PFIZER INITIATES PHASE 1 STUDY OF NOVEL ORAL ANTIVIRAL THERAPEUTIC AGENT AGAINST SARS-COV-2
- In-vitro studies conducted to date show that the clinical candidate PF-07321332 is a potent protease inhibitor with potent anti-viral activity against SARS-CoV-2
- This is the first orally administered coronavirus-specific investigational protease inhibitor to be evaluated in clinical studies, and follows Pfizer’s intravenously administered investigational protease inhibitor, which is currently being evaluated in a Phase 1b multi-dose study in hospitalized clinical trial participants with COVID-19
NEW YORK–(BUSINESS WIRE)– Pfizer Inc. (NYSE: PFE) announced today that it is progressing to multiple ascending doses after completing the dosing of single ascending doses in a Phase 1 study in healthy adults to evaluate the safety and tolerability of an investigational, novel oral antiviral therapeutic for SARS-CoV-2, the virus that causes COVID-19. This Phase 1 trial is being conducted in the United States. The oral antiviral clinical candidate PF-07321332, a SARS-CoV2-3CL protease inhibitor, has demonstrated potent in vitro anti-viral activity against SARS-CoV-2, as well as activity against other coronaviruses, suggesting potential for use in the treatment of COVID-19 as well as potential use to address future coronavirus threats.
“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,” said Mikael Dolsten, MD, PhD., 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 hospitalized or in critical care. At the same time, Pfizer’s intravenous antiviral candidate is a potential novel treatment option for hospitalized 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 bind to a viral enzyme (called a protease), preventing the virus from replicating in the cell. Protease inhibitors have been effective at treating other viral pathogens such as HIV and hepatitis C virus, both alone and in combination with other antivirals. Currently marketed therapeutics that target viral proteases are not generally associated with toxicity and as such, this class of molecules may potentially provide well-tolerated treatments against COVID-19.
The Phase 1 trial is a randomized, double-blind, sponsor-open, placebo-controlled, single- and multiple-dose escalation study in healthy adults evaluating the safety, tolerability and pharmacokinetics of PF-07321332.
Initiation of this study is supported by preclinical studies that demonstrated the antiviral activity of this potential first-in-class SARS-CoV-2 therapeutic designed specifically to inhibit replication of the SARS-CoV2 virus. The structure of PF-07321332, together with the pre-clinical data, will be shared in a COVID-19 session of the Spring American Chemical Society meeting on April 6.
Pfizer is also investigating an intravenously administered investigational protease inhibitor, PF-07304814, which is currently in a Phase 1b multi-dose trial in hospitalized clinical trial participants with COVID-19.
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Drugmaker Pfizer revealed its oral COVID-19 antiviral clinical candidate PF-07321332 on Tuesday at the American Chemical Society Spring 2021 meeting. The compound, which is currently in Phase 1 clinical trials, is the first orally administered compound in the clinic that targets the main protease (also called the 3CL protease) of SARS-CoV-2, the virus that causes COVID-19. By inhibiting the main protease, PF-07321332 prevents the virus from cleaving long protein chains into the parts it needs to reproduce itself. Dafydd Owen, director of medicinal chemistry at Pfizer, presented the compound in a symposium of the Division of Medicinal Chemistry.
Last year, Pfizer reported PF-07304814, a different small molecule inhibitor of SARS-CoV-2’s main protease. The work to develop that compound began during the 2002-2003 outbreak of SARS-CoV, severe acute respiratory syndrome. But that molecule can only be given intravenously, which limits its use to hospital settings.
Because PF-07321332 can be taken orally, as a pill or capsule, it could be given outside of hospitals if it proves to be safe and effective. People who have been exposed to SARS-CoV-2 could take it as a preventative measure, for example.
“For the foreseeable future, we will expect to see continued outbreaks from COVID-19. And therefore, as with all viral pandemics, it’s important we have a full toolbox on how to address it,” Charlotte Allerton, Pfizer’s head of medicine design, told C&EN.
PF-07321332 was developed from scratch during the current pandemic. It’s a reversible covalent inhibitor that reacts with one of the main protease’s cysteine residues. Owen also discussed the chemistry involved in scaling up the compound. The first 7 mg of the compound were synthesized in late July 2020. Encouraged by the early biological data, the Pfizer team aimed to scale up the synthesis. By late October, they’d made 100 g of the compound. Just two weeks later, the chemists had scaled up the synthesis to more than 1 kg. Owen said 210 researchers had worked on the project.
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