Plasma samples were assayed for APV concentrations using a validated assay. The GlaxoSmithKline (GSK) Department of Clinical Pharmacology Modeling and Simulation conducted pharmacokinetic (PK) analysis of the plasma APV concentration-time data using a model-independent approach. As a measure of total drug exposure, the area under the plasma-concentration-versus-time curve over the dosing interval at steady-state (AUC\[0-τ\]), where "τ" is the length of the dosing interval, was calculated by the linear up/log down trapezoidal method. hours, hr.

The maximum concentration at steady state (Cmax) was measured.

The plasma concentration at the end of the dosing interval at steady state (Cτ) was measured.

Apparent clearance of drug from plasma following extravascular administration (CL/F) was calculated using the formulation: APV Dose in mg/kg units divided by AUC(0-τ). For FPV, doses were expressed in APV molar equivalents (50 mg of FPV = 43.2 mg of APV). Normalizing CL/F for bodyweight allows for comparison of CL/F across populations.

Apparent clearance of drug from plasma following extravascular administration (CL/F) was calculated as dose/AUC(0-τ). For FPV, doses were expressed in APV molar equivalents (50 mg of FPV = 43.2 mg of APV).

Participants who are \<2 years old may have reduced protein binding; therefore, plasma unbound APV concentrations were measured to determine dosing recommendations at acceptable dosing volumes. Unbound or "free" APV is the fraction of drug that is not bound to protein. Cτ is the plasma concentration at the end of the dosing interval at steady state.

Participants who are \<2 years old may have reduced protein binding; therefore, plasma unbound APV concentrations were measured to determine dosing recommendations at acceptable dosing volumes. APV %Cτ unbound is the percentage of the total APV Cτ that is unbound.

Blood samples of the participants were collected for the evaluation of ALT and AST. Clinical chemistry analyses were carried out using the observed analysis strategy.

Blood samples of all participants were generally collected under non-fasting conditions (given the age of participants) for the evaluation of cholesterol, serum glucose, HDL cholesterol, LDL cholesterol and triglyceride (TG). Clinical chemistry analyses were carried out using the observed analysis strategy.

Blood samples of all participants were collected for the evaluation of serum lipase. Clinical chemistry analyses were carried out using the observed analysis strategy. Change from Baseline in serum lipase was calculated as the value at the indicated time point minus the value at Baseline.

TE toxicities were presented for each laboratory parameter. A toxicity was considered TE if it was greater than the Baseline grade, and if it was observed on/after the date of the first dose of study drug (SD), and on/before the date of the last dose of SD. Per the Division of AIDS Table for Grading the Severity of Adult and Pediatric AEs, Grade 3=severe; Grade 4=potentially life-threatening.

An AE is any untoward medical occurrence in a patient or clinical investigation subject, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. An AE is considered TE if it has an onset date on or after the date of the first dose of study drug, and on or before the date of the final dose of study drug. As per the Division of AIDS Table for Grading the Severity of Adult and Pediatric AEs, Grade 3=severe; Grade 4=potentially life-threatening.

An AE is any untoward medical occurrence in a patient or clinical investigation subject, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product.