 This study is a multicenter Phase 1, randomized, double-blind, placebo-controlled, multiple-dose, dose-escalation safety and tolerability study of NPT088 or placebo in patients with Probable AD with a MMSE score of 16-27. Enrolled patients will receive an intravenous infusion of NPT088 or placebo once a month for six months during this study. Four dose cohorts are planned with the first two cohorts enrolling 9 patients each 6 NPT088: 3 placebo and the final two cohorts enrolling 24 patients each 16 NPT088: 8 placebo for a total of 66 patients 44 NPT088: 22 placebo. 