Dianthus Therapeutics, Inc. /DE/

(in thousands, except share and per share data, unless otherwise stated)

1. Organization, Description of Business and Liquidity

Business

Dianthus Therapeutics, Inc. (the “Company” or “Dianthus”) is a clinical-stage biotechnology company dedicated to developing potentially best-in-disease therapies for patients living with severe autoimmune diseases. The Company’s corporate headquarters are in New York, New York.

Currently, the Company is devoting substantially all efforts and resources toward product research and development of its product candidates. The Company has incurred losses from operations and negative operating cash flows since its inception. There can be no assurance that its research and development programs will be successful, that products developed, if any, will obtain necessary regulatory approval, or that any approved product, if any, will be commercially viable. In addition, the Company operates in an environment of rapid technological change and is largely dependent on the services of its key employees, consultants, and advisors.

Reverse Merger and Pre-Closing Financing

On September 11, 2023, the Company completed its business combination with Dianthus Therapeutics OpCo, Inc. (formerly Dianthus Therapeutics, Inc.) (“Former Dianthus”) in accordance with the terms of the Agreement and Plan of Merger, dated as of May 2, 2023 (the “Merger Agreement”), by and among the Company, Dio Merger Sub, Inc., a Delaware corporation and a wholly owned subsidiary of the Company (“Merger Sub”), and Former Dianthus, pursuant to which, among other matters, Merger Sub merged with and into Former Dianthus, with Former Dianthus surviving as a wholly owned subsidiary of the Company (the “Reverse Merger”). In connection with the completion of the Reverse Merger, the Company changed its name from “Magenta Therapeutics, Inc.” to “Dianthus Therapeutics, Inc.,” and the business conducted by the Company became primarily the business conducted by Former Dianthus. Unless context otherwise requires, references herein to “Dianthus,” the “Company,” or the “combined company” refer to Dianthus Therapeutics, Inc. (formerly Magenta Therapeutics, Inc.) after completion of the Reverse Merger, the term “Former Dianthus” refers to Dianthus Therapeutics OpCo, Inc. (formerly Dianthus Therapeutics, Inc.), and the term “Magenta” refers to the Company prior to completion of the Reverse Merger. The Company was incorporated in June 2015, and Former Dianthus was incorporated in May 2019.

Immediately prior to the effective time of the Reverse Merger, the Company effected a 1-for-16 reverse stock split of its common stock (the “Reverse Stock Split”). Unless noted otherwise, all references herein to share and per share amounts reflect the Reverse Stock Split.

At the effective time of the Reverse Merger, the Company issued an aggregate of 11,021,248 shares of common stock to the Former Dianthus stockholders, based on the exchange ratio of approximately 0.2181 shares of common stock for each share of Former Dianthus common stock, including those shares of Former Dianthus common stock issued upon the conversion of Former Dianthus preferred stock and those shares of the Former Dianthus common stock issued in the pre-closing financing (as defined below), resulting in 14,817,696 shares of common stock being issued and outstanding following the effective time of the Reverse Merger.

At the effective time of the Reverse Merger, the 2019 Stock Plan (as discussed in Note 11) was assumed by the Company, and each outstanding and unexercised option to purchase shares of Former Dianthus common stock immediately prior to the effective time of the Reverse Merger was assumed by the Company and converted into an option to purchase shares of common stock, with necessary adjustments to the number of shares and exercise price to reflect the exchange ratio, and each outstanding and unexercised warrant to purchase shares of Former Dianthus common stock immediately prior to the effective time of the Reverse Merger (including the Former Dianthus pre-funded warrants sold in the pre-closing financing) was converted into a warrant to purchase shares of common stock, with necessary adjustments to the number of shares and exercise price to reflect the exchange ratio.

The Reverse Merger was accounted for as a reverse recapitalization in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”). Under this method of accounting, Former Dianthus was deemed to be the accounting acquirer for financial reporting purposes. This determination was primarily based on the expectation that, immediately following the Reverse Merger: (i) Former Dianthus’ stockholders would own a substantial majority of the voting rights in the combined company; (ii) Former Dianthus’ largest stockholders would retain the largest interest in the combined company; (iii) Former Dianthus would designate a majority (six of eight) of the initial members of the board of directors of the combined company; and (iv) Former Dianthus’ executive management team would become the management team of the combined company. Accordingly, for accounting purposes: (i) the Reverse Merger was treated as the equivalent of Former Dianthus issuing stock to acquire the net assets of Magenta; (ii) the net assets of Magenta were recorded at their acquisition-date fair value in the consolidated financial statements of Former Dianthus; and (iii) the reported historical operating results of the combined company prior to the Reverse Merger are those of Former Dianthus. Historical common stock figures of Former Dianthus have been retroactively restated based on the exchange ratio of approximately 0.2181.

On September 11, 2023, prior to the effective time of the Reverse Merger, the Company entered into a contingent value rights agreement (the “CVR Agreement”) with a rights agent, pursuant to which pre-Reverse Merger holders of Magenta common stock received one non-transferable contingent value right (each, a “CVR”) for each outstanding share of Magenta common stock held by such stockholder immediately prior to the effective time of the Reverse Merger on September 11, 2023. Subject to, and in accordance with, the terms and conditions of the CVR Agreement, each CVR represented the contractual right to receive a pro rata portion of the proceeds, if any, received by the Company as a result of (i) contingent payments made to the Company, such as milestone, royalty or earnout, when received under any pre-Reverse Merger disposition agreements related to Magenta’s pre-Reverse Merger assets and (ii) the Company’s sale of assets after the effective date of the Reverse Merger and prior to December 31, 2023, in each case, received within a three-year period following the closing of the Reverse Merger. The CVRs expired in accordance with the terms of the CVR Agreement on September 11, 2026, and no payments were made to holders of the CVRs.

Concurrently with the execution and delivery of the Merger Agreement, and in order to provide Former Dianthus with additional capital for its development programs, Former Dianthus entered into a subscription agreement, as amended (the “Subscription Agreement”), with certain investors named therein (the “Investors”), pursuant to which, subject to the terms and conditions of the Subscription Agreement, immediately prior to the effective time of the Reverse Merger, Former Dianthus issued and sold, and the Investors purchased, (i)2,873,988 shares of Former Dianthus common stock and (ii)210,320 pre-funded warrants, exercisable for 210,320 shares of Former Dianthus common stock, at a purchase price of approximately $23.34 per share or $23.34 per warrant, for an aggregate purchase price of approximately $72.0 million (the “pre-closing financing”).

2024 Private Placement

On January 22, 2024, the Company entered into a securities purchase agreement for a private placement with certain institutional and accredited investors. At the closing of the private placement on January 24, 2024, the Company sold and issued 14,500,500 shares of common stock at a price per share of $12.00, and pre-funded warrants to purchase 4,666,332 shares of common stock at a purchase price of $11.999 per pre-funded warrant, which represents the per share purchase price of the common stock less the $0.001 per share exercise price for each pre-funded warrant, for an aggregate purchase price of approximately $230.0 million. The pre-funded warrants are exercisable at any time after the date of issuance. A holder of pre-funded warrants may not exercise the warrant if the holder, together with its affiliates, would beneficially own more than 9.99% of the number of shares of common stock outstanding immediately after giving effect to such exercise. A holder of pre-funded warrants may increase or decrease this percentage to a percentage not in excess of 19.99% by providing at least 61 days’ prior notice to the Company.

Shelf Registration Statements and At-the-Market Offering Programs

On October 1, 2024, the Company filed a registration statement with the SEC for the issuance of common stock, preferred stock, warrants, debt securities, rights and units up to an aggregate of $500.0 million. On October 9, 2024, the registration statement was declared effective by the SEC. The registration statement includes an at-the-market (the “Initial ATM”) offering program for the sale of up to $200.0 million of shares of the Company’s common stock. As of the date of this filing, the Company has sold 3,632,534 shares of its common stock under the Initial ATM offering program, resulting in gross proceeds of $200.0 million.

On January 28, 2026, the Company filed a registration statement with the SEC for the issuance of common stock, preferred stock, warrants, debt securities, rights and units up to an aggregate of $600.0 million. On January 30, 2026, the registration statement was declared effective by the SEC.

On September 18, 2026, the Company filed a registration statement with the SEC, which became effective immediately upon filing, for theissuance of common stock, preferred stock, warrants, debt securities, rights and units. The registration statement includes an at-the-market (the “2026 ATM”) offering program for the sale of up to $500.0 million of shares of the Company’s common stock. To date, the Company has not sold any shares of its common stock under the 2026 ATM offering program.

During the three and nine months ended September 30, 2026, the Company sold 1,005,700 and 2,128,826 shares, respectively, of its common stock under the at-the-market offering programs, resulting in net proceeds of $98.1 million and $156.8 million, respectively. No sales were made under the at-the-market offering programs during the nine months ended September 30, 2025.

September 2025 Public Offering

On September 9, 2025, the Company entered into an underwriting agreement with certain underwriters to issue and sell 7,627,879 shares of the Company’s common stock, including the full exercise by the underwriters of their option to purchase an additional 1,140,000 shares, at a public offering price of $33.00 per share and, in lieu of common stock to certain investors, pre-funded warrants to purchase 1,112,121 shares of the Company’s common stock at a public offering price of $32.999 per share, which represented the per share public offering price for the common stock less the $0.001 per share exercise price for each pre-funded warrant. The gross proceeds from the underwritten offering were $288.4 million, before underwriting discounts and commissions and estimated expenses of the offering. The underwritten offering closed on September 11, 2025.

The pre-funded warrants are exercisable at any time after the date of issuance. A holder of the pre-funded warrants may not exercise the warrant if the holder, together with its affiliates, would beneficially own more than 4.99%,9.99%, or 19.99%, as applicable to each holder, of the number of shares of common stock outstanding immediately after giving effect to such exercise. A holder of the pre-funded warrants may increase or decrease this percentage to a percentage not in excess of 19.99% by providing at least 61 days’ prior notice to the Company.

The Company intends to use the net proceeds from this offering to advance the Company’s preclinical and clinical development activities, as well as for working capital and general corporate purposes. The Company may also use a portion of the proceeds to license, acquire or invest in new product candidates or for drug development activities related to such product candidates, complementary businesses, technology or assets.

The underwritten offering was made pursuant to the shelf registration statement, which became effective on October 9, 2024. A final prospectus supplement dated September 9, 2025 relating to and describing the terms of the underwritten offering was filed with the SEC on September 11, 2025.

March 2026 Public Offering

On March 10, 2026, the Company entered into an underwriting agreement with certain underwriters to issue and sell 8,470,989 shares of the Company’s common stock, including the full exercise by the underwriters of their option to purchase an additional 1,157,407 shares, at a public offering price of $81.00 per share and, in lieu of common stock to certain investors, pre-funded warrants to purchase 402,468 shares of the Company’s common stock at a public offering price of $80.999 per share, which represented the per share public offering price for the common stock less the $0.001 per share exercise price for each pre-funded warrant. The gross proceeds from the underwritten offering were approximately $719.0 million, before underwriting discounts and commissions and estimated expenses of the offering. The underwritten offering closed on March 12, 2026.

The pre-funded warrants are exercisable at any time after the date of issuance. A holder of the pre-funded warrants may not exercise the warrant if the holder, together with its affiliates, would beneficially own more than 4.99%of the number of shares of common stock outstanding immediately after giving effect to such exercise. A holder of the pre-funded warrants may increase or decrease this percentage to a percentage not in excess of 19.99% by providing at least 61 days’ prior notice to the Company.

The Company intends to use the net proceeds from this offering to advance the Company’s preclinical and clinical development activities, commercial readiness activities as well as for working capital and general corporate purposes.

The underwritten offering was made pursuant to a shelf registration statement, which became effective on January 30, 2026 and a related registration statement that was filed with the SEC on March 10, 2026 pursuant to Rule 462(b) under the Securities Act of 1933, as amended (the “Securities Act”), and became automatically effective upon filing. A final prospectus supplement dated March 10, 2026 relating to and describing the terms of the underwritten offering was filed with the SEC on March 11, 2026.

Risks and Uncertainties

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry including, but not limited to, uncertainty of product development and commercialization, lack of marketing and sales history, development by its competitors of new technological innovations, dependence on its key personnel, market acceptance of products, product liability, protection of proprietary technology, ability to raise additional financing and compliance with government regulations. If the Company does not successfully commercialize any of its product candidates, it will be unable to generate recurring product revenue or achieve profitability.

The Company’s current product candidates, as well as any future product candidates, will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure, and extensive compliance-reporting capabilities. Even if its product development efforts are successful, it is uncertain when, if ever, the Company will generate revenue from product sales.

Liquidity

In accordance with Accounting Standards Update No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern(Subtopic 205-40), the Company has evaluated whether there are certain conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the accompanying unaudited condensed consolidated financial statements were issued (the “issuance date”):

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Since its inception, the Company has funded its operations primarily with outside capital and has incurred significant recurring losses, including net losses of$137.7 million and$97.9 million for the nine months ended September 30, 2026 and 2025, respectively. In addition, the Company had an accumulated deficit of$474.4 million as of September 30, 2026;

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The Company expects to continue to incur significant recurring losses and rely on outside capital to fund its operations for the foreseeable future; and

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As of the issuance date, the Company expects that its existing cash, cash equivalents and investments on hand will be sufficient to fund its obligations as they become due for at least twelve months beyond the issuance date. The Company expects that its research and development and general and administrative costs will continue to increase significantly, including in connection with conducting clinical trials and manufacturing for its existing product candidates and any future product candidates to support commercialization and providing general and administrative support for its operations, including the costs associated with operating as a public company.

In the event the Company is unable to secure additional outside capital, management will be required to seek other alternatives which may include, among others, a delay or termination of clinical trials or the development of its product candidates, temporary or permanent curtailment of the Company’s operations, a sale of assets, or other alternatives with strategic or financial partners.

The accompanying unaudited condensed consolidated financial statements do not include any adjustments that might result from the outcome of these uncertainties. Accordingly, the unaudited condensed consolidated financial statements have been prepared on a basis that assumes the Company will continue as a going concern and which contemplates the realization of assets and satisfaction of liabilities and commitments in the ordinary course of business.

2. Summary of Significant Accounting Policies

The Company’s significant accounting policies are disclosed in the audited consolidated financial statements and the notes thereto in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC on March 9, 2026. Except as reflected below, there were no changes to the Company’s significant accounting policies as described in the Annual Report on Form 10-K. Reflected in this note are updates to accounting policies, including the impact of the adoption of new policies.

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements as of September 30, 2026 and for the three and nine months ended September 30, 2026 have been prepared in conformity with U.S. GAAP for interim financial information and pursuant to Article 10 of Regulation S-X of the Securities Act. Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s audited financial statements and include only normal and recurring adjustments that the Company believes are necessary to fairly state the Company’s financial position and the results of its operations and cash flows. The results for the three and nine months ended September 30, 2026 are not necessarily indicative of the results expected for the full fiscal year or any subsequent interim period. The unaudited condensed consolidated balance sheet as of December 31, 2025 has been derived from the audited financial statements at that date but does not include all disclosures required by U.S. GAAP for complete financial statements. Because all of the disclosures required by U.S. GAAP for complete financial statements are not included herein, these unaudited condensed consolidated financial statements and the notes accompanying them should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2025, which are contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025 filed with the SEC on March 9, 2026. Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ materially from those estimates.

Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates including the following: expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. Significant estimates are used in the following areas, among others: the recognition of research and development expense and revenue recognition.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents and investments. The Company regularly maintains deposits in accredited financial institutions in excess of federally insured limits. The Company invests its excess cash primarily in money market funds, U.S. treasury securities, U.S. government agency securities and corporate debt securities in accordance with the Company’s investment policy. The Company’s investment policy defines allowable investments and establishes guidelines relating to credit quality, diversification, and maturities of its investments to preserve principal and maintain liquidity. The Company has not experienced any significant realized losses related to its cash, cash equivalents and investments and management believes the Company is not exposed to significant risks of losses.

Recently Issued Accounting Pronouncements

In November 2024, the FASB issued ASU No. 2024-03, Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses. The amendments in ASU No. 2024-03 address investor requests for more detailed expense information and require additional disaggregated disclosures in the notes to financial statements for certain categories of expenses that are included on the face of the income statement. This guidance is effective for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027, with early adoption permitted. The Company is currently evaluating the impact ASU No. 2024-03 may have on its unaudited condensed consolidated financial statements and related disclosures.

3. Segment Reporting

Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the Chief Operating Decision Maker (the “CODM”) in deciding how to allocate resources and in assessing the Company’s performance. The Company operates as asingle operating segment andhasone reportable segment which focuses on developing next-generation therapies to transform the treatment of severe autoimmune diseases.

The Company’s CODM is its Chief Executive Officer. The CODM manages the Company’s operations on a consolidated basis as one operating segment for the purposes of evaluating financial performance and allocating resources.

The Company has not yet generated any revenue from product sales. The CODM assesses the financial performance of the segment and decides how to allocate resources based on net loss on a consolidated basis. The measure of segment assets is reported on the unaudited condensed consolidated balance sheets as total consolidated assets.

The CODM uses net loss predominantly in the annual operating budget and in the strategic planning and forecasting process. Such profit or loss measure is used to monitor budget versus actual results on an ongoing basis by the CODM and determines how resources are allocated to the various activities of the Company. The CODM also uses net loss to evaluate the Company’s performance and considers net loss when determining management’s incentive compensation.

All of the Company’stangible assets are held in the United States. The Company views its operations and manages its business in one operating segment, operating exclusively in the United States.

The table below provides a summary of the segment profit or loss, including significant segment expenses:

4. Cash Equivalents and Marketable Securities

The Company’sinvestments consist of marketable securities classified as available-for-sale. The following tables provide a summary of the estimated fair value of the Company’s cash equivalents and marketable securities:

Interest and Investment Income

The following table provides a summary of the components of interest and investment income:

5. Prepaid Expenses and Other Current Assets

The following table provides a summary of prepaid expenses and other current assets:

6. Property and Equipment

The following table provides a summary of property and equipment:

Depreciation expense was $37 thousand and $0.1 million for thethree and nine months ended September 30, 2026, respectively, and $27 thousand and $84 thousand for thethree and nine months ended September 30, 2025, respectively.

7. Fair Value of Financial Instruments

The following tables provide a summary of financial assets measured at fair value on a recurring basis:

There wereno transfers between levels during thenine months ended September 30, 2026 or for the year ended December 31, 2025. The weighted-average maturity of the securities held at September 30, 2026 was less than 12 months.

8. Accrued Expenses

The following table provides a summary of accrued expenses:

9. Leases

The Company leases space under operating leases for administrative offices in New York, New York, and Waltham, Massachusetts.

The following table provides a summary of the components of lease costs and rent:

Cash paid for amounts included in the measurement of operating lease liabilities was$0.1 million and$0.3 million for each of the three and nine months ended September 30, 2026 and 2025, respectively.

The Company recorded operating lease costs of $0.1 million and$0.3 million during each of the three and nine months ended September 30, 2026 and 2025, respectively, within the general and administrative expenses line item in the unaudited condensed consolidated statements of operations and comprehensive loss. The Company recorded operating lease costs ofnil during thenine months ended September 30, 2026 andnil and $24 thousand during thethree and nine months ended September 30, 2025, respectively, within the research and development expenses line item in the unaudited condensed consolidated statements of operations and comprehensive loss.

Maturities of operating lease liabilities as of September 30, 2026, are as follows:

The weighted-average remaining term of operating leases was 52 months and the weighted-average discount rate used to measure the present value of operating lease liabilities was 8.4% as of September 30, 2026.

2026 Waltham Lease

In July 2026, the Company entered into an agreement to lease approximately 11,232 square feet of building space in Waltham, Massachusetts (the “2026 Waltham Lease”). The 2026 Waltham Lease will replace the Company’s current lease agreement for office space in Waltham, Massachusetts, which is set to expire in January 2027. Under the 2026 Waltham Lease, the Company is obligated to make aggregate future minimum lease payments totaling approximately $2.4 million over the lease term, exclusive of operating expenses and other common area charges.

The Company determined that, in accordance with ASC 842, Leases, the lease commencement date will be February 15, 2027. Accordingly, the Company has not recorded any right-of-use asset or lease liability related to the 2026 Waltham Lease as of September 30, 2026.

10. Stockholders’ Equity

March 2026 Public Offering

At the closing of the public offering on March 12, 2026, the Company issued and sold 8,470,989 shares of its common stock, including the full exercise by the underwriters of their option to purchase an additional 1,157,407 shares, and pre-funded warrants to purchase 402,468 shares of its common stock with a $0.001 per share exercise price. The gross proceeds from this public offering were approximately $719.0 million, before underwriting discounts and commissions and estimated expenses related to this public offering.

The pre-funded warrants are exercisable at any time after the date of issuance and will not expire. As of September 30, 2026, there were 402,468 pre-funded warrants outstanding related to this public offering.

September 2025 Public Offering

At the closing of the public offering on September 11, 2025, the Company issued and sold 7,627,879 shares of its common stock, including the full exercise by the underwriters of their option to purchase an additional 1,140,000 shares, and pre-funded warrantsto purchase 1,112,121 shares of its common stock with a $0.001 per share exercise price. The gross proceeds from this public offering were $288.4 million, before underwriting discounts and commissions and estimated expenses related to this public offering.

The pre-funded warrants are exercisable at any time after the date of issuance and will not expire. As of September 30, 2026, there were 112,121 pre-funded warrants outstanding related to this public offering.

Shelf Registration Statements and ATM Offering Programs

On October 1, 2024, the Company filed a registration statement with the SEC for the issuance of common stock, preferred stock, warrants, debt securities, rights and units up to an aggregate of $500.0 million. On October 9, 2024, the registration statement was declared effective by the SEC. The registration statement includes an at-the-market offering program for the sale of up to $200.0 million of shares of the Company’s common stock. As of the date of this filing, the Company has sold 3,632,534 shares of its common stock under the Initial ATM offering program, resulting in gross proceeds of $200.0 million.

On January 28, 2026, the Company filed a registration statement with the SEC for the issuance of common stock, preferred stock, warrants, debt securities, rights and units up to an aggregate of $600.0 million. On January 30, 2026, the registration statement was declared effective by the SEC.

On September 18, 2026, the Company filed a registration statement with the SEC, which became effective immediately upon filing, for the issuance of common stock, preferred stock, warrants, debt securities, rights and units. The registration statement includes an at-the-market offering program for the sale of upto $500.0 million of shares of the Company’s common stock. To date, the Company has not sold any shares of its common stock under the 2026 ATM offering program.

During the three and nine months ended September 30, 2026, the Company sold 1,005,700 and 2,128,826 shares, respectively, of its common stock under the at-the-market offering programs, resulting in net proceeds of $98.1 million and $156.8 million, respectively. No sales were made under the at-the-market offering programs during the nine months ended September 30, 2025.

Private Placement Offering

At the closing of the private placement on January 24, 2024, the Company issued 14,500,500 shares of common stock and pre-funded warrants to purchase 4,666,332 shares of common stock with a $0.001 per share exercise price. The pre-funded warrants are exercisable at any time after the date of issuance and will not expire. As of September 30, 2026, there were 832,333 pre-funded warrants outstanding related to this private placement.

Preferred Stock

As of September 30, 2026, the Company was authorized to issue up to 10,000,000 shares of the Company’s preferred stock at a par value of $0.001. As of September 30, 2026, no shares of Company preferred stock were issued and outstanding.

Common Stock

As of September 30, 2026, the Company was authorized to issue up to 150,000,000 shares of common stock at a par value of $0.001. As of September 30, 2026, the Company had issued and outstanding 56,295,226 shares of common stock.

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the Company’s board of directors, if any. No dividends have been declared or paid by the Company through September 30, 2026.

The Company had the following shares of common stock reserved for future issuance as of September 30, 2026 and December 31, 2025:

11. Stock-Based Compensation

2018 Stock Option and Incentive Plan

The Company grants stock-based awards under the Second Amended and Restated Dianthus Therapeutics, Inc. Stock Option and Incentive Plan, which originally became effective on June 19, 2018 as the Magenta Therapeutics, Inc. 2018 Stock Option and Incentive Plan and was amended and restated in September 2023 and renamed the Amended and Restated Dianthus Therapeutics, Inc. Stock Option and Incentive Plan (the “Prior 2018 Incentive Plan”).

On May 23, 2024, the Company’s stockholders approved an amendment and restatement of the Prior 2018 Incentive Plan, and it was renamed the Second Amended and Restated Dianthus Therapeutics, Inc. Stock Option and Incentive Plan (the “2018 Amended Plan”) to:

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provide for an increase in the number of shares of common stock reserved for issuance thereunder by 2,931,820 shares;

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increase the Evergreen Provision (as described below) from 4% to 5% of issued and outstanding shares of common stock on December 31 of the preceding calendar year; and

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extend the expiration date until March 14, 2034.

The 2018 Amended Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, restricted stock units, unrestricted stock awards, cash-based awards and dividend equivalent rights. The 2018 Amended Plan is administered by either the board of directors or the compensation committee of the board of directors. The exercise prices, vesting and other restrictions are determined at the discretion of the administrator, except that the term of stock options and stock appreciation rights may not be greater thanten years(orfive years for certain incentive stock options). Awards typically vest over 12 months tofour years. The exercise price for stock options granted may not be less than the fair value of common stock as of the date of grant (or 110% of the fair value of common stock for certain incentive stock options). The fair value of common stock is based on quoted market prices.

The 2018 Amended Plan also provides for the assumption of shares remaining available for delivery under the 2019 Stock Plan (as defined below) pursuant to the terms of the Reverse Merger, and such shares will be available for the granting of awards under the 2018 Amended Plan in accordance with applicable stock exchange requirements. The Company also has outstanding stock options under the Magenta Therapeutics, Inc. 2016 Stock Option and Grant Plan, as amended (the “2016 Plan”), but is no longer granting awards under the 2016 Plan.

The 2018 Amended Plan provides that the number of shares reserved and available for issuance under the 2018 Amended Plan will automatically increase each January 1 by 5% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31 (the “Evergreen Provision”), or such lesser number of shares as determined by the Company’s board of directors or compensation committee of the board of directors.

Pursuant to the Evergreen Provision, the number of shares reserved for issuance under the 2018 Amended Plan increased by 2,161,025 on January 1, 2026. Shares of common stock underlying any awards under the 2018 Amended Plan, the 2019 Stock Plan and the 2016 Plan that are forfeited, cancelled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without any issuance of stock, expire or are otherwise terminated (other than by exercise) will be available for future awards under the 2018 Amended Plan.

As of September 30, 2026, 1,672,958 shares of common stock were available for grant under the 2018 Amended Plan.

2019 Stock Plan

In July 2019, Former Dianthus’s board of directors adopted, and Former Dianthus’s stockholders approved, the Dianthus Therapeutics, Inc. 2019 Stock Plan (the “2019 Stock Plan”). In connection with the Reverse Merger, the Company assumed options to purchase shares of Former Dianthus’s common stock that were outstanding under the 2019 Stock Plan immediately prior to the Reverse Merger and such options were converted into options to purchase 1,273,454 shares of common stock (the “Assumed Options”). No further awards will be made under the 2019 Stock Plan; however, the Assumed Options will remain outstanding under the 2019 Stock Plan in accordance with their terms, as adjusted to reflect the Reverse Merger.

2019 Employee Stock Purchase Plan

Employees may elect to participate in the Dianthus Therapeutics, Inc. 2019 Employee Stock Purchase Plan, as amended (the “ESPP”). The purchase price of common stock under the ESPP is equal to 85% of the lower of the fair market value of the common stock on (i) the offering date or (ii) the exercise date. The six-month offering periods begin in January and July of each year. During the three and nine months ended September 30, 2026, the Company issued 7,232 and 15,121 shares of common stock pursuant to the ESPP, respectively. During the three and nine months ended September 30, 2025, the Company issued 11,863 and 18,801 shares of common stock pursuant to the ESPP, respectively. As of September 30, 2026,190,656 shares remained available for issuance under the ESPP.

The ESPP provides that the number of shares reserved and available for issuance under the ESPP will automatically increase each January 1 through January 1, 2029, by the lesser of (i)1% of the number of shares issued and outstanding on the immediately preceding December 31, (ii)62,500 shares and (iii) such number of shares as determined by the Company’s board of directors or its appointed administrator. The number of shares reserved for issuance under the ESPP increased by 62,500 on January 1, 2026.

Inducement Plan

In February 2024, the Company’s board of directors approved the Dianthus Therapeutics, Inc. Equity Inducement Plan (the “Inducement Plan”), which provides for up to 300,000 shares of common stock for inducement awards. In December 2025, the Company’s board of directors approved an amendment to the Inducement Plan (the “Amended Inducement Plan”), which increased the number of shares of common stock available for inducement awards to 900,000. As of September 30, 2026, there were 236,000 shares of common stock available for grant under the Amended Inducement Plan.

Stock Options

The following table summarizes stock option activity for thenine months ended September 30, 2026:

The aggregate intrinsic value of options granted, options exercised and options forfeited represents the difference between (i) the exercise price of the option and (ii) the closing market price of the Company’s common stock on (x) September 30, 2026, (y) the date of exercise, or (z) the date of forfeiture, respectively.

The weighted-average grant-date fair value per share of stock options granted during the nine months ended September 30, 2026 was $47.00 per share.

The table below summarizes the assumptions used to determine the grant-date fair value of stock options issued, presented on a weighted-average basis during the three and nine months ended September 30, 2026 and 2025:

Stock Warrants

In April 2021, Former Dianthus issued 4,677 warrants for the purchase of common stock at an exercise price of $1.65 per share. The warrants vested on July 30, 2023 and had a grant-date fair value of $1.16 per warrant. During thenine months ended September 30, 2026, these warrants were exercised in full.

Stock-Based Compensation Expense

The following table provides a summary of stock-based compensation expense:

As of September 30, 2026, there was $131.5 million of total unrecognized compensation cost related to granted stock options. The Company expects to recognize that cost over a remaining weighted-average period of 2.9 years.

12. License Revenues

Zenas BioPharma, Inc.

In September 2020, the Company entered into an Option Agreement (the “Zenas Option”) with Zenas BioPharma, Inc. (formerly Zenas BioPharma Limited) (“Zenas”), formerly considered a related party. Through the Zenas Option, the Company provided Zenas an option to enter into an exclusive license agreement for the development and commercialization of products arising from its research of monoclonal antibody antagonists targeting certain specific complement proteins.

In October 2021, Zenas exercised its option for such clinical candidate under the Zenas Option. Zenas paid the Company a one-time payment of $1.0 millionfor the exercise of the corresponding option. In addition, in connection with the exercise of the Zenas Option, Zenas was required to reimburse the Company for a portion of chemistry, manufacturing and control (“CMC”) costs and expenses from the date of delivery of its option exercise notice through the execution of a license agreement.

In June 2022, pursuant to the Zenas Option, the Company negotiated in good faith a license agreement with Zenas (the “Zenas License Agreement” and, together with the Zenas Option, the “Zenas Agreements”). The Zenas License Agreement provided Zenas with a license in the People’s Republic of China, including Hong Kong, Macau, and Taiwan (“Greater China”) for the development and commercialization of sequences and products under the first antibody sequence. The Company was also obligated to perform certain research and development and CMC services and participate in a joint steering committee (“JSC”).

The consideration under the Zenas Agreements included the following payments by Zenas to the Company: (i) a $1.0 million upfront payment upon the exercise of the corresponding option under the Zenas Option; (ii) an approximately $1.1 million reimbursement payment for a portion of development costs previously incurred by the Company; (iii) reimbursement of a portion of all CMC-related costs and expenses for the first antibody sequence through the manufacture of the first two batches of drug product; (iv) reimbursement of a portion of all non-CMC-related costs and expenses for the development of the first antibody sequence through the first regulatory approval; (v) development milestones totaling up to $11.0 million; and (vi) royalties on net sales ranging from the mid-single digits to the low teen percentages.

The Company previously considered Zenas to be a related party because the sole member of Tellus BioVentures LLC (“Tellus”), who is a significant shareholder in the Company and was a member of the board of directors of the Company until May 2025, is a significant shareholder in Zenas and serves as Chief Executive Officer and Chairman of the board of directors of Zenas. The Company no longer considers Zenas to be a related party.

In September 2020, Zenas issued 156,848 common shares to the Company in exchange for the Zenas Option. Prior to September 12, 2024, the Company used the measurement alternative as the measurement attribute for accounting for the Zenas common stock which did not require it to assess the fair value of the common stock at each reporting period as the fair value of the Zenas common stock was not readily determinable nor was there a reliable source for observable transactions from which the Company could determine a fair value. On September 12, 2024, Zenas announced the pricing of its initial public offering (the “Zenas IPO”) of $17.00 per share, which also included a 1-for-8.6831 reverse stock split of its capital stock. Upon the Zenas IPO, the fair value of the Zenas common stock was deemed readily determinable. The Company reassesses the fair value of the investment at the end of each reporting period, with any adjustments to the fair value recorded as unrealized gains or losses within other income/(expense) in the unaudited condensed consolidated statements of operations and comprehensive loss. As of September 30, 2026 and December 31, 2025, the fair value of the investment in Zenas was $0.5 million and $0.7 million, respectively, which was included within other assets and restricted cash on the Company’s unaudited condensed consolidated balance sheet.

Tenacia Biotechnology (Hong Kong) Co., Limited

On October 21, 2024, Zenas assigned the Zenas Agreements to its affiliated entity, Zenas BioPharma (HK) Limited (“Zenas HK”). After the assignment, the Company entered into a novation agreement (the “Novation Agreement”) with Zenas HK and Tenacia Biotechnology (Hong Kong) Co., Limited (“Tenacia”), and an amendment to the Zenas License Agreement, now with Tenacia (as amended, the “Tenacia License Agreement”), pursuant to which Tenacia replaced Zenas HK as a party to the Zenas Agreements, and certain economic terms under the Zenas License Agreement with respect to cost sharing and development milestones were amended.

Except as otherwise noted below, the terms of the Zenas License Agreement were unchanged when novated by the Novation Agreement and amended by the Tenacia License Agreement.

The consideration under the Tenacia License Agreement, which replaced the consideration of the Zenas License Agreement, related to the first antibody sequence includes the following payments by Tenacia to the Company: (i) a $2.5 million upfront payment, which was paid to the Company in October 2024 upon execution of the Tenacia License Agreement; (ii) reimbursement of a portion of certain clinical costs; (iii) development milestones totaling up to $15.0 million; and (iv) royalties on net sales ranging from the mid-single digits to the low teen percentages. Tenacia is also responsible for paying local development costs in Greater Chinaand a portion of the central development costs based on the number of patients enrolled from China in the Company’s global Phase 3 studies.

Under the Zenas Agreements, Zenas also had the right to exercise an option with respect to a second antibody sequence, which is now held by Tenacia (the “Tenacia Option” and, together with the Tenacia License Agreement, the “Tenacia Agreements”). Pursuant to the Tenacia Option, if Tenacia exercises the option and pays the Company the option exercise fee related to the second antibody sequence, the Company will grant Tenacia an exclusive license to the sequences and products under this second antibody sequence.

Accounting for the Zenas and Tenacia Agreements

Since the Zenas Agreements were negotiated with a single commercial objective, they were treated as a combined contract for accounting purposes. The Company assessed the Zenas Agreements in accordance with ASC 606, Revenue from Contracts with Customers (“ASC 606”), and concluded that they represented a contract with a customer and were within the scope of ASC 606. The Company determined that there was one combined performance obligation that consisted of the license and data transfer, the research and development and CMC services, and the participation in the JSC. The Company determined that Zenas’ right to exercise an option with respect to a second antibody sequence did not represent a material right.

The Company determined that the combined performance obligation would be satisfied over time; therefore, the Company recognized the transaction price from the license agreement over the Company’s estimated period to complete its activities. The Company concluded that it would utilize a cost-based input method to measure its progress toward the completion of its performance obligation and to calculate the corresponding amount of revenue to recognize each period. The Company believed that this was the best measure of progress because other measures did not reflect how the Company transferred its performance obligation to Zenas. In applying the cost-based input method of revenue recognition, the Company used actual costs incurred relative to budgeted costs expected to be incurred for the combined performance obligation. These costs consisted primarily of third-party contract costs. Revenue was recognized based on the level of costs incurred relative to the total budgeted costs for the combined performance obligation. A cost-based input method of revenue recognition required management to make estimates of costs to complete the Company’s performance obligation. In making such estimates, judgment was required to evaluate assumptions related to cost estimates.

The Company assessed the Tenacia Agreements in accordance with ASC 606 and applied the same considerations above to the Tenacia Agreements. With the exception of the cost sharing and development milestones noted below, the key terms of the Zenas License Agreement were unchanged when novated by the Novation Agreement and amended by the Tenacia License Agreement. Therefore, the Company determined that the accounting considerations and resulting conclusions noted above related to the Zenas Agreements also apply to the Tenacia Agreements.

The Company also determined that the milestone payments of $15.0 million (previously $11.0 million under the Zenas License Agreement) are variable consideration under ASC 606 which need to be added to the transaction price when it is probable that a significant revenue reversal will not occur. Based on the nature of the milestones, such as the regulatory approvals which are generally not within the Company’s control, the Company will not consider achievement of each milestone to be probable until the uncertainty associated with such milestone has been resolved. Should it be probable that a significant reversal of revenue will not occur, the milestone payment will be added to the transaction price for which the Company recognizes revenue. No milestones were achieved under the Zenas Agreements prior to novation. As of September 30, 2026,$7.0 million of cumulative milestones were achieved under the Tenacia Agreements and added to the transaction price.

There is a sales or usage-based royalty exception within ASC 606 that applies when a license of intellectual property is the predominant item to which the royalty relates. In accordance with this royalty exception, the Company will recognize royalty revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). The Company hasnot recorded any royalty revenue to date.

The Company recognized license revenue totaling$1.2 million and $2.4 million during thethree and nine months ended September 30, 2026, respectively, and $0.4 million and $1.8 million during thethree and nine months ended September 30, 2025, respectively, associated with the Tenacia License Agreement. As of September 30, 2026, the Company recorded a receivable of $0.5 million, an unbilled receivable of $0.2 million within prepaid expenses and other current assets, current deferred revenue of $1.6 million and noncurrent deferred revenue of $5.4 million on its unaudited condensed consolidated balance sheet. As of December 31, 2025, the Company recorded accounts receivable of $52 thousand, an unbilled receivable of $50 thousand within prepaid expenses and other current assets, current deferred revenue of $1.2 million and noncurrent deferred revenue of $5.8 million on its unaudited condensed consolidated balance sheet.

13. Net Loss Per Share

Basic and diluted net loss per share of common stock were calculated as follows:

Pre-funded warrants have been included in the computation of basic and diluted net loss per share of common stock as the pre-funded warrants are issuable for nominal consideration pursuant to their terms. There were outstanding pre-funded warrants of 1,346,922 and 1,944,454 as of September 30, 2026 and 2025, respectively. The outstanding pre-funded warrants increased the weighted-average number of shares of common stock outstanding by 1,346,922 shares and 1,503,799 shares for thethree and nine months ended September 30, 2026, respectively, and 3,693,979 shares and 3,759,705 shares for thethree and nine months ended September 30, 2025, respectively.

The Company’s potential dilutive securities, which include stock options and warrants for the purchase of common stock, have been excluded from the computation of diluted net loss per share as the effect would be antidilutive. Therefore, the weighted-average number of shares of common stock outstanding used to calculate both basic and diluted net loss per share is the same. The following potential dilutive securities, presented on an as converted basis, were excluded from the calculation of net loss per share due to their anti-dilutive effect:

14. 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. As of September 30, 2026, the Company has paid Leads $30.0 million in upfront and near-term milestone payments. 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 percentage 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 $26 thousand and $0.2 million during thethree and nine months ended September 30, 2026, respectively, for amounts owed to Leads within the research and development expenses line item in the unaudited condensed consolidated statements of operations and comprehensive loss.

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:

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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

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with respect to Alloy antibodies and platform assisted antibodies 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 an annual partnered antibody program fee totaling $50 thousand 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 additional payments to Alloy of up to $1.8 million and $11.0 million, respectively. The Company recorded $0.1 million during each of the three and nine months ended September 30, 2026 and $1.0 million and $1.1 million during the three and nine months ended September 30, 2025, respectively, for amounts owed under the Alloy license agreement within the research and development expenses line item in the unaudited condensed consolidated statements of operations and comprehensive loss.

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 $4.1 million based on the September 30, 2026 exchange rate) and £2.3 million (approximately $3.0 million based on the September 30, 2026 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 $3.3 million based on the September 30, 2026 exchange rate). The Company recorded $0.2 million and $0.8 million during thethree and nine months ended September 30, 2026, respectively, and $1.3 million and $1.6 million during thethree and nine months ended September 30, 2025, respectively, for amounts owed under the IONTAS collaborative research agreement, including milestone payments, within the research and development expenses line item in the unaudited condensed consolidated statements of operations and comprehensive loss.

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 unaudited condensed consolidated financial statements as of September 30, 2026 and December 31, 2025.

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 September 30, 2026 and 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.