Single-asset BLA filing for a fatal childhood brain disease with no approved treatment; FDA alignment confirmed, but accelerated approval path is the bet

Spruce Biosciences is a clinical-stage company developing an enzyme replacement therapy for MPS IIIB, a fatal childhood brain disease with no approved treatment; the therapy is not yet approved and is being submitted for accelerated FDA review.

Tralesinidase alfa is an enzyme replacement therapy delivered intracerebroventricularly for MPS IIIB, a uniformly fatal lysosomal storage disease in children with no approved treatment. The thesis resolves on whether six-year efficacy data, accepted under accelerated approval, survives FDA review of the BLA submitted in Q4 2026. The structural risk is the single-arm, non-randomized nature of the supporting data, with confirmatory trial enrollment of only approximately 14 children creating a fragile post-approval verification backbone.