Biological AvailabilityPhase 1NCT06397144
A Study on 2 Different Combination Tablets of Nirmatrelvir Plus Ritonavir to Compare Them With Marketed Paxlovid in Healthy Participants
A Phase 1 study testing Paxlovid and Nirmatrelvir/ritonavir in people with Biological Availability and Healthy Participants, run by Pfizer.
Trial summary
Medicines that may have different names or be made in different ways but have the same effect on the body are called bioequivalent. The purpose of this study is to learn about the bioequivalence of nirmatrelvir plus ritonavir after taking 2 different combination tablet forms by mouth. Read more about this study
- Who is it for?
- Ages 18 years and olderHealthy volunteers can take part
- Conditions the study is for
- Biological Availability, Healthy Participants
- What is being tested?
- Paxlovid and Nirmatrelvir/ritonavir
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 0 participants
- Where
- No sites listed yet
- Study dates
- 15 Aug 2025to 9 Dec 2025
- Phase
- Phase 1
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Participants who are overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, and standard 12-lead ECG (electrocardiogram).
- Participants who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures.
- Female participants of childbearing potential must have a negative pregnancy test at screening and on Day -1.
- BMI (Body Mass Index) of 16-32 kg/m2; and a total body weight >50 kg (110 lb).
- Capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the ICD (Informed consent Document) and in this protocol.
Who cannot join
- Positive test result for SARS-CoV-2 infection at the time of Screening or Day -1.
- Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurological, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at the time of dosing).
- Any condition possibly affecting drug absorption (eg, gastrectomy, cholecystectomy).
- History of HIV (Human Immunodeficiency Virus) infection, Hepatitis B, or Hepatitis C; positive testing for HIV, HBsAg (Hepatitis B surface Antigen), HBcAb (Hepatitis B core Antibody) or HCVAb (Hepatitis C Virus Antibody). Hepatitis B vaccination is allowed.
- Any medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality or other conditions that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study.
- Use of prescription or nonprescription drugs and dietary and herbal supplements within 7 days or 5 half-lives (whichever is longer) prior to the first dose of study intervention.
- Participants who have received a COVID-19 vaccine within 7 days before screening or admission, or who are to be vaccinated with a COVID-19 vaccine at any time during the study confinement period.
- A positive urine drug test.
About this study
Official title: A PHASE 1, OPEN-LABEL, RANDOMIZED, SINGLE DOSE, CROSSOVER STUDY TO DETERMINE THE BE OF NIRMATRELVIR FOLLOWING ORAL ADMINISTRATION OF FDC TABLETS RELATIVE TO THE PAXLOVID® COMMERCIAL TABLETS IN HEALTHY ADULT PARTICIPANTS UNDER FASTED CONDITIONS
Medicines that may have different names or be made in different ways but have the same effect on the body are called bioequivalent.
The purpose of this study is to learn about the bioequivalence of nirmatrelvir plus ritonavir after taking 2 different combination tablet forms by mouth. These combination tablets are compared to the tablet formulation that is already in the market. This study will be done under fasted conditions in healthy adult participants.
Read more
This study is seeking participants who are:
- Male and non-pregnant female participants aged 18 years and above.
- with a body weight of more than 50 kilograms and Body Mass Index (BMI) between 16 to 32 kilograms per meter squared.
- are healthy as confirmed by medical history, physical examination, laboratory tests.
The study will also look at the safety and tolerability of nirmatrelvir plus ritonavir combination tablet and marketed tablet formulations in healthy adult participants.
The study will consist of 4 treatments:
Treatment A: Single oral dose of nirmatrelvir plus ritonavir 150 (1 × 150)/100 milligrams marketed tablets under fasted conditions (Reference 1) Treatment B (low dose strength): Single oral dose of nirmatrelvir plus ritonavir 150/100 milligrams (2 × [75/50 milligrams]) combination tablets under fasted conditions (Test 1) Treatment C: Single oral dose of nirmatrelvir/ritonavir 300 (2 × 150)/100 milligrams marketed tablets under fasted conditions (Reference 2) Treatment D (high dose strength): Single oral dose of nirmatrelvir/ritonavir 300/100 milligrams (2 × [150/50 milligrams]) combination tablets under fasted conditions (Test 2)
All treatments will be given under fasted conditions. Fasted condition means the participants would not have had anything to eat before taking the medicines.
Around 28 participants will be enrolled in the study. Healthy participants will be tested to see if they can be in the study within 28 days before receiving the study medicine. Selected participants will be admitted to the clinical research unit (CRU) one day before receiving the study medicine and will remain in the CRU until discharge after completing all the treatment periods.
On Day 1 of each period, participants will be given a single dose of study medicine nirmatrelvir/ritonavir 300/100 mg or 150/100 mg by mouth by chance. Study medicine will be given with approximately 240 milliliters of room temperature water under fasted conditions (overnight fast of at least 10 hours and no food until 4 hours after receiving the study medicine). Blood samples will be collected at different times of the day up to 48 hours after taking the study medicine. Participants will be discharged from the CRU on Day 3 of Period 4, after all the study related procedures have been completed.
A follow-up call will be made to participants around 28 to 35 days from receiving the final dose of the study medicine. The study will look at the experiences of participants receiving the study medicine. This will help to understand if the study medicine is safe and effective.
- Conditions
- Biological Availability, Healthy Participants
- Being tested
- Paxlovid, Nirmatrelvir/ritonavir
- Keywords
- Coronavirus disease 2019 (COVID-19), Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), Nirmatrelvir, Paxlovid
- Medical subject headings
- COVID-19
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
PaxlovidDrug
Also called Nirmatrelvir/ritonavir commercial tablets
Reference 1
PaxlovidDrug
Also called Nirmatrelvir/ritonavir commercial tablets
Reference 2
Nirmatrelvir/ritonavirDrug
Also called Nirmatrelvir/ritonavir FDC test tablets formulation 1
Test 1
Nirmatrelvir/ritonavirDrug
Also called Nirmatrelvir/ritonavir FDC test tablets formulation 2
Test 2
| Study group | Role | What they receive |
|---|---|---|
| Paxlovid commercial tablets A (Low Dose) | Active comparator | Single oral dose of nirmatrelvir/ ritonavir 150 (1 × 150)/100 mg commercial tablets under fasted conditions (Reference 1) Receives: Drug: Paxlovid |
| Paxlovid commercial tablets B (High Dose) | Active comparator | Single oral dose of nirmatrelvir/ ritonavir 300 (2 × 150)/100 mg commercial tablets under fasted conditions (Reference 2) Receives: Drug: Paxlovid |
| Nirmatrelvir/ritonavir FDC tablets Test formulation 1 | Experimental | Single oral dose of nirmatrelvir /ritonavir 150/100 mg (2 × [75/50 mg]) FDC tablets Test formulation 1 (Test 1) Receives: Drug: Nirmatrelvir/ritonavir |
| Nirmatrelvir/ritonavir FDC tablets Test formulation 2 | Experimental | Single oral dose of nirmatrelvir/ ritonavir 300/100 mg (2 × [150/50 mg]) FDC tablets Test formulation 2 (Test 2) Receives: Drug: Nirmatrelvir/ritonavir |
What is being measured
The primary outcome is the main question the study is designed to answer.
Area under curve (AUC) from time zero to 48 hours post dose (nirmatrelvir)
Measured: 0 , 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24 and 48 hours
Peak plasma concentration (Cmax) for nirmatrelvir
Measured: 0 , 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24 and 48 hours
Secondary outcomes (6)
AUC from time zero to 48 hours post dose (ritonavir)
Measured: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24 and 48 hours
Cmax for ritonavir
Measured: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24 and 48 hours
Number of Participants With Treatment Emergent Treatment-Related Adverse Events (AEs)
Measured: Baseline (Day 0) up to 28 days after last dose of study medication
Number of Participants With Clinically Notable Vital Signs
Measured: Baseline (Day 0) up to day 3 of treatment period 4
Number of Participants With Clinically Notable Changes in Clinical laboratory results
Measured: Baseline (Day 0) up to day 3 of treatment period 4
Number of Participants With Clinically Notable Abnormality in physical examination
Measured: Baseline (Day 0) up to day 3 of treatment period 4
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted2 May 2024
- Study start15 Aug 2025 (estimated)
- Primary completion9 Dec 2025 (estimated)
- Study completion9 Dec 2025 (estimated)
Why it stopped: Sponsor business decision to terminate study. Decision not due to major safety concerns or requests from any regulatory authorities.
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Biological AvailabilityStudies of the same condition, open and under way.
- More trials run by PfizerThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Enrolment
- 0 participants (actual)
Sponsor and investigators
- Lead sponsor
- Pfizer
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Pfizer CT.gov Call Center, Study director, Pfizer
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06397144
- Sponsor's protocol ID
- C4671009
- Other IDs
- NCT06397144
- Status last verified
- Dec 2025
- First submitted
- 29 Apr 2024
- Last updated
- 26 Dec 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No: 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.
Study at a glance
From the registry record, last updated by the sponsor on 26 Dec 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A PHASE 1, OPEN-LABEL, RANDOMIZED, SINGLE DOSE, CROSSOVER STUDY TO DETERMINE THE BE OF NIRMATRELVIR FOLLOWING ORAL ADMINISTRATION OF FDC TABLETS RELATIVE TO THE PAXLOVID® COMMERCIAL TABLETS IN HEALTHY ADULT PARTICIPANTS UNDER FASTED CONDITIONS
- ClinicalTrials.gov ID
- NCT06397144
- Acronym / sponsor ID
- C4671009
- Conditions
- Biological Availability, Healthy Participants
- Keywords
- Coronavirus disease 2019 (COVID-19), Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), Nirmatrelvir, Paxlovid
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- WithdrawnReason stopped: Sponsor business decision to terminate study. Decision not due to major safety concerns or requests from any regulatory authorities.
- Enrolment
- 0 participants (actual)
- Lead sponsor
- PfizerIndustry (pharma, biotech, devices)
- Study start
- 15 Aug 2025 (estimated)
- Primary completion
- 9 Dec 2025 (estimated)
- Study completion
- 9 Dec 2025 (estimated)
- First posted
- 2 May 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Medicines that may have different names or be made in different ways but have the same effect on the body are called bioequivalent.
The purpose of this study is to learn about the bioequivalence of nirmatrelvir plus ritonavir after taking 2 different combination tablet forms by mouth. These combination tablets are compared to the tablet formulation that is already in the market. This study will be done under fasted conditions in healthy adult participants.
This study is seeking participants who are:
- Male and non-pregnant female participants aged 18 years and above.
- with a body weight of more than 50 kilograms and Body Mass Index (BMI) between 16 to 32 kilograms per meter squared.
- are healthy as confirmed by medical history, physical examination, laboratory tests.
The study will also look at the safety and tolerability of nirmatrelvir plus ritonavir combination tablet and marketed tablet formulations in healthy adult participants.
The study will consist of 4 treatments:
Treatment A: Single oral dose of nirmatrelvir plus ritonavir 150 (1 × 150)/100 milligrams marketed tablets under fasted conditions (Reference 1) Treatment B (low dose strength): Single oral dose of nirmatrelvir plus ritonavir 150/100 milligrams (2 × [75/50 milligrams]) combination tablets under fasted conditions (Test 1) Treatment C: Single oral dose of nirmatrelvir/ritonavir 300 (2 × 150)/100 milligrams marketed tablets under fasted conditions (Reference 2) Treatment D (high dose strength): Single oral dose of nirmatrelvir/ritonavir 300/100 milligrams (2 × [150/50 milligrams]) combination tablets under fasted conditions (Test 2)
All treatments will be given under fasted conditions. Fasted condition means the participants would not have had anything to eat before taking the medicines.
Around 28 participants will be enrolled in the study. Healthy participants will be tested to see if they can be in the study within 28 days before receiving the study medicine. Selected participants will be admitted to the clinical research unit (CRU) one day before receiving the study medicine and will remain in the CRU until discharge after completing all the treatment periods.
On Day 1 of each period, participants will be given a single dose of study medicine nirmatrelvir/ritonavir 300/100 mg or 150/100 mg by mouth by chance. Study medicine will be given with approximately 240 milliliters of room temperature water under fasted conditions (overnight fast of at least 10 hours and no food until 4 hours after receiving the study medicine). Blood samples will be collected at different times of the day up to 48 hours after taking the study medicine. Participants will be discharged from the CRU on Day 3 of Period 4, after all the study related procedures have been completed.
A follow-up call will be made to participants around 28 to 35 days from receiving the final dose of the study medicine. The study will look at the experiences of participants receiving the study medicine. This will help to understand if the study medicine is safe and effective.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 4
| Arm | Type | Receives |
|---|---|---|
| Paxlovid commercial tablets A (Low Dose) | Active comparator | Drug: PaxlovidSingle oral dose of nirmatrelvir/ ritonavir 150 (1 × 150)/100 mg commercial tablets under fasted conditions (Reference 1) |
| Paxlovid commercial tablets B (High Dose) | Active comparator | Drug: PaxlovidSingle oral dose of nirmatrelvir/ ritonavir 300 (2 × 150)/100 mg commercial tablets under fasted conditions (Reference 2) |
| Nirmatrelvir/ritonavir FDC tablets Test formulation 1 | Experimental | Drug: Nirmatrelvir/ritonavirSingle oral dose of nirmatrelvir /ritonavir 150/100 mg (2 × [75/50 mg]) FDC tablets Test formulation 1 (Test 1) |
| Nirmatrelvir/ritonavir FDC tablets Test formulation 2 | Experimental | Drug: Nirmatrelvir/ritonavirSingle oral dose of nirmatrelvir/ ritonavir 300/100 mg (2 × [150/50 mg]) FDC tablets Test formulation 2 (Test 2) |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (5 listed)
- Participants who are overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, and standard 12-lead ECG (electrocardiogram).
- Participants who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures.
- Female participants of childbearing potential must have a negative pregnancy test at screening and on Day -1.
- BMI (Body Mass Index) of 16-32 kg/m2; and a total body weight >50 kg (110 lb).
- Capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the ICD (Informed consent Document) and in this protocol.
Key exclusion criteria (8 listed)
- Positive test result for SARS-CoV-2 infection at the time of Screening or Day -1.
- Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurological, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at the time of dosing).
- Any condition possibly affecting drug absorption (eg, gastrectomy, cholecystectomy).
- History of HIV (Human Immunodeficiency Virus) infection, Hepatitis B, or Hepatitis C; positive testing for HIV, HBsAg (Hepatitis B surface Antigen), HBcAb (Hepatitis B core Antibody) or HCVAb (Hepatitis C Virus Antibody). Hepatitis B vaccination is allowed.
- Any medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality or other conditions that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| PaxlovidAlso: Nirmatrelvir/ritonavir commercial tabletsReference 1 | Drug | Paxlovid commercial tablets A (Low Dose) |
| PaxlovidAlso: Nirmatrelvir/ritonavir commercial tabletsReference 2 | Drug | Paxlovid commercial tablets B (High Dose) |
| Nirmatrelvir/ritonavirAlso: Nirmatrelvir/ritonavir FDC test tablets formulation 1Test 1 | Drug | Nirmatrelvir/ritonavir FDC tablets Test formulation 1 |
| Nirmatrelvir/ritonavirAlso: Nirmatrelvir/ritonavir FDC test tablets formulation 2Test 2 | Drug | Nirmatrelvir/ritonavir FDC tablets Test formulation 2 |
Primary outcome
Area under curve (AUC) from time zero to 48 hours post dose (nirmatrelvir)
Time frame: 0 , 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24 and 48 hours
Peak plasma concentration (Cmax) for nirmatrelvir
Time frame: 0 , 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24 and 48 hours
6 secondary outcomes
AUC from time zero to 48 hours post dose (ritonavir)
Time frame: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24 and 48 hours
Cmax for ritonavir
Time frame: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24 and 48 hours
Number of Participants With Treatment Emergent Treatment-Related Adverse Events (AEs)
Time frame: Baseline (Day 0) up to 28 days after last dose of study medication
Number of Participants With Clinically Notable Vital Signs
Time frame: Baseline (Day 0) up to day 3 of treatment period 4
Number of Participants With Clinically Notable Changes in Clinical laboratory results
Time frame: Baseline (Day 0) up to day 3 of treatment period 4
Number of Participants With Clinically Notable Abnormality in physical examination
Time frame: Baseline (Day 0) up to day 3 of treatment period 4
Results and safety
The study was withdrawn before enrolling participants, so there are no results.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 26 Dec 2025.
- To obtain contact information for a study center near you, click here.Link provided by the sponsor.
- Individual participant dataSharing planned: No. 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.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Pfizer CT.gov Call Center study director
Pfizer
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing Paxlovid and Nirmatrelvir/ritonavir in people with Biological Availability and Healthy Participants, run by Pfizer.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: withdrawn, as of the sponsor's last update on 26 Dec 2025. Status can change between updates, so confirm with the study contact before making plans.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
The study was withdrawn before enrolling participants, so there are no results.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Area under curve (AUC) from time zero to 48 hours post dose (nirmatrelvir) (time frame: 0 , 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24 and 48 hours). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 26 Dec 2025.