"PF-07321332 is an investigational SARS-CoV-2-3CL protease inhibitor antiviral therapy, specifically designed to be administered orally so that it can potentially be prescribed at the first sign of infection or at first awareness of an exposure, without requiring patients to be hospitalized. Protease inhibitors, like PF-07321332, are designed to block the activity of the main protease enzyme that the coronavirus needs to replicate. Co-administration with a low dose of ritonavir is expected to help slow the metabolism, or breakdown, of PF-07321332 in order for it to remain active in the body for longer periods of time at higher concentrations to help combat the virus.
In March 2021, Pfizer progressed PF-07321332 to a Phase 1 study in healthy adults to evaluate the safety, tolerability, and pharmacokinetics of the investigational compound. In July, it progressed to a Phase 2/3 trial, EPIC-HR (Evaluation of Protease Inhibition for COVID-19 in High-Risk Patients), to evaluate efficacy and safety, in combination with ritonavir, in participants with a confirmed diagnosis of SARS-CoV-2 infection who are at high risk of progression to severe illness. In August, Pfizer initiated a Phase 2/3 trial, EPIC-SR (Evaluation of Protease Inhibition for COVID-19 in Standard-Risk Patients), to evaluate efficacy and safety in participants with a confirmed diagnosis of SARS-CoV-2 infection who are at standard risk (i.e., do not have risk factors for severe illness).
PF-07321332 is the first orally administered coronavirus-specific investigational protease inhibitor to be evaluated in clinical studies.
There is no orally administered therapy currently approved for post-exposure or pre-emptive treatment of COVID-19."