PTC to acquire Sangamo’s gene therapy for Fabry disease
Company to seek FDA accelerated approval of one-time therapy
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PTC Therapeutics has been selected as the winning bidder to acquire ST-920 (isaralgagene civaparvovec), a one-time gene therapy candidate for Fabry disease, from the therapy’s original developer, Sangamo Therapeutics, in a competitive bankruptcy auction.
PTC said it will leverage existing regulatory and commercial infrastructure, and expects to submit an application later this year seeking U.S. Food and Drug Administration (FDA) accelerated approval of ST-920, with a potential commercial launch in 2027.
Accelerated approval allows treatments to be marketed based on preliminary clinical trial evidence of their efficacy, with full approval being dependent on additional clinical trial data confirming those benefits.
“The ST-920 gene therapy program puts another innovative and valuable product in the demonstrated capable hands of our customer-facing teams,” Matthew B. Klein, MD, PTC’s CEO, said in a company press release. “We look forward to working to bring ST-920 to all individuals who may benefit from this therapy as quickly as possible.”
PTC also plans to pursue regulatory approval for the therapy outside the U.S.
Orphan drug, fast track designations
Fabry is caused when mutations in the GLA gene disrupt the production and/or function of the enzyme alpha-Gal A, leading to the toxic build-up of fatty molecules inside cells, damaging the kidneys, heart, and nervous system.
ST-920, given as a one-time infusion into the bloodstream, is an experimental gene therapy designed to deliver a working version of the GLA gene to liver cells, the body’s main producers of alpha-Gal A. There, it’s expected to produce active alpha-Gal A on an ongoing basis, allowing cells to clear toxic fatty molecules and ease Fabry symptoms.
ST-920 received orphan drug, fast track, and regenerative medicine advanced therapy designations in the U.S. and orphan drug status in the European Union. These designations are meant to accelerate the therapy’s clinical development and regulatory review.
The planned regulatory filing is based mainly on data from a kidney-related clinical outcome of the international Phase 1/2 STAAR trial (NCT04046224). The study involved 36 adults with Fabry, some of whom had previously been on enzyme replacement therapy (ERT).
Kidney function in STAAR was tracked with a standard measure called estimated glomerular filtration rate (eGFR), which assesses how efficiently the kidneys are able to filter blood.
Top-line data demonstrated that ST-920 improved kidney function one year after infusion. All 18 patients who began the study on ERT permanently discontinued it after ST-920. Reductions in disease severity and gastrointestinal symptoms were also observed, as well as improvements in quality of life.
Longer-term results showed that ST-920 was associated with kidney function improvements and heart function stabilization for up to two years after treatment, regardless of sex, prior ERT use, type of Fabry disease, or degree of kidney impairment before gene therapy.
The one-time therapy has been generally well tolerated. Adverse events were mostly mild to moderate, the most common being fever, headache, COVID-19, cold-like symptoms, fatigue, and nausea.
The FDA had previously confirmed to Sangamo that STAAR data could serve as a basis for accelerated approval. Because all STAAR participants who received the gene therapy had reached the one-year follow-up mark, the FDA allowed Sangamo to take the next step toward accelerated approval.
The terms of PTC’s acquisition of ST-920 include a $111 million upfront payment and up to $100 million in contingent milestone payments based on certain regulatory approvals. This includes definitive documentation, bankruptcy court approval, antitrust review, and other customary closing conditions. The deal is expected to close by the end of the year.
“This transaction advances our strategy of leveraging our accomplished existing rare disease global commercial infrastructure to accelerate short- and intermediate-term revenue growth,” Klein said.
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