Developing a COVID-19 Antiviral for Treatment and Prevention

Dr. Simon Portsmouth of Shionogi discusses the trial results of their once-daily oral COVID-19 antiviral, S-217622, as well as the significance of the therapy as vaccine efficacy wanes in the age of Omicron.

At the recent European Congress of Clinical Microbiology & Infectious Diseases (ECCMID), Shionogi Inc. presented promising study results for their once-daily oral COVID-19 antiviral, S-217622.

Simon Portsmouth, MD, Shionogi’s head of clinical development, sat down with Contagion to further explain the significance of the trial data.

Shionogi presented 2 portions of a 3-part, ongoing study. The study is intended to confirm S-217622 does have antiviral activity against COVID-19, as well as test the safety and efficacy of different dosages. Most trial participants were vaccinated outpatients with mild to moderate COVID-19 disease.

Portsmouth discussed the results of the phase 2A proof-of-concept portion of the study: “What it did show, really gratifyingly, was that this is a very powerful antiviral medicine, and it controlled infectious virus very quickly.”

The phase 2B part of the study included patients infected with COVID-19 in January, so Portsmouth and his team feel confident this evidences how S-217622 combats the highly infectious Omicron variant. During phase 2B, S-217622 cleared respiratory COVID-19 symptoms more rapidly than placebo.

“When we’ve tested in the laboratory against Omicron, even the most recent Omicron variants as well, we’ve seen no change in efficacy,” Portsmouth said.

The second part of the trial had a significantly larger sample size, with over 400 participants, allowing the investigators to examine the safety profile and adverse events of S-217622. Portsmouth noted that it was very well tolerated, with no serious adverse events or toxicities.

Portsmouth said that if COVID-19 behaves like other coronaviruses, we can expect it to become endemic or seasonal, in which case, “There would be a need, I think, for antivirals.” Portsmouth explained these could be used for infection treatment, or for prevention as people lose vaccine antibodies over time. “In addition to giving people vaccines…I think antivirals really play an important part in public health.”

Additionally, Portsmouth noted that he is working on an antibiotic for multidrug-resistant Gram-negative infections. The therapy has been approved for pediatric studies and is close to being approved for neonatal trials as well. “It really is a major unmet need in neonatal populations, these nasty infections that have a very high mortality rate,” Portsmouth explained.