A Study to Evaluate the Safety and Tolerability of ALN-APP in Patients With EOAD

Inclusion Criteria:

• Has mild cognitive impairment or mild dementia due to EOAD

• Has Clinical Dementia Rating (CDR) global score 0.5 or 1.0 and Mini Mental StateExamination (MMSE) >20

Exclusion Criteria:

• Has Non-Alzheimer's disease dementia

• Has alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >2×upperlimit of normal (ULN)

• Has estimated glomerular filtration rate (eGFR) <45 mL/min/1.73m^2 at Screening

• Has recently received an investigational agent

• Has recent treatment with amyloid-targeting antibody

Note: other protocol defined inclusion / exclusion criteria apply