BioCryst withdraws BCX5191 lND following discussion with FDA

US biotech firm BioCryst Pharmaceuticals (Nasdaq: BCRX) says it is withdrawing its Investigational New Drug (IND) application for the antiviral nucleoside, BCX5191, following a discussion with the US Food and Drug Administration where safety issues were raised. Shares of BioCryst fell 30% following the announcement last week.

The news comes shortly after BioCryst announced an agreement to acquire privately-held Presidio Pharmaceutical, aiming to create a major force in the hepatitis setting, with the combined entity owning a unique portfolio of three oral, pan-genotypic antivirals that are suitable either for development in combination with each other or in combination with other direct acting antivirals (DAAs) to treat patients with HCV infection. (The Pharma Letter October 22).

The FDA indicated concerns regarding the preclinical toxicity profile of BCX5191 at exposure levels that the agency believes are likely to be necessary to reduce viral load in patients infected with the hepatitis C virus (HCV). BioCryst continues to believe that BCX5191 may be distinct from other Nucs in exhibiting antiviral potency in man at significantly lower doses than other Nucs in development based on preclinical results, and will therefore conduct additional preclinical studies to determine if low doses - ie, doses that are not associated with toxicity in animals - exhibit meaningful viral load reductions in HCV infected animals. BioCryst will then determine whether to continue development of BCX5191, based on the results of these studies.