Relative Bioavailability Study of Nirmatrelvir/Ritonavir Oral Powder Relative to the Commercial Tablets and Estimation of the Effect of Food on Bioavailability of the Nirmatrelvir/Ritonavir Oral Powder in Healthy Participants.

AUCinf was defined as area under the concentration-time curve from time 0 extrapolated to infinity. AUCinf for nirmatrelvir (under fasted/fed conditions) 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; AUClast was defined as area under the plasma concentration-time profile from time 0 to the time of the last quantifiable concentration.

AUClast was defined as area under the plasma concentration-time profile from time 0 to the time of the last quantifiable concentration. AUClast for nirmatrelvir (under fasted/fed conditions) was calculated by linear/log trapezoidal method.

Cmax was defined maximum observed concentration. Cmax for nirmatrelvir (under fasted/fed conditions) was observed directly from data.

AUCinf was defined as area under the concentration-time curve from time 0 extrapolated to infinity. AUCinf for ritonavir (under fasted/fed conditions) 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; AUClast was defined as area under the plasma concentration-time profile from time 0 to the time of the last quantifiable concentration.

AUClast was defined as area under the plasma concentration-time profile from time 0 to the time of the last quantifiable concentration. AUClast for ritonavir (under fasted/fed conditions) was calculated by linear/log trapezoidal method.

Cmax was defined maximum observed concentration. Cmax for ritonavir (under fasted/fed conditions) was observed directly from data.

An adverse event (AE) was any untoward medical occurrence in a participant who received study intervention without regard to possibility of causal relationship. Treatment-emergent are events between first dose of study intervention and up to 28 days after last dose that were absent before treatment or that worsened relative to pretreatment state. A serious AE (SAE) was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly; suspected transmission via a Pfizer product of an infectious agent, pathogenic or non-pathogenic. TEAEs included SAEs and all non-SAEs that occurred during the study.

The following laboratory test abnormalities (without regard to baseline abnormality) were reported during the study: monocytes/leukocytes (percentage [%]) is larger than (>) 1.2x upper limit of normal (ULN), specific gravity (scalar) >1.030, and urine hemoglobin was larger or equal to (>=) 1.

Supine blood pressure and pulse rate were measured with the participant's arm supported at the level of the heart and recorded after approximately 5 minutes of rest. Vital signs were done predose, 2 hours and 6 hours post dose on Day 1 of each treatment period and also on Day 4 of Period 5. Clinical significance of vital signs was determined at the investigator's discretion.

A single 12-lead ECG was obtained using an ECG machine that automatically calculates the heart rate and measures PR, QT, and QTc intervals and QRS complex. All scheduled ECGs were performed after the participant has rested quietly for at least 5 minutes in a supine position. Clinical significance of ECG values was determined at the investigator's discretion.

A complete physical examination 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.

Completed PE were performed by trained medical personnel at the investigator site at Screening or Period 1 Day 1 only. A brief PE might be performed at other designated time points at the discretion of the investigator. Clinical significance of physical examination values was determined at the investigator's discretion.

The sensory attributes of nirmatrelvir/ritonavir oral powder were evaluated by the participant using a Palatability Questionnaire. Each participant complete the palatability survey immediately following dosing (within 1 min) and at 5, 10, and 20 minutes post oral administration of nirmatrelvir/ritonavir oral powder. For the taste assessment of the study, the data used in the analysis were transcribed and rescaled to a score from 0 (good) to 100 (bad) from the raw measurements on the questionnaire.

The sensory attributes of nirmatrelvir/ritonavir oral powder were evaluated by the participant using a Palatability Questionnaire. Each participant complete the palatability survey immediately following dosing (within 1 min) and at 5, 10, and 20 minutes post oral administration of nirmatrelvir/ritonavir oral powder. For the taste assessment of the study, the data used in the analysis were transcribed and rescaled to a score from 0 (good) to 100 (bad) from the raw measurements on the questionnaire.

The sensory attributes of nirmatrelvir/ritonavir oral powder were evaluated by the participant using a Palatability Questionnaire. Each participant complete the palatability survey immediately following dosing (within 1 min) and at 5, 10, and 20 minutes post oral administration of nirmatrelvir/ritonavir oral powder. For the taste assessment of the study, the data used in the analysis were transcribed and rescaled to a score from 0 (good) to 100 (bad) from the raw measurements on the questionnaire.

The sensory attributes of nirmatrelvir/ritonavir oral powder were evaluated by the participant using a Palatability Questionnaire. Each participant complete the palatability survey immediately following dosing (within 1 min) and at 5, 10, and 20 minutes post oral administration of nirmatrelvir/ritonavir oral powder. For the taste assessment of the study, the data used in the analysis were transcribed and rescaled to a score from 0 (good) to 100 (bad) from the raw measurements on the questionnaire.

The sensory attributes of nirmatrelvir/ritonavir oral powder were evaluated by the participant using a Palatability Questionnaire. Each participant complete the palatability survey immediately following dosing (within 1 min) and at 5, 10, and 20 minutes post oral administration of nirmatrelvir/ritonavir oral powder. For the taste assessment of the study, the data used in the analysis were transcribed and rescaled to a score from 0 (good) to 100 (bad) from the raw measurements on the questionnaire.