BioCryst falls on HCV tox concerns

BioCryst Pharmaceuticals Inc. (NASDAQ:BCRX) fell $1.17 (29%) to $2.91 on Wednesday after withdrawing an IND for BCX5191 after FDA expressed concerns about the HCV candidate's preclinical toxicity profile. According to the company, the agency is concerned that exposure levels of BCX5191 that will be necessary to reduce viral load in humans will be toxic. The company plans to begin additional preclinical studies by year end to determine if low, nontoxic doses of BCX5191 show "meaningful efficacy" in chimpanzees. BioCryst declined to provide a timeline for completing the studies. BCX5191 is an oral adenine nucleoside analog HCV NS5B polymerase inhibitor. ...