Phase 2a Study Published in Antimicrobial Agents and Chemotherapy Shows Potential of Sisunatovir (RV521) to Combat Respiratory Syncytial Virus Infection

London, UK, November 18, 2019 – ReViral Ltd., a clinical-stage company focused on developing novel, antiviral compounds that target respiratory syncytial virus (RSV), today announced that Antimicrobial Agents and Chemotherapy (AAC) has published results from a Phase 2a study of sisunatovir in healthy adult subjects intentionally infected with RSV. ReViral is developing sisunatovir, an orally administered RSV fusion inhibitor, for certain high-risk populations, including: infants, toddlers and young children, immunocompromised patients and the elderly. Globally, RSV affects an estimated 64 million people and causes 160,000 deaths each year. 

Completed in February 2018, this Phase 2a study establishes human proof-of-concept for the antiviral activity of sisunatovir in healthy adults and underlines its potential as a therapy for managing clinical disease in naturally infected patients. The double-blind, placebo-controlled study achieved all of its primary and secondary endpoints with a statistically significant reduction in viral load, clinical symptoms and daily nasal mucus weight. Efficacy was evaluated in healthy adult volunteers who had RSV infection confirmed before treatment. Among 66 subjects (randomised 2:1, sisunatovir to placebo), sisunatovir treatment rapidly reduced viral load to undetectable levels. Total symptom scores, including stuffy nose, cough and sore throat, and daily nasal mucus weight, were also statistically significantly lower for sisunatovir-treated subjects. Safety analysis demonstrated no changes in laboratory-determined safety parameters, such as liver enzymes or haematology, and adverse events were mild and transient. Adverse events in the lower dose were similar to placebo. There were no treatment-related serious adverse events, and no subject withdrew due to compound exposure.

“ReViral is committed to the discovery and development of novel antiviral therapies against RSV infection,” said Dr. Elaine Thomas, ReViral’s Head of Virology. “The results published in Antimicrobial Agents and Chemotherapy further highlight sisunatovir’s potential to effectively treat patients suffering from RSV infection.” 

Open Access AAC Accepted Manuscript Posted Online 11 November 2019 –   


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Notes to Editors

About the Phase 2a Challenge Study

This study was a Phase 2a, randomised, double-blind, placebo-controlled study where healthy adult subjects were intentionally infected with RSV on Study Day 0. Subjects were treated with sisunatovir or placebo when infection was confirmed in the nasal wash, or on Study Day 5, whichever was achieved first. Sisunatovir or placebo was administered orally twice daily for five consecutive days. Subjects were randomised to receive sisunatovir or matched placebo (2:1) at either 200 mg or 350 mg. Upon completion of dosing, subjects were observed until Study Day 12, at which time they were discharged.

About Sisunatovir

Sisunatovir is an orally administered, small molecule fusion inhibitor being evaluated for the treatment of RSV. Sisunatovir is 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, we reported results from a Phase 2a challenge study in healthy adult volunteers, in which sisunatovir produced statistically significant reductions in viral load and clinical symptoms. ReViral is currently preparing to initiate an international multicentre Phase 2 clinical study of sisunatovir in hospitalized infants. 

About RSV

RSV is a pathogen that infects the human respiratory tract, potentially leading to bronchiolitis and pneumonia. While most (but not all) otherwise healthy people recover from the virus, there is an increased risk of severe disease and death in premature infants, individuals with certain pulmonary conditions, the elderly and those who are immune suppressed. In the United States, nearly all children become infected with RSV by age 2, with 75,000 to 125,000 of them hospitalized each year. Globally, RSV affects an estimated 64 million people and causes 160,000 deaths each year.

About ReViral

ReViral is a clinical-stage company focused on developing novel, anti-viral compounds that target RSV. Founded in 2011, ReViral has an experienced R&D leadership team with a successful track record in antiviral drug discovery and development. The company has developed a novel antiviral programme targeting RSV fusion with highly potent, orally bioavailable inhibitors, strong drug-like characteristics and good pharmacokinetic properties offering versatility in the route of administration. The lead candidate, sisunatovir, completed a Phase 2a challenge study in adult volunteers, showing high potency and was well tolerated. The company also has an RSV replication programme at an earlier stage of development and plans to expand its pipeline. In July 2018, ReViral completed a $55 million Series B funding round from a group of leading venture capital investors jointly led by New Leaf Venture Partners and Novo Ventures, part of Novo Holdings A/S, with additional new investment from Perceptive Advisors. Existing investors Andera Partners, OrbiMed and Brace Pharma Capital also participated in the fundraising.

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