Study to Investigate the Safety and Clinical Activity of GSK3326595 and Other Agents to Treat Myelodysplastic Syndrome (MDS) and Acute Myeloid Leukemia (AML)

Inclusion Criteria

• Males and females greater than or equal to (>=)18 years of age (at the time consent is obtained).
• Diagnosis of MDS, CMML or AML
• Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1 or 2
• Adequate organ function
• A woman of childbearing potential (WOCBP) must have a negative highly sensitive serum pregnancy test within 7 days before the first dose of study intervention.

Exclusion Criteria

• History of, or known, central nervous system (CNS) involvement
• Prior solid organ transplantation
• Known allergies, hypersensitivity, or intolerance to GSK3326595 or 5-Azacitidine or its excipient
• Prior therapy with any Protein arginine methyl transferase 5 (PRMT5) inhibitor
• History of a second malignancy, excluding non-melanoma skin cell cancer, within the last three years
• Active severe or uncontrolled infection
• History of optic nerve neuropathy or neuritis.
• History of sensitivity to any of the study medications, or components thereof, or a history of drug or other allergy that, in the opinion of the investigator or Medical Monitor, contraindicates their participation.