CAMBRIDGE, Mass. — January 28, 2026 — Leads & Copy — The U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy Designation to litifilimab (BIIB059) for the treatment of cutaneous lupus erythematosus (CLE), Biogen Inc. announced today.
Litifilimab is a first in-class, humanized IgG1 monoclonal antibody (mAb) targeting blood dendritic cell antigen 2 (BDCA2). CLE is a chronic autoimmune disease affecting the skin that currently has no targeted treatments.
The FDA’s Breakthrough Therapy Designation is intended to expedite the development and review of drugs for serious conditions. It is based on the totality of litifilimab data, including the results from the Phase 2 LILAC study, which were previously published in The New England Journal of Medicine and demonstrated that litifilimab reduced skin disease activity in people with CLE compared to placebo.
According to Victoria Werth, MD, MS, a professor of Dermatology at the Perelman School of Medicine at the University of Pennsylvania, the breakthrough therapy designation for litifilimab illustrates the FDA’s recognition of cutaneous lupus as a serious disease that urgently requires new therapies.
The current standard of care for CLE includes topical steroids, antimalarials and immunosuppressants. While current treatments help manage symptoms, they do not alter the progression of the disease.
Priya Singhal, M.D., M.P.H., Executive Vice President and Head of Development at Biogen, said that the FDA’s designation reinforces Biogen’s belief that litifilimab could be a first-in-class therapy targeting BDCA2 for cutaneous lupus erythematosus.
Biogen is continuing to evaluate the efficacy and safety of litifilimab in the AMETHYST Phase 3 study, with a data readout expected in 2027. More information on the AMETHYST study (NCT05531565) is available at clinicaltrials.gov and BiogenTrialLink.
Albert T. Roy, President & CEO of the Lupus Research Alliance, said that today’s FDA Breakthrough Therapy designation for litifilimab reinforces our shared understanding of cutaneous lupus as a serious, debilitating condition that urgently needs therapies that can alter the course of the disease.
Litifilimab (known as BIIB059), discovered and developed in-house by Biogen scientists, is being investigated for the potential treatment of systemic lupus erythematosus (SLE) and cutaneous lupus erythematosus (CLE). Binding of litifilimab to BDCA2 has been shown to reduce production of pro-inflammatory molecules by pDCs, including type-I interferon (IFN-I) as well as other cytokines and chemokines.
CLE, a type of lupus, is a chronic autoimmune skin disease that can occur with or without systemic manifestations; people with CLE frequently experience symptoms including rash, pain, itch and photosensitivity as well as skin damage that may worsen over time and can include irreversible scarring, alopecia and dyspigmentation that can be disfiguring and substantially impact quality of life.
Founded in 1978, Biogen is a leading biotechnology company that pioneers innovative science to deliver new medicines to transform patients’ lives and to create value for shareholders and our communities.
