DIANTHUS THERAPEUTICS HIGHLIGHTS RECENT BUSINESS ACHIEVEMENTS

AND REPORTS Q3 FINANCIAL RESULTS

Claseprubart achieved statistically significant and clinically meaningful improvements in Myasthenia Gravis Activities of Daily Living (MG-ADL), Quantitative Myasthenia Gravis (QMG), and other efficacy measures at Week 13 in Phase 2 MaGic trial in gMG

New claseprubart data from the MaGic open-label extension supporting potential for 300mg/2mL Q4W dosing and new in vitro data highlighting potential efficacy benefits of upstream (aC1s, claseprubart) vs. downstream (C5, ravulizumab) complement inhibition were presented during the AANEM Annual Meeting in October 2025

Phase 3 gMG trial including two claseprubart treatment arms, 300mg/2mL Q2W and 300mg/2mL Q4W, vs. placebo anticipated to initiate in 2026

Accelerated timing for interim responder analysis for Phase 3 CAPTIVATE trial of claseprubart in Chronic Inflammatory Demyelinating Polyneuropathy (CIDP); now anticipated in Q2’26 (formerly 2H’26) due to faster than expected enrollment

Phase 2 MoMeNtum trial of claseprubart in Multifocal Motor Neuropathy (MMN) ongoing; top-line results anticipated in 2H’26

Announced exclusive license agreement for DNTH212, a bifunctional BDCA2 and BAFF/APRIL inhibitor; Phase 1 healthy volunteer data anticipated in 2H’26

Estimated ~$525 million of cash after DNTH212 upfront and near-term milestone payments provides runway into 2028

New York City and Waltham, Mass., November 5, 2025 – Dianthus Therapeutics, Inc. (Nasdaq: DNTH), a clinical-stage biotechnology company dedicated to developing next-generation therapies to transform the treatment of severe autoimmune diseases, today reported financial results for the third quarter ending September 30, 2025, and provided an update on recent business achievements.

“I’m extremely proud of our team’s outstanding track record of execution against our vision to become a leading biotech company in the I&I field. Just in the past 2 months, we delivered impressive results from the gMG MaGic trial, accelerated the timing of the interim responder analysis from our CIDP CAPTIVATE trial from 2H’26 to Q2'26, and in-licensed DNTH212, a new and exciting clinical-stage bifunctional fusion protein. Both claseprubart and DNTH212 have validated mechanisms of action with pipeline-in-a-product potential, and aim to deliver best-in-class efficacy, safety, and convenience with infrequent, subcutaneous self-administration,” said Marino Garcia, Chief Executive Officer of Dianthus Therapeutics. “The claseprubart efficacy and safety data from the MaGic trial, including the recently presented data for placebo patients transitioning to claseprubart in the OLE and the post-hoc analyses highlighting the impact of QMG screening criteria on MG-ADL results, strongly support our Phase 3 plans to advance both 300mg/2mL Q2W and 300mg/2mL Q4W as a potential best-in-class treatment option in gMG. We remain focused on execution as we aim to deliver first-line biologic therapies that can meaningfully improve the lives of patients with severe autoimmune diseases.”

Claseprubart (DNTH103) Clinical Development

Claseprubart is an investigational, clinical-stage, potent monoclonal antibody engineered to selectively target the classical pathway by inhibiting only the active form of the C1s protein, a clinically validated complement target. Claseprubart is designed to enable a more convenient, subcutaneous, self-administered injection dosed as infrequently as once every two or four weeks. Claseprubart has the potential to be a best-in-class pipeline-in-a-product across a range of autoimmune disorders with high unmet need.

Generalized Myasthenia Gravis (gMG)

Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)

Multifocal Motor Neuropathy (MMN)

DNTH212 Clinical Development

DNTH212 is an investigational, extended half-life bifunctional fusion protein targeting plasmacytoid dendritic cell (pDC) BDCA2 to reduce Type 1 interferon production, while simultaneously inhibiting BAFF/APRIL to suppress B cell function. By targeting both the innate and adaptive immune systems via two clinically validated pathways that are known drivers of autoimmune disease pathogenesis, this complementary and differentiated approach has the potential to address multiple autoimmune indications with improved outcomes.

Corporate Updates

Third-Quarter 2025 Financial Results

About Claseprubart (DNTH103)
Claseprubart is an investigational, clinical-stage, potent monoclonal antibody engineered to selectively target the classical pathway by inhibiting only the active form of the C1s protein, a clinically validated complement target. Claseprubart is enhanced with YTE half-life extension technology designed to enable a more convenient subcutaneous, infrequently dosed, self-administered injection. Additionally, selective inhibition of the classical complement pathway may lower patient risk of infection from encapsulated bacteria by preserving immune activity of the lectin and alternative pathways. As the classical pathway plays a significant role in disease pathology, claseprubart has the potential to be a best-in-class pipeline-in-a-product across a range of autoimmune disorders with high unmet need. Dianthus is building a neuromuscular franchise with claseprubart and expects to initiate a Phase 3 trial in gMG in 2026, the interim responder analysis of the Phase 3 CAPTIVATE trial in Chronic Inflammatory Demyelinating Polyneuropathy in Q2’26, and top-line data from the Phase 2 MoMeNtum trial in Multifocal Motor Neuropathy in 2H’26.

Claseprubart is an investigational agent that is not approved as a therapy in any indication in any jurisdiction worldwide.

About DNTH212
DNTH212 is an investigational, extended half-life bifunctional fusion protein targeting plasmacytoid dendritic cell (pDC) BDCA2 to reduce Type 1 interferon production, while simultaneously inhibiting BAFF/APRIL to suppress B cell function. By targeting both the innate and adaptive immune systems via two clinically validated pathways that are known drivers of autoimmune disease pathogenesis, this complementary and differentiated approach has the potential to address multiple autoimmune indications with improved outcomes. A two-part Phase 1 study in China in healthy volunteers (Part A) and patients with systemic lupus erythematosus (Part B) is expected to initiate by year-end 2025, with top-line results in healthy volunteers expected in the second half of 2026.

DNTH212 is an investigational agent that is not approved as a therapy in any indication in any jurisdiction worldwide.

About Dianthus Therapeutics

Dianthus Therapeutics, Inc. is a clinical-stage biotechnology company dedicated to developing next-generation therapies to transform the treatment of severe autoimmune diseases. Based in New York City and Waltham, Mass., Dianthus is comprised of an experienced team of biotech and pharma executives who aim to deliver transformative medicines for people living with severe autoimmune and inflammatory diseases.

To learn more, please visit www.dianthustx.com and follow us on LinkedIn.

Cautionary Statement Regarding Forward-Looking Statements

Certain statements in this press release, other than purely historical information, may constitute “forward-looking statements” within the meaning of the federal securities laws, including for purposes of the safe harbor provisions under the United States Private Securities Litigation Reform Act of 1995, express or implied statements regarding future plans and prospects, including statements regarding the expectations or plans for discovery, preclinical studies, clinical trials and research and development programs, in particular with respect to claseprubart and DNTH212, and any developments or results in connection therewith, including the target product profile and administration of claseprubart and DNTH212; the anticipated timing of the initiation and results from those studies and trials; expectations regarding the clinical trial designs or indications; expectations regarding the time period over which the Company’s capital resources are expected to be sufficient to fund its anticipated operations; and expectations regarding market size, patient population size, and potential opportunities for complement therapies, in particular with respect to claseprubart and DNTH212. Claseprubart and DNTH212 are investigational agents that are not approved as therapies in any indication in any jurisdiction worldwide. The words “opportunity,” “potential,” “milestones,” “runway,” “will,” “anticipate,” “achieve,” “near-term,” “catalysts,” “pursue,” “pipeline,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “might,” “plan,” “possible,” “predict,” “project,” “should,” “strive,” “would,” “aim,” “target,” “commit,” and similar expressions (including the negatives of these terms or variations of them) generally identify forward-looking statements, but the absence of these words does not mean that statement is not forward looking.

Actual results could differ materially from those included in the forward-looking statements due to various factors, risks and uncertainties, including, but not limited to, that preclinical testing of claseprubart and DNTH212 and data from clinical trials may not be predictive of the results or success of ongoing or later clinical trials, that the development of claseprubart or DNTH212 may take longer and/or cost more than planned, that the Company or its partner may be unable to successfully complete the clinical development of the Company’s compounds, that the Company or its partner may be delayed in initiating, enrolling or completing its planned clinical trials, and that the Company's compounds may not receive regulatory approval or become commercially successful products. These and other risks and uncertainties are identified under the heading "Risk Factors" included in the Company’s Annual Report on Form 10-K for the period ended December 31, 2024, and other filings that the Company has made and may make with the SEC in the future. Nothing in this press release should be regarded as a representation by any person that the forward-looking statements set forth herein will be achieved or that any of the contemplated results of such forward-looking statements will be achieved.

The forward-looking statements in this press release speak only as of the date they are made and are qualified in their entirety by reference to the cautionary statements herein. Dianthus undertakes no obligation to publicly update or revise any forward-looking statement, whether as a result of new information, future events or otherwise, except as required by law.

Contact

Jennifer Davis Ruff

Dianthus Therapeutics

jdavisruff@dianthustx.com

DIANTHUS THERAPEUTICS, INC.

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DIANTHUS THERAPEUTICS, INC.

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