3 March 2021 - - UK-based biopharmaceutical company ReViral Ltd and China-based biotechnology company LianBio have inked an exclusive collaboration and license agreement for the development and commercialization of sisunatovir in mainland China, Hong Kong, Macau, and Singapore, the companies said.

Sisunatovir is ReViral's lead small molecule for the treatment of RSV, currently in Phase 2 clinical studies in pediatric and adult immunocompromised patient populations.

Under the terms of the collaboration, ReViral will receive an upfront cash payment of USD 14m and is eligible to receive development and commercial milestone payments of up to USD 105m.

In addition, ReViral is eligible to receive tiered low double-digit royalties on sisunatovir net sales in the licensed territories.

LianBio will be responsible for the development and commercialization of sisunatovir in the licensed territories, and ReViral will continue to be responsible for the development and commercialization of sisunatovir in all other geographies.

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.

Also, the company has an N-protein replication inhibitor program in preclinical development.

LianBio's mission is to catalyze the development and accelerate the availability of paradigm-shifting medicines to patients in China and major Asian markets through partnerships that provide access to the best science-driven therapeutic discoveries.

LianBio collaborates with world-class partners across a diverse array of therapeutic and geographic areas to build out a pipeline based on disease relevance and the ability to impact patients with transformative mechanisms and precision-based therapeutics.

Sisunatovir is an orally administered fusion inhibitor designed to block RSV replication by inhibiting F-mediated fusion with the host cell. Sisunatovir was recently granted Fast Track designation by the US Food and Drug Administration.

Preclinical tests demonstrated sisunatovir to have an excellent safety profile with an attractive therapeutic index.

In Phase 1 clinical studies, sisunatovir achieved target exposure levels with no reported serious adverse events.

In 2018, results from a Phase 2a challenge study of RSV infection 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 (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 64 m people and causes approximately 160,000 deaths each year.

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

In China, RSV is the leading pathogen causing acute respiratory infection across all ages. Currently, there are no effective therapeutic treatment options for patients who develop RSV infection.