Inclusion Criteria:

1. A confirmed diagnosis of acute myeloid leukemia (AML)   
2. Participants with relapsed/refractory (R/R) acute myeloid leukemia (AML) who have been treated with up to 3 prior lines of therapy and are refractory to or intolerant of all established AML therapies that are known to clearly provide clinical benefit at the judgement of the investigator.

Exclusion Criteria:

1.  Have received a CD33-targeting therapy within 3 months prior to the first dose of ABBV-787.
2. Stem cell transplant within 3 months prior to first dose of study drug.
3. Have received anticancer therapy including chemotherapy, radiation therapy, immunotherapy, biologic, or any investigational therapy within 14 days or 5 half-lives of the drug (whichever is shorter) prior to the first dose of ABBV-787.
4. History of documented pneumonitis that required treatment with systemic steroids within the last 6 months, nor any evidence of active pneumonitis.

Detailed eligibility will be discussed when reaching out to the study team.