Commitments and Contingencies	12 Months Ended
Dec. 31, 2025
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	16. Commitments and Contingencies License Agreement with Nanjing Leads Biolabs Co. Ltd. On October 16, 2025, the Company entered into a License and Collaboration Agreement (the “Leads License Agreement”) with Nanjing Leads Biolabs Co. Ltd. (“Leads”), pursuant to which Leads granted the Company a royalty-bearing, exclusive license outside of Greater China to develop, manufacture, commercialize, or otherwise exploit DNTH212, a bifunctional fusion protein being developed in China by Leads as LBL-047. The Company also obtained certain non-exclusive rights to perform development and manufacturing activities in Greater China to support DNTH212 outside of Greater China. DNTH212 is an investigational, extended half-life bifunctional fusion protein targeting plasmacytoid dendritic cell BDCA2 to reduce Type 1 interferon production, while simultaneously inhibiting BAFF/APRIL to suppress B cell function. On December 23, 2025, Leads and the Company jointly announced the initiation of a Phase 1 clinical trial for LBL-047 (DNTH212). Under the terms of the Leads License Agreement, the Company will pay Leads up to $38.0 million, comprised of $30.0 million in upfront and near-term milestone payments plus an additional $8.0 million milestone, payable in cash or the Company’s common stock at the Company’s election, upon the initiation of a Dianthus-led Phase 1 study, for exclusive rights to develop and commercialize DNTH212 globally outside of Greater China. Leads will also be eligible to receive up to $962.0 million in development and regulatory approval milestones across three key geographies and sales-based milestones across five indications, as well as tiered royalties from mid-single digits up to a low double-digit on ex-Greater China net sales. The Leads License Agreement will remain in effect on a country-by-country and product-by-product basis until expiration of the applicable royalty term, unless earlier terminated. Each party has customary termination rights, including for uncured material breach, insolvency, patent challenge, or, in the case of the Company, for convenience. The Company recorded $30.0 million for amounts owed under the Leads License Agreement, including upfront and near-term milestone payments, within the research and development expenses line item in the consolidated statements of operations and comprehensive loss during the year ended December 31, 2025. During the three months ended December 31, 2025, the Company paid Leads $25.0 million in upfront and near-term milestone payments. In addition, the Company recorded $5.0 million of milestone payments within the accounts payable line item on its consolidated balance sheet as of December 31, 2025. IONTAS Limited In July 2020, the Company entered into a collaborative research agreement with IONTAS Limited (“IONTAS”) to perform certain milestone-based research and development activities for the Company under its first development program. This agreement was amended in January 2023 to extend their services to additional development programs. IONTAS provides dedicated resources to perform the research and development activities and receives compensation for those resources as well as success-based milestone payments. Upon the achievement, with the first development program with IONTAS, of (i) certain development milestones and (ii) certain commercial milestones, the Company is obligated to make payments to IONTAS of up to £3.1 million (approximately $4.2 million based on the December 31, 2025 exchange rate) and £2.3 million (approximately $3.1 million based on the December 31, 2025 exchange rate), respectively. Upon the achievement, with the second development program with IONTAS, of certain development milestones, the Company is obligated to make payments to IONTAS of up to £2.5 million (approximately $3.4 million based on the December 31, 2025 exchange rate). The Company recorded $1.7 million and $2.0 million for amounts owed under the IONTAS collaborative research license agreement, including milestone payments, within the research and development expenses line item in the consolidated statements of operations and comprehensive loss during the years ended December 31, 2025 and 2024, respectively. Alloy Therapeutics, LLC In August 2019, the Company entered into a license agreement with Alloy Therapeutics, LLC (“Alloy”). The license agreement was amended in October 2022. The license agreement with Alloy grants to the Company the following: • a worldwide, non-exclusive license to use the Alloy technology solely to generate Alloy antibodies and platform assisted antibodies for internal, non-clinical research purposes; and • with respect to Alloy antibodies and platform assisted antibowedies that are selected by the Company for inclusion into a partnered antibody program, a worldwide, assignable license to make, have made, use, offer for sale, sell, import, develop, manufacture, and commercialize products comprising partnered antibody programs selected from Alloy antibodies and platform assisted antibodies in any field of use. The Company pays annual license fees and annual partnered antibody program fees totaling $0.1 million to Alloy. The Company is also obligated to pay a $0.1 million fee to Alloy if the Company sublicenses a product developed with Alloy antibodies or platform assisted antibodies. Upon the achievement, with products developed with Alloy, of (i) certain development milestones and (ii) certain commercial milestones, the Company is obligated to make payments to Alloy of up to $1.8 million and $11.0 million, respectively. The Company recorded $1.1 million and $0.6 million for amounts owed under the Alloy license agreement, including milestone payments, within the research and development expenses line item in the consolidated statements of operations and comprehensive loss during the years ended December 31, 2025 and 2024, respectively. Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to employees, consultants, vendors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. To date, the Company has not incurred any material costs as a result of such indemnification agreements. The Company is not aware of any indemnification arrangements that could have a material effect on its financial position, results of operations or cash flows, and has not accrued any liabilities related to such obligations in its consolidated financial statements as of December 31, 2025 or 2024. Litigation From time to time, the Company may be exposed to litigation relating to potential products and operations. The Company is not currently engaged in any legal proceedings that are expected, individually or in the aggregate, to have a material adverse effect on its financial condition, results of operations or cash flows. Other As of December 31, 2025, the Company had standing agreements with consultants, contractors or service providers that generally can be terminated by the Company with 30 to 60 days written notice, unless otherwise indicated.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2025

Commitments and Contingencies Disclosure [Abstract]

16. Commitments and Contingencies

License Agreement with Nanjing Leads Biolabs Co. Ltd.

On October 16, 2025, the Company entered into a License and Collaboration Agreement (the “Leads License Agreement”) with Nanjing Leads Biolabs Co. Ltd. (“Leads”), pursuant to which Leads granted the Company a royalty-bearing, exclusive license outside of Greater China to develop, manufacture, commercialize, or otherwise exploit DNTH212, a bifunctional fusion protein being developed in China by Leads as LBL-047. The Company also obtained certain non-exclusive rights to perform development and manufacturing activities in Greater China to support DNTH212 outside of Greater China. DNTH212 is an investigational, extended half-life bifunctional fusion protein targeting plasmacytoid dendritic cell BDCA2 to reduce Type 1 interferon production, while simultaneously inhibiting BAFF/APRIL to suppress B cell function. On December 23, 2025, Leads and the Company jointly announced the initiation of a Phase 1 clinical trial for LBL-047 (DNTH212).

Under the terms of the Leads License Agreement, the Company will pay Leads up to $38.0 million, comprised of $30.0 million in upfront and near-term milestone payments plus an additional $8.0 million milestone, payable in cash or the Company’s common stock at the Company’s election, upon the initiation of a Dianthus-led Phase 1 study, for exclusive rights to develop and commercialize DNTH212 globally outside of Greater China. Leads will also be eligible to receive up to $962.0 million in development and regulatory approval milestones across three key geographies and sales-based milestones across five indications, as well as tiered royalties from mid-single digits up to a low double-digit on ex-Greater China net sales.

The Leads License Agreement will remain in effect on a country-by-country and product-by-product basis until expiration of the applicable royalty term, unless earlier terminated. Each party has customary termination rights, including for uncured material breach, insolvency, patent challenge, or, in the case of the Company, for convenience.

The Company recorded $30.0 million for amounts owed under the Leads License Agreement, including upfront and near-term milestone payments, within the research and development expenses line item in the consolidated statements of operations and comprehensive loss during the year ended December 31, 2025. During the three months ended December 31, 2025, the Company paid Leads $25.0 million in upfront and near-term milestone payments. In addition, the Company recorded $5.0 million of milestone payments within the accounts payable line item on its consolidated balance sheet as of December 31, 2025.

IONTAS Limited

In July 2020, the Company entered into a collaborative research agreement with IONTAS Limited (“IONTAS”) to perform certain milestone-based research and development activities for the Company under its first development program. This agreement was amended in January 2023 to extend their services to additional development programs. IONTAS provides dedicated resources to perform the research and development activities and receives compensation for those resources as well as success-based milestone payments.

Upon the achievement, with the first development program with IONTAS, of (i) certain development milestones and (ii) certain commercial milestones, the Company is obligated to make payments to IONTAS of up to £3.1 million (approximately $4.2 million based on the December 31, 2025 exchange rate) and £2.3 million (approximately $3.1 million based on the December 31, 2025 exchange rate), respectively. Upon the achievement, with the second development program with IONTAS, of certain development milestones, the Company is obligated to make payments to IONTAS of up to £2.5 million (approximately $3.4 million based on the December 31, 2025 exchange rate). The Company recorded $1.7 million and $2.0 million for amounts owed under the IONTAS collaborative research license agreement, including milestone payments, within the research and development expenses line item in the consolidated statements of operations and comprehensive loss during the years ended December 31, 2025 and 2024, respectively.

Alloy Therapeutics, LLC

In August 2019, the Company entered into a license agreement with Alloy Therapeutics, LLC (“Alloy”). The license agreement was amended in October 2022. The license agreement with Alloy grants to the Company the following:

•

a worldwide, non-exclusive license to use the Alloy technology solely to generate Alloy antibodies and platform assisted antibodies for internal, non-clinical research purposes; and

•

with respect to Alloy antibodies and platform assisted antibowedies that are selected by the Company for inclusion into a partnered antibody program, a worldwide, assignable license to make, have made, use, offer for sale, sell, import, develop, manufacture, and commercialize products comprising partnered antibody programs selected from Alloy antibodies and platform assisted antibodies in any field of use.

The Company pays annual license fees and annual partnered antibody program fees totaling $0.1 million to Alloy. The Company is also obligated to pay a $0.1 million fee to Alloy if the Company sublicenses a product developed with Alloy antibodies or platform assisted antibodies. Upon the achievement, with products developed with Alloy, of (i) certain development milestones and (ii) certain commercial milestones, the Company is obligated to make payments to Alloy of up to $1.8 million and $11.0 million, respectively. The Company recorded $1.1 million and $0.6 million for amounts owed under the Alloy license agreement, including milestone payments, within the research and development expenses line item in the consolidated statements of operations and comprehensive loss during the years ended December 31, 2025 and 2024, respectively.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to employees, consultants, vendors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. To date, the Company has not incurred any material costs as a result of such indemnification agreements. The Company is not aware of any indemnification arrangements that could have a material effect on its financial position, results of operations or cash flows, and has not accrued any liabilities related to such obligations in its consolidated financial statements as of December 31, 2025 or 2024.

Litigation

From time to time, the Company may be exposed to litigation relating to potential products and operations. The Company is not currently engaged in any legal proceedings that are expected, individually or in the aggregate, to have a material adverse effect on its financial condition, results of operations or cash flows.

Other

As of December 31, 2025, the Company had standing agreements with consultants, contractors or service providers that generally can be terminated by the Company with 30 to 60 days written notice, unless otherwise indicated.