Pfizer Launches Trial of COVID-19 Treatment for Post-Exposure

Pfizer recently announced the start of a Phase 2/3 study to evaluate its COVID-19 treatment in combination with ritonavir to prevent coronavirus disease.

The randomized, double-blind EPIC-PEP study will evaluate PF-07321332 with a low dose of ritonavir in 2,660 healthy adults 18 years of age and older living in the same household as an individual with confirmed symptomatic SARS-CoV-2 infection. 

Patients will either receive PF-07321332/ritonavir or placebo twice daily for five or ten days. 

Researchers will observe safety and efficacy to prevent COVID-19 and its symptoms through Day 14.

“We believe this therapy could help stop the virus early – before it has had a chance to replicate extensively – potentially preventing symptomatic disease in those who have been exposed and inhibiting the onset of infection in others,” Mikael Dolsten, MD, PhD, chief scientific officer and president of worldwide research, development, and medical at Pfizer, said in the announcement.

PF-07321332 is a SARS-CoV-2-3CL protease inhibitor antiviral therapy. The therapy is administered orally at the first sign of infection or first awareness of exposure, without requiring patients to be hospitalized. 

In March 2021, Pfizer progressed PF-07321332 to a Phase 1 study in healthy adults to evaluate the therapy’s safety, tolerability, and pharmacokinetics.

Phase 1 clinical trial results showed that PF-07321332 was safe and well-tolerated. Overall, the therapy has an encouraging pre-clinical profile, including potent in vitro antiviral SARS-CoV-2 and broad coronavirus activity, a Pfizer spokesperson explained. 

The global EPIC program also consists of various ongoing clinical trials, including one in SARS-CoV-2 infected patients at high risk of severe illness, which began in July 2021. The second EPIC clinical trial began in August and enrolled infected patients at standard risk. 

PF-07321332 is the first orally administered coronavirus-specific protease inhibitor in clinical studies.

But in August, FDA updated the emergency use authorization for Regeneron’s COVID-19 antibody cocktail to include post-exposure prophylaxis in individuals at high risk of severe disease who are not fully vaccinated or may not mount an adequate response to vaccination.

Providers can now administer REGEN-COV monthly to those who require dosing for ongoing exposure. Notably, this is the only COVID-19 antibody therapy available across the US for both treatment and post-exposure prophylaxis.