Study to Assess the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Efficacy of TB006 in Participants With Alzheimer's Disease

Study to Assess the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Efficacy of TB006 in Participants With Alzheimer's Disease

A Seamless Phase 1b/2a Double-blind, Randomized, Multiple Dose, Multi-center, Sequential Dose-escalation Study to Assess the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics and Efficacy of TB006 in Patients With Mild to Severe Alzheimer's Disease

Part 1 of this study will be conducted to determine the safety, tolerability, and pharmacokinetic (PK) profile of multiple doses of TB006, as well as the maximum tolerated dose of TB006, and to assess the immunogenicity of TB006 (production of anti-TB006 antibody). Part 2 of this study will be conducted to determine the clinical efficacy of TB006 in participants with mild to severe Alzheimer's Disease.

Participants will be randomized to 1 of 3 ascending dose groups to receive a total of 5 once-weekly doses of TB006, infused over 1 hour.

Participants will receive the highest safe and well-tolerated dose identified in Part 1, infused over 1 hour. Randomization will be stratified according to severity at Baseline (mild versus moderate Alzheimer's Disease).

Participants will be randomized to receive matching placebo. Randomization will be stratified according to severity at Baseline (mild versus moderate Alzheimer's Disease).

Pre-dose, end of infusion, then 1, 2, 4, and 6 hours after the end of infusion on Days 1, 8, and 29; single time point on Days 36, 64, and 104

Pre-dose, end of infusion, then 1, 2, 4, and 6 hours after the end of infusion on Days 1, 8, and 29; single time point on Days 36, 64, and 104

Pre-dose, end of infusion, then 1, 2, 4, and 6 hours after the end of infusion on Days 1, 8, and 29; single time point on Days 36, 64, and 104

Pre-dose, end of infusion, then 1, 2, 4, and 6 hours after the end of infusion on Days 1, 8, and 29; single time point on Days 36, 64, and 104

Pre-dose, end of infusion, then 1, 2, 4, and 6 hours after the end of infusion on Days 1, 8, and 29; single time point on Days 36, 64, and 104

Pre-dose, end of infusion, then 1, 2, 4, and 6 hours after the end of infusion on Days 1, 8, and 29; single time point on Days 36, 64, and 104

Pre-dose, end of infusion, then 1, 2, 4, and 6 hours after the end of infusion on Days 1, 8, and 29; single time point on Days 36, 64, and 104

Part 1: Concentrations of TB006 in Cerebrospinal Fluid (CSF), as a Measure of the Extent of CSF Distribution

Part 2: Change from Baseline through Day 104 on the Clinical Dementia Rating Scale - Sum of Boxes Total Score

Part 2: Change from Baseline through Day 36 on the Clinical Dementia Rating Scale - Sum of Boxes Total Score

Part 2: Change from Baseline to Days 36 and 104 on the Cognitive Drug Research System Battery, Composite Scores and Individual Task Measures

Inclusion Criteria: Body weight of ≥ 50 kilograms (kg) and body mass index (BMI) between 18 and 35 kg/meters squared (m^2), inclusive Mini-Mental State Examination (MMSE) score of 24 or less Must be ambulatory Clinical diagnosis of Alzheimer's Disease (AD) consistent with the following: Probable AD, according to National Institute of Neurological and Communicative Disorders and Stroke - Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) Meets the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) - Criteria for Major Neurocognitive Disorder (previously dementia) Participants or caregiver has the ability to understand the purpose and risks of the study and provide signed and dated informed consent which includes compliance with the requirements and restrictions listed in the inform consent form (ICF) and in this protocol. Participants whose caregiver signs the informed consent must provide their assent. Exclusion Criteria: Any medical or neurological condition other than AD that in the opinion of the investigator could be a contributing cause of the participant's dementia (e.g., medication use, vitamin B12 deficiency, abnormal thyroid function, stroke or other cerebrovascular condition, diffuse Lewy body disease, head trauma) History within the past 6 months or evidence of clinically significant psychiatric illness (e.g., major depression, schizophrenia, or bipolar affective disorder) Diagnosis of a dementia-related central nervous system (CNS) disease other than AD (e.g., Parkinson's Disease, Huntington's Disease, frontotemporal dementia, multi-infarct dementia, dementia with Lewy bodies, normal pressure hydrocephalus) Identification of other known cause of dementia or any other clinically significant contributing co-morbid pathologies at screening magnetic resonance imaging (MRI), in the opinion of the investigator Participation in any other drug, biologic, device, or clinical study or treatment with any investigational drug or approved therapy for investigational use within 30 days (or 5 half lives, whichever is longer) prior to screening, and/or participation in any other clinical study involving experimental medications for AD within the 60 days (or 5 half lives, whichever is longer) prior to screening