Double blind, placebo controlled, parallel group ascending dose study evaluating single and multiple (x8 days) dose levels of F901318 in groups of male healthy subjects with the objective of defining a dosing schedule for phase ll clinical trials. F901318, a novel and potent antifungal agent for the treatment of invasive aspergillosis, will be delivered intravenously in a range of dosing schedules driven by pharmacokinetic evaluation in real time. Safety and tolerability of those schedules will also be assessed.