AstraZeneca is doing this research study to see if there are any side effects to taking an investigational drug called AZD5991 and find out if AZD5991 has any effect in treating patients with relapsed or refractory blood cell cancers. An investigational drug is one that is being tested and is not approved for sale in any country, but may be used in research studies like this one. In addition, this study will help to understand how well AZD5991 is taken up by the body (pharmacokinetics) and to study biological markers (i.e. biomarkers such as proteins and gene alterations) to help understand how AZD5991 might work and who will benefit most from treatment. This segment of the study is called the mono-treatment study design.
Secondly, this research will study the effect of AZD5991 in combination with a drug called venetoclax (Venclexta™) on patients with acute myeloid leukemia (AML) or Myelodysplastic syndrome (MDS). This part of the study is called combination treatment. Venetoclax is a drug (tablet) that can be prescribed by a doctor for the treatment of adults with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL). It is also used as part of a combination treatment for AML.