A 2-Part Study to Learn Whether Litifilimab (BIIB059) Injections Can Improve Symptoms of Adult Participants Who Have Active Cutaneous Lupus Erythematosus (AMETHYST)

Litifilimab is a humanized immunoglobulin G1 (IgG1) monoclonal antibody targeting blood dendritic cell antigen 2 and is being investigated for the potential treatment of systemic lupus erythematosus and cutaneous lupus erythematosus. The primary objectives of the study are to evaluate the efficacy of litifilimab compared with placebo in reducing skin disease activity measured by the CLA-IGA-R score [Parts A and B (US)] and the Cutaneous Lupus Erythematosus Disease Area and Severity Index Activity (CLASI-A) score [Part B (ROW)] in participants with active SCLE and/or CCLE with or without systemic manifestations and refractory and/or intolerant to antimalarials. The secondary objectives of the study are to evaluate the efficacy of litifilimab in reducing SCLE and/or CCLE disease activity by CLA-IGA-R, CLASI-A; to evaluate additional efficacy parameters of litifilimab in reducing SCLE and/or CCLE disease activity; safety; tolerability; and immunogenicity of litifilimab [Parts A and B].