Commitments and Contingencies, Including License and Sponsored Research Agreements	12 Months Ended
Dec. 31, 2025
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies, Including License and Sponsored Research Agreements	6. Commitments and contingencies, including license and sponsored research agreements License Agreements Dr. Reddy's License and Supply Agreement In 2023, the Company entered into an exclusive DRL Agreement with DRL which allowed for the Company to in-license DRL’s abatacept biosimilar for use in the development of Coya’s combination product for neurodegenerative diseases ("COYA 302"). COYA 302 is a dual biologic intended to suppress neuroinflammation via multiple immunomodulatory pathways, for the treatment of neurodegenerative conditions. The DRL Agreement also provides for the license of the Company's low dose IL-2 ("COYA 301") to DRL to permit the commercialization by DRL of COYA 302 in territories not otherwise granted to Coya. In consideration for the license the Company has paid a non-refundable upfront fee of $0.4 million. The Company will pay to DRL up to an aggregate of approximately $2.9 million of pre-approval regulatory milestone payments for the first indication in the Field (as defined in the DRL Agreement), and an additional approximately $20.0 million if all other development, regulatory approval and sales milestones are incurred under the DRL Agreement. The Company will also pay to DRL a low-six figure milestone payment per additional indication. Further, pursuant to the DRL Agreement, the Company will pay to DRL single-digit royalties on Net Sales (as defined in the DRL Agreement). The Company has paid an aggregate of $1.2 million in milestone payments to DRL through December 31, 2025. In 2023, the Company granted DRL an exclusive, royalty-bearing right and license to commercialize COYA 302 (Note 9). During the year ended December 31, 2025, the Company incurred $1.0 million in milestone payments to DRL as in-process research and development expense, in connection with the U.S. Food and Drug Administration's (the "FDA") acceptance of the Investigational New Drug ("IND") application for COYA 302 for the treatment of ALS (the "ALS IND Milestone"), the dosing of the first patient in the Company's ALSTARS trial evaluating COYA 302 for the treatment of ALS (the "Dosing Milestone"), and FDA acceptance of the IND application for COYA 302 for the treatment of frontotemporal dementia ("FTD") (the "FTD IND Milestone", together with the ALS IND Milestone, the "IND Milestones"). As of December 31, 2025, $0.2 million was included in accrued expenses in the accompanying balance sheets. ARS Agreement In 2022, the Company entered into a License Agreement (the “ARS License Agreement”) with ARScience Biotherapeutics, Inc. (“ARS”) pursuant to which ARS granted the Company an option, which was exercised in December 2022, to acquire an exclusive, royalty-bearing license for two patents, with the right to grant sublicenses through multiple tiers under these patents (the “ARS Option”). The Company may owe tiered payments to ARS based on its achievement of certain developmental milestones. Under the ARS License Agreement, the Company will pay an aggregate of $13.3 million in developmental milestone payments for the first Combination Product (as defined in the ARS License Agreement) in a new indication. The Company will then pay an aggregate of $11.6 million in developmental milestone payments for each Combination Product in each subsequent new indication. Further, for the first Mono Product (as defined In the ARS License Agreement) the Company will pay an aggregate of $11.8 million in developmental milestone payments. The Company will then pay an aggregate of $5.9 million in developmental milestone payments for each Mono Product in each subsequent new indication, and an aggregate of $5.9 million if all developmental milestones are achieved for each new indication. The Company will also owe royalties on net sales of licensed products ranging from low to mid-single digit percentages. In the event the Company sublicenses its rights under the ARS License Agreement, the Company will owe royalties on sublicense income within the range of 10% to 20%. During the year ended December 31, 2025, the Company incurred $1.1 million in milestone payments to ARS as in-process research and development expense, in connection with Company's IND Milestones and Dosing Milestone. As of December 31, 2025, $0.7 million was included in accrued expenses in the accompanying balance sheets. Houston Methodist Agreements In 2022, the Company entered into an Amended and Restated Patent Know How and License Agreement (the “Methodist License Agreement”), with The Methodist Hospital (“Methodist”) to make, sell and sublicense products and services using the intellectual property and know-how of Methodist. As part of the Methodist License Agreement, the Company will pay Methodist a four-figure license maintenance fee annually until the first sale of licensed product occurs. The term of the Methodist License Agreement is effective until no intellectual property patent rights remain, unless terminated sooner by (1) bankruptcy or insolvency, (2) the failure by the Company to monetize the intellectual property within five years of the date of the agreement (further discussed below), (3) due to breach of contract, or (4) at our election for any or no reason. Patent reimbursements paid by the Company to Methodist and its attorneys are included in general and administrative expenses in the accompanying statements of operations. Such costs were immaterial for the years ended December 31, 2025 and 2024. In addition to the equity issued to Methodist in 2020 and reimbursement of patent related expenses, the Methodist License requires the Company to make payments of up to $0.4 million per product candidate in aggregate upon the achievement of specific development and regulatory milestone events by such licensed product. The Company is also required to pay Methodist, on a licensed product-by-licensed product and country-by-country basis, tiered royalties (subject to customary reductions) equal to high-single digit to low-double digit percentages of annual worldwide net sales of such licensed product during a defined royalty term. The Company is also required to pay a low single digit percentage for certain licensed services. Effective January 1, 2025, the minimum amount which will be owed by the Company once commercialization occurs is $0.1 million annually. The Methodist License Agreement provides that in the event the Company sublicense products and services covered by the Methodist License Agreement, then royalties owed to Houston Methodist would be computed as a percentage of payments received by the Company from the sublicensee. In addition, the termination provisions provide that Houston Methodist may terminate the Methodist License Agreement, among other things, in the event that after five years the Company is not “Actively Attempting to Develop or Commercialize,” as such term is defined in the Methodist License Agreement. During the year ended December 31, 2025, the Company incurred $0.1 million in milestone payments to Methodist as in-process research and development expense, in connection with Company's FTD IND Milestone and Dosing Milestone. As of December 31, 2025, $0.1 million was included in accrued expenses in the accompanying balance sheets. Sponsored Research Agreement In May 2023, the Company entered into a Sponsored Research Agreement (“SRA”) with Houston Methodist Research Institute (“HMRI”), a Texas nonprofit corporation and an affiliate of Methodist, in which the Company agreed to fund approximately $0.5 million through May 2024. The Company and HMRI have subsequently amended the SRA multiple times to increase agreed funding and, at times, extend the term. In June 2025, the SRA was amended to increase the total funding from $1.2 million to $1.4 million and to extend the term through December 31, 2025. As of December 31, 2025, the Company funded the commitment and the SRA expired. During the years ended December 31, 2025 and 2024, the Company incurred $1.0 million and $0.5 million, respectively, in research and development expenses related to the SRA. On January 1, 2026, the Company entered into another SRA with HMRI in which the Company agreed to fund research through the earlier of completion of the research or 12 months. The maximum funding commitment is $0.6 million. Employment contracts The Company has entered into employment contracts with its officers and certain employees that provide for severance and continuation of benefits in the event of termination of employment either by the Company without cause or by the employee for good reason, both as defined in the agreements. In addition, in the event of termination of employment following a change in control, as defined in each agreement, either by the Company without cause or by the employee for good reason, any unvested portion of the employee’s initial stock option grant becomes immediately vested. Litigation Liabilities for loss contingencies arising from claims, assessments, litigation, fines, penalties, and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. There are no matters currently outstanding.

Commitments and Contingencies, Including License and Sponsored Research Agreements

12 Months Ended

Dec. 31, 2025

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies, Including License and Sponsored Research Agreements

6. Commitments and contingencies, including license and sponsored research agreements

License Agreements

Dr. Reddy's License and Supply Agreement

In 2023, the Company entered into an exclusive DRL Agreement with DRL which allowed for the Company to in-license DRL’s abatacept biosimilar for use in the development of Coya’s combination product for neurodegenerative diseases ("COYA 302"). COYA 302 is a dual biologic intended to suppress neuroinflammation via multiple immunomodulatory pathways, for the treatment of neurodegenerative conditions. The DRL Agreement also provides for the license of the Company's low dose IL-2 ("COYA 301") to DRL to permit the commercialization by DRL of COYA 302 in territories not otherwise granted to Coya. In consideration for the license the Company has paid a non-refundable upfront fee of $0.4 million. The Company will pay to DRL up to an aggregate of approximately $2.9 million of pre-approval regulatory milestone payments for the first indication in the Field (as defined in the DRL Agreement), and an additional approximately $20.0 million if all other development, regulatory approval and sales milestones are incurred under the DRL Agreement. The Company will also pay to DRL a low-six figure milestone payment per additional indication. Further, pursuant to the DRL Agreement, the Company will pay to DRL single-digit royalties on Net Sales (as defined in the DRL Agreement). The Company has paid an aggregate of $1.2 million in milestone payments to DRL through December 31, 2025.

In 2023, the Company granted DRL an exclusive, royalty-bearing right and license to commercialize COYA 302 (Note 9). During the year ended December 31, 2025, the Company incurred $1.0 million in milestone payments to DRL as in-process research and development expense, in connection with the U.S. Food and Drug Administration's (the "FDA") acceptance of the Investigational New Drug ("IND") application for COYA 302 for the treatment of ALS (the "ALS IND Milestone"), the dosing of the first patient in the Company's ALSTARS trial evaluating COYA 302 for the treatment of ALS (the "Dosing Milestone"), and FDA acceptance of the IND application for COYA 302 for the treatment of frontotemporal dementia ("FTD") (the "FTD IND Milestone", together with the ALS IND Milestone, the "IND Milestones"). As of December 31, 2025, $0.2 million was included in accrued expenses in the accompanying balance sheets.

ARS Agreement

In 2022, the Company entered into a License Agreement (the “ARS License Agreement”) with ARScience Biotherapeutics, Inc. (“ARS”) pursuant to which ARS granted the Company an option, which was exercised in December 2022, to acquire an exclusive, royalty-bearing license for two patents, with the right to grant sublicenses through multiple tiers under these patents (the “ARS Option”).

The Company may owe tiered payments to ARS based on its achievement of certain developmental milestones. Under the ARS License Agreement, the Company will pay an aggregate of $13.3 million in developmental milestone payments for the first Combination Product (as defined in the ARS License Agreement) in a new indication. The Company will then pay an aggregate of $11.6 million in developmental milestone payments for each Combination Product in each subsequent new indication. Further, for the first Mono Product (as defined In the ARS License Agreement) the Company will pay an aggregate of $11.8 million in developmental milestone payments. The Company will then pay an aggregate of $5.9 million in developmental milestone payments for each Mono Product in each subsequent new indication, and an aggregate of $5.9 million if all developmental milestones are achieved for each new indication. The Company will also owe royalties on net sales of licensed products ranging from low to mid-single digit percentages. In the event the Company sublicenses its rights under the ARS License Agreement, the Company will owe royalties on sublicense income within the range of 10% to 20%. During the year ended December 31, 2025, the Company incurred $1.1 million in milestone payments to ARS as in-process research and development expense, in connection with Company's IND Milestones and Dosing Milestone. As of December 31, 2025, $0.7 million was included in accrued expenses in the accompanying balance sheets.

Houston Methodist Agreements

In 2022, the Company entered into an Amended and Restated Patent Know How and License Agreement (the “Methodist License Agreement”), with The Methodist Hospital (“Methodist”) to make, sell and sublicense products and services using the intellectual property and know-how of Methodist. As part of the Methodist License Agreement, the Company will pay Methodist a four-figure license maintenance fee annually until the first sale of licensed product occurs. The term of the Methodist License Agreement is effective until no intellectual property patent rights remain, unless terminated sooner by (1) bankruptcy or insolvency, (2) the failure by

the Company to monetize the intellectual property within five years of the date of the agreement (further discussed below), (3) due to breach of contract, or (4) at our election for any or no reason.

Patent reimbursements paid by the Company to Methodist and its attorneys are included in general and administrative expenses in the accompanying statements of operations. Such costs were immaterial for the years ended December 31, 2025 and 2024. In addition to the equity issued to Methodist in 2020 and reimbursement of patent related expenses, the Methodist License requires the Company to make payments of up to $0.4 million per product candidate in aggregate upon the achievement of specific development and regulatory milestone events by such licensed product. The Company is also required to pay Methodist, on a licensed product-by-licensed product and country-by-country basis, tiered royalties (subject to customary reductions) equal to high-single digit to low-double digit percentages of annual worldwide net sales of such licensed product during a defined royalty term. The Company is also required to pay a low single digit percentage for certain licensed services. Effective January 1, 2025, the minimum amount which will be owed by the Company once commercialization occurs is $0.1 million annually.

The Methodist License Agreement provides that in the event the Company sublicense products and services covered by the Methodist License Agreement, then royalties owed to Houston Methodist would be computed as a percentage of payments received by the Company from the sublicensee. In addition, the termination provisions provide that Houston Methodist may terminate the Methodist License Agreement, among other things, in the event that after five years the Company is not “Actively Attempting to Develop or Commercialize,” as such term is defined in the Methodist License Agreement. During the year ended December 31, 2025, the Company incurred $0.1 million in milestone payments to Methodist as in-process research and development expense, in connection with Company's FTD IND Milestone and Dosing Milestone. As of December 31, 2025, $0.1 million was included in accrued expenses in the accompanying balance sheets.

Sponsored Research Agreement

In May 2023, the Company entered into a Sponsored Research Agreement (“SRA”) with Houston Methodist Research Institute (“HMRI”), a Texas nonprofit corporation and an affiliate of Methodist, in which the Company agreed to fund approximately $0.5 million through May 2024. The Company and HMRI have subsequently amended the SRA multiple times to increase agreed funding and, at times, extend the term. In June 2025, the SRA was amended to increase the total funding from $1.2 million to $1.4 million and to extend the term through December 31, 2025. As of December 31, 2025, the Company funded the commitment and the SRA expired. During the years ended December 31, 2025 and 2024, the Company incurred $1.0 million and $0.5 million, respectively, in research and development expenses related to the SRA. On January 1, 2026, the Company entered into another SRA with HMRI in which the Company agreed to fund research through the earlier of completion of the research or 12 months. The maximum funding commitment is $0.6 million.

Employment contracts

The Company has entered into employment contracts with its officers and certain employees that provide for severance and continuation of benefits in the event of termination of employment either by the Company without cause or by the employee for good reason, both as defined in the agreements. In addition, in the event of termination of employment following a change in control, as defined in each agreement, either by the Company without cause or by the employee for good reason, any unvested portion of the employee’s initial stock option grant becomes immediately vested.

Litigation

Liabilities for loss contingencies arising from claims, assessments, litigation, fines, penalties, and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. There are no matters currently outstanding.