HM15421/GC1134A could become the first subcutaneous enzyme replacement therapy for Fabry disease, with BioMarin paying $70 million upfront.
BioMarin Pharmaceutical (BioMarin) announced on October 29, 2026, that it has entered into an
"This agreement reflects our growing commitment to the Fabry community, building on the acquisition of Amicus earlier this year," said
BioMarin will make an up-front payment of $70 million.¹ GC and Hanmi are jointly eligible to receive up to an additional $405 million upon completion of certain development and commercial milestones, plus tiered royalties on net sales.¹ Following an
HM15421/GC1134A is a human recombinant alpha-galactosidase A (α-Gal A) enzyme. It is designed to extend half-life and improve stability relative to currently available ERTs, supporting subcutaneous dosing.¹ According to BioMarin, it has the potential to be the first subcutaneous ERT for Fabry disease.¹ The company said the candidate showed differentiated efficacy in preclinical studies across measures including renal function, vascular health, and peripheral nervous system outcomes.¹ FDA granted HM15421/GC1134A orphan drug designation in 2024.¹
The phase 1/2 study (NCT06858397) is an open-label, nonrandomized proof-of-concept trial sponsored by GC Biopharma, with Hanmi as a collaborator. It plans to enroll 18 adults with Fabry disease across low-, mid-, and high-dose cohorts of subcutaneous HM15421/GC1134A.² The primary endpoint is the incidence and nature of adverse events over 48 weeks.²
BioMarin completed its acquisition of Amicus Therapeutics, valued at approximately $4.8 billion, in April 2026.³ The deal added migalastat (Galafold), the first oral treatment for Fabry disease, and the Pompe disease therapy cipaglucosidase alfa-atga (Pombiliti) plus miglustat (Opfolda).³ Because migalastat is used only in patients whose GLA mutations are amenable to the drug, an ERT could give BioMarin a Fabry option for patients outside that group.¹
Fabry disease is a rare, X-linked lysosomal storage disorder caused by variants in the GLA gene that reduce α-Gal A activity.¹ The resulting buildup of globotriaosylceramide (GL-3) in lysosomes is believed to cause symptoms including pain, kidney failure, and increased risk of heart attack and stroke.¹ The reported annual incidence of 1 in 100,000 may underestimate the disease's true prevalence, and heterozygous females can have symptoms ranging from very mild to severe.⁴ ERT using recombinant human α-Gal A is a disease-specific treatment.⁴ If its clinical profile is confirmed, a long-acting,
HM15421/GC1134A remains in early clinical development, and no clinical efficacy or safety data have been reported. The ongoing study's primary endpoint is safety, not efficacy. Efficacy claims are based on preclinical studies, which may not predict outcomes in patients. The companies did not disclose dosing frequency, the milestone schedule, or royalty rates, and most of the deal's value depends on future milestones.
