BioMarin Pays $70 Million to Widen Its Fabry Franchise With Subcutaneous Enzyme Therapy

BioMarin Pharmaceutical is doubling down on Fabry disease, and the math behind the move is straightforward: roughly 60% to 70% of Fabry patients cannot use the company's flagship oral therapy. That gap is now the target of a fresh licensing deal.

The San Rafael, California company announced Thursday it has secured exclusive worldwide rights, excluding South Korea, to HM15421/GC1134A, a clinical-stage enzyme replacement therapy developed by GC Biopharma and Hanmi Pharm. BioMarin is paying $70 million upfront. GC and Hanmi retain rights in South Korea and stand to collect up to $405 million in additional milestone payments, plus royalties on any approved product.

Fabry disease is a rare, inherited lysosomal storage disorder. Mutations in the GLA gene leave patients deficient in alpha-galactosidase A, the enzyme responsible for breaking down a fatty substance called globotriaosylceramide, or Gb3. Without enough of the enzyme, Gb3 accumulates in tissue, driving organ damage and raising cardiovascular risk. It is a small but persistent market, and BioMarin has been building a presence in it piece by piece.

A Second Asset, A Different Mechanism

The current standard of care is enzyme replacement therapy delivered by infusion. Sanofi and Chiesi Group each market engineered versions of alpha-galactosidase A, and Takeda's Replagal holds approvals in Europe, Japan, and other markets, though not in the United States. All three require infusions every other week, a dosing burden that has long frustrated patients and physicians alike.

HM15421/GC1134A is designed to be different. It has an extended half-life and improved stability, properties that allow for subcutaneous dosing rather than infusion. BioMarin has cited preclinical data showing efficacy on renal function, vascular health, and peripheral nervous system outcomes, though the companies have not disclosed what dosing interval they expect to pursue. GC and Hanmi have advanced the candidate into a global Phase 1/2 trial, and once that study wraps, BioMarin takes over clinical development and any eventual commercialization outside South Korea.

This is not BioMarin's first move in Fabry. The company entered the disease area through its $4.8 billion acquisition of Amicus Therapeutics, which closed earlier this year and brought Galafold into the fold. Galafold works differently than the enzyme replacement drugs on the market. It is a small molecule that binds to and stabilizes a patient's own alpha-Gal A enzyme, helping it reach the lysosome where it can do its job. The catch is eligibility. Only patients with a GLA gene variant amenable to the drug can use it, which leaves a majority of the Fabry population without access.

Galafold has performed well commercially. Amicus reported $521.7 million in sales for the drug in 2025, up nearly 14% from the prior year. But that revenue ceiling is defined by genetics, not demand. HM15421/GC1134A is BioMarin's answer to the patients Galafold cannot reach.

Galafold is one of seven enzyme therapies now in BioMarin's broader portfolio, a reminder that the company's core competency, and its acquisition strategy, centers on this therapeutic class. William Blair analyst Lachlan Hanbury-Brown framed the logic of the deal plainly in a research note. "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," he wrote.

That framing matters. BioMarin is not entering Fabry disease cold. It already has the commercial infrastructure, physician relationships, and regulatory experience to support a launch if HM15421/GC1134A clears trials. The $70 million upfront payment is modest relative to the $4.8 billion Amicus deal, but it extends the same strategic thesis: use existing Fabry infrastructure to capture adjacent patient populations through licensing rather than outright acquisition.

Competition is not standing still. PTC Therapeutics won the Sangamo Therapeutics bankruptcy auction over the summer for Fabry gene therapy ST-920, closing that acquisition in September. PTC has said a rolling FDA submission is expected to be complete in the fourth quarter of this year. A one-time gene therapy, if approved, would represent a fundamentally different value proposition than any enzyme replacement product, subcutaneous or otherwise. Patients weighing lifelong dosing against a single treatment may lean toward the latter if efficacy and safety hold up.

The Bottom Line

BioMarin's bet is incremental rather than transformative. The $70 million outlay is small change against the company's balance sheet, and the $405 million in potential milestones is backloaded against years of clinical development and regulatory review that have not yet started in earnest. The real prize is addressable market expansion: moving from the 30% to 40% of Fabry patients eligible for Galafold toward something closer to the full patient population, assuming HM15421/GC1134A clears Phase 1/2 and subsequent trials.

Risks are clear. The drug is early stage, dosing intervals remain undisclosed, and gene therapy competition from PTC's ST-920 could reshape the competitive landscape before BioMarin's asset reaches the market. Investors should watch for Phase 1/2 readouts, particularly around dosing frequency, since that detail will determine whether HM15421/GC1134A meaningfully improves on the every-other-week infusion standard or merely matches it with a different delivery method. For a company whose Fabry strategy now rests on two distinct mechanisms acquired through two distinct deals, execution on this second asset will be the real test of whether the broader Amicus-driven push into rare disease enzyme therapy pays off.