License Agreements	3 Months Ended
Mar. 31, 2026
Research and Development [Abstract]
License Agreements	7. License Agreements BioMarin Pharmaceutical, Inc. On October 4, 2024, the Company entered into that certain Asset Purchase Agreement (the “Allievex Purchase Agreement”) with AVX (ABC), LLC, a Delaware limited liability company, in its sole and limited capacity as the assignee for the benefit of creditors of Allievex Corporation (“Allievex”). Pursuant to the Allievex Purchase Agreement, the Company acquired all intellectual property and inventory relating to Allievex's product candidates and that certain Exclusive License Agreement, by and between BioMarin Pharmaceutical Inc. (“BioMarin”) and Allievex, dated October 22, 2019 (the “BioMarin License Agreement”). As consideration, the Company paid $5.0 million to Allievex in November 2024. The Company also assumed certain liabilities of Allievex of $7.8 million, which have been fully paid as of March 31, 2026. The Company also recorded an estimated receivable of $2.6 million in other current assets on the balance sheet related to the completed Allievex bankruptcy proceedings which was fully collected by the Company in January 2026. The Company also assumed the obligations of Allievex to pay BioMarin up to $25.5 million for the first MPS IIIB product and up to an aggregate of $100.0 million per licensed product upon the achievement of certain sales milestones. In addition, the Company is required to pay to BioMarin certain (i) high-single digit to low-double digit tiered royalties on aggregate annual net sales of licensed MPS IIIB products during the applicable royalty term, subject to certain customary reductions and floors. No amounts were paid by the Company to BioMarin nor were any due as of March 31, 2026. The Company may terminate the BioMarin License Agreement at any time for convenience upon prior written notice provided within a specified period of time. BioMarin may terminate the BioMarin License Agreement upon written notice if the Company (i) challenges the validity, enforceability or scope of any of the patents licensed by the Company under the BioMarin License Agreement, subject to certain conditions, or (ii) ceases all material research and development activity for any licensed product for a specified period of time, subject to certain exceptions. Either the Company or BioMarin may also terminate the BioMarin License Agreement (i) in the event the other party shall have materially breached its obligations thereunder and such default shall have continued for a specified period after written notice thereof or (ii) upon the bankruptcy or insolvency of the other party. HBM Alpha Therapeutics, Inc. On January 15, 2025, the Company entered into a collaboration and license agreement (the “HBM License Agreement”) with HBM Alpha Therapeutics, Inc. (“HBM”). Under the terms of the HBM License Agreement, HBM granted the Company a limited exclusivity, royalty bearing, and sublicensable license to certain technology, patent rights, manufacturing rights, know-how, and proprietary materials relating to SPR202. As consideration, the Company made a one-time upfront payment to HBM of $5.0 million in February 2025. Additionally, in January 2025, the Company issued pre-funded warrants to HBM and its affiliates that in total were to be equal to 4.99% of the Company's outstanding common stock as of the date of exercise of such pre-funded warrants. In June 2025, the Company amended the pre-funded warrants to extend the exercise period to December 2025. In December 2025, these pre-funded warrants were fully exercised. The Company concluded that the rights acquired under the HBM License Agreement have no alternative future use. Therefore, the consideration paid of $5.0 million, along with the initial fair value of the pre-funded warrants issued of $0.7 million, was recognized as acquired in-process research and development expense, which was reported as a component of research and development expense for the three months ended March 31, 2025. The Company is also obligated to pay HBM up to an aggregate of $390.0 million upon the achievement of certain development, regulatory, and sales milestones. In addition, the Company is required to pay to HBM certain mid to high-single digit tiered royalties on aggregate annual net sales of licensed products during the applicable royalty term, subject to certain customary reductions. The Company may terminate the HBM License Agreement on a licensed product-by-licensed product basis or in its entirety at any time for convenience upon prior written notice provided within a specified period of time. Either the Company or HBM may also terminate the HBM License Agreement (i) in the event the other party shall have materially breached its obligations thereunder and such default shall have continued for a specified period after written notice thereof or (ii) upon the bankruptcy or insolvency of the other party. HBM may terminate the HBM License Agreement upon prior written notice if the Company (i) ceases all development or commercialization activities for a specified period of time, subject to certain exceptions, or (ii) challenges the validity, enforceability or scope of any of the patents licensed by the Company to HBM under the HBM License Agreement, subject to certain conditions.

License Agreements

3 Months Ended

Mar. 31, 2026

7. License Agreements

BioMarin Pharmaceutical, Inc.

On October 4, 2024, the Company entered into that certain Asset Purchase Agreement (the “Allievex Purchase Agreement”) with AVX (ABC), LLC, a Delaware limited liability company, in its sole and limited capacity as the assignee for the benefit of creditors of Allievex Corporation (“Allievex”). Pursuant to the Allievex Purchase Agreement, the Company acquired all intellectual property and inventory relating to Allievex's product candidates and that certain Exclusive License Agreement, by and between BioMarin Pharmaceutical Inc. (“BioMarin”) and Allievex, dated October 22, 2019 (the “BioMarin License Agreement”).

As consideration, the Company paid $5.0 million to Allievex in November 2024. The Company also assumed certain liabilities of Allievex of $7.8 million, which have been fully paid as of March 31, 2026. The Company also recorded an estimated receivable of $2.6 million in other current assets on the balance sheet related to the completed Allievex bankruptcy proceedings which was fully collected by the Company in January 2026.

The Company also assumed the obligations of Allievex to pay BioMarin up to $25.5 million for the first MPS IIIB product and up to an aggregate of $100.0 million per licensed product upon the achievement of certain sales milestones. In addition, the Company is required to pay to BioMarin certain (i) high-single digit to low-double digit tiered royalties on aggregate annual net sales of licensed MPS IIIB products during the applicable royalty term, subject to certain customary reductions and floors. No amounts were paid by the Company to BioMarin nor were any due as of March 31, 2026.

The Company may terminate the BioMarin License Agreement at any time for convenience upon prior written notice provided within a specified period of time. BioMarin may terminate the BioMarin License Agreement upon written notice if the Company (i) challenges the validity, enforceability or scope of any of the patents licensed by the Company under the BioMarin License Agreement, subject to certain conditions, or (ii) ceases all material research and development activity for any licensed product for a specified period of time, subject to certain exceptions. Either the Company or BioMarin may also terminate the BioMarin License Agreement (i) in the event the other party shall have materially breached its obligations thereunder and such default shall have continued for a specified period after written notice thereof or (ii) upon the bankruptcy or insolvency of the other party.

HBM Alpha Therapeutics, Inc.

On January 15, 2025, the Company entered into a collaboration and license agreement (the “HBM License Agreement”) with HBM Alpha Therapeutics, Inc. (“HBM”). Under the terms of the HBM License Agreement, HBM granted the Company a limited exclusivity, royalty bearing, and sublicensable license to certain technology, patent rights, manufacturing rights, know-how, and proprietary materials relating to SPR202.

As consideration, the Company made a one-time upfront payment to HBM of $5.0 million in February 2025. Additionally, in January 2025, the Company issued pre-funded warrants to HBM and its affiliates that in total were to be equal to 4.99% of the Company's outstanding common stock as of the date of exercise of such pre-funded warrants. In June 2025, the Company amended the pre-funded warrants to extend the exercise period to December 2025. In December 2025, these pre-funded warrants were fully exercised.

The Company concluded that the rights acquired under the HBM License Agreement have no alternative future use. Therefore, the consideration paid of $5.0 million, along with the initial fair value of the pre-funded warrants issued of $0.7 million, was recognized as acquired in-process research and development expense, which was reported as a component of research and development expense for the three months ended March 31, 2025.

The Company is also obligated to pay HBM up to an aggregate of $390.0 million upon the achievement of certain development, regulatory, and sales milestones. In addition, the Company is required to pay to HBM certain mid to high-single digit tiered royalties on aggregate annual net sales of licensed products during the applicable royalty term, subject to certain customary reductions.

The Company may terminate the HBM License Agreement on a licensed product-by-licensed product basis or in its entirety at any time for convenience upon prior written notice provided within a specified period of time. Either the Company or HBM may also terminate the HBM License Agreement (i) in the event the other party shall have materially breached its obligations thereunder and such default shall have continued for a specified period after written notice thereof or (ii) upon the bankruptcy or insolvency of the other party. HBM may terminate the HBM License Agreement upon prior written notice if the Company (i) ceases all development or commercialization activities for a specified period of time, subject to certain exceptions, or (ii) challenges the validity, enforceability or scope of any of the patents licensed by the Company to HBM under the HBM License Agreement, subject to certain conditions.