SPRB

• Unveiled new corporate strategy focused on developing and commercializing first-in-class therapies for neurological disorders with unmet medical needs. • Acquired Tralesinidase Alfa Enzyme Replacement Therapy (TA-ERT) for the treatment of MPS IIIB, anticipating BLA submission in first half of 2026. • Discontinued development of Tralesinidase for CAH after it failed primary efficacy measures in clinical studies. • Discussed MPS IIIB disease details, including its cause, progression, and lack of existing treatments. • Highlighted clinical data of TA-ERT showing normalization of heparan sulfate levels, liver volume normalization, and stabilization of cortical gray matter volume in patients. • Outlined commercial plans for TA-ERT, including building a specialized commercial organization, leveraging marketing blueprints of other MPS drugs, and patient-centric initiatives.

• Anticipate submitting BLA for TA-ERT to FDA in first half of 2026. • Plan to initiate confirmatory Phase 3 trial for TA-ERT prior to potential accelerated approval. • Expect TA-ERT to be eligible for a priority review voucher if BLA is submitted and approved by September 2026. • Guide to approximately $10 million per quarter spend in 2025 for TA-ERT development, with an uptick to $15 million per quarter in subsequent years reflecting BLA enabling activities and commercial build.

No specific product segment financial performance with revenue contribution % provided as the focus is on the acquisition and development of Tralesinidase Alfa for MPS IIIB.

• Regulatory uncertainties regarding the accelerated approval pathway, though there are precedents with other companies using heparan sulfate as a surrogate endpoint. • Financial constraints given limited cash resources and potential impacts of the market environment on securing additional financing. • Risks associated with discontinuing prior programs and reallocating resources to TA-ERT development.

Q: What's your read on the depth of buy-in for the accelerated approval pathway at CBER currently and the realistic likelihood of it?

A: There's a regulatory precedent with companies like Ultragenyx and Denali using heparan sulfate as a surrogate for accelerated approval. FDA has honored prior commitments, and we have confidence FDA will honor agreements with the prior sponsor.

Q: What are your latest thoughts on the financing plan given limited financial resources and market environment?

A: Current cash resources extend operating plan through end of 2025. We have confidence in advancing TA-ERT program as it's highly derisked with regulatory guidance and strong clinical data, fitting market investment opportunities.

Q: Walk us down the funnel of MPS IIIB patients from TAM to eligible patients for TA-ERT?

A: Based on claims database, there are ~3.3k MPS patients in US, ~1k pediatric MPS patients, ~300 with MPS III, and we believe ~135 prevalent patients in US with ~50% addressable by TA-ERT. Incidence is ~18 new patients per year. Decision to treat based on neurocognitive stabilization/improvement and other functional aspects.

Q: Comment on the cadence of R&D spend over 2025?

A: For 2025, roughly $10 million per quarter spend on ongoing TA-ERT development. Next fiscal year, uptick to $15 million per quarter reflecting BLA enabling activities and commercial build.

Q: Talk about the confirmatory trial, FDA's view on surrogate heparan sulfate endpoint and clinical endpoint, and details on starting the trial?

A: Confirmatory trial will be 14-patient, 1:1 randomization. FDA accepts heparan sulfate as surrogate endpoint for accelerated approval. Primary clinical endpoint will be neurocognitive outcome like Bayleys questionnaire cognitive raw score. Intend to initiate trial while under review.

Q: How many identified patients in US and on TA-ERT today?

A: Prevalent patient population in US is ~135, but we haven't mapped out specific patients on TA-ERT today. Intend to have early access programs and patient self programs for eligible patients.

Q: Capital needs for plans going forward, including confirmatory study and commercial launch?

A: Need incremental capital, ~$60 million to potential approval for TA-ERT, with ~$30 million needed for BLA submission. PRV eligibility under current framework expiring Sept 30, 2026. Pricing expected to be high given meaningful benefit to patients, similar to other MPS drugs.