#2-23E. Targeting BDCA2: The Pharmacodynamic Link Between Type I IFN Suppression and Clinical Response in Lupus (Arthritis Rheum, 2025)

How critical is the Type I Interferon (IFN) pathway to achieving clinical remission in patients with Systemic Lupus Erythematosus (SLE) and Cutaneous Lupus Erythematosus (CLE)? We explore this question by examining the pharmacodynamic results of the Phase 2 LILAC trial, which investigated litifilimab, a monoclonal antibody targeting BDCA2 on plasmacytoid dendritic cells. The study found that in IFNGS-high participants, litifilimab induced rapid and sustained reductions in IFN gene signature (IFNGS) scores and serum IFN-alpha concentrations. Crucially, these robust pharmacodynamic effects correlated with measured clinical responses, including improved total active joint count and CLASI-A scores. This provides strong support for BDCA2 antagonism as a viable therapeutic strategy in lupus. However, clinicians must note a key limitation: the results are restricted almost entirely to the IFNGS-high population, as too few IFNGS-low participants were enrolled to draw definitive conclusions regarding treatment response in that subgroup. This research is vital for physicians as it reinforces the Type I IFN pathway as a core therapeutic target and validates IFNGS and IFN_α_ as potential biomarkers for monitoring therapeutic efficacy in daily practice.

Citation: Furie R, Werth VP, Milliman E, et al. Pharmacodynamic Effects of Litifilimab in Lupus in a Randomized, Placebo-Controlled Phase 2 Study: Rapid and Sustained Reductions in Type I Interferon-Associated Gene Expression and Cytokines. Arthritis & Rheumatology. 2025. DOI: 10.1002/art.43271

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