Phase II AMETHYST trial Part A: 52-week results of litifilimab in CLE

Results from the extended treatment period of Part A of the phase II, double-blind, placebo-controlled AMETHYST (NCT05531565) trial evaluating litifilimab in adults with cutaneous lupus erythematosus (CLE) were presented by Joseph F. Merola at the European Academy of Dermatology and Venereology (EADV) Congress 2026, September 30–October 3, 2026, Vienna, AT. Patients received litifilimab (n = 59) or placebo (n = 34) until Week 24. At Week 24, patients in the litifilimab group continued treatment, while those in the placebo group switched to litifilimab through Week 52. Week 24 results were reported previously, including attainment of the primary endpoint: achievement of a Cutaneous Lupus Activity Investigator’s Global Assessment-Revised (CLA-IGA-R) erythema score of 0 or 1 at Week 16. Here, response rates from Week 24 through Week 52 are summarized.

Key data: At Week 24, litifilimab demonstrated higher response rates of CLA-IGA-R erythema 0/1 (19.0% vs 4.2; p < 0.05), Cutaneous Lupus Erythematosus Disease Area and Severity Index 70% (CLASI-70; 21.7% vs 5.8%; p < 0.05), CLASI-50 (40.8% vs 21.0; p < 0.05), and CLASI-Activity score of 0–3 (CLASI-A 0–3; 16.3% vs 0.0%; p < 0.01) vs placebo. Patients continuing litifilimab showed sustained responses at Week 52 across CLA-IGA-R erythema 0/1 (27.2%), CLASI-70 (28.8%), CLASI-50 (46.0%), and CLASI-A 0–3 (16.7%). Among patients who switched from placebo to litifilimab, responses emerged within 4 weeks of switching, reaching 33.7%, 35.4%, 48.5%, and 22.2% at Week 52 for CLA-IGA-R erythema 0/1, CLASI-70, CLASI-50, and CLASI-A 0–3, respectively. From Weeks 24 to 52, 76.8% and 78.1% of patients in the continued litifilimab and placebo–litifilimab groups, respectively, experienced an adverse event (AE) of any grade, with serious AEs (SAEs) in 3.6% and 3.1% of patients, respectively.

Key learning: In Part A of the AMETHYST trial, litifilimab demonstrated progressive improvements in disease activity measures in patients with CLE over 52 weeks, including in those who switched from placebo to litifilimab at Week 24, with no new safety signals reported. These findings support continued investigation of litifilimab in this patient population.