New York, N.Y., September 1, 2021Pfizer Inc. (NYSE:PFE) today shared that the first participant has been dosed in a pivotal Phase 2/3 clinical trial to evaluate the safety and efficacy of PF-07321332 – an investigational orally administered protease inhibitor antiviral therapy designed specifically to combat COVID-19 – in non-hospitalized, symptomatic adult participants who have a confirmed diagnosis of SARS-CoV-2 infection and are not at increased risk of progressing to severe illness, which may lead to hospitalization or death.

The randomized, double-blind trial will enroll approximately 1,140 participants, who will receive PF-07321332/ritonavir or placebo orally every 12 hours for five days.

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 in the body for longer periods of time at higher concentrations, thereby working continuously to help combat the virus. Ritonavir has previously been used in combination with other antivirals to similarly inhibit metabolism.

This study is part of a global clinical development program, consisting of multiple ongoing and planned clinical trials to evaluate this early-intervention, outpatient therapeutic candidate for potential use in a broad population of patients. The first registrational trial in this program, a pivotal Phase 2/3 study of PF-07321332/ritonavir in non-hospitalized, symptomatic adult participants who have been diagnosed with SARS-CoV-2 infection and are at increased risk of progressing to severe illness, began enrollment in July 2021.

If successful, PF-07321332/ritonavir has the potential to address a significant unmet medical need, providing patients with a novel oral therapy that could be prescribed at the first sign of infection, without requiring hospitalization.

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