argenx reports positive Phase 3 ALKIVIA data in autoimmune myositis

argenx SE announced on November 7, 2026 that its Phase 3 "ALKIVIA" study of efgartigimod (marketed as VYVGART Hytrulo) met its goals in patients with autoimmune myositis, with findings to be presented in a late-breaking session at the American College of Rheumatology Convergence 2026 on November 11, 2026.

In the combined population of immune-mediated necrotizing myopathy (IMNM) and dermatomyositis (DM) patients, patients treated with efgartigimod achieved a statistically significant and clinically meaningful 15.4-point greater improvement in mean Total Improvement Score at Week 52 versus placebo, with a p-value of 0.0011 and scores of 48.0 versus 32.6.¹ The study also met key secondary endpoints in the combined population, including response rate, time to response, muscle strength, and disease activity.¹

Looking at IMNM alone, patients treated with efgartigimod demonstrated a clinically meaningful 14.8-point greater improvement in mean TIS versus placebo at Week 52, with a p-value of 0.0048 and scores of 45.1 versus 30.2.¹ Based on these results, argenx said it intends to file a Supplemental Biologics License Application with the FDA for efgartigimod in IMNM before the end of 2026, a path supported by the drug's Breakthrough Therapy Designation.¹

In DM, the treatment effect was smaller and did not reach statistical significance: a 14.5-point greater improvement versus placebo in mean TIS at Week 52 was observed, with a p-value of 0.1093 and scores of 51.5 versus 37.0, in a smaller patient cohort.¹

On safety, efgartigimod was generally well tolerated, and the observed safety profile was consistent with prior studies and the known safety profile of the drug.¹ The trial randomized 265 patients 1:1 to weekly efgartigimod or placebo, with 175 patients receiving treatment in the Phase 3 portion.¹