End of sisunatovir research signals ReViral misfire for Pfizer

Some two-and-a-half years after buying the Novo Holdings portfolio company ReViral and its respiratory syncytial virus (RSV) candidate sisunatovir in a deal worth up to $525 million, US pharma giant Pfizer (NYSE: PFE) may have signalled an early end to the pricey project.

Pfizer has brought its Phase II/III research program of sisunatovir - comparing the orally-available small molecule inhibitor of RSV to placebo in non-hospitalized adults with RSV infection who are at risk of progression to sever illness - to an end.

Sisunatovir had earlier reduced viral load in a Phase II RSV human challenge study in healthy adults and it was hoped that the drug would prove impactful in both adult and pediatric populations.