Study to Evaluate the Efficacy, Safety, and Tolerability of an Anti-MTBR Tau Monoclonal Antibody (BMS-986446) in Participants With Early Alzheimer's Disease

Inclusion Criteria * Mild cognitive impairment (MCI) due to Alzheimer's disease (AD) or mild AD dementia consistent with the National Institute on Aging and the Alzheimer's Association (NIA-AA) core clinical criteria. * Global Clinical Dementia Rating (CDR) score of 0.5 to 1.0 and a CDR-Memory Box score of 0.5 and greater at screening and Baseline. * Evidence of AD pathology. * Objective impairment in episodic memory as indicated by at least 1 standard deviation below age-adjusted mean in the Wechsler Memory Scale IV-Logical Memory Subtest II (WMS-IV LM II). * Mini Mental Status Examination (MMSE) score ≥ 20 to 28 (inclusive). Exclusion Criteria * Any evidence of a condition that may affect cognition other than AD. * Contraindications to PET imaging. * Inability to tolerate or contraindication to magnetic resonance imaging. * Any serious medical condition that could, in the opinion of the investigator, affect the participant's safety or interfere with study assessments. * Geriatric Depression Scale (GDS) score greater than or equal to 8 at screening. * Other protocol-defined Inclusion/Exclusion criteria apply.