Study to Evaluate the Effect of GSK3640254 on the Pharmacokinetics of Tenofovir Alafenamide/Emtricitabine

Inclusion Criteria

• Subject must be 18 to 55 years of age inclusive, at the time of signing the informed consent.
• Subjects who are healthy as determined by the investigator or medically qualified designee based on a medical evaluation including medical history, physical examination, laboratory tests, and cardiac monitoring (history and ECG).
• Body weight >=50.0 kilograms (kg) (110 pound [lbs]) for men and >=45.0 kilograms [kg] (99 lbs) for women and body mass index (BMI) within the range 18.5 to 31.0 kilograms per meter square (kg/m^2) (inclusive).
• Male or female; A female subject is eligible to participate if she is not pregnant, not breastfeeding and not a woman of childbearing potential (WOCBP).
• Capable of giving signed informed consent which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and protocol.

Exclusion Criteria

• Current or chronic history of liver disease, or known hepatic or biliary abnormalities (with the exception of Gilbert's syndrome or asymptomatic gallstones).
• A pre-existing condition interfering with normal gastrointestinal (GI) anatomy or motility (e.g.,gastroesophageal reflux disease, gastric ulcers, gastritis), hepatic and/or renal function, that could interfere with the absorption, metabolism and/or excretion of the study drugs or render the subject unable to take oral study intervention.
• Any history of significant underlying psychiatric disorder including, but not limited to, schizophrenia, bipolar disorder with or without psychotic symptoms, other psychotic disorders, or schizotypal (personality) disorder.
• Any history of major depressive disorder with or without suicidal features or anxiety disorders, that required medical intervention (pharmacologic or not) such as hospitalization or other inpatient treatment and/or chronic (>6 months) outpatient treatment. Subjects with other conditions such as adjustment disorder or dysthymia that have required shorter term medical therapy ( 1.5 × upper limit of normal (ULN). A single repeat of ALT is allowed within a single screening period to determine eligibility.
• Bilirubin >1.5 × ULN (isolated bilirubin >1.5 × ULN is acceptable if bilirubin is fractionated and direct bilirubin 100 beats per minute (bpm) and for females: 100 bpm; PR interval: 200 milliseconds (msec); QRS duration: 110 msec and QTcF interval for male: >450 msec and for female: >470 msec. A heart rate from 100 to 110 bpm can be rechecked by ECG or vital signs within 30 minutes to verify eligibility.
• History of regular alcohol consumption within 6 months of the study defined as: an average weekly intake of >14 units. One unit is equivalent to 8 grams of alcohol: a half-pint (equivalent to 240 mL) of beer, 1 glass (125 mL) of wine, or 1 (25 mL) measure of spirits.
• Regular use of tobacco- or nicotine-containing products within 3 months prior to Screening.
• History of sensitivity to any of the study medications or components thereof or a history of drug or other allergy that, in the opinion of the investigator or medical monitor, contraindicates their participation.