BMS-986446 for Early Alzheimer's Disease and Healthy Adults

Inclusion Criteria * Participants must have a BMI of 18.0 to 35.0 kg/m2. * For Parts A and B: Participants must be healthy as determined by medical history, Physical Examination (PE), neurological examination, vital signs, 12-lead ECG, Columbia Suicide-Severity Rating Scale (C-SSRS), and clinical laboratory evaluations. * For Part C: Participants must meet diagnostic criteria for MCI or mild AD dementia, consistent with the National Institute on Aging and the Alzheimer's Association (NIA-AA) diagnostic criteria. * For Part C: Participants must have an Mini Mental State Examination (MMSE) score of ≥ 20 to 28 (inclusive). * For Part C: Participants must have evidence of positive plasma pTau217. Exclusion Criteria * For Parts A and B: Participants must not have a general history of any clinically significant gastrointestinal, renal, hepatic, broncho-pulmonary, neurological, psychiatric, cardiovascular, endocrinological, immune-mediated disorder, hematological, ongoing allergic disorder requiring treatment, metabolic disorder, cancer, or cirrhosis. * For Parts A and B: Participants must not have donated or lost 500 mL blood or more within 60 days prior to study intervention administration. * For Part C: Participants must not have a neurological condition that in the opinion of the investigator may be contributing to cognitive impairment aside from the AD diagnosis, including but not limited to: Parkinson's disease, vascular dementia, dementia with Lewy bodies, frontotemporal dementia, Huntington's disease, normal pressure hydrocephalus, brain tumor, progressive supranuclear palsy, seizure disorder, subdural hematoma, multiple sclerosis, long COVID, or baseline intellectual disability. * For Part C: Participants must not have any current primary psychiatric diagnosis (eg, major depression, schizoaffective disorder or bipolar disorder) other than AD or symptoms (eg, hallucination or delusions). * Other protocol-defined Inclusion/Exclusion criteria apply.