A Study to Learn About a Repeat 5-Day Treatment With the Study Medicines (Called Nirmatrelvir/Ritonavir) in People 12 Years Old or Older With Return of COVID-19 Symptoms and SARS-CoV-2 Positivity After Finishing Treatment With Nirmatrelvir/Ritonavir
![]() |
The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Know the risks and potential benefits of clinical studies and talk to your health care provider before participating. Read our disclaimer for details. |
ClinicalTrials.gov Identifier: NCT05567952 |
Recruitment Status :
Recruiting
First Posted : October 5, 2022
Last Update Posted : February 21, 2023
|
- Study Details
- Tabular View
- No Results Posted
- Disclaimer
- How to Read a Study Record
The purpose of this study is to learn about the safety and effects of nirmatrelvir/ritonavir for the potential treatment of COVID-19 rebound.
The study is seeking participants who:
- Have completed treatment with nirmatrelvir/ritonavir
- Have a rebound in COVID-19 symptoms
- Are SARS-CoV-2 (COVID-19) positive
All study medications will be taken 2 times a day by mouth for 5 days. The first dose of study medication is taken at the study clinic and the rest at home.
We will examine the experiences of people receiving the study medicines to those who do not. This will help us determine if the study medicines are safe and effective.
People taking part will be in this study for about 24 weeks. Enrolled participants will need to visit the study clinic at least 8 times during the study.
Condition or disease | Intervention/treatment | Phase |
---|---|---|
COVID-19 | Drug: nirmatrelvir Drug: ritonavir Drug: placebo for nirmatrelvir | Phase 2 |
Study Type : | Interventional (Clinical Trial) |
Estimated Enrollment : | 411 participants |
Allocation: | Randomized |
Intervention Model: | Parallel Assignment |
Masking: | Triple (Participant, Care Provider, Investigator) |
Primary Purpose: | Treatment |
Official Title: | AN INTERVENTIONAL, EFFICACY AND SAFETY, PHASE 2, RANDOMIZED, DOUBLE-BLIND, 2-ARM STUDY TO INVESTIGATE A REPEAT 5-DAY COURSE OF NIRMATRELVIR/RITONAVIR COMPARED TO PLACEBO/RITONAVIR IN PARTICIPANTS AT LEAST 12 YEARS OF AGE WITH REBOUND OF COVID-19 SYMPTOMS AND RAPID ANTIGEN TEST POSITIVITY |
Actual Study Start Date : | October 19, 2022 |
Estimated Primary Completion Date : | July 10, 2023 |
Estimated Study Completion Date : | November 28, 2023 |

Arm | Intervention/treatment |
---|---|
Experimental: nirmatrelvir plus ritonavir for 5 days
Nirmatrelvir (2 tablets) plus ritonavir (1 capsule) will be given by mouth every 12 hours for 5 days
|
Drug: nirmatrelvir
Participants will receive 2 tablets of nirmatrelvir every 12 hours Drug: ritonavir Participants will receive 1 capsule of ritonavir every 12 hours |
placebo plus ritonavir for 5 days
placebo (2 tablets) plus ritonavir (1 capsule) will be given by mouth every 12 hours for 5 days
|
Drug: ritonavir
Participants will receive 1 capsule of ritonavir every 12 hours Drug: placebo for nirmatrelvir Participants will receive 2 tablets of placebo for nirmatrelvir every 12 hours. A placebo does not have any medicine in it but looks just like the medicine being studied. |
- The change in viral SARS-CoV-2 RNA level as measured in nasopharyngeal (NP) swabs [ Time Frame: Baseline to Day 5 ]To compare the effect of nirmatrelvir/ritonavir to placebo/ritonavir on viral RNA level in NP swabs in participants with mild-to-moderate COVID-19.
- Time to 2 consecutive negative rapid antigen test results obtained at least 24 hours apart through Day 28 [ Time Frame: Day 1 through Day 28 ]To compare the effect of nirmatrelvir/ritonavir to placebo/ritonavir on the duration of viral shedding.
- Time to sustained alleviation of all targeted signs and symptoms defined as the first of two consecutive days when symptoms scored moderate/severe at baseline are scored mild/absent and symptoms scored mild/absent at baseline are scored absent. [ Time Frame: Day 1 through Day 28 ]To compare the effect of nirmatrelvir/ritonavir to placebo/ritonavir on the duration and severity of signs and symptoms in participants with mild-to-moderate COVID-19.
- Incidence of treatment emergent adverse events. [ Time Frame: Day 1 through Week 24 ]To describe the safety and tolerability of nirmatrelvir/ritonavir in participants with mild-to-moderate COVID-19.
- Incidence of serious adverse events and adverse events leading to discontinuation. [ Time Frame: Day 1 through Week 24 ]To describe the safety and tolerability of nirmatrelvir/ritonavir in participants with mild-to-moderate COVID-19.

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.
Ages Eligible for Study: | 12 Years and older (Child, Adult, Older Adult) |
Sexes Eligible for Study: | All |
Accepts Healthy Volunteers: | No |
Inclusion Criteria:
- Documentation of nirmatrelvir/ritonavir treatment with patient-reported 100% compliance. Symptom alleviation or resolution in COVID-19 signs/symptoms followed by a worsening (rebound) of signs/symptoms after completing an initial 5-day course of nirmatrelvir/ritonavir
- Onset of rebound in COVID-19 symptoms within 2 weeks (14 days) after the completion of the initial 5-day course of nirmatrelvir/ritonavir.
- Onset of rebound in signs/symptoms attributable to COVID-19 within 48 hours prior to randomization and ≥1 sign/symptom attributable to COVID-19 present on the day of randomization.
- SARS-CoV-2 infection as determined by rapid antigen testing within 24 hours prior to randomization
- At least 1 characteristic or underlying medical condition associated with an increased risk of developing severe illness from COVID-19.
Exclusion Criteria:
- Current need for hospitalization, hospitalized for the COVID-19 infection or anticipated need for hospitalization within 24 hours after randomization
- History of severe chronic liver disease
- Receiving dialysis or have known age-specific estimated glomerular filtration rate (eGFR) or estimated creatinine clearance (eCrCl) <30 mL/min/1.73 m2 at screening as measured by a serum creatinine point of care device
- Oxygen saturation of <92% on room air obtained at rest within 24 hours prior to randomization
- Immunocompromised.
- Current use of any prohibited concomitant medication(s)
- Females who are pregnant and <14 weeks gestation

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT05567952
Contact: Pfizer CT.gov Call Center | 1-800-718-1021 | ClinicalTrials.gov_Inquiries@pfizer.com |

Study Director: | Pfizer CT.gov Call Center | Pfizer |
Responsible Party: | Pfizer |
ClinicalTrials.gov Identifier: | NCT05567952 |
Other Study ID Numbers: |
C4671042 2022-002827-36 ( EudraCT Number ) |
First Posted: | October 5, 2022 Key Record Dates |
Last Update Posted: | February 21, 2023 |
Last Verified: | February 2023 |
Individual Participant Data (IPD) Sharing Statement: | |
Plan to Share IPD: | Yes |
Plan Description: | Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests. |
URL: | https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests |
Studies a U.S. FDA-regulated Drug Product: | Yes |
Studies a U.S. FDA-regulated Device Product: | No |
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Coronavirus disease 2019 (COVID-19) COVID-19 rebound Paxlovid Nirmatrelvir |
COVID-19 Pneumonia, Viral Pneumonia Respiratory Tract Infections Infections Virus Diseases Coronavirus Infections Coronaviridae Infections Nidovirales Infections RNA Virus Infections Lung Diseases Respiratory Tract Diseases Ritonavir |
Nirmatrelvir HIV Protease Inhibitors Viral Protease Inhibitors Protease Inhibitors Enzyme Inhibitors Molecular Mechanisms of Pharmacological Action Anti-HIV Agents Anti-Retroviral Agents Antiviral Agents Anti-Infective Agents Cytochrome P-450 CYP3A Inhibitors Cytochrome P-450 Enzyme Inhibitors |