Pfizer has completed its previously announced acquisition of UK-based ReViral for a total consideration of up to $525m, including upfront and development milestone payments.

In April this year, the US drugmaker signed an acquisition agreement with ReViral.

The clinical-stage biopharmaceutical company is engaged in the discovery, development, and commercialisation of novel antiviral therapeutics that target respiratory syncytial virus (RSV).

Pfizer will gain ReViral’s portfolio of therapeutic candidates, including sisunatovir, an oral drug designed to block the fusion of the RSV virus to the host cell.

Sisunatovir significantly reduced viral load in healthy adults, in a Phase 2 RSV human challenge study, and is currently in Phase 2 clinical development in infants.

It is being developed in both adult and paediatric populations and has received Fast Track designation from the US Food and Drug Administration (FDA).

Another lead candidate, focused on the inhibition of RSV replication targeting the viral N protein, is being studied in an ongoing Phase 1 clinical development programme.

Pfizer estimates that the candidates may generate more than $1.5bn in annual revenues if the development programs are successful.

Pfizer chief scientific officer and worldwide research, development and medical president Mikael Dolsten said: “We are excited to bring ReViral’s promising investigational treatments for RSV into our anti-infective pipeline at Pfizer.

“This acquisition further demonstrates our commitment to advancing pioneering science, both through our in-house expertise and our work with leading, innovative companies, with the goal of delivering new breakthroughs to patients suffering from serious infectious diseases.

“We believe these therapeutic candidates, and the scientific expertise that has advanced their development, will complement our ongoing work to help combat RSV infections, and we look forward to welcoming our new colleagues to further support these endeavours.”

Clifford Chance served as legal advisor to Pfizer, while Centerview Partners and BofA Securities served as financial advisors and Goodwin Procter as legal advisor to ReViral on the transaction.