Shares of Anthera Pharmaceuticals Inc. struggled to find a floor Thursday after the company reported following the market's close Wednesday afternoon that its Phase IIb PEARL-SC study of blisibimod in systemic lupus erythematosus (SLE) failed to meet the primary efficacy endpoint – clinical improvement at 24 weeks in the SLE responder index for the pooled blisibimod dose groups – due to lack of efficacy in two low-dose groups.