Proof of Mechanism in ELT

Inclusion Criteria: * Heterosexual male subject with self-reported moderate or severe primary Premature ejaculation with ejaculation occurring on or before penetration, or shortly there after with minimal stimulation * Baseline Ejaculation Latency time \< 3 minutes * Subjects must agree to use a contraception methods as per protocol * Body weight \> or = 50 kg and Body Mass Index within the range 19.0-29.9 Kg/m2 * Subject with normal visual acuity (with appropriate correction if needed) * Subject able to cooperate in all study procedure including the eye examination with use of mydriatics Exclusion Criteria: * Erectile dysfunction * History of migraine * Current clinically relevant abnormality * History of psychiatric illness or suicidal attempts or behaviours * History of any eye disorder or colour blind, excluding myopia and presbyopia * Cardiac conduction disorder or other clinically significant cardiac disease * Positive at pre-study drug/alcohol screen and to Hepatitis or HIV tests * Regular consumption of alcohol * History of sensitivity or intolerance to drugs * Consumption of red wine, seville oranges, grapefruit or grapefruit juice \[and/or pummelos, exotic citrus fruits, grapefruit hybrids\] from 7 days prior to the first dose of study medication * Subject has received or is continuing to receive any treatment for premature ejaculation in the four weeks prior to the study start * Use of prescription or non-prescription drugs, including vitamins, herbal and dietary supplements prior to the first dose of study medication * Participation in another clinical trial in the previous month * Exposure to more than four new experimental drugs within the previous 12 months * Where participation in the study would result in donation of blood or blood products in excess of 500 mL within a 56 day period. * Unwillingness or inability to follow the procedures outlined in the protocol.