A Study of Donanemab (LY3002813) in Participants Who Completed Study AACM (TRAILBLAZER-ALZ 3-EXT).

Inclusion Criteria:

* Have completed study AACM Addendum 7.
* Have a reliable study partner and backup study partner familiar with overall function and behavior, such as day-to-day activities and cognitive abilities.
* Are individuals assigned female at birth who are not of childbearing potential, or are individuals assigned male at birth.
* Contraceptive use by participants should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.

Exclusion Criteria:

* Current serious or unstable illnesses that, in the investigator's opinion, could interfere with participation in this study.
* Have any contraindications for magnetic resonance imaging (MRI), including claustrophobia or the presence of contraindicated metal (ferromagnetic) implants/cardiac pacemaker.
* Have any intracranial abnormality or lesion, including but not limited to macrohemorrhage, inflammation, or structural findings that, in the opinion of the investigator, may pose an unacceptable safety risk to the participant. Screening MRI finding of amyloid-related imaging abnormalities with edema (ARIA-E) may be monitored for resolution.
* Contraindication to florbetapir F 18 PET.
* Have had history of amyloid-targeting therapy treatment outside donanemab trials.
* Have participated, within the last 30 days, in a clinical trial involving a study intervention judged not to be scientifically or medically compatible with this study.