BioMarin Adds a Second Fabry Program With a $70 Million Bet on Less Burdensome Dosing
BioMarin Pharmaceutical is deepening its push into Fabry disease with a new clinical-stage enzyme replacement therapy that could reach patients who are not candidates for its existing oral asset. The company paid $70 million upfront for global rights, excluding South Korea, to HM15421/GC1134A, a long-acting therapy developed by GC Biopharma and Hanmi Pharm. If the program succeeds, BioMarin would control development and commercialization outside South Korea after the ongoing Phase 1/2 study is complete.
Fabry disease is a lysosomal storage disorder driven by mutations in the GLA gene, which leave patients deficient in alpha-galactosidase A. Without that enzyme, globotriaosylceramide, or Gb3, accumulates inside tissues and drives progressive organ injury. The clinical burden is familiar to anyone who treats this disease: renal involvement, vascular disease, neuropathic symptoms, and a cardiovascular risk profile that can worsen over time as substrate continues to build up. The biology explains why replacement strategies remain central. When the missing enzyme is restored, lysosomal clearance can resume and downstream tissue injury may slow.
BioMarin’s new asset is designed to make that replacement approach easier to administer. HM15421/GC1134A is described as a long-acting enzyme replacement therapy with an extended half-life and improved stability, features that allow subcutaneous dosing. Current standard enzyme replacement therapies from Sanofi and Chiesi Group are infused every other week, a schedule that can be burdensome for patients and care teams alike. Takeda’s Replagal is also an engineered enzyme, though it is not approved in the U.S. The new candidate has not yet had a dosing interval disclosed, but the development concept is clear: reduce the treatment burden without sacrificing the biologic effect of enzyme replacement.
The contrast with BioMarin’s existing Fabry asset is sharp.
Galafold, which came with the company’s acquisition of Amicus Therapeutics earlier this year, works differently. It is a small molecule that binds to a patient’s own alpha-Gal A enzyme, stabilizing it so the enzyme can reach the lysosome and do its work. That mechanism is useful, but only for patients with GLA variants considered amenable to the drug. In practical terms, eligibility excludes a large share of the Fabry population. William Blair analyst Lachlan Hanbury-Brown estimated that HM15421/GC1134A could help BioMarin address a broader segment of patients, including the 60% to 70% who are ineligible for Galafold.
A Broader Commercial Reach Than Galafold Alone
BioMarin now has two distinct Fabry strategies: one centered on pharmacologic chaperoning of residual enzyme function, and another centered on direct enzyme replacement. The commercial logic is straightforward. Galafold already generated $521.7 million in 2025 sales, nearly 14% above the prior year, but it is limited by genotype eligibility. A new enzyme therapy expands the company’s reach to patients who cannot benefit from that mechanism. In a rare disease franchise, that matters because treatment options are often dictated less by physician preference than by molecular eligibility.
Long-acting enzyme replacement could also shift the treatment experience. Every-other-week infusions are effective for some patients, but they remain time-consuming and system dependent. A subcutaneous option, even before its final schedule is known, carries a different kind of promise: fewer infusion visits, less dependence on infusion infrastructure, and potentially better adherence over years of chronic therapy. For a disease that demands lifelong management, those operational differences can shape whether patients stay on treatment.
BioMarin has not given dosing details for HM15421/GC1134A, but the company cited preclinical evidence across renal function, vascular health, and peripheral nervous system outcomes. Those are not random endpoints in Fabry disease. They track with the organ systems most affected by ongoing Gb3 accumulation. Renal injury can drive long-term morbidity, vascular dysfunction can raise cardiovascular risk, and peripheral nerve involvement contributes to pain and functional decline. A therapy that can reach those compartments more efficiently would fit the disease biology well, though the clinical proof still has to be earned in humans.
Development Risk Remains Even as the Asset Fits the Franchise
BioMarin is not buying a marketed product. It is buying a clinical-stage program with real promise and real uncertainty. The ongoing Phase 1/2 trial remains the first major proof point, and after that BioMarin will assume responsibility for further development and potential commercialization outside South Korea. The deal structure reflects the usual balance between upfront conviction and downstream risk: $70 million now, up to $405 million more in development and commercialization milestones, plus royalties if the therapy reaches the market.
The timing also places BioMarin in a more crowded Fabry field. PTC Therapeutics acquired ST-920, a Fabry gene therapy, through the Sangamo bankruptcy process, and the company has said a rolling FDA submission is expected to be complete in the fourth quarter of this year. Gene therapy and enzyme replacement are not interchangeable, but they do compete for clinical attention in the same disease area. A one-time genetic treatment would be structurally different from chronic replacement therapy, while a long-acting enzyme product aims to solve a narrower problem: improving durability and convenience within the existing treatment paradigm.
If approved, HM15421/GC1134A would not replace every other Fabry therapy. It would likely sit alongside them, filling a specific gap for patients who need enzyme replacement but want a less burdensome route of administration than biweekly infusion. That niche may be large enough to matter clinically and commercially, especially given the sizable share of patients outside Galafold’s eligibility window. The question left open by the deal is not whether Fabry patients need more options. They do. The question is whether a subcutaneous, longer-acting enzyme can deliver the right balance of biologic activity, durability, and tolerability in a disease where treatment decisions are often made for the long haul.
For now, the transaction gives BioMarin a second path in Fabry disease and a stronger foothold in a therapeutic area already familiar to the company. The price buys access to a candidate that may extend enzyme replacement to patients left out by chaperone therapy, while leaving the hardest work — human efficacy, safety, and the final dosing strategy — still ahead in development.