ObjectivesTo determine the safety, tolerability and signs of efficacy of MOR103, a human monoclonal antibody to granulocyte–macrophage colony-stimulating factor (GM-CSF), in patients with rheumatoid arthritis (RA).MethodsPatients with active, moderate RA were enrolled in a randomised, multicentre, double-blind, placebo-controlled, dose-escalation trial of intravenous MOR103 (0.3, 1.0 or 1.5 mg/kg) once a week for 4 weeks, with follow-up to 16 weeks. The primary outcome was safety.ResultsOf the 96 randomised and treated subjects, 85 completed the trial (n=27, 24, 22 and 23 for pooled placebo and MOR103 0.3, 1.0 and 1.5 mg/kg, respectively). Treatment emergent adverse events (AEs) in the MOR103 groups were mild or moderate in intensity and generally reported at frequencies similar to those in the placebo group. The most common AE was nasopharyngitis. In two cases, AEs were classified as serious because of hospitalisation: paronychia in a placebo subject and pleurisy in a MOR103 0.3 mg/kg subject. Both patients recovered fully. In exploratory efficacy analyses, subjects in the MOR103 1.0 and 1.5 mg/kg groups showed significant improvements in Disease Activity Score-28 scores and joint counts and significantly higher European League Against Rheumatism response rates than subjects receiving placebo. MOR103 1.0 mg/kg was associated with the largest reductions in disease activity parameters.ConclusionsMOR103 was well tolerated and showed preliminary evidence of efficacy in patients with active RA. The data support further investigation of this monoclonal antibody to GM-CSF in RA patients and potentially in those with other immune-mediated inflammatory diseases.Trial registration numberNCT01023256
Murine autoimmune hemolytic anemia resulting from Fc gamma receptor- mediated erythrophagocytosis: protection by erythropoietin but not by interleukin-3, and aggravation by granulocyte-macrophage colony- stimulating factor