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

Key Points

• 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 assess longer-term data as the review advances. He added that FDA correspondence reviewed during diligence included confirmation from current agency leadership regarding the plan to use eGFR slope at week 52 for accelerated approval and eGFR slope at week 104 for confirmation.

Commercial Opportunity and Patient Reach

PTC estimates there are approximately 11,000 people with Fabry disease in the United States, with similar prevalence rates in other countries where it intends to seek registration. Klein said Fabry patients are concentrated in centers of excellence, and newborn screening programs in several U.S. states and countries may support earlier diagnosis.

Eric Pauwels, PTC’s chief business officer, said the company sees potential for broad use across Fabry patients, including those previously treated with ERT. He noted that ERT is used by roughly two-thirds of patients in key markets including the U.S., Japan, Europe and Brazil, but requires infusions every two weeks and may involve pre-medication and travel to clinics.

“Early diagnosis and early treatment means better outcomes,” Pauwels said, adding that ST-920’s one-time administration and durability data in kidney and heart function could support its value proposition.

Klein said the clinical trial had broad inclusion criteria covering men and women, varied genetic backgrounds and differing treatment histories. However, he noted that patients with AAV6 antibodies would not be eligible under the trial criteria, and the study required participants to have a GFR above 40.

Manufacturing, Infrastructure and Financial Impact

PTC said it performed detailed clinical, regulatory, manufacturing and quality diligence before becoming the successful bidder. Klein said Thermo Fisher is the contract development and manufacturing organization for the product and described it as a “best-in-brand” manufacturer. He said process specifications are established, process-performance qualification lots are underway, and supply generated through those lots is expected to support launch readiness.

The company also said it reviewed comparability between products used during different phases of clinical development and the planned commercial product, concluding that the manufacturing transition should not be an issue.

Klein said PTC has existing commercial, market-access and regulatory capacity to support a launch without a significant build-out. The company plans to evaluate registration sequencing beyond the U.S., including in Japan, Europe, Latin America, the Middle East and other markets where it has an established rare disease presence.

Management said the acquisition is not expected to alter its goal of reaching cash flow breakeven in 2026. Klein said the transaction preserves financial flexibility for further business-development activity while giving PTC the opportunity to pursue what it views as a meaningful global Fabry disease treatment opportunity.

About PTC Therapeutics (NASDAQ:PTCT)

PTC Therapeutics, Inc is a biopharmaceutical company focused on the discovery, development and commercialization of small molecule and biologic therapies for the treatment of rare genetic disorders. Since its founding in 1998, PTC has dedicated its efforts to addressing high unmet medical needs by targeting underlying genetic causes of disease. The company's research platform emphasizes mechanisms such as nonsense suppression and RNA modulation, enabling the development of novel treatments for conditions with limited therapeutic options.

Among PTC's approved products is Translarna (ataluren), a first-in-class therapy designed to treat nonsense mutation Duchenne muscular dystrophy in select markets.

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