Biogen’s AMETHYST phase 2/3 study (Part A) of litifilimab in people living with cutaneous lupus erythematosus (CLE) has shown positive results. 

Litifilimab could become the first innovative CLE therapy approved in 70 years  as the first humanised IgG1 monoclonal antibody (mAb) targeting blood dendritic cell antigen 2 (BDCA2). 

Affecting millions of people around the world, CLE is a complex, heterogenous disease with no approved targeted therapy treatments. 

Evaluating the efficacy and safety of the treatment, part A of the AMETHYST trial studied the treatment’s ability to reduce skin disease activity over 24 weeks. 

Previous results from the phase 2 LILAC and AMETHYST trials formed the basis for the treatment’s recent US FDA Breakthrough Therapy Designation.

Currently ongoing, AMETHYST is a two-part, multicentre, randomised study in which participants receive either subcutaneous treatment with litifilimab and standard of care (SoC) or placebo every four weeks with SoC. 

The trial met its primary endpoint with the treatment showing an 11.8% higher reduction of disease activity in people with CLE, as measured by the Cutaneous Lupus Activity Investigators’ Global Assessment Revised (CLA-IGA-R) erythema score of 0-1 (clear/almost clear) at Week 16, compared to placebo. 

Litifilimab was associated with rapid and continued improvement in skin disease activity with separation from placebo observed as early as Week 4 (19.3% vs. 5.5%), as measured by Cutaneous Lupus Erythematosus Disease Area and Severity Index Activity-50 (CLASI-50) response to Week 24 (40.8% vs. 21%).

More participants receiving litifilimab achieved a response compared to placebo (21.7% vs 5.8%), as measured by CLASI-70 at Week 24. CLASI-50 and CLASI-70 responses are defined as 50% and 70% improvements from baseline in CLASI-A score, respectively. Additionally, one in six participants receiving litifilimab achieved a CLASI 0-3 score, defined as no or minimal disease activity, compared to placebo at Week 24.