Ascletis Pharma has received approval from the US Food and Drug Administration (FDA) to conduct a Phase IIa clinical trial of ASC10 for the treatment of respiratory syncytial virus (RSV) infection.

The placebo-controlled, double-blind, randomised Phase IIa trial has been designed for assessing the tolerability, pharmacokinetics, antiviral activity, and safety of ASC10 tablets in mild or moderate RSV infection patients.

An ASC10 800mg dose twice a day was selected for the trial, based on available data.

The oral double prodrug ASC10 is quickly and completely converted in vivo into the active metabolite ASC10-A, also called as β-D-N4-hydroxycytidine (NHC) or EIDD-1931, following oral administration.

In preclinical research, it was found that ASC10-A (NHC) is a potent inhibitor, with 0.51 to 0.6 uM EC50 against two RSV clinical isolates in HEp-2 cells using in vitro infection assay.

ASC10-A (NHC) was also found to be efficacious in a mouse RSV infection model in this research.

Ascletis founder, chairman and CEO Dr Jinzi Wu said: “RSV poses a persistent threat to infants and the elderly population, and so far there is no effective drug available worldwide.

“We are glad that ASC10 has obtained the US FDA approval to conduct a Phase IIa study to treat RSV infection in patients, which is a new milestone of Ascletis’ research and development (R&D) in treatment for viral diseases.

“Preclinical research showed that ASC10-A is a potent inhibitor against RSV both in vitro and in vivo, and we will accelerate the Phase IIa clinical study to benefit patients worldwide.”

The United States Patent and Trademark Office (USPTO) has granted a patent for ASC10 and its derivatives, as well as their uses for the treatment of multiple virus infections including the monkeypox virus, RSV, and SARS-CoV-2.