Pfizer has completed its acquisition of UK-based ReViral, a clinical-stage biopharmaceutical company focused on novel antiviral therapeutics that target respiratory syncytial virus (RSV).

The purchase, which is valued at up to $525 million including upfront and potential milestone payments, adds ReViral’s sisunatovir, an oral drug that blocks replication of RSV, to Pfizer’s pipeline of anti-infective products.

The FDA granted sisunatovir Fast Track designation in August 2020 for treatment of serious RSV infections. The investigational drug has also shown promising results in a phase 2 study.