Overview

The purpose of this study is to see how LY3439539 affects certain proteins found in the spinal fluid of participants with Alzheimer's disease.

Participation in the study will last approximately 9 months with visits about once a month.

Eligibility

Inclusion Criteria:

• Have gradual and progressive change in memory function reported by the participant or informant for 6 months or longer consistent with a diagnosis of dementia due to Alzheimer's disease
• Have a Mini Mental Score Examination score of 16 to 24, inclusive
• Meet plasma pTau criteria, as defined by the sponsor
• Have body mass index within the range of 17 and 32 kilograms per square meter (kg/m²) (inclusive) at screening
• Are women not of childbearing potential and men willing to practice effective contraception throughout the study.
• Have adequate premorbid literacy, vision, and hearing throughout the study duration and able to complete study procedures.
• Have at least 1, and up to 2, study partners who are in frequent contact with the participant (defined as at least 10 hours per week).

Exclusion Criteria:

• Have any contraindications for magnetic resonance imaging (MRI), including claustrophobia or the presence of contraindicated metal (ferromagnetic) implants/cardiac pacemaker.
• Have a screening MRI that shows evidence of significant abnormality.
• Have history of suicidal behavior, or a lifetime history of suicide attempt or acute suicidality.
• Have a history of
  • Severe or ongoing allergy or hypersensitivity reactions
  • Hypersensitivity to immunizations or immunoglobulins
  • Two or more clinically significant or severe drug allergies,
  • Intolerance to topical corticosteroids or severe posttreatment hypersensitivity reactions
• Have current serious or unstable illnesses, including hepatic, renal, gastroenterological, respiratory, cardiovascular, neurologic (other than AD), psychiatric, endocrinologic, immunologic, hematologic disease, or other conditions
• Require treatment with another monoclonal antibody or have received treatment with biologic agents (such as monoclonal antibodies, including marketed drugs) within 3 months or 5 half-lives (whichever is longer) prior to dosing.
• Have criteria that would preclude a lumbar puncture (LP).
• Are currently enrolled in a clinical study involving an investigational product (IP) or any other type of medical research judged not to be scientifically or medically compatible with this study.
• Have a current exposure to amyloid-targeting therapies (ATTs). Prior exposure to ATTs greater than 1 year from the last dose may be permitted at the discretion of the investigator and in consultation with the sponsor.