PTC Therapeutics Targets Fabry Gene Therapy in $111M Bankruptcy Auction Deal

PTC Therapeutics plans to acquire ST-920, a one-time Fabry disease gene therapy, through a competitive bankruptcy auction for $111 million in cash, plus up to $100 million in U.S. regulatory milestones. The deal includes no international milestones, sales milestones or royalties. ST-920’s accelerated-approval application is expected to rely on 52-week eGFR data from the Phase I/II STAAR study, which showed sustained enzyme activity and renal-function improvements. The therapy has FDA Regenerative Medicine Advanced Therapy, Orphan Drug and Fast Track designations, with confirmatory 104-week data planned for full approval. PTC expects to leverage its existing rare-disease commercial and regulatory infrastructure, with manufacturing preparations underway through Thermo Fisher. Management says the transaction should not change its target of reaching cash-flow breakeven in 2026.

PTC Therapeutics NASDAQ: PTCT plans to acquire the ST-920 Fabry disease gene therapy asset through a competitive bankruptcy auction, positioning the company to add a potential one-time treatment to its rare disease portfolio while using its existing global commercial and regulatory infrastructure. Chief Executive Officer Matthew Klein said the transaction includes a $111 million cash payment at closing, subject to customary conditions, along with up to $100 million in U.S. regulatory milestones. PTC would pay $80 million upon U.S. accelerated approval and $20 million upon U.S. full approval. Klein said the agreement includes no additional international regulatory milestones, sales milestones or royalties.

“This was an opportunity to advance our strategy of leveraging our accomplished existing rare disease global commercial infrastructure and accelerate short- and intermediate-term revenue growth,” Klein said.

ST-920 Program and Regulatory Path ST-920 is a one-time intravenous adeno-associated virus, or AAV, gene replacement therapy intended to enable production of alpha-galactosidase A, an enzyme deficient in people with Fabry disease. Klein said treatment does not require pre-treatment or concurrent immunosuppression. The planned biologics license application, or BLA, for accelerated approval is based on results from the Phase I/II STAAR study, which enrolled 33 adult patients with Fabry disease. The key efficacy endpoint for the BLA is the mean positive estimated glomerular filtration rate, or eGFR, slope from baseline through week 52 following treatment. Klein said the company views the positive eGFR slope as differentiated from other Fabry therapies, which have demonstrated improved renal function but continued negative eGFR slopes from baseline. The study also showed increased alpha-galactosidase A activity maintained for as long as four and a half years in the earliest treated participant, alongside evidence of sustained renal-function improvement, according to the company. All 18 participants who were receiving enzyme replacement therapy, or ERT, at the start of the study were withdrawn from ERT during the trial, Klein said. The most common adverse events reported were fever, COVID-19 and headache. ST-920 has received Regenerative Medicine Advanced Therapy, Orphan Drug and Fast Track designations from the FDA. The nonclinical and clinical modules of the rolling BLA submission have already been submitted, while the chemistry, manufacturing and controls package is expected to be submitted in the fourth quarter of 2026. The 104-week STAAR data are planned to provide confirmatory evidence for full approval. Klein said PTC’s base case assumes accelerated approval based on the existing regulatory plan, though the company will