POS0698 BIIB059 DEMONSTRATED A CONSISTENT THERAPEUTIC EFFECT ON SRI-4 RESPONSE ACROSS SUBGROUPS OF PARTICIPANTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS IN THE LILAC PHASE 2 STUDY

Background: Type I interferons and other inflammatory mediators derived from plasmacytoid dendritic cells (pDCs) are implicated in systemic lupus erythematous (SLE) pathology. BIIB059 is a humanized monoclonal antibody that targets blood cell antigen 2 (BDCA2), pDC-specific receptor. The binding of to BDCA2 leads rapid internalization the surface pDCs subsequent inhibition interferon, cytokine, chemokine production. In Part A 2-part, phase LILAC study ( NCT02847598 ), significantly reduced SLE activity, as evidenced by total active joint count (primary endpoint) higher Responder Index (SRI-4) 1 response (a secondary versus placebo. Objectives: To evaluate SRI-4 for placebo at Week 24 participant subgroups. Methods: Enrollment was open adults fulfilling ≥ 4 11 revised 1997 ACR criteria classification SLE, with tender swollen joints, skin disease, positive antibodies. Participants were randomized receive either 450 mg or subcutaneously every weeks 20 (with an additional dose 2). analyzed subgroups, though analyses limited small sample sizes not powered statistical testing. Results: A, 64 56 participants dosed placebo, respectively. At week 24, rate observed favor regardless baseline disease such SLEDAI-2K <10 ≥10, presence BILAG-2004 grade B arthritis, oral corticosteroid usage, positivity anti-ds DNA autoantibody and/or complement status, point estimates least-squares mean differences well corresponding 95% CIs consistently favoring (Figure 1). incidence adverse events overall population similar between groups. Conclusion: treatment associated greater rate, consistent among different subgroups activity measured BILAG-2004, glucocorticoid dosage, serology. These findings provide evidence potential benefit patients SLE. References: [1]Furie RA, et al. Arthritis Rheum. 2009;61(9):1143-1151. 2. Furie Rheumatol. 2020;72(suppl 10). Abstract 0935. Acknowledgements: This sponsored Biogen (Cambridge, MA, USA). Writing editorial support provided Excel Scientific Solutions (Fairfield, CT, USA); funding Biogen. Disclosure Interests: Ronald van Vollenhoven Consultant of: AbbVie, AstraZeneca, Biotest, Bristol Myers Squibb, Celgene, GlaxoSmithKline, Janssen, Lilly, Medac, Merck, Novartis, Pfizer, Roche, UCB, Grant/research from: Arthrogen, Richard Biogen, Kenneth Kalunian Amgen, Eli Equillium, Genentech, Gilead, ILTOO, Nektar, Viela, Lupus Research Alliance, Sanford Consortium, Sandra Navarra Speakers bureau: Astellas, Johnson & Johnson, Juanita Romero-Diaz Boehringer Ingelheim, Victoria Werth EMD Serono, Kyowa Kirin, Resolve, XIAOBI HUANG Shareholder Employee HUA CARROLL Cristina Musselli Catherine Barbey NATHALIE FRANCHIMONT OMass Therapeutics,