Biogen announces AMETHYST Part A met primary endpoint with litifilimab

Biogen (BIIB) announced positive results from the Phase 2 part of the AMETHYST Phase 2/3 study of litifilimab in people living with cutaneous lupus erythematosus, CLE. Litifilimab is the first humanized IgG1 monoclonal antibody targeting blood dendritic cell antigen 2, BDCA2, which has the potential to become the first innovative therapy approved for CLE in 70 years. Part A of AMETHYST evaluated the efficacy and safety of litifilimab through week 24, with reductions in skin disease activity reported across several measures. Results are consistent with the earlier positive Phase 2 LILAC study reported in The New England Journal of Medicine. AMETHYST Part A met its primary endpoint with litifilimab demonstrating a statistically significant 11.8% higher reduction in disease activity in people living with CLE as measured by the Cutaneous Lupus Activity Investigators’ Global Assessment Revised erythema score of 0-1 at Week 16, compared to placebo. Secondary endpoints, including the following, were not adjusted for multiplicity in Part A and therefore statistical significance cannot be demonstrated. Litifilimab was associated with rapid and continued improvement in skin disease activity with separation from placebo observed as early as Week 4, as measured by Cutaneous Lupus Erythematosus Disease Area and Severity Index Activity-50 response through Week 24. More participants receiving litifilimab achieved a response compared to placebo, as measured by CLASI-70 at Week 24. CLASI-50 and CLASI-70 responses are defined as 50 percent and 70 percent improvements from baseline in CLASI-A score, respectively.