Phase I, prospective, randomized, placebo-controlled, double-blinded study. To evaluate the safety and efficacy of Longeveron Mesenchymal Stem Cells (LMSCs) for the treatment of AD. 25 subjects will be randomized to (2 : 2:1) to receive peripheral intravenous infusions of low-dose LMSCs (20×10∧6), high-dose LMSCs (100×10∧6) or placebo (Plasmalyte A and 1% human serum albumin (HSA)). Subjects will be followed up at 2, 4, 13, 26, 39, and 52-week post-study product infusion. The gene discussed is ALB; the disease is Alzheimer disease.