ReViral is set to start Part B of the Phase II REVIRAL1 clinical study of sisunatovir to treat respiratory syncytial virus (RSV) infections in hospitalised infants.

An oral fusion inhibitor, sisunatovir is made to prevent RSV replication by hindering F-mediated fusion with the host cell.

Sisunatovir showed a favourable safety profile with a good therapeutic index in preclinical trials.

The latest development comes after the company concluded Part A of the REVIRAL trial and the Data Safety Monitoring Committee (DSMB) recommendation continuation of the trial on reviewing the available data.

DSMB noted that that the drug showed promising safety and pharmacokinetic exposure profile to advance to Part B.

An international, three-part adaptive study, REVIRAL1 is assessing single and multiple doses of sisunatovir in infants aged between one and 36 months who are hospitalised with RSV lower respiratory tract infections.

The objective of the randomised, double-blind, placebo-controlled Part B of the study is to evaluate the safety, tolerability, pharmacokinetics and antiviral activity of the drug.

The subjects will be categorised in a 3:1 ratio to receive sisunatovir or placebo twice daily for five days.

On concluding Part B, a double-blind, placebo-controlled Part C of the study will be initiated to analyse sisunatovir’s safety, tolerability, pharmacokinetics, antiviral activity, and clinical improvement.

ReViral CEO Alex Sapir said: “Despite the diminished RSV season over the past 18 months brought on by the coronavirus pandemic, we achieved two important goals established for this open-label stage of the study.

“First, we safely delivered sisunatovir to infants, and second, in doing so, we established a drug exposure profile that we can now take into the next phase of our study.”

ReViral entered a licencing deal with LianBio in March to develop and market sisunatovir in mainland China, Hong Kong, Macau and Singapore.

In a separate development, the Indian Defence Research and Development Organisation’s (DRDO) anti-Covid-19 drug, 2-DG, was found to be effective against all SARS-CoV-2 variants and even lowered virus replication in a new study.