Shionogi’s Oral Antiviral S-217622 Rapidly Clears COVID-19 Virus

Today at the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID), Shionogi presented late-breaking data from their phase 2/3 clinical trial for S-217622, an investigational 3CL protease inhibitor. On day 4 of treatment with Shionogi’s S-217622, COVID-19 positive viral titers decreased by 90%.

Today, Shionogi & Co., Ltd. announced positive trial data for their once-daily oral COVID-19 antiviral, S-217622. The studies examined the safety and efficacy of S-217622, an investigational 3CL protease inhibitor, in mainly vaccinated low-risk patients within 5 days of symptomatic COVID-19 infection.

This late-breaking data was presented April 23 at the 32nd European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) in Lisbon, Portugal. In stage 2/3 clinical trials, S-217622 was able to rapidly clear the COVID-19 virus.

In 2 different presentations, Shionogi shared the results from their phase 2/3 clinical trial of S-217622. The multicenter, randomized, placebo-controlled, double-blinded study included patients with asymptomatic, mild, or moderate COVID-19 infection. Participants were 12-70 years of age and had COVID-19 onset within 120 hours of study randomization.

Phase 1 and phase 2a included 69 patients, and phase 2b included 428 COVID-19 patients from Japan and South Korea. The primary purpose of the phase 2/3 clinical trial was to confirm S-217622’s antiviral effect and clinical symptom improvement when administered once a day for 5 days.

Compared to placebo, S-217622 significantly reduced viral RNA on days 2, 4, 6, and 9. On day 4 of the treatment (after receiving 3 doses), the proportion of patients with positive viral titer decreased by 90% compared to placebo. S-217622 also reduced infectious virus shedding by 1-2 days versus placebo.

Notably, there was no significant difference in the total score of 12 different COVID-19 symptoms between the S-217622 group and placebo group. However, the S-217622 group did report improvement in the composite score of 5 “respiratory and feverish” symptoms in post-hoc analysis.

The clinical trials showed S-217622 was well-tolerated; Shionogi reported few discontinuations due to drug, no serious adverse events, and no mortalities. Adverse events induced by S-217622 were mild-to-moderate and resolved without treatment.

Phase 3 of the phase 2/3 clinical trial is still ongoing. In the preliminary in vitro study, S-217622 exhibited similar antiviral activity against the Omicron BA.2 variant as it did against other, less infectious COVID-19 variants.

S-217622 was developed through the research efforts of Shionogi and Hokkaido University. SARS-CoV-2, the virus that causes COVID-19 infection, utilizes the 3CL enzyme for reproduction. By inhibiting the 3CL protease, S-217622 hinders the virus’s replication.

A separate global phase 3 study, Stopping COVID-19 pRogression with early Protease InhibitOr treatment (SCORPIO-HR), plans to recruit 1700 participants this year.