SPRB: First-Mover in MPS IIIB White Space; Initiating with a Buy Rating and $123 PT

Research evidence excerpt

SPRB: First-Mover in MPS IIIB White Space; Initiating with a Buy Rating and $123 PT

June 16, 2026

Debjit Chattopadhyay, Ph.D. debjit.chattopadhyay@guggenheimpartners.com SPRB: First-Mover in MPS IIIB White Space; Initiating

212 823 6584 with a Buy Rating and $123 PT

Hannah Wei

hannah.wei@guggenheimpartners.com

212 518 5896 Key Message: We are initiating coverage of Spruce Biosciences, Inc. (SPRB) with a BUY

rating and $123 price target. The company expects a BLA submission for its lead asset Moritz Reiterer, Ph.D.

moritz.reiterer@guggenheimpartners.com TA-ERT during 4Q26. If approved, TA-ERT is positioned to become the first and only

212 372 6368 FDA-approved therapy for MPS IIIB, an ultra-orphan indication with significant pricing

power. The regulatory path has been potentially de-risked by AVLAYAH (DNLI), which Ry Forseth, Ph.D. was granted a biomarker-based accelerated approval. Our physician checks point to ry.forseth@guggenheimpartners.com

212 518 9226 broad utilization with peak sales exceeding $300M, which, along with a long IP, could

turn TA-ERT into a cash flow generator that can be leveraged to bolster the pipeline.

Spruce could be first-to-market in MPS IIIB, with compelling biomarker /

SPRB BUY functional data.

Spruce Biosciences, Inc. There is no FDA-approved therapy for mucopolysaccharidosis type IIIB (MPS IIIB). TA-ERT

Sector: Biotechnology is positioned to fill that white space in the ultra-orphan, CNS-penetrant lysosomal storage

disorder. With N=22 patients followed for up to six years, the clinical package provides

Initiating Coverage substantial burden of proof beyond biomarkers. Patients treated with TA-ERT experienced

Share Price $49.91 a mean decline of 91.5 ng/mL in CSF HS-NRE by week 240, with 86% of patients (19 of 22)