This is a randomized, double-blind, placebo-controlled, single-dose, design investigating the safety, tolerability and efficacy of NA-1, a peptide designed to reduce ischemic brain damage. Up to 200 male and female patients undergoing endovascular repair of brain aneurysm will be dosed with 2.60 mg/kg of NA-1 or placebo as a 10 minute intravenous infusion after completion of the endovascular procedure on Day 1 of the study period. Subjects will undergo interim procedures Days 2-4 and end-of study procedures on Day 30. Standard safety criteria will be analysed. Efficacy endpoints include the ability of NA-1 to: 1) reduce the volume of ischemic embolic strokes, 2) reduce the number of ischemic embolic strokes, 3) reduce vascular cognitive impairment, and 4) reduce the frequency of large strokes induced by the endovascular procedure. The plasma concentrations of NA-1 will also be analyzed.