Biogen Inc. shares (NASDAQ:BIIB) sank 12.8 percent to close at $252.86 on Tuesday after the company said that opicinumab missed both the primary and secondary efficacy endpoints in the phase II study Synergy, which evaluated the candidate as a therapy for people with relapsing forms of multiple sclerosis (MS). Despite the miss, the company said, "evidence of a clinical effect with a complex, unexpected dose-response was observed."