Biogen Idec has suffered a setback with the news that disappointing data from a mid-stage trial means that the firm is to terminate development of investigational rheumatoid arthritis drug baminercept.

The US biotechnology firm says Phase II trials of (BG9924) baminercept in RA patients who have had an inadequate response to conventional therapy with a disease-modifying antirheumatic drug did not meet its primary endpoint. The latter was defined as the proportion of baminercept-treated patients who achieved an ACR50 response, a standard measure of disease improvement, compared to placebo at 14 weeks.

The study also did not meet any of the pre-specified secondary endpoints either. These included improvements in swollen and tender joint counts.

Biogen said it will continue to analyse the study results and will submit the data for presentation at an upcoming medical meeting. However, based on these results as well as preliminary data from a Phase II trial of baminercept in RA patients who have had an inadequate response to a tumor necrosis factor inhibitor, it has decided to discontinue the development of the compound.

Baminercept was not expected to be a major growth driver for Biogen, according to a research note from BMO Capital Markets analyst Jason Zhang. He wrote that “therefore we do not expect this news to significantly impact the stock," although the firm’s shares did fall 3.4% on the news to $44.76.

Biogen is scheduled to report third-quarter earnings on October 21 and Mr Zhang said that the growth seen in the last two quarters will likely slow down in the third quarter following the recent announcement of two new cases of a rare brain infection, progressive multifocal leukoencephalopathy, linked to the multiple sclerosis drug Tysabri (natalizumab).