To investigate the safety and tolerability of a single subcutaneous (SC) dose of ofatumumab, a fully human anti-CD20 monoclonal antibody, in patients with rheumatoid arthritis (RA) taking background methotrexate (MTX). Secondary objectives included characterizing pharmacokinetics and pharmacodynamics.
In this single-blind, phase I/II study, 35 patients with RA were randomized in 5 cohorts to receive a single subcutaneous (SC) ofatumumab dose ranging from 0.3 to 100 mg, or placebo, following premedication with oral acetaminophen and antihistamine. Patients were followed for 24 weeks with extended followup to monitor B cell and immunoglobulin recovery for up to 2 years if required.
Thirty-five patients received the following treatment: 0.3 mg, n = 4; 3 mg, n = 6; 30 mg, n = 8; 60 mg, n = 6; 100 mg, n = 3; placebo, n = 8. The most common adverse events in the combined ofatumumab groups were headache, nausea, and upper respiratory tract infection. Because of tolerability concerns, only 3 patients were given 100 mg. For the 30-100 mg doses, median maximum plasma concentration values ranged from 4.02 to 4.49 days. Mean elimination half-life values ranged from 5.20 to 6.83 days. Increasing peripheral median B cell depletion was observed from 0.3 mg up to 30 mg, and full target B cell depletion was achieved with 30 mg, 60 mg, and 100 mg.
Treatment of RA patients with SC ofatumumab doses of 30 mg or higher resulted in profound and prolonged B cell depletion in blood. Single doses up to 60 mg were tolerated without glucocorticoid premedication. (ClinicalTrials.gov identifier NCT00686868).