Additional Study Information: You are being asked to take part in this study because you have acute myeloid leukemia (AML) that has come back after initial treatment (relapsed) with venetoclax combination therapy or because you did not get a complete response from your initial treatment (refractory) with venetoclax combination therapy. The purpose of this research study is to determine the effectiveness (how well something works) and safety of an investigational compound called alvocidib when used either in a combination treatment regimen (low-dose cytarabine) or as a single therapy (alvocidib alone). Investigational means that the Food and Drug Administration (FDA) has not yet approved this treatment as a prescription medicine; it is only available through research studies like this. Alvocidib was previously known as flavopiridol. Alvocidib is an investigational product being developed by Tolero Pharmaceuticals in AML. Cytarabine (also known as Ara-C) is one of the medicines considered as standard of care for the treatment of patients with AML.