This is a two-part study. Part 1 will evaluate relative bioavailability of temsavir (TMR) following single dose administration of the reference fostemsavir (FTR) compared to two low-dose ER tablet formulations of FTR. In Part 2, the effect of food on the bioavailability of TMR will be assessed on the selected low-dose ER tablet formulation from Part 1.

Inclusion Criteria:

• 18 to 50 years of age inclusive.
• Healthy as determined by the investigator or medically qualified designee.
• A participant with a clinical abnormality or laboratory parameter(s) which is/are not specifically listed in the inclusion or exclusion criteria, outside the reference range for the population being studied may be included only if the investigator, in consultation with the Medical Monitor, agree and document that the finding is unlikely to introduce additional risk factors and will not interfere with the study procedures.
• Body weight >= 50 kilograms (kg) (110 pounds [lbs.]) for men and >= 45 kg (99 lbs.) for women and body mass index (BMI) within the range 18.5-31.0 kilogram per meter square (kg/m^2) (inclusive).
• Male participants are eligible to participate if they agree to use contraceptive methods.
• A female participant is eligible to participate if she is not pregnant or breastfeeding and one of the following conditions applies: Is a woman of non-childbearing potential (WONCBP). OR Is a woman of childbearing potential (WOCBP) and using a contraceptive method that is highly effective.
• Capable of giving signed informed consent.

Exclusion Criteria:

• History or presence of/significant history of or current cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, hematological, or neurological disorders capable of significantly altering the absorption, metabolism, or elimination of drugs; constituting a risk when taking the study intervention or interfering with the interpretation of data.
• Alanine transaminase (ALT) >1.5x upper limit of normal (ULN).
• Total bilirubin >1.5xULN (isolated bilirubin >1.5xULN is acceptable if total bilirubin is fractionated and direct bilirubin <35%).
• Current or chronic history of liver disease or known hepatic or biliary abnormalities (with the exception of Gilbert's syndrome or asymptomatic gallstones).
• QT interval corrected for heart rate according to Fridericia's formula (QTcF) >450 millisecond (msec) for males and QTcF>470 msec for females.
• Unable to refrain from the use of prescription or non-prescription drugs, including vitamins, herbal and dietary supplements (including St John's Wort) within 7 days (or 14 days if the drug is a potential enzyme inducer) or 5 half-lives (whichever is longer) prior to the first dose of study medication, unless in the opinion of the Investigator and ViiV/GlaxoSmithKline (GSK) Medical Monitor the medication will not interfere with the study procedures or compromise participant safety.
• Participation in the study would result in loss of blood or blood products in excess of 500 milliliters (mL) within 56 days.
• Exposure to more than 4 new chemical entities within 12 months prior to the first dosing day.
• Current enrollment or past participation within the last 30 days or five half-lives whichever is longer, before signing of consent in any other clinical study involving an investigational study intervention or any other type of medical research.
• Presence of hepatitis B surface antigen (HBsAg) [or hepatitis B core antibody (HBcAb)] at screening or within 3 months prior to first dose of study intervention.
• Positive hepatitis C antibody test result at screening or within 3 months prior to first dose of study intervention.
• Positive hepatitis C Ribonucleic acid (RNA) test result at screening or within 3 months prior to first dose of study intervention.
• Positive Human immunodeficiency virus (HIV)-1 and -2 antigen/antibody immunoassay.
• Cotinine levels indicative of smoking or history or regular use of tobacco- or nicotine-containing products within 6 months prior to screening.
• Regular alcohol consumption within 6 months of the study defined as: An average weekly intake of >14 drinks for males or >7 drinks for females.
• Regular use of known drugs of abuse.
• Sensitivity to heparin or heparin-induced thrombocytopenia.
• Sensitivity to any of the study interventions, or components thereof, or drug or other allergy that, in the opinion of the investigator or medical monitor, contraindicates participation in the study.
• A participant with a history of beta-lactam allergy, regardless of severity/seriousness.
• A participant with known or suspected active Coronavirus disease-2019 (COVID-19) infection OR contact with an individual with known COVID-19, within 14 days of study enrollment.

IPD for this study will be made available via the Clinical Study Data Request site.

IPD will be made available within 6 months of publishing the results of the primary endpoints, key secondary endpoints and safety data of the study.

Access is provided after a research proposal is submitted and has received approval from the Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months but an extension can be granted, when justified, for up to another 12 months.

This is an open-label study