argenx reports Phase 3 ALKIVIA results showing efgartigimod improved disease activity in IMNM and dermatomyositis, meeting the primary endpoint at Week 52.
Written By: Mayuri Vaja, PharmD
Reviewed By: Pharmacally Editorial Team
argenx reported that subcutaneous efgartigimod met the primary endpoint in the Phase 3 ALKIVIA study, improving disease activity in patients with immune-mediated necrotizing myopathy (IMNM) and dermatomyositis (DM). The findings support further evaluation of neonatal Fc receptor (FcRn) blockade in autoimmune muscle diseases with limited targeted treatment options.
The global Phase 3 ALKIVIA trial showed that efgartigimod alfa with hyaluronidase PH20 produced a 15.4-point greater improvement in Total Improvement Score (TIS) at Week 52 than placebo, meeting the primary endpoint in the combined IMNM and DM population. argenx will present the results at the American College of Rheumatology (ACR) Convergence 2026 meeting in Orlando, Florida, on November 11.
Phase 3 ALKIVIA Trial Demonstrates Sustained Improvement
The study reported a mean TIS of 47.95 with efgartigimod compared with 32.56 with placebo at Week 52, a between-group difference of 15.4 points (p=0.0011).
Improvements in disease activity emerged as early as Week 4 and continued through 52 weeks of treatment, despite a protocol-mandated corticosteroid taper. A greater proportion of patients receiving efgartigimod achieved a TIS of at least 40, with a shorter median time to reach this threshold than with placebo in both IMNM and DM.
TIS is an American College of Rheumatology/European Alliance of Associations for Rheumatology-validated composite measure ranging from 0 to 100. It incorporates six core set measures of disease activity, including muscle strength and function. A score of 40 or higher indicates a clinically meaningful improvement.
The reported results combine patients with IMNM and DM. Although the company also reported favorable findings in each subtype, the supplied announcement does not provide the separate numerical effect estimates needed to assess the magnitude of benefit within each group.
Targeting IgG Autoantibodies in Autoimmune Muscle Disease
Efgartigimod binds to the neonatal Fc receptor (FcRn), reducing circulating immunoglobulin G (IgG), including disease-associated autoantibodies. These antibodies contribute to muscle injury and other manifestations of autoimmune myositis.
The disease spectrum includes IMNM, DM and polymyositis (PM), with proximal muscle weakness a common feature. DM can also involve the skin and other organs. Treatment commonly relies on corticosteroids and broad immunosuppressants, which can cause cumulative metabolic, cardiovascular, musculoskeletal and infectious complications.
No approved treatment options currently exist specifically for IMNM, according to argenx. The company estimates that approximately 20,000 people in the United States have IMNM and 40,000 have DM.
Study Design and Safety Findings
ALKIVIA was a global, randomized, double-blind, placebo-controlled Phase 2/3 study evaluating subcutaneous efgartigimod across IMNM, DM and PM.
The trial randomized 265 patients with active disease receiving background treatment. Participants received weekly subcutaneous injections of efgartigimod PH20 or matched placebo. Following analysis of the initial 89-patient Phase 2 portion, the Phase 3 portion enrolled 176 patients, of whom 175 received treatment.
The Phase 3 primary endpoint assessed mean TIS at Week 52. Prespecified analyses evaluated the combined IMNM and DM population and each subtype separately.
Efgartigimod was well tolerated, with a safety profile consistent with previous studies and its established safety experience. The announcement did not provide detailed adverse-event rates, limiting further assessment of specific safety risks.
Implications for Development
Luc Truyen, chief medical officer at argenx, said the results provide Phase 3 evidence supporting FcRn inhibition in autoimmune myositis, where treatment options remain limited.
The findings strengthen the clinical rationale for reducing pathogenic IgG autoantibodies in IMNM and DM. However, the combined primary analysis does not establish the same magnitude of benefit in each subtype, and the available announcement does not provide detailed subgroup estimates or event-level safety data.
The late-breaking oral presentation, titled Efgartigimod PH20 SC in Adults with Idiopathic Inflammatory Myopathy: Results from the Phase 3, Randomized, Placebo-Controlled ALKIVIA Trial (LB24), is scheduled for November 11, 2026, from 9:15 to 9:30 a.m. ET.
The results mark an important clinical development milestone, but regulatory submissions, approval timelines and potential commercialization plans for autoimmune myositis were not specified in the announcement.
Reference
argenx to Present Phase 3 ALKIVIA Results in Autoimmune Myositis as a Late-Breaking Oral Presentation at ACR Convergence 2026, argenx, 19 October 2026
A Study to Investigate the Efficacy and Safety of Efgartigimod PH20 SC in Adult Participants with Active Idiopathic Inflammatory Myopathy. (ALKIVIA), ClinicalTrials.gov ID NCT05523167
About the Writer
Mayuri Vaja (Linkedin) is a Pharm.D professional with a strong interest in clinical research, pharmacovigilance, and medical writing, supported by certifications in pharmacovigilance and academic projects exploring AI in healthcare and drug safety.
With a growing focus on evidence-based healthcare and scientific communication, she is developing expertise in clinical research and translating healthcare evidence into clear, meaningful content.
As a Pharmacally healthcare writer, Mayuri is committed to creating accurate, research-driven, and clinically relevant healthcare content while continuously strengthening her professional skills.