Phase II WILLOW LTE study: Long-term enpatoran in CLE and/or SLE

Results at 48 weeks from the phase II WILLOW LTE (NCT05540327) study evaluating enpatoran in patients with cutaneous lupus erythematosus (CLE) and/or systemic lupus erythematosus (SLE) were presented by Eric F. Morand at the European Alliance of Associations for Rheumatology (EULAR) 2026 Congress, June 3–6, 2026, London, UK. Patients completing the WILLOW trial (NCT05162586) entered the long-term extension (LTE); the safety set included patients receiving enpatoran 25 mg twice daily (BID; n = 77), 50 mg BID (n = 87), or 100 mg BID (n = 215). The primary endpoint was adverse events (AEs).

Key data: The rates of treatment-emergent AEs (TEAEs) in the 25 mg, 50 mg, and 100 mg groups were 71.4%, 69.0%, and 66.5%, respectively, with 23.4%, 21.8%, and 20.5% being treatment related. Serious AEs (SAEs) occurred in 14.3%, 5.7%, and 5.1% of patients, respectively. The most common treatment-related TEAEs included upper respiratory tract infection (URTI; 5.2%, 5.7%, and 2.3%), urinary tract infection (UTI; 2.6%, 3.4%, and 2.8%), headache (3.9%, 1.1%, and 1.9%), lymphocyte count decreased (2.6%, 0.0%, and 1.9%), and bronchitis (1.3%, 2.3%, and 0.9%). Decreases in Cutaneous Lupus Erythematosus Disease Area and Severity Index (CLASI)-A score and high rates of CLASI-50 and -70 responses were maintained through Week 48.

Key learning: Enpatoran demonstrated long-term safety and tolerability, with no new safety signals reported, and clinically meaningful reductions in CLE disease activity. Further evaluation of the efficacy and safety of enpatoran in active cutaneous manifestations of lupus with/without systemic disease is ongoing in the phase III ELOWEN-1 (NCT07332481) and ELOWEN-2 (NCT07355218) trials.