argenx Shows Durable Efgartigimod Benefits in Myositis and Sjögren’s Disease

argenx presented new long-term data at the EULAR 2026 Congress showing that efgartigimod delivered sustained clinical benefits and maintained a consistent safety profile in autoimmune myositis and Sjögren’s disease. Findings from the ALKIVIA+ (NCT05979441) and RHO+ (NCT06203457) extension studies further support FcRn blockade as a potential treatment approach for autoantibody-driven rheumatic diseases with significant unmet need.

Durable Benefits in Autoimmune Myositis

Autoimmune myositis is a chronic inflammatory disease that causes progressive muscle weakness and can affect multiple organs. New data from the ALKIVIA+ open-label extension demonstrated sustained clinical improvement through 52 weeks of treatment.

The study enrolled patients who completed the Phase 2 ALKIVIA trial and either continued efgartigimod or switched from placebo. Total Improvement Score (TIS), a composite measure of disease activity and physical function, remained durable across both groups.

Among continuously treated patients, 37.5% (6/16) maintained major improvement achieved at Week 24, while 75.0% (12/16) sustained moderate improvement. In patients who crossed over from placebo, 33.3% (5/15) achieved major improvement and 66.7% (10/15) achieved moderate improvement. Mean TIS reached 52.19 in the continuous-treatment group and 49.62 in crossover patients at Week 52. No increase in adverse events was observed with longer treatment exposure.

According to study investigator Hector Chinoy, M.D., Ph.D., the findings suggest efgartigimod may provide meaningful and sustained symptom improvement with favorable long-term tolerability in a disease with limited treatment options.

Sustained Responses in Sjögren’s Disease

Sjögren’s disease is a systemic autoimmune disorder characterized by dry eyes, dry mouth, fatigue, joint pain, and organ involvement. In the 48-week RHO+ extension study, patients who continued efgartigimod treatment or crossed over from placebo maintained or achieved clinical responses.

Patients who transitioned to biweekly dosing maintained improvements in disease activity and Composite of Relevant Endpoints for Sjögren’s Syndrome (CRESS) responses. At Week 72, median ClinESSDAI scores remained low at 2.5 in continuously treated patients and 2.0 in crossover patients, indicating sustained low disease activity. Investigators reported no new safety signals during long-term treatment.

Consistent Safety Across Indications

A pooled safety analysis evaluated 834 patients across multiple global studies, representing more than 1,300 patient-years of follow-up. Efgartigimod demonstrated a consistent safety profile across myositis, Sjögren’s disease, lupus nephritis, pemphigus vulgaris, immune thrombocytopenia, and other IgG-mediated autoimmune disorders.

Most adverse events were mild to moderate, and no increase in event rates was observed with longer treatment duration.

Regulatory Outlook

Efgartigimod is a FcRn-blocking antibody fragment that lowers circulating pathogenic IgG autoantibodies. The therapy is approved globally for generalized myasthenia gravis and chronic inflammatory demyelinating polyneuropathy, with additional development programs underway.

Topline Phase 3 ALKIVIA results in autoimmune myositis are expected in the third quarter of 2026, while Phase 3 UNITY results in moderate-to-severe Sjögren’s disease are anticipated in the second half of 2027.

Reference

argenx | argenx Presents New Efgartigimod Data Showing Long-Term Sustained Patient Benefit in Myositis and Sjogren’s Disease at EULAR 2026