Pfizer Inc. has acquired rights to respiratory syncytial virus (RSV) drug candidate sisunatovir from Lianbio Co. Ltd. in a deal worth up to $155 million covering development and commercialization rights in mainland China, Hong Kong, Macau and Singapore. With this agreement, Pfizer now holds global development and commercialization rights to the candidate, an orally administered fusion inhibitor is designed to block RSV replication by inhibiting F-mediated fusion with the host cell.