AUCinf = Area under the plasma concentration versus time curve (AUC) from time zero (pre-dose) to extrapolated infinite time (0-inf). It is obtained from AUC (0-t) plus AUC (t-inf).

Area under the plasma concentration time-curve from zero to the last measured concentration (AUClast)

AUClast was calculated using linear/log trapezoidal method. Treatment A = sisunatovir 200 mg PIC under fasted condition; reference treatment. Treatment B = sisunatovir 200 mg WGT under fasted condition; test treatment.

AUCinf was calculated as AUClast + (Clast\*/kel), where Clast is 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 loglinear concentration-time curve. Treatment A = sisunatovir 200 mg PIC under fasted condition; reference treatment. Treatment B = sisunatovir 200 mg WGT under fasted condition; test treatment.

Treatment A = sisunatovir 200 mg PIC under fasted condition; reference treatment. Treatment B = sisunatovir 200 mg WGT under fasted condition; test treatment.

The relationship between sisunatovir plasma concentration and change from baseline in Fridericia's heart-rate corrected QT interval were analyzed using a model-based concentration-QTc analysis consistent with the Scientific White Paper on Concentration-QT Modeling. Baseline was defined as the mean of the 3 averages of the triplicate electrocardiogram (ECG) measurements taken before dosing on Day 1 within each period. Mean and CI statistics were based on the individual (within subject) corrected differences between sisunatovir and placebo exposures.