Pfizer Inc. (NYSE: PFE) today shared data from the Phase 2/3 EPIC-SR (Evaluation of Protease Inhibition for COVID-19 in Standard-Risk Patients) study evaluating the use of PAXLOVID™ (nirmatrelvir [PF-07321332] tablets and ritonavir tablets) in patients who are at standard risk for developing severe COVID-19. In previously reported interim analyses, the company disclosed that the novel primary endpoint of self-reported, sustained alleviation of all symptoms for four consecutive days was not met, and a non-significant 70% relative risk reduction was observed in the key secondary endpoint of hospitalization or death (treatment arm: 3/428; placebo: 10/426).An updated analysis from 1,153 patients enrolled through December 2021 showed a non-significant 51% relative risk reduction (treatment arm: 5/576; placebo: 10/569). A sub-group analysis of 721 vaccinated adults with at least one risk factor for progression to severe COVID-19 showed a non-significant 57% relative risk reduction in hospitalization or death (treatment arm: 3/361; placebo: 7/360).
Additional analyses of secondary endpoint data showed that treatment with PAXLOVID resulted in a nominally significant 62% decrease in COVID-19-related medical visits per day across all patients, relative to placebo (p=0.0228). Types of medical visits included trips to the emergency room, urgent care, hospital admissions, and telehealth calls, among others. This observation is consistent with data from a secondary endpoint of the EPIC-HR1 study, which showed a 67% reduction in medical visits per day versus placebo (p
"Results from our Phase 2/3 EPIC-HR and EPIC-SR studies, as well as post-authorization experience, support the efficacy and safety profile for PAXLOVID in the treatment of mild-to-moderate COVID-19 patients with at least one risk factor for progressing to severe COVID-19, regardless of vaccination status," said Albert Bourla, Chairman and Chief Executive Officer, Pfizer. "With up to 40-50% of people around the world estimated to be high risk, we believe there remains a significant unmet need for treatment options to help combat this disease, and we will continue to prioritize efforts to advance the development of PAXLOVID."
Treatment-emergent adverse events were comparable between PAXLOVID (23.1%) and placebo (23.4%), most of which were mild in intensity. Rates of serious adverse events (1.4% vs. 1.9%) and discontinuation of study drug due to adverse events (1.7% vs. 1%) were also comparable between PAXLOVID and placebo.
Due to a very low rate of hospitalization or death observed in the standard-risk patient population, Pfizer has decided to cease enrollment into EPIC-SR and include available data in this month's planned New Drug Application (NDA) submission to the U.S. Food and Drug Administration (FDA) to support the use of PAXLOVID in appropriate individuals at high risk of progression to severe illness.2 The company will focus efforts on generating further data on PAXLOVID in vulnerable populations, including longer treatment durations in immunocompromised individuals, as well as exploring other clinical development opportunities, such as its potential use in hospitalized patients with severe disease.
The results from these additional analyses are not expected to impact Pfizer's full-year 2022 revenue guidance. Analyses of the data are ongoing, and final results will be made available via publication or presentation.
PAXLOVID is currently approved or authorized for conditional or emergency use in more than 65 countries across the globe to treat high-risk COVID-19 patients. Available safety data for PAXLOVID have been generally consistent in more than 3,500 PAXLOVID-treated participants across the EPIC-HR, EPIC-SR and EPIC-PEP3 studies, as well as in reported post-authorization safety experience.
Please see Full Emergency Use Authorization (EUA) Prescribing Information available at www.fda.gov and www.COVID19oralRx.com.
About PAXLOVID™ (nirmatrelvir [PF-07321332] tablets and ritonavir tablets)
PAXLOVID is a SARS-CoV-2 main protease (Mpro) inhibitor (also known as SARS-CoV-2 3CL protease inhibitor) therapy. It was developed to be administered orally so that it can be prescribed at the first sign of infection, potentially helping patients avoid severe illness (which can lead to hospitalization and death). Nirmatrelvir [PF-07321332], which originated in Pfizer laboratories, is designed to block the activity of the Mpro, an enzyme that the coronavirus needs to replicate. Co-administration with a low dose of ritonavir helps slow the metabolism, or breakdown, of nirmatrelvir in order for it to remain active in the body for longer periods of time at higher concentrations to help combat the virus.
Nirmatrelvir is designed to inhibit viral replication at a stage known as proteolysis, which occurs before viral RNA replication. In preclinical studies, nirmatrelvir did not demonstrate evidence of mutagenic DNA interactions.
Current variants of concern can be resistant to treatments that work by binding to the spike protein found on the surface of the SARS-CoV-2 virus. PAXLOVID, however, works intracellularly by binding to the highly conserved Mpro of the SARS-CoV-2 virus to inhibit viral replication. Nirmatrelvir has shown consistent in vitro antiviral activity against the following variants: Alpha, Beta, Delta, Gamma, Lambda, Mu, and Omicron BA.1.
PAXLOVID is generally 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. One carton contains five blister packs of PAXLOVID, as co-packaged nirmatrelvir tablets with ritonavir tablets, providing all required doses for a full five-day treatment course.
About the Phase 2/3 EPIC-SR Study
The study initially enrolled 1,153 standard-risk individuals who had (1) a confirmed diagnosis of SARS-CoV-2 infection within five days prior to randomization, (2) onset of symptoms within five days of randomization, and (3) at least one characteristic or underlying medical condition associated with an increased risk of developing severe illness from COVID-19 and were fully vaccinated against COVID-19 OR no characteristics associated with risk of severe COVID-19 and were unvaccinated. Following the Emergency Use Authorization of PAXLOVID for individuals at high risk of progression to severe COVID-19, the protocol was amended to exclude high-risk individuals and allow enrollment of patients without risk factors for progression to severe COVID-19 who were either unvaccinated, or whose last COVID-19 vaccination occurred more than 12 months from enrollment. Data from patients enrolled following this protocol amendment are not yet available.
Each patient was randomized (1:1) to receive PAXLOVID or placebo orally twice daily for five days.
Additional secondary endpoints for this study will be released in the coming months and submitted to a peer-reviewed publication. Additional information is available on clinicaltrials.gov (NCT05011513).
U.S. FDA Emergency Use Authorization Statement
PAXLOVID has not been approved but has been authorized for emergency use by FDA under an EUA, for the treatment of mild-to-moderate COVID-19 in adults and pediatric patients (12 years of age and older weighing at least 40 kg) with positive results of direct SARS CoV-2 viral testing, and who are at high-risk for progression to severe COVID-19, including hospitalization or death.
The emergency use of PAXLOVID is only authorized for the duration of the declaration that circumstances exist justifying the authorization of the emergency use of drugs and biological products during the COVID-19 pandemic under Section 564(b)(1) of the Act, 21 U.S.C. § 360bbb-3(b)(1), unless the declaration is terminated or authorization revoked sooner.
AUTHORIZED USE
The U.S. Food and Drug Administration (FDA) has issued an Emergency Use Authorization (EUA) for the emergency use of the unapproved product PAXLOVID for the treatment of mild-to-moderate coronavirus disease 2019 (COVID-19) in adults and pediatric patients (12 years of age and older weighing at least 40 kg) with positive results of direct severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death.
LIMITATIONS OF AUTHORIZED USE
- PAXLOVID is not authorized for initiation of treatment in patients requiring hospitalization due to severe or critical COVID-19
- PAXLOVID is not authorized for use as pre-exposure or post-exposure prophylaxis for prevention of COVID-19
- PAXLOVID is not authorized for use for longer than 5 consecutive days
PAXLOVID may only be prescribed for an individual patient by physicians, advanced practice registered nurses, and physician assistants that are licensed or authorized under state law to prescribe drugs in the therapeutic class to which PAXLOVID belongs (i.e., anti-infectives).
PAXLOVID is not approved for any use, including for use for the treatment of COVID-19.
PAXLOVID is authorized only for the duration of the declaration that circumstances exist justifying the authorization of the emergency use of PAXLOVID under 564(b)(1) of the Food Drug and Cosmetic Act unless the authorization is terminated or revoked sooner.
IMPORTANT SAFETY INFORMATION
PAXLOVID is contraindicated in patients with a history of clinically significant hypersensitivity reactions (eg, toxic epidermal necrolysis [TEN] or Stevens-Johnson syndrome) to its active ingredients (nirmatrelvir or ritonavir) or any other components of the product.
PAXLOVID is contraindicated with drugs that are highly dependent on CYP3A for clearance and for which elevated concentrations are associated with serious and/or life-threatening reactions:
- Alpha1-adrenoreceptor antagonist: alfuzosin
- Analgesics: pethidine, propoxyphene
- Antianginal: ranolazine
- Antiarrhythmic: amiodarone, dronedarone, flecainide, propafenone, quinidine
- Anti-gout: colchicine
- Antipsychotics: lurasidone, pimozide, clozapine
- Ergot derivatives: dihydroergotamine, ergotamine, methylergonovine
- HMG-CoA reductase inhibitors: lovastatin, simvastatin
- PDE5 inhibitor: sildenafil (Revatio®) when used for pulmonary arterial hypertension
- Sedative/hypnotics: triazolam, oral midazolam
PAXLOVID is contraindicated with drugs that are potent CYP3A inducers where significantly reduced nirmatrelvir or ritonavir plasma concentrations may be associated with the potential for loss of virologic response and possible resistance. PAXLOVID cannot be started immediately after discontinuation of any of the following medications due to the delayed offset of the recently discontinued CYP3A inducer:
- Anticancer drugs: apalutamide
- Anticonvulsant: carbamazepine, phenobarbital, phenytoin
- Antimycobacterials: rifampin
- Herbal Products: St. John's Wort (hypericum perforatum)
There are limited clinical data available for PAXLOVID. Serious and unexpected adverse events may occur that have not been previously reported with PAXLOVID use.
Risk of Serious Adverse Reactions Due to Drug Interactions: Initiation of PAXLOVID, a CYP3A inhibitor, in patients receiving medications metabolized by CYP3A or initiation of medications metabolized by CYP3A in patients already receiving PAXLOVID, may increase plasma concentrations of medications metabolized by CYP3A. Initiation of medications that inhibit or induce CYP3A may increase or decrease concentrations of PAXLOVID, respectively. These interactions may lead to:
- Clinically significant adverse reactions, potentially leading to severe, life-threatening, or fatal events from greater exposures of concomitant medications
- Clinically significant adverse reactions from greater exposures of PAXLOVID
- Loss of therapeutic effect of PAXLOVID and possible development of viral resistance
Consult Table 1 of the Fact Sheet for Healthcare Providers for clinically significant drug interactions, including contraindicated drugs. Drugs listed in Table 1 are a guide and not considered a comprehensive list of all possible drugs that may interact with PAXLOVID. Consider the potential for drug interactions prior to and during PAXLOVID therapy; review concomitant medications during PAXLOVID therapy and monitor for the adverse reactions associated with the concomitant medications.
Hypersensitivity reactions have been reported with PAXLOVID including urticaria, angioedema, dyspnea, mild skin eruptions, and pruritus. Cases of anaphylaxis, TEN, and Stevens-Johnson syndrome have also been reported with components of PAXLOVID (refer to NORVIR labeling). If signs and symptoms of a clinically significant hypersensitivity reaction or anaphylaxis occur, immediately discontinue PAXLOVID and initiate appropriate medications and/or supportive care.
Hepatotoxicity: Hepatic transaminase elevations, clinical hepatitis, and jaundice have occurred in patients receiving ritonavir. Therefore, caution should be exercised when administering PAXLOVID to patients with pre-existing liver diseases, liver enzyme abnormalities, or hepatitis.
Because nirmatrelvir is co-administered with ritonavir, there may be a risk of HIV-1 developing resistance to HIV protease inhibitors in individuals with uncontrolled or undiagnosed HIV-1 infection.
Adverse events in the PAXLOVID group (≥1%) that occurred at a greater frequency (≥5 subject difference) than in the placebo group were dysgeusia (6% and
The following adverse reactions have been identified during post-authorization use of PAXLOVID. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Immune System Disorders: Hypersensitivity reactions
Required Reporting for Serious Adverse Events and Medication Errors: The prescribing healthcare provider and/or the provider's designee is/are responsible for mandatory reporting of all serious adverse events and medication errors potentially related to PAXLOVID within 7 calendar days from the healthcare provider's awareness of the event.
Submit adverse event and medication error reports to FDA MedWatch using one of the following methods:
- Online: https://www.fda.gov/medwatch/report.htm
- Complete and submit a postage-paid FDA Form 3500 and returning by mail/fax
- Call 1-800-FDA-1088 to request a reporting form
