BioMarin Pharmaceutical’s extensive experience in enzyme replacement expanded to Fabry disease through a business deal. Now the company is expanding its scope in Fabry, acquiring rights to a clinical-stage GC Biopharma and Hanmi Pharm drug that could reach a wider range of patients, offering them less burdensome dosing than currently available enzyme replacement therapies.
According to deal terms announced Thursday, BioMarin is paying $70 million up front for the drug, HM15421/GC1134A. San Rafael, California-based BioMarin gains global rights excluding South Korea, where GC and Hanmi retain rights to the enzyme replacement therapy.
Fabry is a lysosomal storage disorder, an inherited condition in which mutations in the GLA gene lead to a deficiency of alpha-galactosidase A. This enzyme is needed to break down a type of fat called globotriaosylceramide (Gb3). Lacking the key enzyme, Gb3 builds up in patients’ tissues, leading to a range of organ problems and a higher risk of cardiovascular complications.
Standard Fabry treatment is enzyme replacement therapy. Sanofi and Chiesi Group each market engineered versions of the key enzyme. Takeda Pharmaceutical’s Replagal, also an engineered enzyme, has regulatory approvals in Europe, Japan, and other markets around the world, but not the U.S. All three products are administered as infusions every other week.
HM15421/GC1134A is a long-acting enzyme replacement therapy designed with an extended half-life and improved stability, properties that enable subcutaneous dosing. According to BioMarin, preclinical research showed the drug demonstrated efficacy on measures such as renal function, vascular health, and peripheral nervous system outcomes. The companies have not specified the dosing interval they expect for HM15421/GC1134A. GC and Hanmi have advanced this therapeutic candidate to a global Phase 1/2 trial.
BioMarin’s presence in Fabry is through Galafold, a commercialized drug that came with the $4.8 billion acquisition of Amicus Therapeutics that closed earlier this year. Galafold works with the alpha-Gal A enzyme that a patient already has. This small molecule binds to the enzyme, stabilizing it so it can travel to a part of the cell called the lysosome. There, the enzyme can carry out its role of breaking down fatty substances. But eligibility for Galafold requires a patient to have a GLA gene variant that is amenable to the drug.
Galafold is one of seven enzyme therapies in BioMarin’s portfolio. According to Amicus’s financial reports, this product generated $521.7 million in sales in 2025, a nearly 14% increase compared to the previous year. In a research note, Willliam Blair analyst Lachlan Hanbury-Brown said HM15421/GC1134 will enable BioMarin to address a broader range of patients who are ineligible for Galafold, which is about 60% to 70% of the Fabry disease population.
“This acquisition makes sense given the company’s current footprint in Fabry disease, expertise in [enzyme replacement therapies], and global capabilities to drive potential successful HM15421/GC1134 launch, if approved,” Hanbury-Brown said.
After the ongoing Phase 1/2 study, BioMarin will take over responsibility for further clinical development and potential commercialization of HM15421/GC1134A outside of South Korea. Beyond BioMarin’s upfront payment, GC and Hanmi could receive up to $405 million more if the Fabry therapy achieves development and commercialization milestones. GC and Hanmi are also eligible for royalties from sales of an approved product.
While HM15421/GC1134A gives BioMarin the opportunity to bring Fabry patients less burdensome and less frequent dosing, patients may soon have the option of a one-time treatment. Over the summer, PTC Therapeutics won the Sangamo Therapeutics bankruptcy auction for Fabry gene therapy ST-920. When the acquisition closed in September, PTC said a rolling FDA submission is expected to be complete in the fourth quarter of this year.
Photo Illustration: Piotr Swat/SOPA Images/LightRocket, via Getty Images
