Global pharmaceutical company Eli Lilly is halting one of three phase III rheumatoid arthritis (RA) registration studies of tabalumab, an anti-BAFF monoclonal antibody, due to insufficient efficacy.

The decision followed a planned interim futility analysis of the FLEX-M study investigating tabalumab, also known as LY2127399, for the treatment of patients with moderate-to-severe RA who had an inadequate response to methotrexate therapy. The decision was not based on safety concerns, and patients currently enrolled in other tabalumab RA studies will continue treatment.

The FLEX-M study was designed to support registration of tabalumab as a potential treatment for RA, including an assessment of its effect on structural progression. Lilly continues to evaluate tabalumab in two other phase III RA registration studies as well as an open-label extension study and several other smaller studies. Lilly is suspending enrollment of new patients in the RA program until additional analysis from other ongoing RA studies is completed in early 2013. These other studies are in different patient populations.

Phase III studies for systemic lupus erythematosus are ongoing and will continue to enroll new patients. Currently, there is no evidence to suggest that efficacy results from the FLEX-M study in RA are indicative of potential efficacy in the lupus population. Lilly remains committed to the ongoing phase III lupus program.

"The results of this study were unexpected given the data generated in earlier phase II clinical studies of tabalumab," said Eiry Roberts, M.D., vice president of autoimmune product development at Lilly. "We remain committed to patients with rheumatoid arthritis and lupus and will move rapidly to evaluate the impact of these data on the overall tabalumab clinical development program.”

The decision to stop the FLEX-M study is expected to result in a fourth-quarter charge in the range of $20 million to $35 million (pre-tax), or approximately $0.02 per share (after-tax). The company's previously issued financial guidance for 2012 remains unchanged.