Japanese drugmaker Shionogi has launched a clinical trial evaluating the first once-daily pill for treatment of COVID-19 patients.

The investigational drug, S-217622, works by inhibiting an enzyme that the SARS-CoV-2 virus needs to make copies of itself inside human cells.

The phase 1 trial will evaluate the small molecule drug’s pharmacokinetic profile, safety and tolerability. No adverse events were observed after the initial dose administered last week, the company said.