Eli Lilly is to stop one of three Phase III studies of its investigational rheumatoid arthritis drug tabalumab due to insufficient efficacy.

The US major said the decision followed a planned interim futility analysis of the FLEX-M study investigating tabalumab, an anti-B cell activating factor (BAFF) monoclonal antibody for patients with moderate-to-severe RA who had an inadequate response to methotrexate. The decision was not based on safety concerns, and patients currently enrolled in other tabalumab RA studies will continue treatment.

Nevertheless, Lilly noted that it is suspending enrollment of new patients in the RA programme until additional analysis from other ongoing studies is completed in early 2013. Eiry Roberts, head of autoimmune product development, said the results "were unexpected given the data generated in earlier Phase II clinical studies".

She added that "we remain committed to patients with RA and lupus [the drug is in Phase III for the latter] and will move rapidly to evaluate the impact of these data on the overall tabalumab clinical development programme". Dr Roberts went on to say that beyond tabalumab, Lilly will continue to develop additional treatments for autoimmune diseases; the company recently announced its janus kinase (JAK) inhibitor baricitinib, partnered with Incyte, has moved into Phase III.

The decision to stop the FLEX-M study is expected to result in a fourth-quarter charge in the range of $20-$35 million.

Another late-stage study for solanezumab

The tabalumab news comes a day after Lilly said it will conduct another Phase III trial for solanezumab, its investigational drug for patients with mild Alzheimer’s disease. The decision was taken following discussions with regulators in the USA, Europe and Canada, and the study will begin no later than the third quarter of 2013.

David Ricks, president of Lilly Bio-Medicines, said that "we remain encouraged and excited by the solanezumab data," but this means that any filing is now some way off.