ALKIVIA: Efgartigimod Improves Myositis, Hits Phase 3 Primary End Point

Efgartigimod alfa and hyaluronidase-qvfc (VYVGART Hytrulo) met the primary endpoint of the phase 3 ALKIVIA trial in adults with autoimmune myositis, producing a 15.4-point greater improvement in mean Total Improvement Score (TIS) at week 52 versus placebo in the combined immune-mediated necrotizing myopathy (IMNM) and dermatomyositis (DM) population (47.95 vs 32.56; P = .0011), according to argenx.¹

ALKIVIA (NCT05523167) is a global, randomized, double-blind, placebo-controlled, operationally seamless phase 2/3 trial that enrolled 264 patients with active autoimmune myositis on background treatment, including an initial 89-patient phase 2 portion followed by a 175-patient phase 3 portion with a protocol-mandated corticosteroid taper.¹ Participants were randomized 1:1 to weekly subcutaneous efgartigimod PH20 or matched placebo PH20.¹

“For decades, people living with autoimmune myositis have relied on corticosteroids and broad immunosuppression, and those with IMNM have had no approved option at all. These are the first phase 3 results to show that precision targeting of FcRn with efgartigimod can deliver meaningful benefit in this disease,” said Luc Truyen, MD, PhD, chief medical officer at argenx. “The patient response to efgartigimod was durable and multidimensional: separation from placebo emerged early and held through a full year of treatment, with a treatment effect of comparable magnitude in IMNM and DM.”¹

What were Efgartigimod TIS results across IMNM and DM subtypes?

In prespecified subtype analyses, efgartigimod also met the primary endpoint in IMNM alone, with a 14.8-point greater improvement in mean TIS at week 52 versus placebo (45.05 vs 30.24; P = .0048).¹ In DM, a similar clinically meaningful 14.5-point improvement was observed (51.51 vs 36.96), though this did not reach statistical significance in the smaller DM cohort (P = .1093).¹ Treatment differences over placebo were apparent starting at week 4 and were sustained through the full 52 weeks despite the mandated steroid taper.¹

All 6 core set measures that comprise TIS, spanning muscle strength, everyday physical function, and extramuscular disease activity, favored efgartigimod over placebo in both IMNM and DM.¹ In DM specifically, improvement in skin disease activity was also observed.¹ argenx said the consistent treatment effect across subtypes supports pathogenic IgG autoantibodies as key drivers of autoimmune myositis.¹

What was efgartigimod’s safety profile?

Efgartigimod was well tolerated in ALKIVIA, with a safety profile consistent with prior studies and the established safety profile of efgartigimod.¹ Detailed results from the trial are expected to be presented at an upcoming medical meeting.¹

“For people living with myositis, the goal is straightforward: regain strength and function, and get off long-term steroids,” said Rohit Aggarwal, MD, MS, professor of medicine and co-director of the Myositis Center at the University of Pittsburgh and an ALKIVIA investigator. “IMNM is the most refractory form of this disease and many of these patients carry irreversible muscle damage, which makes meaningful improvement genuinely difficult to achieve. That is what makes these results so compelling and groundbreaking.”¹

An estimated 100,000 people in the US live with autoimmune myositis, including approximately 20,000 with IMNM and 40,000 with DM, and up to 80% report long-term disability despite treatment.¹ Care currently relies primarily on corticosteroids and broad immunosuppressants, which carry cumulative metabolic, cardiovascular, musculoskeletal, and infectious risks.¹ argenx is also evaluating efgartigimod in other autoimmune rheumatologic diseases, including Sjögren's disease and systemic sclerosis.¹

References

1. argenx. argenx Announces Positive Topline Results from Phase 3 ALKIVIA Trial of Efgartigimod in Autoimmune Myositis. Published August 17, 2026. Accessed August 17, 2026. https://argenx.com/news/2026/press-release-3345813

2. ClinicalTrials.gov. A Study to Investigate the Efficacy and Safety of Efgartigimod PH20 SC in Adult Participants With Active Idiopathic Inflammatory Myopathy. NCT05523167. Accessed August 17, 2026. https://clinicaltrials.gov/study/NCT05523167