Drug-Drug Interaction Study to Estimate the Effect of PF-07321332/Ritonavir and Ritonavir on Midazolam in Healthy Participants

Cmax for midazolam following single dose administration with and without PF-07321332/ritonavir was observed directly from data. Natural log-transformed Cmax for Midazolam were analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. The ratios (PF-07321332/ritonavir + midazolam [test]/midazolam [reference] and 90% CIs) were expressed as percentages.

AUCinf for midazolam following single dose administration with and without PF-07321332/ritonavir was calculated by AUClast + (Clast/kel), where Clast was the predicted plasma concentration at the last quantifiable time point estimated from the log-linear regression analysis. Natural log-transformed AUCinf for Midazolam were analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. The ratios (PF-07321332/ritonavir + midazolam [test]/midazolam [reference] and 90% CIs) were expressed as percentages.

AUClast for midazolam following single dose administration with and without PF-07321332/ritonavir was calculated by Linear/Log trapezoidal method. Natural log-transformed AUClast for Midazolam were analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. The ratios (PF-07321332/ritonavir + midazolam [test]/midazolam [reference] and 90% CIs) were expressed as percentages.

An adverse event was considered a TEAE if the event started during the effective duration of treatment. All events that start on or after the first dosing day and time/ start time, if collected, but before the last dose plus the lag time (28 days) were flagged as TEAEs. The algorithm did consider any events that started prior to the first dose date. Any events occurring following start of treatment or increasing in severity were counted as treatment emergent. Events that occur in a non-treatment period (for example, Washout or Follow-up) were counted as treatment emergent and attributed to the previous treatment taken.

The haematological, clinical chemistry (serum) and urinalysis safety tests were assessed against the criteria specified in the sponsor reporting standards to determine if there were any clinically significant laboratory abnormalities. The assessment took into account whether each participant's baseline test result was within or outside the laboratory reference range for the particular laboratory parameter. Baseline was defined as the last planned predose measurement taken in each study period.

Baseline was the last predose recording in each study period. Only post baseline values are included in this analysis

Baseline and changes from baseline in PR, QT, QRS, heart rate and QTcF were summarized by treatment and time postdose. Baseline was defined as the average of the triplicate predose recordings in each study period. ECG endpoints and changes from baseline (QTcF, PR, QRS), over all measurements taken postdose, were also summarized descriptively by treatment using categories as defined in the Criteria for Safety Values of Potential Clinical Concern appendix of the protocol and for QTc values corresponding to ICH E14 thresholds, which are: QTcF (msec): 450<value≤480; 480<value≤500; >500; QTcF (msec) increase from baseline: 30<change≤60; change>60

Cmax for midazolam following single dose administration with and without ritonavir was observed directly form data. Natural log-transformed Cmax for Midazolam were analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. The ratios (ritonavir + midazolam [test]/midazolam [reference] and 90% CIs) were expressed as percentages.

AUCinf for midazolam following single dose administration with and without ritonavir was calculated by AUClast + (Clast/kel), where Clast was the predicted plasma concentration at the last quantifiable time point estimated from the log-linear regression analysis. Natural log-transformed AUCinf for Midazolam were analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. The ratios (ritonavir + midazolam [test]/midazolam [reference] and 90% CIs) were expressed as percentages.

AUClast for midazolam following single dose administration with and without ritonavir was calculated by Linear/Log trapezoidal method. Natural log-transformed AUClast for Midazolam were analyzed using a mixed effect model with sequence, period and treatment as fixed effects and participant within sequence as a random effect. The ratios (ritonavir + midazolam [test]/midazolam [reference] and 90% CIs) were expressed as percentages.

CL/F for midazolam following single dose administration with and without PF-07321332/ritonavir or ritonavir was calculated by Dose/AUCinf.

Vz/F for midazolam following single dose administration with and without PF-07321332/ritonavir or ritonavir was calculated by Dose/(AUCinf • kel).

Tmax for midazolam following single dose administration with and without PF-07321332/ritonavir or ritonavir was calculated by observed directly from data as time of first occurrence.

t½ for midazolam following single dose administration with and without PF-07321332/ritonavir or ritonavir was calculated by Loge(2)/kel, where kel was the terminal phase rate constant calculated by a linear regression of the log-linear concentration-time curve. Only those data points judged to describe the terminal log-linear.