A study testing increasing amounts (doses) of CC-91633 to find out what dose can be tolerated without serious side effects in patients with acute myeloid leukemia (AML) that has come back after treatment or cannot be cured or treated by any other known therapies, also called relapsed or refractory AML (R/R AML) and in patients with relapsed or refractory higher-risk myeloid dysplastic syndrome (R/R HR-MDS).