Study to compare PK of a new 100mg capsule with four 25mg capsules. This is required because we plan to have only single capsules administered in the later phase clinical trials but we have not had a 100mg strength before. As this is a new previously untested strength we need to ensure that the PK is similar to that achieved using 4 x 25mg. The study will also assess the effect of high fat food on the PK of the 100mg capsule. The study is planned to consist of a single part , with three dosing periods, periods 1-3 consisting of 16 subjects. There will be a week wash out between each dose. In the three dosing periods subjects will either received 4x25 mg GSK598809 capsule in a fasted state, 100mg capsule in a fasted state or 100mg GSK598809 capsule in a fed state. Subjects will return to the centre for follow-up 7-14 days after the final dose. It is expected that the total duration of the study should be approximately eight weeks.

Inclusion:

• Healthy as determined by responsible physician.
• Male or female between 18 to 65 years old.
• Females of non-child bearing potential and females of child-bearing potential that agree to use appropriate method of contraception for appropriate amount of time.
• Males that agree to use appropriate method of contraception for appropriate amount of time.
• Neither too fat nor too thin.
• Capable of giving written informed consent and being compliant with requirements within the informed consent.

Exclusion:

• Any current medical or psychiatric illness.
• Any history of chronic medical or psychiatric illnesses.
• Previous or current alcohol or drug abuse/dependence including nicotine.
• Female subjects must not be breastfeeding or been breastfeeding for a month.
• Serum prolactin exceeding normal range.
• Personal or family history of prolonged QTc syndrome.