LY4006895 for Alzheimer's Disease

Inclusion Criteria for Part A and Part B: \- Have a body mass index (BMI) within the range 18 to 40 kilogram per square meter (kg/m²) For Part A: * Are overtly healthy as determined by medical evaluation. Rescreening is not allowed in this study For Part B: * Have early symptomatic AD, as defined by: * Gradual and progressive change in memory function for at least 6 months, as reported by the participant or informant * A Mini-Mental State Exam (MMSE) score of 18 to 30 at screening * A Clinical Dementia Rating (CDR) global score of 0.5 to 1.0 (inclusive), with a memory box score greater than or equal to 0.5 at screening * Have up to 2 reliable study partners who are in frequent contact with the participant (defined as at least 10 hours per week), one of whom at any one occasion: will accompany the participant to the study visits, will be available by telephone at designated times, and will provide a separate written informed consent to participate Exclusion Criteria for Part A and Part B: * Current serious or unstable illnesses including cardiovascular, hepatic, renal, gastroenterological, respiratory, endocrinologic, neurologic (MAD: other than AD), psychiatric, immunologic, or hematologic disease and other conditions that, in the investigator's opinion, could interfere with the participant's ability to complete the study; or has a life expectancy of less than 24 months * Have screening hemoglobin (Hb) less than 12 grams per deciliter (g/dL) or evidence of iron-deficiency (ferritin less than 30 nanograms per milliliter (ng/mL), or presence/history of hemoglobinopathy * Are, in the judgment of the investigator, actively suicidal and therefore deemed to be at significant risk for suicide * Regularly use known drugs of abuse and/or show positive findings on urinary drug screening that cannot be explained by regular concomitant medications * Have previous exposure to any anti-tau therapy * Are pregnant or intend to become pregnant or to breastfeed during the study For Part B: * Have a current exposure to an amyloid targeted therapy. Prior exposure to amyloid targeted therapies greater than 1 year from the last dose may be permitted at the discretion of the investigator and in consultation with the sponsor. A listing of amyloid targeted therapies will be provided * Have a sensitivity to florataucipir 18F * Have contraindication to magnetic resonance imaging (MRI) including claustrophobia or the presence of contraindicated metal (ferrogmagnetic) implants/cardiac pacemaker