Fully Human Monoclonal Antibody Passes Phase III Test for RA

November 19, 2011

Ofatumumab significantly improved rheumatoid arthritis symptoms without triggering any more serious response than mild infusion reactions during 24 weeks.

As complete remission becomes a realistic goal for many patients with rheumatoid arthritis (RA), progress continues toward finding ways to dampen the autoimmune response without causing either reactions or infections. A monoclonal antibody derived entirely from human sources has taken another step toward replacing rituximab, a chimeric antibody that reduces RA symptoms but provokes adverse reactions due to its non-human components.

A team from Imperial College in London reports results of the Phase III placebo-controlled randomized trial of ofatumumab for RA  in the Annals of the Rheumatic Diseases. Among 265 RA patients in Europe, South America, and the Asia Pacific region, half of those who received two 700-mg infusions of the drug, in addition to continuing methotrexate, achieved the standard endpoint of ACR20 (a 20% improvement in symptoms) at 24 weeks. Among those randomized to placebo, only 27% showed that level of improvement.

The most commonreactions to the antibody were mild or moderate skin reactions shortly after the first infusion. Serious infections were less common in the treatment group than the placebo group.

Ofatumumab binds to a different part of the same B-cell antigen that rituximab addresses, inducing potent lysis of B cells. It is currently FDA-approved only for the treatment of chronic lymphyocytic leukemia.