Argenx SE (ARGX), a commercial-stage biopharmaceutical company, announced new clinical data from Phase 2 extension studies for efgartigimod in the treatment of myositis and Sjogren's disease.
Myositis and Sjogren's disease are chronic progressive autoimmune rheumatic diseases that disproportionately affect women. Myositis significantly impairs the skeletal muscles and certain organs of the body, potentially resulting in functional impairment. Sjogren's disease is characterized by elevated autoantibody levels that primarily affect the exocrine glands and extraglandular organs throughout the body.
Efgartigimod (efgartigimod alfa fcab), known commercially as VYVGART is a human IgG1 antibody fragment that attaches to the neonatal Fc receptor (FcRn) leading to a reduction of circulating IgG antibodies. VYVGART was approved by the FDA in 2023 to treat generalized myasthenia gravis (gMG) and chronic inflammatory demyelinating polyneuropathy (CIDP).
ALKIVIA+ is an ongoing 28-week open-label, double-blind, placebo-controlled extension study of the Phase 2 ALKIVIA trial treating myositis patients with efgartigimod, and those transitioning from placebo. The primary endpoint measured long-term safety and tolerability. Clinical progress was also determined using the Total Improvement Score (TIS), which assesses disease activity, physical function, enzyme levels, and extra muscular activity.
According to the ALKIVIA+ results, at 52 weeks, 37.5% of patients on efgartigimod and 33.3% of patients who switched from placebo to efgartigimod showed a sustained major TIS improvement of 75% and 66.7%, respectively. Additionally, those who received continuous efgartigimod demonstrated a sustained mean TIS of 52.19, compared to the sustained mean TIS of 49.62 in patients who switched from placebo. The results further support the mechanistic relevance of FcRn blockade in myositis, indicating that pathogenic autoantibodies are the underlying driver of disease.
The RHO+ trial is an ongoing 48-week extension study of the Phase 2 RHO study for efgartigimod in Sjogren's disease. The primary endpoint was measured using Composite of Relevant Endpoints for Sjogren's Syndrome (CRESS) designed to capture overall treatment benefit across clinical domains, including disease activity as measured by ClinESSDAI.
Patients transitioned from the efgartigimod group to biweekly dosing showed maintenance of clinical response, recording a median ClinESSDAI of 2.5 at week 72, while those transitioned from the placebo arm to the drug showed a ClinESSDAI of 2 with improved CRESS scores.
The ongoing Phase 3 UNITY trial is further assessing the safety of efgartigimod in Sjogren's disease, with topline data expected in the second half of 2027.
Efgartigimod was found to have a favourable safety and tolerability profile across 834 tested patients in trials for myositis, Sjogren's disease, and lupus nephritis.
AGRX closed Tuesday at $802.17, down 4.06%. In the pre-market shares are trading down 1.25% to $792.13.
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