BioavailabilityPhase 1NCT05263895

Relative Bioavailability Study of 4 Different Formulations of PF-07321332 Relative to the Commercial Tablet Formulation

A Phase 1 study testing PF-07321332/ritonavir and PF-07321332 in people with Bioavailability, run by Pfizer at 1 site in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record

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Trial summary

The purpose of this study is to estimate the relative bioavailability of PF-07321332 in different formulations in healthy adult participants. Read more about this study

Who is it for?: Ages 18 years and olderHealthy volunteers can take part
Conditions the study is for: Bioavailability
What is being tested?: PF-07321332/ritonavir and PF-07321332
Type of treatment: Pill or oral medicine
Could I receive a placebo?: No, everyone receives an active treatment
How many people: 12 participants
Where: 1 siteUnited States
Study dates: 3 Mar 2022to 16 May 2022
Phase: Phase 1
Are there results?: Yes, posted in the registrySummary in the doctors' view

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 (PE), laboratory tests, vital signs and standard 12 lead ECGs.
Body mass index (BMI) of 17.5 to 30.5 kg/m2; and a total body weight >50 kg (110 lb).
Participants who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures

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).
Clinically relevant abnormalities requiring treatment (eg, acute myocardial infarction, unstable ischemic conditions, evidence of ventricular dysfunction, serious tachy or brady arrhythmias) or indicating serious underlying heart disease (eg, prolonged PR interval, cardiomyopathy, heart failure greater than New York Heart Association (NYHA) 1, underlying structural heart disease, Wolff Parkinson-White syndrome).
Any condition possibly affecting drug absorption (eg, gastrectomy, cholecystectomy).
History of human immunodeficiency virus (HIV) infection, hepatitis B, or hepatitis C; positive testing for HIV, hepatitis B surface antigen (HBsAg), or hepatitis B surface antibody (HCVAb). Hepatitis B vaccination is allowed.
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.
Participant 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.

Trial locations and contacts

1 site in 1 country.

United States1 site

Pfizer Clinical Research Unit - New Haven
New Haven, Connecticut, 06511

Other trials in United States

About this study

Official title: A PHASE 1, OPEN-LABEL, RANDOMIZED, SINGLE-DOSE, CROSSOVER STUDY TO ESTIMATE THE RELATIVE BIOAVAILABILITY OF PF-07321332 FOLLOWING ORAL ADMINISTRATION OF 4 DIFFERENT FORMULATIONS RELATIVE TO THE COMMERCIAL TABLET FORMULATION IN HEALTHY ADULT PARTICIPANTS UNDER FASTED CONDITIONS

The purpose of this study is to estimate the relative bioavailability of PF-07321332 in different formulations in healthy adult participants.

Conditions: Bioavailability
Being tested: PF-07321332/ritonavir, PF-07321332
Keywords: coronavirus disease 2019 (COVID-19), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
Medical subject headings: COVID-19

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

PF-07321332/ritonavirDrug
PF-07321332 ritonavir will be administered as single dose orally
PF-07321332/ritonavirDrug
PF-07321332 ritonavir will be administered as single oral dose orally.
PF-07321332/ritonavirDrug
PF-07321332 ritonavir will be administered as single oral dose orally.
PF-07321332/ritonavirDrug
PF-07321332 ritonavir will be administered as single oral dose orally.
PF-07321332Drug
PF-07321332 will be administered as single oral dose orally.

Study groups in NCT05263895
Study group	Role	What they receive
Treatment A: PF-0732133/ritonavir	Active comparator	PF-07321332 ritonavir Receives: Drug: PF-07321332/ritonavir
Treatment B: PF-07321332/ritonavir	Experimental	PF-07321332 ritonavir Receives: Drug: PF-07321332/ritonavir
Treatment C: PF-07321332/ritonavir	Experimental	PF-07321332 ritonavir Receives: Drug: PF-07321332/ritonavir
Treatment D: PF-07321332/ritonavir	Experimental	PF-07321332 ritonavir Receives: Drug: PF-07321332/ritonavir
Treatment E: PF-07321332	Experimental	PF-07321332 Receives: Drug: PF-07321332

What is being measured

The primary outcome is the main question the study is designed to answer.

Area Under the Plasma Concentration-Time Profile From Time 0 to the Time of the Last Quantifiable Concentration (Clast) (AUClast) of Nirmatrelvir
AUClast for nirmatrelvir was calculated by Linear/Log trapezoidal method. Natural log-transformed AUClast for nirmatrelvir (slower dissolution tablets and large particle size tablets) was analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. Natural log-transformed AUClast for Nirmatrelvir (SDD suspension) was analyzed using a mixed effect model with sequence and treatment as fixed effects and participant within sequence as a random effect.
Measured: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24, 48 and 72 hours postdose
Area Under the Plasma Concentration-Time Profile From Time 0 Extrapolated to Infinite Time (AUCinf) of Nirmatrelvir
AUCinf for nirmatrelvir was calculated by AUClast + (Clast/kel), where Clast was the predicted plasma concentration at the last quantifiable time point from the log-linear regression analysis and kel is the terminal phase rate constant calculated by a linear regression of the log-linear concentration time curve. Natural log-transformed AUCinf for nirmatrelvir (slower dissolution tablets and large particle size tablets) was analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. Natural log-transformed AUCinf for Nirmatrelvir (SDD suspension) was analyzed using a mixed effect model with sequence and treatment as fixed effects and participant within sequence as a random effect.
Measured: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24, 48 and 72 hours postdose
Maximum Plasma Concentration (Cmax) of Nirmatrelvir
Cmax for nirmatrelvir was observed directly from data. Natural log-transformed Cmax for nirmatrelvir (slower dissolution tablets and large particle size tablets) was analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. Natural log-transformed Cmax for Nirmatrelvir (SDD suspension) was analyzed using a mixed effect model with sequence and treatment as fixed effects and participant within sequence as a random effect.
Measured: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24, 48 and 72 hours postdose

Secondary outcomes (5)

Number of Participants With Treatment-Emergent Adverse Events (TEAEs)
An adverse event (AE) was any untoward medical occurrence in a participant or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. AEs might arise from symptoms or other complaints reported to the investigator by the participant (or, when appropriate, by a caregiver, surrogate, or the participant's legally authorized representative), or they might arise from clinical findings of the investigator or other healthcare providers (clinical signs, test results, etc.). TEAEs were those with initial onset or increasing in severity after the first dose of study treatment.
Measured: Baseline up to 35 days after last dose of study intervention (up to 12 weeks)
Number of Participants With Laboratory Abnormalities (Without Regard to Baseline Abnormality)
The laboratory abnormality parameters included Chemistry: bicarbonate (milliequivalents per liter [mEq/L]) <0.9 x lower limit of normal (LLN), urobilinogen (ehrlich units per deciliter [EU/dL]) >=1, and fibrinogen (milligram/deciliter [mg/dL]) >1.25 x baseline; Urinalysis: URINE hemoglobin (Scalar) >=1, only those categories in which at least 1 participant had data were reported. All the safety laboratory samples were collected following at least a 4 hour fast. Clinical laboratory evaluations only included treatments of nirmatrelvir SDD suspension/ritonavir 300/100 mg and nirmatrelvir SDD suspension 300 mg. No participant was evaluable for clinical laboratory evaluations for the other treatments.
Measured: Screening (from Day-28 to Day-2), Day-1 of Period 1 (before 1st dose) and Day4 of Period 5 (4 days after the last dose on study discharge day). Each treatment period was 4 days long (Day1 to Day4) with a minimum of 4 days washout between each period
Number of Participants With Vital Signs Abnormalities
Single supine blood pressure (BP) and pulse rate (PR) were measured with the participant's arm supported at the level of the heart and recorded to the nearest mm Hg after approximately 5 minutes of rest. The same arm (preferably the dominant arm) was used throughout the study. Participants were instructed not to speak during measurements.
Measured: Screening (D28-D2), D1 of Period 1 (before 1st dose), D1 hr 0,2,and 6 of each period, and D4 of Period 5 (4 days after the last dose on study discharge day). Each treatment Period was 4 days long (D1-D4) with a minimum 4 days washout between each period
Number of Participants With ECG Abnormalities
Standard 12-lead ECGs utilizing limb leads (with a 10 second rhythm strip) were collected. All scheduled ECGs were performed after the participant had rested quietly for at least 5 minutes in a supine position.
Measured: Screening (from D-28 to D-2), D1, hr0 of Period 1 (before 1st dose) and D4 of Period 5 (4 days after last dose on study discharge day). Each treatment period was 4 days long (D1 to D4) with a minimum of 4 days washout between each period
Number of Participants With Physical Examination Abnormalities
A complete PE included, at a minimum, head, ears, eyes, nose, mouth, skin, heart and lung examinations, lymph nodes, and gastrointestinal, musculoskeletal, and neurological systems. A brief physical examination included, at a minimum, assessments of general appearance, the respiratory and cardiovascular systems, and participant reported symptoms.
Measured: Screening (from Day-28 to Day-2), Day-1 of Period 1 (before 1st dose. Each treatment period was 4 days long (Day1 to Day4) with a minimum of 4 days washout between each period

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

3 Mar 202216 May 2022

First posted3 Mar 2022
Study start3 Mar 2022
Primary completion16 May 2022
Study completion16 May 2022

Resources

Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
Publications (1)Papers the sponsor has linked to this study.
Other trials for BioavailabilityStudies 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: 12 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT05263895
Sponsor's protocol ID: C4671008
Other IDs: NCT05263895
Status last verified: May 2025
First submitted: 25 Feb 2022
Last updated: 11 Jun 2025
Results posted: Yes, on ClinicalTrials.gov
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.

Publications

Sagawa K, Lin J, Jaini R, Di L. Physiologically-Based Pharmacokinetic Modeling of PAXLOVID with First-Order Absorption Kinetics. Pharm Res. 2023 Aug;40(8):1927-1938. doi: 10.1007/s11095-023-03538-5. Epub 2023 May 25.
PubMed 37231296

Want to know more?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

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Study at a glance

From the registry record, last updated by the sponsor on 11 Jun 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 ESTIMATE THE RELATIVE BIOAVAILABILITY OF PF-07321332 FOLLOWING ORAL ADMINISTRATION OF 4 DIFFERENT FORMULATIONS RELATIVE TO THE COMMERCIAL TABLET FORMULATION IN HEALTHY ADULT PARTICIPANTS UNDER FASTED CONDITIONS
ClinicalTrials.gov ID: NCT05263895
Acronym / sponsor ID: C4671008
Conditions: Bioavailability
Keywords: coronavirus disease 2019 (COVID-19), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
Phase: Phase 1
Study type: Interventional
Recruitment status: Completed
Enrolment: 12 participants (actual)
Lead sponsor: PfizerIndustry (pharma, biotech, devices)
Study start: 3 Mar 2022 (actual)
Primary completion: 16 May 2022 (actual)
Study completion: 16 May 2022 (actual)
First posted: 3 Mar 2022 (actual)
Results: Posted 11 Jun 2025

Clinical summary

The research question as the sponsor registered it. This describes what the study plans to test, not what it found.

The purpose of this study is to estimate the relative bioavailability of PF-07321332 in different formulations in healthy adult participants.

Study design

Primary purpose: Basic science
Allocation: Randomised
Intervention model: Crossover
Masking: None (open label)
Number of arms: 5

Arm	Type	Receives
Treatment A: PF-0732133/ritonavir	Active comparator	Drug: PF-07321332/ritonavirPF-07321332 ritonavir
Treatment B: PF-07321332/ritonavir	Experimental	Drug: PF-07321332/ritonavirPF-07321332 ritonavir
Treatment C: PF-07321332/ritonavir	Experimental	Drug: PF-07321332/ritonavirPF-07321332 ritonavir
Treatment D: PF-07321332/ritonavir	Experimental	Drug: PF-07321332/ritonavirPF-07321332 ritonavir
Treatment E: PF-07321332	Experimental	Drug: PF-07321332PF-07321332

Who may qualify

Ages: 18 years and older
Sex: All
Healthy volunteers: Accepted
Age groups: Adult, Older adult

Key inclusion criteria (3 listed)

Participants who are overtly healthy as determined by medical evaluation including medical history, physical examination (PE), laboratory tests, vital signs and standard 12 lead ECGs.
Body mass index (BMI) of 17.5 to 30.5 kg/m2; and a total body weight >50 kg (110 lb).
Participants who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures

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).
Clinically relevant abnormalities requiring treatment (eg, acute myocardial infarction, unstable ischemic conditions, evidence of ventricular dysfunction, serious tachy or brady arrhythmias) or indicating serious underlying heart disease (eg, prolonged PR interval, cardiomyopathy, heart failure greater than New York Heart Association (NYHA) 1, underlying structural heart disease, Wolff Parkinson-White syndrome).
Any condition possibly affecting drug absorption (eg, gastrectomy, cholecystectomy).
History of human immunodeficiency virus (HIV) infection, hepatitis B, or hepatitis C; positive testing for HIV, hepatitis B surface antigen (HBsAg), or hepatitis B surface antibody (HCVAb). Hepatitis B vaccination is allowed.

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
PF-07321332/ritonavirPF-07321332 ritonavir will be administered as single dose orally	Drug	Treatment A: PF-0732133/ritonavir
PF-07321332/ritonavirPF-07321332 ritonavir will be administered as single oral dose orally.	Drug	Treatment B: PF-07321332/ritonavir
PF-07321332/ritonavirPF-07321332 ritonavir will be administered as single oral dose orally.	Drug	Treatment C: PF-07321332/ritonavir
PF-07321332/ritonavirPF-07321332 ritonavir will be administered as single oral dose orally.	Drug	Treatment D: PF-07321332/ritonavir
PF-07321332PF-07321332 will be administered as single oral dose orally.	Drug	Treatment E: PF-07321332

Primary outcome

Area Under the Plasma Concentration-Time Profile From Time 0 to the Time of the Last Quantifiable Concentration (Clast) (AUClast) of Nirmatrelvir
Time frame: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24, 48 and 72 hours postdose
AUClast for nirmatrelvir was calculated by Linear/Log trapezoidal method. Natural log-transformed AUClast for nirmatrelvir (slower dissolution tablets and large particle size tablets) was analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. Natural log-transformed AUClast for Nirmatrelvir (SDD suspension) was analyzed using a mixed effect model with sequence and treatment as fixed effects and participant within sequence as a random effect.
Area Under the Plasma Concentration-Time Profile From Time 0 Extrapolated to Infinite Time (AUCinf) of Nirmatrelvir
Time frame: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24, 48 and 72 hours postdose
AUCinf for nirmatrelvir was calculated by AUClast + (Clast/kel), where Clast was the predicted plasma concentration at the last quantifiable time point from the log-linear regression analysis and kel is the terminal phase rate constant calculated by a linear regression of the log-linear concentration time curve. Natural log-transformed AUCinf for nirmatrelvir (slower dissolution tablets and large particle size tablets) was analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. Natural log-transformed AUCinf for Nirmatrelvir (SDD suspension) was analyzed using a mixed effect model with sequence and treatment as fixed effects and participant within sequence as a random effect.
Maximum Plasma Concentration (Cmax) of Nirmatrelvir
Time frame: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24, 48 and 72 hours postdose
Cmax for nirmatrelvir was observed directly from data. Natural log-transformed Cmax for nirmatrelvir (slower dissolution tablets and large particle size tablets) was analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. Natural log-transformed Cmax for Nirmatrelvir (SDD suspension) was analyzed using a mixed effect model with sequence and treatment as fixed effects and participant within sequence as a random effect.

5 secondary outcomes

Number of Participants With Treatment-Emergent Adverse Events (TEAEs)
Time frame: Baseline up to 35 days after last dose of study intervention (up to 12 weeks)
Number of Participants With Laboratory Abnormalities (Without Regard to Baseline Abnormality)
Time frame: Screening (from Day-28 to Day-2), Day-1 of Period 1 (before 1st dose) and Day4 of Period 5 (4 days after the last dose on study discharge day). Each treatment period was 4 days long (Day1 to Day4) with a minimum of 4 days washout between each period
Number of Participants With Vital Signs Abnormalities
Time frame: Screening (D28-D2), D1 of Period 1 (before 1st dose), D1 hr 0,2,and 6 of each period, and D4 of Period 5 (4 days after the last dose on study discharge day). Each treatment Period was 4 days long (D1-D4) with a minimum 4 days washout between each period
Number of Participants With ECG Abnormalities
Time frame: Screening (from D-28 to D-2), D1, hr0 of Period 1 (before 1st dose) and D4 of Period 5 (4 days after last dose on study discharge day). Each treatment period was 4 days long (D1 to D4) with a minimum of 4 days washout between each period
Number of Participants With Physical Examination Abnormalities
Time frame: Screening (from Day-28 to Day-2), Day-1 of Period 1 (before 1st dose. Each treatment period was 4 days long (Day1 to Day4) with a minimum of 4 days washout between each period

Results and safety

Results posted to the registry on 11 Jun 2025, as reported by the sponsor. Figures are copied from the record, not re-analysed. Full results on ClinicalTrials.gov.

Participant flow

Group	Started	Completed
Sequence 1	2	2
Sequence 2	2	2
Sequence 3	2	2
Sequence 4	2	2
Sequence 5	2	2
Sequence 6	2	2

Primary outcome: Area Under the Plasma Concentration-Time Profile From Time 0 to the Time of the Last Quantifiable Concentration (Clast) (AUClast) of Nirmatrelvir

Time frame: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24, 48 and 72 hours postdose. Geometric mean (Geometric Coefficient of Variation). Unit: nanogram*hour per milliliter (ng*hr/mL)

Measure	Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (Slower Dissolution Tablets)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (Large Particle Size Tablets)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (SDD Suspension)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (SDD Suspension) 300 mg n = 12
Value	35020 (15)	31700 (26)	35990 (26)	48380 (15)	10530 (50)

Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg vs Nirmatrelvir (Slower Dissolution Tablets)/Ritonavir 300/100 mg: Ratio of Adjusted Geometric means: 90.54 (90% CI 79.85 to 102.65)
Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg vs Nirmatrelvir (Large Particle Size Tablets)/Ritonavir 300/100 mg: Ratio of Adjusted Geometric Means: 102.78 (90% CI 90.65 to 116.53)
Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg vs Nirmatrelvir (SDD Suspension)/Ritonavir 300/100 mg: Ratio of Adjusted Geometric Means: 138.15 (90% CI 118.03 to 161.69)

Population analysed: All participants who took at least 1 dose of study intervention and in whom at least 1 of the PK parameters of primary interest were reported.

Primary outcome: Area Under the Plasma Concentration-Time Profile From Time 0 Extrapolated to Infinite Time (AUCinf) of Nirmatrelvir

Time frame: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24, 48 and 72 hours postdose. Geometric mean (Geometric Coefficient of Variation). Unit: ng*hr/mL

Measure	Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (Slower Dissolution Tablets)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (Large Particle Size Tablets)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (SDD Suspension)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (SDD Suspension) 300 mg n = 12
Value	35540 (14)	32430 (26)	36420 (25)	48680 (15)	10580 (50)

Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg vs Nirmatrelvir (Slower Dissolution Tablets)/Ritonavir 300/100 mg: Ratio of Adjusted Geometric Means: 91.26 (90% CI 80.46 to 103.51)
Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg vs Nirmatrelvir (Large Particle Size Tablets)/Ritonavir 300/100 mg: Ratio of Adjusted Geometric Means: 102.49 (90% CI 90.36 to 116.26)
Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg vs Nirmatrelvir (SDD Suspension)/Ritonavir 300/100 mg: Ratio of Adjusted Geometric Means: 136.99 (90% CI 117.09 to 160.27)

Population analysed: All participants who took at least 1 dose of study intervention and in whom at least 1 of the PK parameters of primary interest were reported.

Primary outcome: Maximum Plasma Concentration (Cmax) of Nirmatrelvir

Time frame: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24, 48 and 72 hours postdose. Geometric mean (Geometric Coefficient of Variation). Unit: ng/mL

Measure	Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (Slower Dissolution Tablets)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (Large Particle Size Tablets)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (SDD Suspension)/Ritonavir 300/100 mg n = 12	Nirmatrelvir (SDD Suspension) 300 mg n = 12
Value	3347 (16)	3155 (23)	3635 (27)	8840 (14)	4871 (30)

Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg vs Nirmatrelvir (Slower Dissolution Tablets)/Ritonavir 300/100 mg: Ratio of Adjusted Geometric Means: 94.28 (90% CI 80.77 to 110.05)
Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg vs Nirmatrelvir (Large Particle Size Tablets)/Ritonavir 300/100 mg: Ratio of Adjusted Geometric Means: 108.60 (90% CI 93.04 to 126.76)
Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg vs Nirmatrelvir (SDD Suspension)/Ritonavir 300/100 mg: Ratio of Adjusted Geometric Means: 264.12 (90% CI 232.32 to 300.27)

Population analysed: All participants who took at least 1 dose of study intervention and in whom at least 1 of the PK parameters of primary interest were reported.

5 secondary outcomes are reported in the full results.

Adverse events

Time frame: Baseline up to 35 days after last dose of study intervention (up to 12 weeks). Other adverse events reported at 5% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
Nirmatrelvir (Commercial Tablets)/Ritonavir 300/100 mg	0 of 12 (0%)	4 of 12 (33.3%)	0 of 12
Nirmatrelvir (Slower Dissolution Tablets)/Ritonavir 300/100 mg	0 of 12 (0%)	1 of 12 (8.3%)	0 of 12
Nirmatrelvir (Large Particle Size Tablets)/Ritonavir 300/100 mg	0 of 12 (0%)	3 of 12 (25%)	0 of 12
Nirmatrelvir (SDD Suspension)/Ritonavir 300/100 mg	0 of 12 (0%)	0 of 12 (0%)	0 of 12
Nirmatrelvir (SDD Suspension) 300 mg	0 of 12 (0%)	1 of 12 (8.3%)	0 of 12

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 11 Jun 2025.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Derived from this study: PubMed 37231296Sagawa K, Lin J, Jaini R, Di L. Physiologically-Based Pharmacokinetic Modeling of PAXLOVID with First-Order Absorption Kinetics. Pharm Res. 2023 Aug;40(8):1927-1938. doi: 10.1007/s11095-023-03538-5. Epub 2023 May 25.
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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Tacrolimus C:D Ratio Measured in Renal Transplant Recipients Treated With Once-daily Prolonged-release Drugs
Immunosuppression

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

1 site in 1 country: see every site and its status.

Questions about this trial

What is this clinical trial studying?

A Phase 1 study testing PF-07321332/ritonavir and PF-07321332 in people with Bioavailability, run by Pfizer at 1 site in United States.

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 3 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: finished, as of the sponsor's last update on 11 Jun 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

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?

Yes. Results are posted in the registry (first posted 11 Jun 2025). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.

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 the Plasma Concentration-Time Profile From Time 0 to the Time of the Last Quantifiable Concentration (Clast) (AUClast) of Nirmatrelvir (time frame: 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 16, 24, 48 and 72 hours postdose). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT05263895, which also lists 1 linked publication.

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 11 Jun 2025.