argenx SE ((Euronext &, NASDAQ:ARGX), a global immunology company committed to improving the lives of people suffering from severe autoimmune diseases, today announced the presentation of new data evaluating VYVGART® (IV: efgartigimod alfa-fcab and SC or Hytrulo: efgartigimod alfa and hyaluronidase-qvfc) across autoimmune rheumatic diseases, including myositis and Sjogren's disease, to be presented at the European Alliance of Associations for Rheumatology (EULAR) 2026 Congress from June 3-6, 2026, in London, UK.

"Our presentations at EULAR further support the rationale for targeting FcRn in autoimmune rheumatic diseases and underscore its potential to address significant unmet patient need," said Luc Truyen, M.D., Ph.D., Chief Medical Officer at argenx. "We are encouraged by the consistency of the long-term data as well as data underscoring efgartigimod's favorable safety profile across multiple autoimmune rheumatic diseases. We are looking forward to additional results evaluating efgartigimod in myositis later this year as well as in Sjogren's disease next year."

Myositis and Sjogren's disease are both chronic, progressive autoimmune diseases that are generally more common in women than men. Myositis can cause serious and irreversible damage to muscles and organs, leading to a loss of independence and a significant burden for patients. Sjogren's disease can cause dry eyes and mouth, chronic fatigue, and joint pain. It can also affect multiple organ systems and lead to nervous system complications.

Efgartigimod provides sustained functional improvement in patients with myositis

ALKIVIA+ is an ongoing open-label extension study that enrolled patients who completed the 24-week, double-blind, placebo-controlled Phase 2 ALKIVIA trial, including those who continued efgartigimod treatment and those who transitioned from placebo to efgartigimod. Results presented at EULAR are an interim analysis through Week 52.

A key metric in ALKIVIA+ is Total Improvement Score (TIS). TIS is a composite index based on six core set measures, including muscle strength, physician and patient global assessments of disease activity, physical function, enzyme levels, and extramuscular activity. Higher TIS values reflect greater overall clinical improvement. Moderate and major improvement are defined as TIS ≥40 and ≥60, respectively.

Results showed:

  • At 52 weeks, 37.5% of patients who had continuously received efgartigimod maintained their major TIS improvement from week 24. 33.3% of patients switching from placebo to efgartigimod achieved a similar major TIS improvement. Rates of moderate TIS improvement were also similar between the groups, at 75.0% and 66.7%, respectively.
  • Sustained mean TIS benefit: Patients receiving continuous efgartigimod maintained clinically meaningful improvement through 52 weeks, with a mean TIS of 52.19. Patients who switched from placebo to efgartigimod achieved comparable improvement, with a mean TIS of 49.62 at week 52.
  • The safety profile was consistent over the course of the study, with no increase in adverse events with longer exposure.
  • These results further support the mechanistic relevance of FcRn blockade in myositis, providing further evidence that pathogenic autoantibodies are the underlying driver of disease.

"Patients with autoimmune myositis face the serious challenge that their immune system attacks their own body, causing irreversible muscle loss, weakness, pain and reduced quality of life, while the limited available treatments can carry significant side effects and be difficult to tolerate long term," said Hector Chinoy, M.D., Ph.D., presenting study author and Professor of Rheumatology and Neuromuscular Disease at The University of Manchester. "Emerging results from the ALKIVIA+ study suggest that efgartigimod has the potential to deliver meaningful and sustained clinical benefit for patients with myositis, with a favorable tolerability profile."

Topline results from the Phase 3 ALKIVIA study are expected in the third quarter of 2026.

Efgartigimod achieved maintenance of response in Sjogren's disease

RHO+, a 48-week open-label extension study, evaluated patients with Sjogren's disease who continued to receive efgartigimod, and those who transitioned from placebo to efgartigimod after completing the 24-week double-blind treatment period of the Phase 2 RHO study.

Response to efgartigimod was assessed using the Composite of Relevant Endpoints for Sjogren's Syndrome (CRESS), a composite endpoint designed to capture overall treatment benefit across multiple clinical domains, including disease activity as measured by ClinESSDAI. Patients in the efgartigimod arm were switched to biweekly dosing based on ClinESSDAI response.

Results showed:

  • Patients in the efgartigimod arm switching to biweekly dosing experienced maintenance of response on clinical measures.
  • Patients in the placebo arm switching to efgartigimod experienced improvements in ClinESSDAI and increased CRESS response.
  • At week 72, median ClinESSDAI scores were low in both groups: 2.5 in the efgartigimod arm and 2.0 in patients who transitioned from placebo to efgartigimod. Low disease activity is indicated by a ClinESSDAI score of <5.
  • Efgartigimod was well tolerated, with no new safety signals identified following long-term use in participants with Sjogren's disease.

The Phase 3 UNITY trial is currently ongoing to assess efficacy and safety of efgartigimod in patients with moderate to severe Sjogren's disease. Topline results are expected in the second half of 2027.

Efgartigimod safety profile reinforced across autoantibody-driven autoimmune diseases

A cross-indication safety analysis of efgartigimod spanning multiple global clinical studies, including autoimmune rheumatic diseases, indicated that efgartigimod is consistently well-tolerated across diseases and administration methods.

  • Data showed a consistent safety profile across 834 treated patients and more than 1,300 patient-years of follow-up. Efgartigimod was well tolerated in participants with autoimmune rheumatic diseases (myositis, Sjogren's disease, and lupus nephritis), consistent with findings from prior studies in other IgG-mediated autoimmune diseases and also consistent with what has been observed in approved indications globally.
  • Adverse events were predominantly mild-to-moderate, and no increased event rates were seen in studies with a longer treatment duration.