5 August 2020 - - The US Food and Drug Administration has granted Fast Track designation to sisunatovir for the treatment of patients with serious RSV infection, UK-based biopharmaceutical company ReViral Ltd said.

Sisunatovir is the company's most advanced product candidate, with two international multicentre Phase 2 clinical studies recently initiated in pediatric and high-risk adult patient populations.

Fast Track is a process intended to facilitate the development and expedite the review of drug candidates that treat serious conditions and fill an unmet medical need.

A drug candidate with Fast Track designation is eligible for greater access to the FDA for the purpose of expediting the drug product candidate's development, review, and potential approval.

Sisunatovir is an orally administered fusion inhibitor designed to block RSV replication by inhibiting RSV F-mediated fusion of RSV with the host cell.

Preclinical tests showed sisunatovir to have an excellent toxicity profile with an attractive therapeutic index. In Phase 1 clinical studies, sisunatovir showed excellent exposure with no serious adverse events being reported.

In 2018, results from a Phase 2a challenge study in healthy adult volunteers were reported in which sisunatovir produced statistically significant reductions in viral load and clinical symptoms.

ReViral has recently initiated two international multicentre Phase 2 clinical studies of sisunatovir in pediatric and adult high-risk patient populations.

RSV is a respiratory pathogen that can lead to severe and life-threatening lower respiratory tract infections, or LRTIs, in high-risk populations, such as infants, immunocompromised patients, and the elderly. RSV constitutes a substantial disease burden.

The US-based National Institute of Health estimates that, globally, RSV affects approximately 64m people and causes approximately 160,000 deaths each year.

Globally, there are an estimated 33m cases of RSV LRTI each year in children younger than five years of age, with about 3m of them being hospitalized and approximately 60,000 dying each year from complications associated with the infection.

Currently, there are no effective therapeutic treatment options for patients who develop RSV infection.

ReViral is a clinical-stage biopharmaceutical company focused on discovering, developing, and commercializing antiviral therapeutics, with an initial focus on the treatment of respiratory syncytial virus.

The company's lead product candidate, sisunatovir, is an orally administered fusion inhibitor currently being evaluated in two global Phase 2 clinical studies: one in a pediatric patient population and the other in an adult stem-cell transplant patient population.

In addition, the company has an N-protein inhibitor program in late preclinical development. Both programs were discovered in-house and the company has retained worldwide development and commercialization rights.