NCT05047601 is a Phase 2, PHASE3 clinical trial of PF-07321332 in COVID-19, sponsored by Pfizer.

Who is sponsoring NCT05047601?

NCT05047601 is sponsored by Pfizer.

What drugs are being tested in NCT05047601?

Interventions in NCT05047601: PF-07321332, Placebo for PF-07321332, Placebo for Ritonavir, Ritonavir.

Is NCT05047601 still recruiting?

NCT05047601 is currently completed. Last updated 6 May 2023.

Are results published for NCT05047601?

Yes — primary outcome results have been posted to ClinicalTrials.gov. See the outcomes section above for details.

Last reviewed 2023-05-06 · How we verify

NCT05047601

Name: Drug Landscape Pharmaceutical Database
Creator: Drug Landscape
Published: 2026-01-01
License: https://creativecommons.org/licenses/by/4.0/

A Study of a Potential Oral Treatment to Prevent COVID-19 in Adults Who Are Exposed to Household Member(s) With a Confirmed Symptomatic COVID-19 Infection

Completed Phase 2, PHASE3 Results posted Last updated 6 May 2023

What this trial tests

Phase 2, PHASE3 trial testing PF-07321332 in COVID-19 in 2,954 participants. Completed in 12 April 2022.

Timeline

9 September 2021

Primary endpoint
12 April 2022

12 April 2022

Quick facts

Lead sponsor	Pfizer
Phase	Phase 2, PHASE3
Status	Completed
Study type	INTERVENTIONAL
Allocation	randomized
Design	parallel
Masking	quadruple
Primary purpose	prevention
Enrollment	2,954
Start date	9 September 2021
Primary completion	12 April 2022
Estimated completion	12 April 2022
Sites	170 locations across Colombia, Japan, Russia, South Africa, Malaysia, Ukraine, Hungary, Mexico

Drugs / interventions tested

PF-07321332 (pf-07321332) — full drug profile →
Placebo for PF-07321332 — full drug profile →
Placebo for Ritonavir — full drug profile →
Ritonavir (ritonavir) — full drug profile →

Conditions studied

COVID-19 — all drugs for COVID-19 →

Sponsor

Pfizer — full company profile →

Who can join

18 and older, any sex, with COVID-19. Patients with the condition only — healthy volunteers not accepted.

Results — posted to ClinicalTrials.gov

Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.

Percentage of Participants Who Developed Symptomatic RT-PCR or RAT Confirmed SARS-CoV-2 Infection Through Day 14: Among Participants With Negative RT-PCR at Baseline Primary · From Day 1 to Day 14

Percentage of participants who developed symptomatic Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) or Rapid Antigen Test (RAT) confirmed SARS-Cov-2 infection were reported in this outcome measure. Index case was defined as participants with symptomatic COVID-19.

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	2.607
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	2.410
Placebo	3.929

Number of Participants With Treatment Emergent Adverse Events (TEAEs), Serious AEs and AEs Leading to Study and Study Drug Discontinuation Secondary · From start of study intervention (Day 1) up to end of safety follow-up (Day 38)

An AE was defined as any untoward medical occurrence in a participant temporally associated with the use of study intervention, whether or not considered related to the study intervention. An SAE was defined as any untoward medical occurrence at any dose that resulted in any of the following outcomes: death; life-threatening ; required inpatient hospitalization or prolongation of existing hospitalization; persistent or significant disability/incapacity ; congenital anomaly/birth defect; or that was considered as an important medical event. TEAEs were defined as events that started on or after

TEAEs

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	218
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	212
Placebo	195

SAEs

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	3
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	1
Placebo	2

AEs led to discontinuation of study

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	0
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	0
Placebo	0

AEs led to discontinue study intervention and continued study

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	10
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	11
Placebo	14

Percentage of Participants Who Developed Symptomatic RT-PCR or RAT Confirmed SARS-CoV-2 Infection Through Day 14: Among Participants With Negative RT-PCR at Baseline With Increased Risk of Severe COVID-19 Illness Secondary · From Day 1 to Day 14

Percentage of participants who had a symptomatic RT-PCR or RAT confirmed SARS-Cov-2 infection were reported in this outcome measure. The risk factors associated with severe covid-19 illness included age greater than or equal to 60 years, body mass index greater than 25, social history of smoking and presence of comorbidities. Index case was defined as participants with symptomatic COVID-19.

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	2.871
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	2.645
Placebo	3.465

Percentage of Participants With COVID-19 Related Hospitalization or Death From Any Cause Through Day 28: Among Participants With Negative RT-PCR at Baseline With Increased Risk of Severe COVID-19 Illness Secondary · From Day 1 to Day 28

The risk factors associated with severe covid-19 illness included age greater than or equal to 60 years, body mass index greater than 25, social history of smoking and presence of comorbidities.

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	0
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	0
Placebo	0.165

Percentage of Participants With Asymptomatic RT-PCR or RAT Confirmed SARS-CoV-2 Infection Through Day 14: Among Participants With Negative RT-PCR at Baseline Secondary · From Day 1 to Day 14

Percentage of participants who had asymptomatic RT-PCR or RAT confirmed SARS-CoV-2 infection through day 14 among participants with negative RT-PCR at baseline were reported in this outcome measure. Index case was defined as participants with symptomatic COVID-19.

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	2.014
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	1.928
Placebo	3.095

Time to RT-PCR or RAT Confirmed SARS-CoV-2 Infection Through Day 14: Among Participants With Negative RT-PCR at Baseline Secondary · From Day 1 to Day 14

Number of days between first dose and confirmation of the SARS-CoV-2 infection by RT-PCR or RAT was reported in this outcome measure.

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	NA	NA – NA
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	NA	NA – NA
Placebo	NA	NA – NA

Percentage of Participants With Symptomatic RT-PCR or RAT Confirmed SARS-CoV-2 Infection Through Day 14: Among Participants With Positive RT-PCR at Baseline Secondary · From Day 1 to Day 14

Percentage of participants with a positive RT-PCR result at baseline who had a symptomatic SARS-CoV-2 infection confirmed by RAT or RT-PCR through Day 14 were reported in this outcome measure. Index case was defined as participants with symptomatic COVID-19.

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	28.947
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	45.833
Placebo	37.931

Percentage of Participants With Symptomatic RT-PCR or RAT Confirmed SARS-CoV-2 Infection Through Day 14: Among Participants With Negative, Positive or Missing RT-PCR at Baseline Secondary · From Day 1 to Day 14

Percentage of participants with a negative, positive, or missing RT-PCR result at baseline, who had a symptomatic SARS-CoV-2 infection confirmed by RAT or RT-PCR through Day 14 were reported in this outcome measure. Index case was defined as participants with symptomatic COVID-19.

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	3.712
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	4.848
Placebo	5.269

Percentage of Participants With no, Mild, Moderate, or Severe Signs and Symptoms Attributed to COVID-19 Through Day 28: Among Participants With Negative RT-PCR at Baseline Secondary · From Day 1 to Day 28

Participants were categorized according to severity of signs and symptoms as no, mild, moderate, severe in this outcome measure. The 12 signs and symptoms included stuffy or runny nose, sore throat, shortness of breath or difficulty breathing, cough, low energy or tiredness, muscle or body aches, headache, chills or shivering, feeling hot or feverish, nausea, vomiting, diarrhea. Participants recorded their daily severity rating of their symptoms over the past 24 hours based on a 4-point scale in which 0 was reported if no symptoms were present; 1 if mild; 2 if moderate; and 3 if severe.

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	81.517
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	83.373
Placebo	81.667

Mild

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	7.820
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	8.193
Placebo	7.619

Moderate

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	6.872
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	5.060
Placebo	7.143

Severe

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	2.133
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	2.048
Placebo	2.738

Missing

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	1.659
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	1.325
Placebo	0.833

Number of Days of Symptomatic RT-PCR or RAT Confirmed SARS-CoV- 2 Infection Through Day 28: Among Participants With Negative RT-PCR at Baseline Secondary · From Day 1 to Day 28

This outcome measure has been reported in terms of number of participants according to days of symptomatic SARS-CoV-2 infection through Day 28.

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	1
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	7
Placebo	2
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	2
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	0
Placebo	1
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	0
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	1
Placebo	4
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	5
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	0
Placebo	2

Plasma Concentration Versus Time Summary of Nirmatrelvir (PF-07321332) Secondary · Day 1: 1 hour post dose; Day 5: 2 hours pre-dose

Day 1 (1 hour post-dose)

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	1489	± 1481.4
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	1472	± 1488.2

Day 5 (2 hours pre-dose)

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	1688	± 2093.3
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	1657	± 2068.2

Percentage of Participants With Death Event Through Day 38: Among Participants With Negative RT-PCR at Baseline Secondary · From Day 1 to Day 38

Percentage of participants with death (all-cause) event were reported in this outcome measure.

Group	Value	95% CI
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days	0
Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days	0
Placebo	0

Adverse events — posted to ClinicalTrials.gov

Time frame: From Day 1 to Day 38. Reporting threshold: 1%. Adverse-event reports describe events observed during the trial — not all are caused by the drug.

Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 5 Days

Serious: 3/912 (0%)

Deaths: 0/912

Nirmatrelvir (PF-07321332) 300 mg + Ritonavir 100 mg 10 Days

Serious: 1/911 (0%)

Deaths: 0/911

Placebo

Serious: 2/898 (0%)

Deaths: 0/898

Serious adverse events (5 terms)

Reaction	System	Nirmatrelvir (PF-07321332)…	Nirmatrelvir (PF-07321332)…	Placebo
Cholecystitis acute	Hepatobiliary disorders	—	—	—
COVID-19 pneumonia	Infections and infestations	—	—	—
Overdose	Injury, poisoning and procedural complications	—	—	—
Road traffic accident	Injury, poisoning and procedural complications	—	—	—
Tibia fracture	Injury, poisoning and procedural complications	—	—	—

Other adverse events (15 terms — click to expand)

Reaction	System	Nirmatrelvir (PF-07321332)…	Nirmatrelvir (PF-07321332)…	Placebo
Dysgeusia	Nervous system disorders	—	—	—
COVID-19	Infections and infestations	—	—	—
Headache	Nervous system disorders	—	—	—
Diarrhoea	Gastrointestinal disorders	—	—	—
Activated partial thromboplastin time prolonged	Investigations	—	—	—
Upper respiratory tract infection	Infections and infestations	—	—	—
Fibrin D dimer increased	Investigations	—	—	—
Asthenia	General disorders	—	—	—
Nausea	Gastrointestinal disorders	—	—	—
Blood creatine phosphokinase increased	Investigations	—	—	—
Nasopharyngitis	Infections and infestations	—	—	—
Cough	Respiratory, thoracic and mediastinal disorders	—	—	—
Alanine aminotransferase increased	Investigations	—	—	—
Blood thyroid stimulating hormone increased	Investigations	—	—	—
Nasal congestion	Respiratory, thoracic and mediastinal disorders	—	—	—

Most-reported serious reactions: Cholecystitis acute, COVID-19 pneumonia, Overdose, Road traffic accident, Tibia fracture.

Data from ClinicalTrials.gov NCT05047601 adverse events section.

Sponsor's own description

The purpose of this clinical trial is to learn whether the study medicine prevent symptoms of COVID-19 in adults who have been exposed to household member(s) with a confirmed symptomatic COVID-19 infection. All participants in the study will receive treatment for COVID-19 as needed, based on their regular doctor's recommendation. Two-thirds of participants will also receive two study medicines (PF-07321332 and ritonavir) by mouth twice a day for either five or ten days. We will compare the experiences of people receiving the study medicines to those of the people who do not. This will help us determine if the study medicines are safe and effective

Publications & conference data

8 peer-reviewed publications reference this trial (live from Europe PMC):

Nirmatrelvir Plus Ritonavir: First Approval.
Lamb YN. · · 2022 · cited 218× · PMID 35305258 · DOI 10.1007/s40265-022-01692-5
The oral protease inhibitor (PF-07321332) protects Syrian hamsters against infection with SARS-CoV-2 variants of concern.
Abdelnabi R, Foo CS, Jochmans D, Vangeel L, et al · · 2022 · cited 106× · PMID 35169114 · DOI 10.1038/s41467-022-28354-0
Molnupiravir and Its Antiviral Activity Against COVID-19.
Tian L, Pang Z, Li M, Lou F, et al · · 2022 · cited 99× · PMID 35444647 · DOI 10.3389/fimmu.2022.855496
Small molecules in the treatment of COVID-19.
Lei S, Chen X, Wu J, Duan X, et al · · 2022 · cited 74× · PMID 36464706 · DOI 10.1038/s41392-022-01249-8
Two Years into the COVID-19 Pandemic: Lessons Learned.
da Silva SJR, do Nascimento JCF, Germano Mendes RP, Guarines KM, et al · · 2022 · cited 63× · PMID 35940589 · DOI 10.1021/acsinfecdis.2c00204
Oral Nirmatrelvir/Ritonavir Therapy for COVID-19: The Dawn in the Dark?
Hung YP, Lee JC, Chiu CW, Lee CC, et al · · 2022 · cited 57× · PMID 35203821 · DOI 10.3390/antibiotics11020220
Antiviral cyclic peptides targeting the main protease of SARS-CoV-2.
Johansen-Leete J, Ullrich S, Fry SE, Frkic R, et al · · 2022 · cited 50× · PMID 35432913 · DOI 10.1039/d1sc06750h
Potential Resistance of SARS-CoV-2 Main Protease (Mpro) against Protease Inhibitors: Lessons Learned from HIV-1 Protease.
Mótyán JA, Mahdi M, Hoffka G, Tőzsér J. · · 2022 · cited 50× · PMID 35408866 · DOI 10.3390/ijms23073507

Verify or expand the search:

Other trials of PF-07321332

Trials testing the same drug.

NCT05263895 — Relative Bioavailability Study of 4 Different Formulations of PF-07321332 Relative to the Commercial Tablet Formulation · Phase 1 · completed
NCT05005312 — Study to Estimate the Effects of Hepatic Impairment on the Pharmacokinetics (PK) of PF-07321332 · Phase 1 · completed
NCT05011513 — Evaluation of Protease Inhibition for COVID-19 in Standard-Risk Patients (EPIC-SR). · Phase 2, PHASE3 · terminated
NCT04960202 — EPIC-HR: Study of Oral PF-07321332/Ritonavir Compared With Placebo in Nonhospitalized High Risk Adults With COVID-19 · Phase 2, PHASE3 · completed

Other recruiting trials for COVID-19

Currently open trials in the same condition.

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Other Pfizer trials

Trials by the same sponsor.

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Verify against primary sources

ClinicalTrials.gov — authoritative US registry record
WHO ICTRP — international registry index
EU Clinical Trials Register
Sponsor press releases (Google)

Data sources for this page

Trial protocol + status: ClinicalTrials.gov NCT05047601 (US National Library of Medicine, public domain)
Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Pfizer
Last refreshed: 6 May 2023

Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT05047601.

Primary sources · FDA · ClinicalTrials.gov · EMA · SEC EDGAR · ChEMBL · Wikidata · full sourcing