argenx SE has announced positive topline results from the ALKIVIA phase 3 study evaluating VYVGART Hytrulo (efgartigimod alfa and hyaluronidase-qvfc) in adults with autoimmune myositis.

In the combined Immune-Mediated Necrotising Myopathy (IMNM) and dermatomyositis (DM) population, patients treated with efgartigimod demonstrated statistically significant and clinically meaningful 15.4-point greater improvement in mean Total Improvement Score (TIS) at week 52 versus placebo (47.95 vs 32.56).

In the combined population, patients treated with efgartigimod consistently showed improvements over placebo starting at week 4 that were statistically significant and sustained through the full year of treatment, even with steroid tapering.

In pre-specified subtype analyses, the primary endpoint of Mean TIS at 52 weeks was also met in IMNM patients treated with efgartigimod (p=0.0048), with a 14.8-point greater improvement over placebo (45.05 vs 30.24). In DM, a similar clinically meaningful improvement of 14.5 points (p=0.1093) was observed (51.51 vs 36.96), though statistical significance was not reached in this smaller cohort.

In both IMNM and DM, all 6 core set measures of TIS contributed to the treatment effect, each favoring efgartigimod over placebo, spanning muscle strength, everyday physical function, and disease activity beyond the muscle. In DM, improvement in skin disease activity was also observed.

Efgartigimod was well-tolerated by patients in the ALKIVIA study. The observed safety profile was consistent with prior studies and the known safety profile of efgartigimod.

Luc Truyen, MD, PhD, Chief Medical Officer (CMO), argenx, said, "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. 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. This confirms that pathogenic IgG autoantibodies are key drivers of autoimmune myositis. We are grateful to the patients, caregivers, and investigators who made this pioneering study possible."

Detailed results from the ALKIVIA study will be presented at an upcoming medical meeting.

Efgartigimod continues to be evaluated as a potential treatment in other autoimmune rheumatologic diseases, including Sjögren’s disease and systemic sclerosis.

Rohit Aggarwal, MD, MS, Professor of Medicine and Co-Director, Myositis Center, University of Pittsburgh, and an ALKIVIA investigator, said, “For people living with myositis, the goal is straightforward: regain strength and function, and get off long-term steroids. Until now, we have had limited targeted therapies to offer patients. 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. In DM, the magnitude of improvement was comparable–and for a community where treatment options remain limited and the burden of chronic steroids is just as heavy, that matters. Together, these results tell us that reducing pathogenic autoantibodies is clinically meaningful and a major step forward for patients who are in need of a targeted treatment.”