A Study to Assess the Adverse Events, Change in Disease Activity, and How Intravenous ABBV-1758 Moves Through the Body of Adult Participants With Alzheimer's Disease

Alzheimer's disease (AD) is a progressive, irreversible neurological disorder and is the most common cause of dementia in the elderly population. Clinical symptoms of the disease may begin with occasional forgetfulness such as misplacement of items, forgetting important dates or events, and may progress to noticeable memory loss, increased confusion and agitation, and eventually, loss of independence and non-responsiveness. This study is to assess the adverse events, change in disease activity, and how intravenous ABBV-1758 moves through the body of adult participants with Alzheimer's Disease

ABBV-1758 is an investigational drug being developed for the treatment of Alzheimer's disease in adults. This study is conducted in 3 stages. Stage A is a multiple ascending dose study with a 1 in 5 chance (4:1 randomization) that participants are assigned to receive placebo. Stage B is a dose expansion phase, also using 4:1 randomization for ABBV-1758 or placebo. Stage C enrolls Japanese and Chinese participants with the same randomization scheme. This may be followed by a 12-month, blinded Extension Period where participants receive ABBV-1758 or placebo based on their amyloid positron emission tomography (PET) results. Approximately 210 participants will be enrolled at about 65 sites in the United States, China, and Japan.

Participants will receive intravenous (IV) or subcutaneous (SC) doses of ABBV-1758 or placebo once every 4 weeks (Q4W) for 24 weeks and will be followed for an additional 12 weeks. Participants will have the option of participating in a 12-month, blinded Extension Period receiving ABBV-1758 or placebo based on amyloid PET results.

There may be higher treatment burden for participants in this trial compared to their standard of care due to study procedures. Participants will attend regular visits during the study at a hospital or clinic. The safety of the treatment will be checked by medical assessments, blood tests, and completing questionnaires.