Pfizer doubles down on respiratory syncytial virus

Pfizer’s purchase of the respiratory syncytial virus therapy specialist Reviral is not a sign of a lack of confidence in its late-stage RSV vaccine, the company insisted today. Instead the acquisition, worth $525m in biodollars including an undisclosed up-front sum, is “complementary” to its vaccine efforts, a spokesperson told Evaluate Vantage. Pfizer clearly hopes to repeat its success with a similar two-pronged approach in Covid. With Reviral it is getting hold of the mid-stage RSV fusion inhibitor sisunatovir and a phase 1 N-protein inhibitor. With no approved treatments for the infection, the big pharma reckons the market for these drugs could exceed $1.5bn per year. However, RSV has proven a tough nut to crack, with Gilead’s presatovir, for instance, failing to live up to promising human challenge data. And Pfizer is not the only group looking at these targets: Johnson & Johnson’s fusion inhibitor rilematovir is already in phase 3 in children, while the phase 2 RSVP adult study of Enanta’s N-protein inhibitor EDP-938 will soon yield results. It looks like efficacy data with sisunatovir will not be available until next year; before then, though, Pfizer has the small matter of pivotal results with its RSV vaccine candidate, RSVpreF.

Selected oral projects in development for RSV treatment
Project Company Description Status
Rilematovir (JNJ-53718678) Johnson & Johnson RSV F-protein fusion inhibitor Ph3 Daisy in hospitalised children completes May 2025; ph2 Primrose in adult outpatients completes Nov 2023
EDP-938 Enanta N-protein inhibitor Data due Q2 2022 from ph2 RSVP in adult outpatients; RSVPEDs in hospitalised/non-hospitalised children & RSVTx in immunocompromised adults complete Dec 2022
Sisunatovir Pfizer (via Reviral) RSV F-protein fusion inhibitor Ph2 Reviral 1 in hospitalised infants completes Nov 2023; Reviral 2 in immunocompromised adults completes Jun 2023 
RSV-N* Pfizer (via Reviral) N-protein inhibitor Ph1
*Route of admin for this project not disclosed, assumed oral. Source: Evaluate Pharma &

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