Shionogi has reported late-breaking data from two clinical trials of oral Covid-19 antiviral, S-217622, which concluded in Asia, demonstrated rapid clearance of the virus.

An investigational drug for Covid-19, S-217622 is an inhibitor of 3CL protease designed through a research collaboration between Hokkaido University and Shionogi. 

The SARS-CoV-2 virus uses the 3CL protease enzyme, which is required for its replication. S-217622 stops the viral replication by selectively hindering the enzyme.

The Phase II trial that concluded in Japan and Korea had two parts, Phase IIa and IIb. 

Enrolling 428 patients in Japan and South Korea, the Phase IIb trial analysed the antiviral effect and improvement of clinical symptoms following treatment with an oral once-a-day dose of S-217622 given for five days versus placebo.

Subjects in the trial receiving S-217622 showed a substantial and quick decline of nearly 90% in viral titer and/or viral ribonucleic acid (RNA) on the fourth day following the third drug dose versus placebo.

Furthermore, no serious safety issues were observed in the trial. 

No substantial variations in the total score of 12 Covid-19 symptoms were reported between treatment groups but S-217622 demonstrated improvement in the composite score of five ‘respiratory and feverish’ symptoms.

In addition, late-breaking data from a Phase I trial and the Phase IIa portion of the Phase II/III trial concluded in Japan showed that S-217622 was well-tolerated and offered quick viral clearance.

In February this year, the company sought manufacturing and sales approvals in Japan.

Shionogi president and CEO Isao Teshirogi said: “These results demonstrate that S-217622 rapidly eliminates SARS-CoV-2 in patients versus placebo, marking its potential, if approved, as an effective treatment option for Covid-19. 

“As infections continue to rise in areas worldwide, it is important we have access to a range of easily administered treatment options to ease the pressures on our healthcare systems.” 

In July last year, the company launched a Phase I trial of S-217622 to treat Covid-19.