The combination of the diuretics amiloride hydrochloride (HCl) and hydrochlorothiazide (HCTZ) (GSK3542503) is indicated for the treatment of hypertension, congestive heart failure and hepatic cirrhosis with ascites and edema. This first time in human (FTIH) study is aimed to determine whether the test product GSK3542503 is bioequivalent to the reference (ref) hydrochlorothiazide 50 milligram (mg)/amiloride hydrochlorothiazide 5 mg in healthy adult participants under fasting conditions based on pharmacokinetic (PK) endpoints. This is a phase I, open label, balanced, randomized, single dose, two-way crossover study, enroling approximately 42 healthy participants at a single center. Study participants will be randomized to one of two treatment sequences (A-B or B-A) in accordance with the randomization schedule. A single dose of one of the two treatments A (Test: GSK3542503, a hydrochlorothiazide 50 mg and amiloride hydrochloride 5 mg fixed dose combination) or B (Reference: Moduretic, a hydrochlorothiazide 50 mg and amiloride hydrochloride 5 mg fixed dose combination), will be administered on Day 1, in each treatment period. Each participant will participate in both treatment periods and receive a single dose of each treatment. The treatment periods will be separated by a washout period of at least 7 days and no more than 14 days. The total duration in the study for each participant is expected to be 5 to 7 weeks, from screening to his or her last visit. A maximum of 42 participants will be randomized such that at least 32 evaluable participants complete the study.

Inclusion Criteria:

• Participants must be between18 and 65 years of age inclusive, at the time of signing the informed consent.

• Healthy, non-smoker, as determined by the investigator or medically qualified designee based on a medical evaluation including medical history, physical examination, laboratory tests, and cardiac monitoring.

• A participant with a clinical abnormality or laboratory parameter(s) which is/are not specifically listed in the inclusion or exclusion criteria, outside the normal reference range for the population being studied may be included only if the investigator in consultation with the medical monitor if required, agree and document that the finding is unlikely to introduce additional risk factors and will not interfere with the study procedures.

• Body weight >=50 kilogram (kg) and body mass index (BMI) within the range 19-30 kg/meter^2(inclusive).

• Healthy male or female participants

  • Male participants must agree to use contraception for 3 days after each dose of study treatment and refrain from donating sperm during that period.
  • A female participant is eligible to participate if she is not pregnant, not breastfeeding, and at least one of the following conditions applies: not a woman of childbearing potential (WOCBP), or a WOCBP who agrees to follow the contraceptive guidance during the treatment period and for at least 30 days after the last dose of study treatment.

The investigator is responsible for ensuring that male and female study participants understand how to correctly use the methods of contraception.

- Capable of giving signed informed consent, which includes compliance with the requirements and restrictions.

Exclusion Criteria:

• History or presence of 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 treatment; or interfering with the interpretation of data.
• Abnormal renal function measured by creatinine clearance.
• Presence of hyperkalemia where the serum potassium is greater than upper limit of normal (ULN).
• History or known acute angle closure glaucoma or ocular complaints, which could increase the risk of ophthalmic reactions as deemed by the investigator.
• Abnormal BP as determined by the investigator.
• Alanine transaminase (ALT) >1.5 times ULN.
• Bilirubin >1.5 times ULN (isolated bilirubin >1.5 times ULN is acceptable if bilirubin is fractionated and direct bilirubin <35 percentage).
• 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 Bazett's formula (QTcB) >450 milliseconds (msec). For purposes of data analysis, only QTcB, will be used.
• Past or intended use of over-the-counter or prescription medication including herbal medications, within 14 days prior to dosing. Specific medications listed in protocol of this study may be allowed.
• Where participation in the study would result in loss of blood or blood products in excess of 500 milliliter (mL) within 90 days.
• Exposure to more than 4 new chemical entities within 12 months prior to the first dosing day.
• Current enrolment or past participation within the last 90 days before signing of consent in this or any other clinical study involving an investigational study treatment.
• Presence of hepatitis B surface antigen (HBsAg) at screening, or a positive hepatitis C antibody test result at screening. Participants with positive hepatitis C antibody due to prior resolved disease can be enrolled, only if a confirmatory negative hepatitis C ribonucleic acid (RNA) test is obtained.
• Positive pre-study drug/alcohol screen.
• Positive human immunodeficiency virus (HIV) antibody test.
• Regular use of known drugs of abuse.
• Sensitivity to heparin or heparin-induced thrombocytopenia.
• Sensitivity to any of the study treatments, or components thereof, or drug or other allergy including allergy to penicillin and sulfonamides that, in the opinion of the investigator or medical monitor, contraindicates participation in the study.
• Regular alcohol consumption within 6 months prior to the study defined as an average weekly intake of >21 units for males or > 14 units for females. One unit is equivalent to 8 gram of alcohol: a half-pint (approximately 240 mL) of beer, 1 glass (125 mL) of wine or 1 (25 mL) measure of spirits.
• Urinary cotinine levels indicative of smoking or history of regular use of tobacco- or nicotine-containing products within 6 months prior to screening.
• Participants with any risk as defined in protocol of this study should be excluded from participation in this study.

IPD for this study is available via the Clinical Study Data Request site.

IPD is available via the Clinical Study Data Request site (copy the URL below to your browser)

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.