Novel oral antiviral for SARS-CoV-2 progresses in Phase I trial

Pfizer is progressing its novel oral antiviral candidate against SARS-CoV-2 into multiple ascending doses after completing the dosing of single ascending doses in a Phase I study in healthy adults. The trial is evaluating the safety and tolerability of PF-07321332, a SARS-CoV2-3CL protease inhibitor, which demonstrated potent in vitro antiviral activity against SARS-CoV-2 and other coronaviruses. SARS-CoV-2 is the virus that causes COVID-19.

“Tackling the COVID-19 pandemic requires both prevention via vaccine and targeted treatment for those who contract the virus. Given the way that SARS-CoV-2 is mutating and the continued global impact of COVID-19, it appears likely that it will be critical to have access to therapeutic options both now and beyond the pandemic,” stated Dr Mikael Dolsten, Chief Scientific Officer and President, Worldwide Research, Development and Medical of Pfizer. “We have designed PF-07321332 as a potential oral therapy that could be prescribed at the first sign of infection, without requiring that patients are hospitalised or in critical care. At the same time, Pfizer’s intravenous antiviral candidate is a potential novel treatment option for hospitalised patients. Together, the two have the potential to create an end-to-end treatment paradigm that complements vaccination in cases where disease still occurs.”

Protease inhibitors such as PF-07321332 bind to a viral enzyme, called a protease, which is vital for the virus to successfully replicate in human cells. Through their interaction with the enzyme, this class of medicines prevent the virus from replicating. Protease inhibitors have been used to treat various other viral pathogens, including HIV and hepatitis C virus, both alone and in combination with other antivirals. Currently marketed protease inhibitors are not generally associated with toxicity and as such, this class of molecules may potentially provide well-tolerated treatments against COVID-19.

The Phase I trial is a randomised, double-blind, sponsor-open, placebo-controlled, single- and multiple-dose escalation study in healthy adults evaluating the safety, tolerability and pharmacokinetics of PF-07321332.

Pfizer is also investigating an intravenously administered investigational protease inhibitor, PF-07304814, in a Phase Ib multi-dose trial in hospitalised patients with COVID-19.