A Study of LY4006895 in Healthy Participants With Early Symptomatic Alzheimer's Disease (AD)

Inclusion Criteria for Part A and Part B:

* Are overtly healthy as determined by medical evaluation. Rescreening is not allowed in this study
* Have a body mass index (BMI) within the range 18 to 40 kilogram per square meter (kg/m²)

For Part A:

* 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

For Part B:

* 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