Spruce Biosciences has acquired Allievex’s tralesinidase alfa ERT (previously AX 250) for the treatment of Sanfilippo Type B (MPS IIIB).
Spruce has publicly announced its intent to seek U.S. accelerated approval and commercialize in North America, the European Union, the United Kingdom, Latin America, Turkey, Asia, and other international markets.
Spruce Biosciences, Inc., a late-stage biopharmaceutical company focused on developing and commercializing novel therapies for neurological disorders with significant unmet medical need, announced on March 15 its new corporate strategy and acquisition of tralesinidase alfa enzyme replacement therapy (TA-ERT) for the treatment of Sanfilippo Syndrome Type B (MPS IIIB).
Statement from Spruce
According to Spruce’s press release, it entered into an Asset Purchase Agreement under which the company acquired an exclusive worldwide license agreement with BioMarin Pharmaceutical Inc. for TA-ERT and other enzyme replacement therapy products. TA-ERT is a fusion protein comprised of recombinant human alpha-N-acetylglucosaminidase (rhNAGLU) with modified human insulin-like growth factor 2 via an amino acid linker. TA-ERT is intended as an enzyme replacement therapy for the treatment of patients with MPS IIIB who lack rhNAGLU enzyme activity.
Spruce shares that in March 2025, “The FDA also confirmed that the completed clinical and non-clinical studies of TA-ERT were sufficient for a BLA submission and provided guidance around key design elements of a confirmatory trial, which must be initiated prior to potential accelerated approval of TA-ERT. TA-ERT has received fast-track designation, rare pediatric disease designation, and orphan drug designation in the U.S. and EU. Spruce intends to submit the BLA of TA-ERT for the treatment of MPS IIIB in the first half of 2026.”
It says that, “If the BLA is approved, Spruce intends to build a highly specialized commercial and medical affairs organization to support the commercialization of TA-ERT. Given that a relatively small number of clinicians and specialists treat most of the patients with MPS IIIB, the company believes this market can be effectively addressed with a modest-sized and targeted patient-centric field team, alongside various high-touch patient initiatives.”
“We extend our gratitude to the patient and caregiver advocates, clinicians and industry leaders who have contributed to the TA-ERT program,” said Javier Szwarcberg, MD, MPH, Chief Executive Officer of Spruce. “With no FDA-approved treatments currently available, TA-ERT has the potential to be a groundbreaking advancement for patients and families impacted by MPS IIIB.”
History of this tralesinidase alfa enzyme replacement therapy
The therapy was first developed by BioMarin Pharmaceutical. In October 2019, Allievex obtains an exclusive worldwide license for tralesinidase alfa from BioMarin. Researchers published full results from the trial, which are generally consistent with the interim findings, (“Tralesinidase Alfa ERT Found to Benefit Sanfilippo Type B Children”) in The Journal of Clinical Investigation in November 2022.
Allievex terminated its business operations in October 2023 and in July 2024 announced that it was unable to find a path forward for a potential acquiror.
In November 2024, Allievex announced that acquisition of the AX 250 (tralesinidase alfa) program had been completed. The program would transition to a new team with deep expertise, funding, and resources necessary to advance this important therapy with urgency and care.