A Study of LY4560736 in Healthy Participants and Participants With Alzheimer's Disease (AD)

The purpose of this study is to see how safe LY4560736 is and to see how much and how quickly LY4560736 gets into the bloodstream. For healthy participants, the study also looks at how much LY4560736 gets into the brain. This part of the study lasts up to 13 weeks which includes staying in the Clinical Research Unit (CRU) for at least 4 days. This group will include Japanese participants, and the Sponsor may choose to enroll Chinese participants. For participants with Alzheimer's Disease, the study will also look at levels of a specific Alzheimer's-related protein in the brain and will last up to 13 weeks which includes staying in the CRU twice, each lasts about 1 to 2 days. Japanese participants, and potentially Chinese participants, may also be enrolled in this group.

Inclusion Criteria: * Participants must meet eligibility criteria in the A1D-MC-ATMP screening protocol before entry into the treatment study. * To qualify as a participant of first-generation Japanese origin, the participant, the participant's biological parents, and all the participant's biological grandparents must be of exclusive Japanese descent and born in Japan. * To qualify as Chinese for this study, all four of the participant's biological grandparents must be of exclusive Chinese descent and born in China. Exclusion Criteria: * Have a condition that predisposes the participant to an infection. * Have a current or recent acute, active infection. * Have active tuberculosis (TB), have or have had latent TB. * Are receiving therapeutic antibodies or expected to initiate treatment with therapeutic antibodies during the study.