Argenx: Efgartigimod Confirms Long-Term Efficacy in Two Autoimmune Diseases
On Wednesday, Argenx will present long-term efficacy data for its immunosuppressant efgartigimod in two rheumatic autoimmune diseases, myositis and Sjogren's syndrome, at the EULAR congress in London. The results demonstrate sustained clinical improvement and a consistent tolerance profile in both indications.
Myositis: Sustained Improvement Over 52 Weeks
In the ALKIVIA+ study, an open-label extension of the phase 2 trial, efgartigimod maintained significant clinical benefit in continuously treated patients. At 52 weeks, 37.5% of patients on continuous efgartigimod preserved a major improvement measured by the Total Improvement Score (TIS), a composite score including six rheumatology criteria (muscle strength, overall assessments from the doctor and patient, physical function, enzyme levels, extra-muscular activity).
Among patients who switched from placebo to efgartigimod, 33.3% achieved a similar major improvement. Moderate improvement rates (TIS ≥ 40) were 75.0% in the continuous group and 66.7% in the transition group. The average TIS score was 52.19 in continuously treated patients and 49.62 in those who switched groups, reflecting a clinically significant sustained improvement. No increase in adverse events was observed with prolonged exposure.
Sjogren: Maintaining Response at Reduced Dose
The RHO+ study, an open-label extension of phase 2, assessed the maintenance of response in patients with Sjogren's syndrome. Patients in the efgartigimod arm switched to a biweekly dosing based on their clinical response (ClinESSDAI). At week 72, patients maintaining efgartigimod retained their response to clinical measures. In patients transitioning from placebo to efgartigimod, improvements in ClinESSDAI and an increase in composite response (CRESS) were observed.
The median ClinESSDAI scores at week 72 were low in both groups (2.5 for the efgartigimod arm, 2.0 for patients transitioning from placebo), reflecting low disease activity.
Consistent Safety Profile in Rheumatic Diseases
A cross-sectional analysis of efgartigimod data in rheumatic diseases supports the consistency of the tolerance profile across a broad patient population. These results support the mechanism of action based on the inhibition of the FcRn receptor, suggesting that pathogenic autoantibodies are the underlying drivers of these diseases.
Luc Truyen, the medical director of Argenx, emphasized that the consistency of long-term data and the favorable safety profile support the rationale for targeting FcRn in autoimmune rheumatic diseases. Complete phase 3 results for ALKIVIA in myositis are expected in the third quarter of 2026, and additional data in Sjogren's syndrome are anticipated next year.
