A Study to Compare the Effect on Heart Rhythm of 3 Days of GSK189075, Placebo, or Moxifloxacin in Healthy Adults

Inclusion Criteria: * Healthy males or non-pregnant, non-lactating females between 18 and 50 years of age (inclusive), at the time of signing the informed consent form. * Body mass index (BMI) in the range of 19 to 32 (inclusive) * Healthy as determined by a qualified physician on the basis of a satisfactory medical evaluation. * Negative serum pregnancy test for all female subjects. * Subject has given informed consent to participate in the study as indicated by providing a signed and dated written informed consent form prior to any study procedures. * The subject is able to understand and comply with protocol requirements, instructions and protocol-stated restrictions. Exclusion Criteria: * Cardiac conduction and repolarization abnormalities described in the protocol. * Any history of myocardial infarction, syncope, or cardiac arrhythmias or a history of uncontrolled hypertension or unstable heart disease. * Subjects with a systolic blood pressure outside the range of 90 to 150mmHg or diastolic blood pressure outside the range of 50 to 100mmHg, or a greater than30mmHg change in systolic blood pressure or greater than 20mmHg change in diastolic blood pressure upon orthostatic vital signs. * Subjects with a personal or family history of QTc prolongation or unexplained cardiac arrest. * Liver function studies (ALT, AST, Total bilirubin, and alkaline phosphatase above 2 X the upper limit of the normal reference range at Screening and Day -2. * Has a history of illicit drug use or alcohol abuse within the past year or a positive test for alcohol, cotinine, or drugs of abuse at Screening or prior to the start of dosing in Period 1. * A history of regular alcohol consumption averaging \>7 drinks/week for females or \>14 drinks/week for males within 6 months of Screening. * Use of tobacco or nicotine-containing products within 6 months prior to Screening and during the course of the study is prohibited. * A positive test at Screening for Hepatitis B, Hepatitis C, or Human Immunodeficiency Virus (HIV). If documented negative test results have been obtained within the last 2 months, it will not be necessary to repeat these tests. * Any abnormalities of K+, Ca++ and Mg++ * TSH levels outside the normal range. * Use of any prescription or non-prescription drugs, vitamins herbal and dietary supplements within fourteen days or 5 half-lives (whichever is longer) prior to the first dose of study drug. Drugs known to inhibit or induce CYP3A4 enzymes are restricted. * Females of child-bearing potential who are unwilling or unable to use appropriate contraception as defined in the protocol. * Pregnant or nursing females. * Females who are using any oral contraception, implants of levonorgestrel, or injectable progesterone. * Subjects whose participation in the study would result in donation of blood in excess of 500mL within a 56 day period. * History of hypersensitivity to GSK189075, moxifloxacin, or drugs of these classes, or history of drug or other allergy that, in the opinion of the physician responsible, contraindicates their participation. * The subject has received an investigational drug or participated in any other research trial within 30 days or 5 half-lives, or twice the duration of the biological effect of any drug (whichever is longer) prior to the first dose of current study drug.