabry disease is a rare inherited lysosomal storage disorder caused by mutations in the GLA gene.
Those mutations result in deficient alpha-galactosidase A enzyme activity and can lead to accumulation of globotriaosylceramide, or Gb3, in cells.
The disease can affect the kidneys, heart, nervous system, eyes, gastrointestinal system and skin.
PTC estimates approximately 11,000 people in the U.S. live with Fabry disease, with similar prevalence in other markets where the company could potentially commercialize ST-920.
The gene therapy is designed to provide long-term production of the deficient alpha-galactosidase A enzyme following a single administration.
PTC said ST-920 has demonstrated sustained increases in enzyme activity and reductions in Gb3 levels, potentially reducing the burden associated with chronic enzyme replacement therapy.
ST-920 has received Regenerative Medicine Advanced Therapy, Orphan Drug and Fast Track designations from the FDA.
The regulatory submission is supported by results from the Phase 1/2 STAAR study.
At 52 weeks, the study demonstrated a positive mean annualized estimated glomerular filtration rate slope following ST-920 administration, along with evidence of favorable effects on cardiac function and quality of life.
PTC highlighted the renal results as a differentiating feature compared with other Fabry treatments that showed improved kidney function but still produced a negative eGFR slope from baseline.
All study participants who were receiving enzyme replacement therapy at the beginning of the trial were subsequently withdrawn from ERT.
The company said durability has been observed for as long as 4.5 years in the earliest treated participant, with sustained increases in alpha-galactosidase A activity.
ST-920 also does not require routine prophylactic or post-infusion systemic immunosuppressive treatment.
The accelerated approval BLA is based on annualized eGFR at Week 52 as an intermediate clinical endpoint aligned with the FDA.
Results at 104 weeks are planned to provide confirmatory evidence supporting traditional approval.
The nonclinical and clinical portions of the rolling BLA have already been submitted.
The chemistry, manufacturing and controls package is expected to be submitted during the fourth quarter of 2026.
PTC also intends to seek regulatory approvals outside the U.S. using its existing international rare disease infrastructure.
Completion of the acquisition remains subject to definitive documentation, bankruptcy court approval, antitrust review and other customary closing conditions.
The transaction is expected to close in late third quarter or early fourth quarter 2026.
KEY QUOTES:
“This transaction advances our strategy of leveraging our accomplished existing rare disease global commercial infrastructure to accelerate short- and intermediate-term revenue growth.”
“The ST-920 gene therapy program puts another innovative and valuable product in the demonstrated capable hands of our customer-facing teams. 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.”
“We look forward to working to bring ST-920 to all individuals who may benefit from this therapy as quickly as possible.”
Matthew B. Klein, M.D., CEO of PTC Therapeutics
