Phase 3 CAPTIVATE Trial of Claseprubart in CIDP Now Enrolling, Trial Design Presented at PNS 2026

Details of the pivotal phase 3 CAPTIVATE trial (NCT06858579) of claseprubart (DNTH103; Dianthus Therapeutics), an investigational selective C1s complement inhibitor, in chronic inflammatory demyelinating polyneuropathy (CIDP) were presented at the 2026 Peripheral Nerve Society (PNS) Annual Meeting in Maastricht, Netherlands.¹ The trial, which launched in 2025 and is actively enrolling participants across North and South America, Europe, and Asia, represents the first phase 3 evaluation of claseprubart in CIDP.

Background

Claseprubart is a potent monoclonal antibody engineered to selectively bind only the active form of C1s, inhibiting the classical complement pathway while preserving lectin and alternative pathway activity. This design is intended to reduce infection risk relative to broader complement inhibition, and the agent incorporates YTE half-life extension technology to support biweekly, self-administered subcutaneous dosing.³

Jeffrey Allen, MD, Associate Professor of Neurology at the University of Minnesota and a specialist in inflammatory neuropathies, presented the trial design as part of Dianthus Therapeutics' broader development program for claseprubart across neuromuscular indications. Prior to CAPTIVATE, the agent was evaluated in the phase 2 MaGic trial (NCT06282159) in patients with acetylcholine receptor antibody-positive generalized myasthenia gravis (gMG).

That study demonstrated statistically significant improvements in myasthenia Gravis-Activities of Daily Living scores (placebo-adjusted improvement, 1.8 points at 300 mg; P = .0013) and Quantitative Myasthenia Gravis scores (placebo-adjusted improvement, 2.4 points; P = .0144), with effects observed as early as week 1 and no serious adverse events in the active group.² Based on those results, Dianthus is planning a phase 3 trial in gMG, with initiation expected in mid-2026. Claseprubart is also under evaluation in the phase 2 MoMeNtum trial in multifocal motor neuropathy, with topline data anticipated in the second half of 2026.³

In March 2026, Dianthus announced an early GO decision from the CAPTIVATE interim responder analysis, after 20 confirmed Part A responders were achieved with fewer than 40 participants completing the open-label phase, ahead of the company's prior Q2 2026 guidance. The independent data safety monitoring board confirmed the GO decision, with no related serious infections, no clinical symptoms of autoimmune activation, and no related serious adverse events or discontinuations. Following that decision, Dianthus revised planned Part A enrollment from up to 480 to up to 256 patients, with 128 patients to be randomized into Part B.³

CAPTIVATE Trial Design

By design, CAPTIVATE is a global, multicenter, randomized, double-blind, placebo-controlled phase 3 study evaluating the efficacy and safety of claseprubart in adults aged 18 to 75 with a CIDP diagnosis confirmed per 2021 EAN/PNS guidelines by an independent adjudication panel.¹ The trial enrolls a broad population, including patients who are responders to standard-of-care (SOC) therapy (immunoglobulins or oral corticosteroids), refractory to SOC, or treatment-naive.

The study is structured in two sequential parts. Part A is an open-label induction phase in which all participants receive an initial intravenous loading dose followed by biweekly subcutaneous claseprubart for up to 13 weeks. In SOC-responder participants, immunoglobulin therapy is discontinued 1 week before dosing while oral corticosteroids are tapered and continued.

Responders in Part A, defined as achieving at least a 1-point improvement in adjusted Inflammatory Neuropathy Cause and Treatment (INCAT) score, are then randomized into Part B, a 52-week double-blind, placebo-controlled withdrawal period (N = 64 per arm). The primary endpoint is time to relapse, with relapse defined as at least a 1-point worsening in adjusted INCAT score. Key secondary endpoints assess change in Inflammatory Rasch-built Overall Disability Scale (I-RODS) score and grip strength.¹

Participants who complete Part B or experience relapse may enter an optional open-label extension of up to 104 weeks, followed by a 40-week safety follow-up upon discontinuation. This enriched responder design is consistent with approaches used in pivotal trials of other approved CIDP therapies and is intended to maximize the ability to detect a treatment difference in relapse prevention.

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REFERENCES
1. Allen J, Querol L, Eftimov F, et al. CAPTIVATE Trial Design: A Pivotal Phase 3 Study of Claseprubart in Chronic Inflammatory Demyelinating Polyneuropathy. Abstract presented at: Peripheral Nerve Society Annual Meeting; 2026; Maastricht, Netherlands. Abstract P 423.
2. Dianthus Therapeutics announces positive data for claseprubart (DNTH103) from the phase 2 MaGic trial in generalized myasthenia gravis, supporting its potential best-in-class profile. News release. Dianthus Therapeutics. September 8, 2025. Accessed June 11, 2026. https://investor.dianthustx.com/news-releases/news-release-details/dianthus-therapeutics-announces-positive-data-claseprubart
3. Dianthus Therapeutics announces early GO decision following interim responder analysis in phase 3 CAPTIVATE trial of claseprubart in chronic inflammatory demyelinating polyneuropathy (CIDP). News release. Dianthus Therapeutics. March 9, 2026. Accessed June 11, 2026. https://investor.dianthustx.com/news-releases/news-release-details/dianthus-therapeutics-announces-early-go-decision-following
4. Van den Bergh PYK, van Doorn PA, Hadden RDM, et al. European Academy of Neurology/Peripheral Nerve Society guideline on diagnosis and treatment of chronic inflammatory demyelinating polyradiculoneuropathy. J Peripher Nerv Syst. 2021;26(3):242-268. doi:10.1111/jns.12455. https://doi.org/10.1111/jns.12455