Biogen announced positive results from the Phase 2 part of the AMETHYST Phase 2/3 study evaluating litifilimab in people with cutaneous lupus erythematosus (CLE). Litifilimab is a humanized IgG1 monoclonal antibody targeting blood dendritic cell antigen 2 (BDCA2) and could become the first innovative therapy approved for CLE in approximately 70 years if successful in later-stage development. In Part A of AMETHYST, the trial met its primary endpoint, demonstrating a statistically significant reduction in skin disease activity at Week 16 compared with placebo, as measured by the CLA-IGA-R erythema score of 0–1 (clear or almost clear).
According to Biogen, reductions in skin disease activity were observed across multiple measures, with separation from placebo seen as early as Week 4 and maintained through Week 24 on CLASI-50 and CLASI-70 responder analyses. Results were consistent with the earlier positive Phase 2 LILAC study, making litifilimab the only investigational program to show positive efficacy in multiple CLE trials to date.
The Phase 2 data from LILAC and AMETHYST supported the U.S. Food and Drug Administration’s Breakthrough Therapy Designation for litifilimab in CLE. Litifilimab was generally well tolerated in AMETHYST Part A, with a safety profile consistent with prior studies; most adverse events were mild to moderate, and serious adverse events occurred infrequently. The Phase 3 portion of AMETHYST is ongoing and remains blinded, while all participants in the study transition to open-label litifilimab treatment from Weeks 24 to 48.
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