A Study to Evaluate Efficacy and Safety of Intravenous Sabirnetug in Participants with Early Alzheimer's Disease (ALTITUDE-AD)

Inclusion Criteria:

• Body weight of at least 30 kilograms (kg) (66 pounds [lbs]) and no more than 160 kg (352 lbs) at Screening

• Must consent to apolipoprotein E4 (APOE4) genotype status assessment

• Must meet all of the following criteria

1. National Institute on Aging-Alzheimer's Association (NIA-AA) criteria for mildcognitive impairment (MCI) due to Alzheimer's Disease (AD) or probable AD

2. Screening score between 22 and 30 (inclusive) on the Mini-Mental StateExamination (MMSE)

3. Screening score of 0.5 or 1.0 on the Clinical Dementia Rating Global Score (CDR-GS) and Screening score ≥0.5 on the CDR Memory Box score

4. Evidence of cerebral amyloid accumulation by either PET scan or CSF

• If using cholinesterase inhibitors or memantine to treat symptoms related to AD,doses must be stable for at least three months (12 weeks) prior to Baseline andevery attempt should be made to keep them at stable doses throughout the study

• Must have a reliable informant or study partner who is willing and able to performall the roles as specified in the study partner Informed Consent Form (ICF)

• Female participants must be surgically sterile or be at least one-yearpost-menopausal. Male participants with a female partner of child-bearing potentialmust use adequate contraception

Exclusion Criteria:

• Has any contraindications for MRI studies, including claustrophobia, the presence ofmetal (ferromagnetic) implants, or a cardiac pacemaker that is not compatible withMRI

• MRI of the brain that is inconsistent with MCI or AD or results showing greater thanfour ARIA-H, presence of any ARIA-E, or superficial siderosis

• History of significant or unstable neurological disease, other than AD, which mayaffect cognition or ability to complete the study, such as other dementias, seriousinfection of the brain, significant head trauma, uncontrolled seizures, stroke, orParkinson´s disease

• Current serious or unstable clinically important illness that, in the judgment ofthe site investigator, is likely to affect cognitive assessment including visual andhearing impairment or affect the participant's safety or ability to complete thestudy

• Malignant disease in the last five years except for resected cutaneous squamous cellcarcinoma in situ, basal cell carcinoma, cervical carcinoma in situ, or in situprostate cancer with a normal posttreatment prostate-specific antibody (PSA)

• Geriatric Depression Scale-Short Form (GDS-SF) score >10 or current symptoms meetingDiagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V),criteria for major depressive disorder or any current primary psychiatric diagnosisother than AD if, in the judgment of the site investigator, the psychiatric disorderor symptom is likely to confound interpretation of drug effect, affect cognitiveassessments, or affect the participant´s ability to complete the study

• Suicide risk, as determined by meeting any of the following criteria:

1. Any suicide attempt or preparatory acts/behavior on the C-SSRSBaseline/Screening in the last six months

2. Suicidal ideation in the last six months as defined by a positive response toQuestion 5 (Suicidal Ideation) on the C-SSRS Baseline/Screening

3. Significant risk of suicide, as judged by the site investigator

• Conditions that may affect cognitive assessments during the study

• Alcohol use disorder and/or substance use disorder within the last five years