Spruce Biosciences (Nasdaq: SPRB) said it has completed two pre-Biologics License Application (BLA) meetings with the U.S. Food and Drug Administration (FDA) and confirmed its BLA submission for tralesinidase alfa enzyme replacement therapy (TA-ERT) remains on track for the fourth quarter of 2026.

TA-ERT is being developed as a treatment for Sanfilippo Syndrome Type B (MPS IIIB), an ultra-rare fatal genetic disease affecting fewer than one in 200,000 people in the United States. There are currently no FDA-approved therapies for the condition.

According to a company statement, the FDA found Spruce's drug substance and drug product analytical comparability strategies reasonable to support the BLA following a technology transfer to a commercial-scale biologics manufacturer. The two parties also aligned on the overall content and format of the planned BLA, including the structure of integrated efficacy and safety summaries.

Spruce said it is pursuing accelerated approval based on reduction of cerebrospinal fluid heparan sulfate non-reducing ends (CSF HS-NRE) as a surrogate biomarker. The FDA previously indicated that integrated data from Spruce's completed clinical studies, combined with natural-history data, could potentially support review of TA-ERT's effect on this biomarker.

The company completed the first process performance qualification (PPQ) batch in July 2026 and said it is on track to complete the second PPQ batch in the fourth quarter of 2026. The FDA and Spruce previously agreed that data from the first PPQ batch would be included in the BLA submission, with data from the second batch provided prior to midcycle of BLA review.

TA-ERT holds Breakthrough Therapy, Fast Track, Rare Pediatric Disease, and Orphan Drug designations in the United States, and Orphan Drug Designation in the European Union. The therapy may be eligible for a rare pediatric disease priority review voucher upon approval.

TA-ERT has been administered to 22 individuals with MPS IIIB across three clinical studies, with six years of integrated safety data compiled.