The purpose of this study is to compare the effects of single and repeat doses of GSK256073 with placebo in HVT subjects.

Inclusion criteria:

• Healthy Adult males or females between 18 and 55 years of age, inclusive.
• Female subjects must be of non-childbearing potential
• Body weight > 50 kg (110 pounds) and body mass index (BMI) 19 and 31 where:
• Subjects with QTc < 450 msec at screening (or QTc < 480 msec for subjects with Bundle Branch Block).
• A signed and dated written informed consent prior to admission to the study.
• The subject is able to understand and comply with protocol requirements, instructions and protocol-stated restriction

Exclusion criteria:

• Systolic blood pressure < 100 mmHg or 150 mmHg and/or diastolic blood pressure = 100 mmHg at screening.
• History of significant cardiac arrhythmias
• Active peptic ulcer disease (PUD) and/or history of PUD within 1 year.
• A serum uric acid concentration 8mg/dL
• Screening test positive for H. Pylori using the non-radioactive breath test
• History of gout and/or hyperuricemia
• History of Gilbert's syndrome
• A serum creatinine concentration above the normal reference range
• History of kidney stones
• PT and/or aPTT above the reference range
• History of recurrent indigestion, stomach upset or diarrhea
• Liver function tests (LFTs) or creatinine phosphokinase (CPK) 1.5X ULN
• Screening stool test positive for occult blood
• Screening peripheral blood smear with abnormal RBCs
• CBC, MCV, and/or reticulocyte count corrected for haemoglobin level above the reference range at screening
• Reduced G6PD activity
• Serum haptoglobin outside the reference range at screening
• Total serum LDH > 1.25% above the ULN at screening
• Positive HIV, Hepatitis B or Hepatitis C at screening
• The subject has a positive pre-study urine drug/ serum alcohol screen.
• History of alcohol consumption exceeding, on average, 7 drinks/week for women or 14 drinks/week for men within 6 months of the first dose of study medication or a positive alcohol test at screening
• History of use of tobacco or nicotine containing products within 6 months of screening or a positive urine cotinine screen
• Use of prescription (including hormone replacement therapy) or non-prescription drugs and vitamins within 7 days or 5 half-lives prior to administration of study medication. An exception is acetaminophen which is allowed at doses of 2g/day.
• Use of dietary/herbal supplements within 14 days prior to treatment with study medication
• Treatment with an investigational drug within 30 days or 5 half-lives (whichever is longer) prior to dosing.
• Exposure to more than four new chemical entities within 12 months prior to the first dosing day.
• 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 physician responsible, contraindicates their participation.
• Where participation in study would result in donation of blood in excess of 500 mL within a 56 day period.
• Unwillingness of male subjects to use a condom/spermicide
• Pregnant or nursing women.
• History of flushing (>1 episode annually).
• Fasting blood glucose 110 mg/dl and/or history of type I or type II DM
• History of intra-ocular pathology
• History of recurrent gum bleeding
• History of bleeding haemorrhoids