RecruitingPhase 1Biological interventionAV-1980R (Tau Vaccine) in Preclinical Alzheimer's Disease (TAURUS-1980)This is a Phase 1, multicenter, randomized, double-blind, placebo-controlled, multiple dose-escalating trial to evaluate the safety, tolerability, and immune response of AV-1980R, an investigational vaccine targeting tau protein, in participants with preclinical Alzheimer's disease. Up to 48 cognitively unimpaired adults aged 65-80 with biomarker evidence of early Alzheimer's disease will be enrolled into three ascending dose cohorts. The study is designed as a secondary prevention trial to test whether therapeutic immunization at the preclinical stage is safe, induces an immune response, and, exploratorily, may favorably affect biomarkers associated with disease progression.