Trial of Anti-BDCA2 Antibody Litifilimab for Systemic Lupus Erythematosus

BACKGROUND Antibody-binding of blood dendritic cell antigen 2 (BDCA2), which is expressed exclusively on plasmacytoid dendritic cells, suppresses the production of type I interferon that is involved in the pathogenesis of systemic lupus erythematosus (SLE). The safety and efficacy of subcutaneous litifilimab, a humanized monoclonal antibody that binds to BDCA2, in patients with SLE have not been extensively studied. METHODS We conducted a phase 2 trial of litifilimab involving participants with SLE. The initial trial design called for randomly assigning participants to receive litifilimab (at a dose of 50, 150, or 450 mg) or placebo administered subcutaneously at weeks 0, 2, 4, 8, 12, 16, and 20, with the primary end point of evaluating cutaneous lupus activity. The trial design was subsequently modified; adults with SLE, arthritis, and active skin disease were randomly assigned to receive either litifilimab at a dose of 450 mg or placebo. The revised primary end point was the change from baseline in the total number of active joints (defined as the sum of the swollen joints and the tender joints) at week 24. Secondary end points were changes in cutaneous and global disease activity. Safety was also assessed. RESULTS A total of 334 adults were assessed for eligibility, and 132 underwent randomization (64 were assigned to receive 450-mg litifilimab, 6 to receive 150-mg litifilimab, 6 to receive 50-mg litifilimab, and 56 to receive placebo). The primary analysis was conducted in the 102 participants who had received 450-mg litifilimab or placebo and had at least four tender and at least four swollen joints. The mean (+/- SD) baseline number of active joints was 19.0 +/- 8.4 in the litifilimab group and 21.6 +/- 8.5 in the placebo group. The least-squares mean (+/- SE) change from baseline to week 24 in the total number of active joints was -15.0 +/- 1.2 with litifilimab and -11.6 +/- 1.3 with placebo (mean difference, -3.4; 95% confidence interval, -6.7 to -0.2; P=0.04). Most of the secondary end points did not support the results of the analysis of the primary end point. Receipt of litifilimab was associated with adverse events, including two cases of herpes zoster and one case of herpes keratitis. CONCLUSIONS In a phase 2 trial involving participants with SLE, litifilimab was associated with a greater reduction from baseline in the number of swollen and tender joints than placebo over a period of 24 weeks. Longer and larger trials are required to determine the safety and efficacy of litifilimab for the treatment of SLE.