Toreforant, A Histamine H4 Receptor Antagonist, in Patients with Active Rheumatoid Arthritis Despite Methotrexate Therapy: Results of 2 Phase II Studies

Objective. To assess toreforant (selective histamine H-4 receptor antagonist) in active rheumatoid arthritis (RA). Methods. In a phase IIa, double-blind, placebo-controlled test, 86 patients were randomized (2: 1) to once-daily toreforant 100 mg or placebo for 12 weeks. In phase IIb, double-blind, placebo-controlled, dose-range-finding evaluations, 272 patients were randomized (1: 1: 1: 1) to once-daily placebo or toreforant 3/10/30 mg. Primary efficacy endpoints for both studies were Week 12 changes in 28-joint Disease Activity Score-C-reactive protein (DAS28-CRP). Results. Phase IIa testing was terminated prematurely (patient fatality; secondary hemophagocytic lymphohistiocytosis). Posthoc analyses indicated toreforant 100 mg/day reduced RA signs/symptoms through Week 12. Phase IIb testing, however, showed no significant Week 12 improvement in DAS28-CRP with toreforant. Conclusion. Toreforant was not effective in phase IIb testing.