Anacor Pharmaceuticals (UNKNOWN:ANAC.DL) announced today that its onychomycosis drug tavaborole successfully met both its primary and secondary endpoints in its first phase 3 trial. Rather than celebrate this news, however, investors saw shares drop around 20% today. Why did this happen?Could the fall have something to do with a rival drug that Valeant Pharmaceuticals (NYSE:BHC) is seeking FDA approval for? In this video, health care analyst Max Macaluso breaks down this news.