A Phase I, Single-Centre, Open-Label, Randomized, Four-Period Crossover Study to Assess the Effect of Food on the Pharmacokinetics of Avanafil, to Determine The Relative Bioavailability of Two Avanafil Tablet Formulations and to Investigate Dose Proportionality in Healthy Male Subjects

In this Phase I, single-centre, open-label, randomized, four-period crossover study, each eligible subject will be randomized to receive the 4 treatments in a 4-way crossover fashion. The 4 treatments are as follows: * Treatment A: 2x100 mg Formulation II avanafil tablet, fasted * Treatment B: 2x100 mg Formulation II avanafil tablet, fed * Treatment C: 2x100 mg Formulation I avanafil tablet, fasted * Treatment D: 1x50 mg Formulation II avanafil tablet, fasted Subjects will report to the study site on the evening before each treatment and will remain at the site until the 24-hour PK sample has been drawn. A single oral dose of avanafil tablets will be administered with 240 mL of water. A washout period of at least 5 days will occur between the treatments. Subjects in treatment groups A, C and D will fast at least 10 hours prior to and for at least 4 hours following dosing. Subjects in treatment group B will eat a standardized high fat breakfast 30 prior to dosing. Standard meals will be provided uniformly to all subjects at approximately 4 and 9 hours after dosing, and an evening snack will be provided approximately 12 - 13 hours after dosing. Blood samples for the determination of plasma avanafil and its metabolite concentrations will be obtained from each subject at 0 (30 minutes pre-dose), 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2, 3, 4, 8, 12, 18 and 24 hours post-dose in each treatment period. Adverse events; laboratory evaluations; color vision testing (Treatment A only), electrocardiogram and physical examination, vital signs will be assessed at various times during the study.