In a bid to compete in the race to develop an all-oral treatment regimen for chronic hepatitis C virus (HCV) infection, BioCryst Pharmaceuticals has agreed to acquire Presidio Pharmaceuticals in an all-stock merger agreement. The combined entity will have three early-stage oral HCV drug candidates with different mechanisms of action. However, news of the agreement was followed by the announcement that BioCryst had withdrawn its IND application for the antiviral nucleoside BCX5191 following concerns raised by the US FDA over the drug’s preclinical toxicity profile.