Biogen reports positive Phase 2 AMETHYST results for litifilimab in cutaneous lupus erythematosus, showing significant skin disease improvement and supporting ongoing Phase 3 development.
Written By: Samiksha Jadhav, BPharm
Reviewed By: Pharmacally Editorial Team
Biogen has reported positive results from the Phase 2 portion (Part A) of the AMETHYST Phase 2/3 trial evaluating litifilimab (BIIB059) in patients with cutaneous lupus erythematosus (CLE), a chronic autoimmune skin disease with no approved targeted therapies. The findings, presented at the American Academy of Dermatology Annual Meeting, showed statistically significant improvements in skin disease activity and a favorable safety profile.
Litifilimab is a first-in-class humanized IgG1 monoclonal antibody targeting BDCA2, a receptor expressed on plasmacytoid dendritic cells. By binding BDCA2, the drug reduces production of type I interferons and other inflammatory mediators that play a central role in lupus pathogenesis.
Supported by data from both the AMETHYST (NCT05531565) and earlier LILAC studies (NCT02847598), litifilimab has received U.S. Food and Drug Administration Breakthrough Therapy Designation, highlighting its potential in a disease area with high unmet need.
AMETHYST is a randomized, double-blind, placebo-controlled study evaluating litifilimab in patients with varying severities of CLE. In Part A (Weeks 0–24), the study met its primary endpoint, demonstrating an 11.8% greater reduction in disease activity versus placebo (14.7% vs. 2.9%; p<0.05), measured using the CLA-IGA-R erythema score at Week 16.
Key secondary findings further supported the efficacy of litifilimab, demonstrating early separation from placebo as soon as Week 4, with CLASI-50 responses of 19.3% compared to 5.5%. This improvement was sustained through Week 24, where CLASI-50 responses reached 40.8% versus 21% with placebo.
Higher response rates were also observed with CLASI-70 (21.7% vs. 5.8%). 16.3% of patients treated with litifilimab achieved minimal or no disease activity (CLASI 0–3), while no patients in the placebo group reached this outcome, highlighting both the rapid onset and durability of response.
These results indicate both rapid onset and durable efficacy in reducing CLE skin disease burden.
Litifilimab was generally well tolerated, with adverse events reported in 74.6% of treated patients versus 64.7% with placebo. Most events were mild to moderate. Serious adverse events occurred in 6.8% of patients receiving litifilimab compared to 2.9% in the placebo group, consistent with prior studies including LILAC.
Joseph F. Merola, Professor and Chair, Department of Dermatology and Professor of Internal Medicine in the Division of Rheumatic Diseases, UT Southwestern Medical Center highlighted consistent Phase 2 results showing meaningful skin improvement, supporting litifilimab’s potential in CLE where no targeted therapies exist. He also noted the safety consistency, FDA Breakthrough designation, and globally representative study population, strengthening confidence in the program.
Daniel Quirk, Chief Medical Officer at Biogen emphasized the significant unmet need in CLE and the disease’s physical and psychosocial burden. He added that the results show good tolerability and clinical benefit, reinforcing momentum toward Phase 3 and Biogen’s focus on high-need diseases.
The AMETHYST trial is an ongoing two-part Phase 2/3 study enrolling a globally representative patient population, including individuals with moderate to severe disease. All participants will receive litifilimab during the extension phase (Weeks 24–48).
The Phase 3 portion remains ongoing, with results still blinded. Positive Phase 2 findings are expected to support further regulatory discussions and potential future approval pathways.
Cutaneous lupus erythematosus is a chronic autoimmune condition characterized by rash, photosensitivity, pain, and potential permanent skin damage such as scarring and alopecia. Despite its significant physical and psychosocial burden, no targeted therapies have been approved for CLE in over 70 years, underscoring the importance of emerging treatments like litifilimab.
Reference
Biogen Announces Second Positive Phase 2 Litifilimab Trial in Cutaneous Lupus Erythematosus at 2026 American Academy of Dermatology Annual Meeting, Showing a Significant Reduction in Skin Disease Activity, 28 March 2026, https://investors.biogen.com/news-releases/news-release-details/biogen-announces-second-positive-phase-2-litifilimab-trial
A 2-Part Study to Learn Whether Litifilimab (BIIB059) Injections Can Improve Symptoms of Adult Participants Who Have Active Cutaneous Lupus Erythematosus (AMETHYST), ClinicalTrials.gov ID NCT05531565, https://clinicaltrials.gov/study/NCT05531565
Study to Evaluate BIIB059 (Litifilimab) in Cutaneous Lupus Erythematosus (CLE) With or Without Systemic Lupus Erythematosus (SLE) (LILAC), ClinicalTrials.gov ID NCT02847598, https://clinicaltrials.gov/study/NCT02847598
About the Writer
Samiksha Vikram Jadhav is a B.Pharm graduate with a strong academic foundation in pharmaceutical sciences, pharmacology, and drug development. She has a keen interest in healthcare advancements, clinical research, medical writing, and emerging therapies. Her work focuses on presenting developments in the pharmaceutical and healthcare sectors through clear and accurate scientific communication.