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PAXLOVID™ Oral Antiviral (PF-07321332)

PAXLOVID Oral Antiviral (nirmatrelvir, PF-07321332, and ritonavir tablets) Description

Pfizer’s PAXLOVID™ (nirmatrelvir (PF-07321332) tablets, and ritonavir tablets) is an oral antiviral therapeutic targeting the SARS-CoV-2 betacoronavirus to prevent COVID-19. In addition, PAXLOVID is a protease inhibitor that has demonstrated potent in vitro antiviral activity against SARS-CoV-2 and other coronaviruses, suggesting potential for use in the treatment of COVID-19, as well as potential use against future virus threats, says Pfizer.

By inhibiting the main protease, PF-07321332 prevents the virus from cleaving long protein chains into the parts it needs to reproduce itself. Protease inhibitors, like PF-07321332, are designed to block the activity of the main protease enzyme that the coronavirus needs to replicate.

Protease inhibitors bind to a viral enzyme (protease), preventing the virus from replicating in the cell. Protease inhibitors have effectively treated other viral pathogens such as HIV and hepatitis C virus alone and other antivirals.

PF-07321332 is the first orally administered coronavirus-specific investigational protease inhibitor to be evaluated in phase 3 clinical studies. Co-administration with a low dose of ritonavir helps slow the metabolism, or breakdown of (PF-07321332), to remain active in the body for more extended periods at higher concentrations to help combat the virus.

PAXLOVID inhibits viral replication at a stage known as proteolysis, which occurs before viral RNA replication. It is an analog of GC373, where the aldehyde covalent cysteine acceptor replaced a nitrile. In this combination, ritonavir slows down the metabolism of PF-07321332 by cytochrome enzymes to maintain higher circulating concentrations of the primary drug. In preclinical studies, PF-07321332 did not demonstrate evidence of mutagenic DNA interactions.

On December 16, 2021, the European Medicines Agency announced the human medicines committee (CHMP) has issued advice on the use of Paxlovid (PF-07321332 and ritonavir) for the treatment of COVID-19. The CHMP advice is based on interim results from the main study in non-hospitalized, unvaccinated patients who had the symptomatic disease and at least one underlying condition putting them at risk of severe COVID-19. These data showed that Paxlovid reduced the risk of hospitalization and death when treatment started within 5 days of the start of symptoms. About 1% of patients (6 out of 607) who took Paxlovid within five days of the start of symptoms were hospitalized within 28 days of starting treatment compared with 6.7% of patients (41 out of 612) given a placebo; none of the patients in the Paxlovid group died compared with 10 patients in the placebo group. In terms of safety, the most common side effects reported during treatment and up to 34 days after the last dose of Paxlovid were dysgeusia (taste disturbance), diarrhea, and vomiting.

Pfizer Inc. announced results from its Phase 2/3 EPIC-HR clinical trial on December 14, 2021, showing PAXLOVID (nirmatrelvir [PF-07321332] tablets and ritonavir tablets) significantly reduced the risk of hospitalization or death for any cause by 89% compared to placebo in non-hospitalized, high-risk adult patients with COVID-19 treated within three days of symptom onset. In addition, in a secondary study endpoint, PAXLOVID reduced the risk of hospitalization or death for any cause by 88% compared to placebo in patients treated within five days of symptom onset, an increase from the 85% observed in the interim analysis.

Chemical Formula: C23H32F3N5O4; DrugBank Accession Number DB16691; CAS Number 2628280-40-8; PubChem CID 155903259; Molecular Weight: 499.5;

To learn more, please visit New York-based Pfizer Inc. at www.Pfizer.com. (NYSE: PFE). Pfizer is also investigating an intravenously administered investigational protease inhibitor, PF-07304814, which is currently in Phase 1b multi-dose trial in hospitalized clinical trial participants with COVID-19.

PAXLOVID Oral Antiviral (nirmatrelvir, PF-07321332, and ritonavir tablets) History

Pfizer developed PF-07321332 by modification of PF-07304814 (Lufotrelvir), a covalent inhibitor. PF-07304814 needs to be administered intravenously, not orally. PF-07321332 is also a covalent inhibitor, but its warhead is a phosphate prodrug of a hydroxyketone.

A scheduled interim analysis announced on November 5, 2021, showed an 89% reduction in risk of COVID-19-related hospitalization or death from any cause compared to placebo in patients treated within three days of symptom onset; 0.8% of patients who received PAXLOVID™ were hospitalized through Day 28 following randomization, compared to 7.0% of patients who received placebo and were hospitalized or died.

PAXLOVID Oral Antiviral (nirmatrelvir, PF-07321332, and ritonavir tablets) Indication

PAXLOVID (PF-07321332) oral antiviral therapy is indicated to prevent the SARS-CoV-2 virus from replicating in human host cells. If authorized or approved, PAXLOVID would be the first oral antiviral of its kind, a 3CL protease inhibitor specifically designed to combat SARS-CoV-2 that could be prescribed as an at-home treatment to high-risk patients at the first sign of infection, potentially helping patients avoid severe illness, which can lead to hospitalization and death.

PAXLOVID Oral Antiviral (nirmatrelvir, PF-07321332, and ritonavir tablets) and Pregnant and Breastfeeding Women

Paxlovid is not recommended during pregnancy and in women who can become pregnant and who are not using contraception. Breastfeeding should be interrupted during treatment. These recommendations are because laboratory studies in animals suggest that high doses of Paxlovid may impact the growth of a fetus.

PAXLOVID Oral Antiviral (nirmatrelvir, PF-07321332, and ritonavir tablets) Distribution

Under the terms of the head license agreement between Pfizer and MPP, announced on November 16, 2021, qualified generic medicine manufacturers worldwide that are granted sub-licenses will be able to supply PF-07321332 in combination with ritonavir to 95 countries, covering up to approximately 53% of the world’s population. This agreement includes all low- and lower-middle-income countries and some upper-middle-income countries in Sub-Saharan Africa, as well as countries that have transitioned from lower-middle to upper-middle-income status in the past five years.

PAXLOVID Oral Antiviral (nirmatrelvir, PF-07321332, and ritonavir tablets) Dosage

PAXLOVID intends to be administered at a dose of 300 mg (two 150 mg tablets) of nirmatrelvir with one 100 mg tablet of ritonavir, given twice daily for five days. In addition, one box contains five blister packs of PAXLOVID, as co-packaged nirmatrelvir tablets with ritonavir tablets, providing all required doses for an entire five-day treatment course.

The EMA says ‘Paxlovid must not be used with certain other medicines, either because due to its action it may lead to harmful increases in their blood levels, or because conversely, some medicines may reduce the activity of Paxlovid itself. The list of medicines that must not be used with Paxlovid is included in the proposed conditions for use. Paxlovid must also not be used in patients with severely reduced kidney or liver function.’

PAXLOVID Oral Antiviral (nirmatrelvir, PF-07321332, and ritonavir tablets) Price

Pfizer Inc. sold PAXLOVID to the U.S. government for $529 per course in 2021.

PAXLOVID Oral Antiviral (nirmatrelvir, PF-07321332, and ritonavir tablets) Revenues

Pfizer Inc. announced a potential PAXLOVID sale of $5.29 billion to be recognized as revenue in 2021 and 2022. In addition, the company recently raised Full-Year 2021 Guidance for Revenues to a Range of $81.0 to $82.0 Billion.

PAXLOVID Oral Antiviral (nirmatrelvir, PF-07321332, and ritonavir tablets) News

December 14, 2021 – Science.org published an article: Pfizer’s Paxlovid Holds Up – So Paxlovid looks to have the most effect when you’d want it the most, in patients who are at high risk of bad outcomes.

December 14, 2021 – Pfizer Inc. announced final results from its Phase 2/3 EPIC-HR trial analysis. These results were consistent with the interim analysis announced in November 2021, showing PAXLOVID significantly reduced the risk of hospitalization or death for any cause by 89% compared to placebo in non-hospitalized, high-risk adult patients with COVID-19 treated within three days of symptom onset. In addition, in a secondary endpoint, PAXLOVID reduced the risk of hospitalization or death for any cause by 88% compared to placebo in patients treated within five days of symptom onset, an increase from the 85% observed in the interim analysis.

December 7, 2021 – CNBC’s Meg Tirrell tweeted ‘Pfizer CEO says he expects Paxlovid to be available this year. He says FDA would like to see final data from Pfizer’s study, noting Merck’s final numbers “created a change.”

December 3, 2021 – Filomena Tassi, Canada’s minister of public services and procurement, told reporters the government had signed agreements with Pfizer Inc. to buy up to 1 million courses of PF-07321332.

November 30, 2021 – Pfizer’s CEO @AlbertBourla Tweeted, ‘if authorized, we’re confident our oral antiviral therapy can help reduce the severity of illness, and we now anticipate we can deliver 80M treatment courses, up from our original estimate of 50M.’

November 29, 2021 – CNBC reported Pfizer estimates it can manufacture 80M treatment courses of Paxlovid, up from 50M projected a few weeks ago.

November 19, 2021 – The EMA announced it is reviewing currently available data on the use of Paxlovid to support national authorities who may decide on its use in emergency use settings before marketing authorization.

November 18, 2021 – Pfizer Inc. announced an agreement with the U.S. government to supply 10 million treatment courses of PAXLOVID™ (PF-07321332; ritonavir), subject to regulatory authorization beginning later this year and concluding in 2022. Under the agreement terms, Pfizer will receive $5.29 billion from the U.S. government. Pricing for PAXLOVID is based on the principles of advance commitment, volume, equity, and affordability. The company has also entered into advance purchase agreements with several other countries and has initiated bilateral outreach to approximately 100 countries worldwide.

November 16, 2021 – Pfizer Inc. announced it is seeking Emergency Use Authorization of its investigational oral antiviral candidate, PAXLOVID™ (PF-07321332; ritonavir), for the treatment of mild to moderate COVID-19 in patients at increased risk of hospitalizations or death. Rolling submission of non-clinical data for PAXLOVID was initiated with the U.S. FDA in October 2021.

November 16, 2021 – Pfizer Inc. and the Medicines Patent Pool announced the signing of a voluntary license agreement for Pfizer’s COVID-19 oral antiviral treatment candidate PF-07321332, which is administered in combination with low dose ritonavir (PF-07321332; ritonavir). The agreement will enable MPP to facilitate additional production and distribution of the investigational antiviral, pending regulatory authorization or approval, by granting sub-licenses to qualified generic medicine manufacturers to facilitate greater access to the global population.

November 13, 2021 – i24News reported an agreement with Pfizer has been reached. The Paxlovid shipment will be despatched as soon as Pfizer receives U.S. FDA approval.

November 10, 2021 – The journal Nature published an article: COVID antiviral pills: what scientists still want to know.

November 8, 2021 – The BMJ published an article: Commenting on the PAXLOVID announcement, England’s health and social care secretary, Sajid Javid, said, “If approved, this could be another significant weapon in our armory to fight the virus alongside our vaccines and other treatments, including molnupiravir, which the UK was the first country in the world to approve this week.”

November 5, 2021 – Pfizer Inc. announced its investigational novel COVID-19 oral antiviral candidate, PAXLOVID™, significantly reduced hospitalization and death, based on an interim analysis of the Phase 2/3 EPIC-HR randomized, double-blind study of non-hospitalized adult patients with COVID-19. They are at high risk of progressing to severe illness. The scheduled interim analysis showed an 89% reduction in risk of COVID-19-related hospitalization or death from any cause compared to placebo in patients treated within three days of symptom onset (primary endpoint); 0.8% of patients who received PAXLOVID™ were hospitalized through Day 28 following randomization (3/389 hospitalized with no deaths), compared to 7.0% of patients who received placebo and were hospitalized or died (27/385 hospitalized with seven subsequent deaths). The statistical significance of these results was high (p<0.0001). Similar reductions in COVID-19-related hospitalization or death were observed in patients treated within five days of symptom onset; 1.0% of patients who received PAXLOVID™ were hospitalized through Day 28 following randomization (6/607 hospitalized, with no deaths), compared to 6.7% of patients who received a placebo (41/612 hospitalized with ten subsequent deaths), with high statistical significance (p<0.0001). In addition, in the overall study population through Day 28, no casualties were reported in patients who received PAXLOVID™ as compared to 10 (1.6%) deaths in patients who received placebo.

October 5, 2021 – Australia announced the TGA had granted provisional determination to Pfizer Australia concerning a new combination medicine containing PF-07321332 and ritonavir to treat adult patients with symptomatic, confirmed coronavirus infection. The granting of an interim judgment means that the TGA has decided that Pfizer Australia is now eligible to apply for provisional registration of this treatment in the Australian Register of Therapeutic Goods.

September 27, 2021 – Pfizer Inc. announced the start of the Phase 2/3 EPIC-PEP study to evaluate the investigational novel oral antiviral candidate PF-07321332, co-administered with a low dose of ritonavir, for the prevention of COVID-19 infection. This Phase 2/3 trial is part of a global clinical research program. It enrolls individuals at least 18 years old and live in the same household as an individual with a confirmed symptomatic SARS-CoV-2 infection.

September 1, 2021 – Pfizer Inc. 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 explicitly designed to combat COVID-19 – in non-hospitalized, symptomatic adult participants who have a confirmed diagnosis of SARS-CoV-2 virus infection and are not at increased risk of progressing to severe illness, which may lead to hospitalization or death.

July 28, 2021 – Pfizer today provided further details on its oral protease inhibitor program for the treatment of COVID-19. PF-07321332 exhibits potent, selective in vitro antiviral activity against SARS-CoV-2 and other coronaviruses. Additionally, it has demonstrated robust preclinical antiviral effects in human cells in vitro and SARS-CoV-2 infected animals. In Phase 1 pharmacokinetic study in healthy volunteers, PF-07321332 has shown high drug exposure over ten days, – 12 – exceeding the level of exposure predicted to inhibit SARS-CoV-2 viral replication by more than five-fold. Based on these data, Pfizer initiated a Phase 2/3 trial in COVID-19 patients in July 2021. Data from the trial are expected in the fourth quarter of 2021.

May 4, 2021 – Pfizer Inc. published today its ‘Key Near-term Potential Milestones for COVID-19 Vaccine Program (2021)’ on slide #8 within its financial report.

April 7, 2021 – Chemical & Engineering News published: Pfizer unveils its oral SARS-CoV-2 inhibitor.

March 23, 2021 – Pfizer Inc. announced 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 therapy for SARS-CoV-2, the virus that causes COVID-19. This Phase 1 trial is being conducted in the United States.

PAXLOVID PF-07321332 Protease Inhibitor Antiviral Clinical Trials

Phase 1, double-blind, sponsor open, single, and multiple ascending dose study evaluates the safety, tolerability, and pharmacokinetics of PF-07321332 in healthy participants.

ClinicalTrials.gov Identifier: NCT04960202 – The purpose of this Phase 2/3 study is to determine whether PF-07321332/ritonavir is safe and effective for the treatment of adults who are ill with COVID-19 and do not need to be in the hospital but are at an increased risk of developing severe illness. A provision will be made throughout the study period to allow study visits to be conducted at a participant’s home or another non-clinic location if available. The total study duration is up to 24 weeks. Estimated Primary Completion Date: October 5, 2021. Last update date: September 1, 2021.

The Phase 2/3 EPIC-PEP trial is a randomized, double-blind, placebo-controlled study and will enroll up to 2,660 healthy adult participants aged 18 and older. Participants will be randomly assigned (1:1:1) to receive PF-07321332/ritonavir or placebo orally twice daily for 5 or 10 days. The primary objective will assess safety and efficacy to prevent confirmed SARS-CoV-2 infection and its symptoms through Day 14. PF-07321332 is an oral antiviral SARS-CoV-2-3CL protease inhibitor, which has an encouraging preclinical profile, including potent in vitro antiviral SARS-CoV-2 and broad coronavirus activity. Results from the Phase 1 clinical trial demonstrated that PF-07321332 was safe and well-tolerated.

For more information on the EPIC Phase 2/3 clinical trials for PAXLOVID, visit clinicaltrials.gov.





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