The effects of four multiple ascending doses of orally administered Neu-P11 will be evaluated in a double- blind, placebo-controlled, crossover design. Following a screening visit, the recruited subjects will undergo an inclusion/habituation full night PSG screening recording in the sleep clinic to exclude subjects with sleep disorders. Eligible subjects will be divided into 2 cohorts of 12 subjects each. Following screening, each cohort will be randomised to receive Neu-P11 or placebo for a first period of 5 days and will be crossed over following at least 21 days to receive placebo or a higher dose of Neu-P11 for a second period of 5 days. Each cohort will receive a different dose of Neu-P11, chosen from 2, 5, 20 and 50 mg. The starting dose is 5 mg but a smaller dose (2 mg) is also included for the purpose of pharmacodynamic evaluation. Before proceeding from 5mg to the next higher dose safety will be evaluated based on adverse events, clinical and biological data. Subjects of Cohort A will be randomised to dose levels 2 and 3 (doses 5 and 20 mg). Subjects of Cohort B will be randomised to dose levels 1 and 4 (doses 2 and 50 mg).