Argenx: Phase 3 results of efgartigimod in myositis to be presented in November
Argenx announced on October 19, 2026, the forthcoming presentation of results from the phase 3 ALKIVIA study in autoimmune myositis, whose primary endpoint was met with a difference of 15.4 points in favor of efgartigimod on the Total Improvement Score (TIS) at 52 weeks. This result applies to the combined population of patients with immune-mediated necrotizing myopathy (IMNM) and dermatomyositis (DM). According to the group, therapeutic options are limited in these two forms, and there is no approved treatment in IMNM.
This publication comes shortly after the discontinuation, announced on October 8, 2026, of the phase 3 UNITY trial of the same molecule in Sjögren's disease, on the recommendation of an independent data monitoring committee which determined that the study would not be able to achieve its primary endpoint. ALKIVIA, presented by Argenx as the first registration study of an FcRn blocker in autoimmune myositis, will be detailed on November 11, 2026 at the ACR Convergence congress in Orlando.
A difference of 15.4 points on the TIS score versus placebo at 52 weeks
On the primary endpoint, patients treated with efgartigimod achieved an average TIS score of 47.95 at week 52, compared to 32.56 in the placebo arm, a difference of 15.4 points (p = 0.0011). The TIS, scored from 0 to 100, is a composite endpoint validated by the ACR and EULAR, based on six reference measures, including muscle strength and function. A higher score reflects greater overall clinical improvement.
According to Argenx, improvement in disease activity was observed as early as week 4 and was sustained over the 52 weeks of treatment, while the protocol required progressive reduction of corticosteroids throughout the study. The laboratory indicates that a higher proportion of IMNM and DM patients achieved a TIS of at least 40 with efgartigimod, a threshold that the clinical community associates with perceptible improvement in muscle strength and function.
The median time to reach this threshold was also shorter with efgartigimod in both subtypes, according to the company. In terms of tolerability, the laboratory reports that the molecule was well tolerated and that the safety profile observed is consistent with that of previous studies.
A global randomized trial including 175 treated patients
All study participants had active disease and were receiving background treatment. The placebo arm thus also showed an average TIS of 32.56: the effect attributable to efgartigimod is therefore read in the difference of 15.4 points between the two arms, and not in the raw score of 47.95.
ALKIVIA is a global, randomized, double-blind, placebo-controlled study, designed as a seamless phase 2/3 trial. It randomized 265 patients in a 1:1 ratio: 89 in the phase 2 portion, then 176 in phase 3, of whom 175 received treatment by weekly subcutaneous injections. The trial included three myositis subtypes (IMNM, DM, and polymyositis), and the results highlighted by the group apply to the combined IMNM and DM population.
The medical need addressed is documented by the company: approximately 100,000 people live with autoimmune myositis in the United States, of whom approximately 20,000 have IMNM and approximately 40,000 have DM. Up to 80% of patients report persistent disability despite treatments, which rely mainly on corticosteroids and broad-spectrum immunosuppressants, associated according to Argenx with significant cumulative toxicity.
Oral presentation on November 11 at the ACR congress
The data will be presented in a late-breaking oral session (reference LB24) on November 11, 2026, from 9:15 a.m. to 9:30 a.m. Eastern Time, by Dr. Rohit Aggarwal, lead author. Luc Truyen, Medical Director of Argenx, stated that ALKIVIA provides "the first phase 3 evidence" that targeting FcRn with efgartigimod can provide clinically meaningful benefit to patients with autoimmune myositis.
Efgartigimod is already approved in generalized myasthenia gravis and chronic inflammatory demyelinating polyneuropathy (CIDP), as well as in Japan for primary immune thrombocytopenia. The study was conducted in North America, Europe, and Asia-Pacific, including China and Japan. Zai Lab, which holds an exclusive license for Vyvgart and Vyvgart Hytrulo in Greater China, recruited Chinese patients for the trial.
This result adds to that announced on October 8, 2026 for FB102, whose phase 2 study in celiac disease achieved its primary endpoint. For ALKIVIA, the key element established by the press release remains a difference of 15.4 points on the TIS score versus placebo at 52 weeks (p = 0.0011), in a phase 3 involving 175 treated patients.
