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

A Phase I/II Study to Investigate the Safety and Clinical Activity of GSK3326595 and Other Agents in Participants With Myelodysplastic Syndrome and Acute Myeloid Leukaemia

This study will evaluate the safety, tolerability, and clinical activity of GSK3326595 in participants with relapsed and refractory MDS, chronic myelomonocytic leukemia (CMML), and AML. The study will be conducted in 2 parts: Part 1 will determine the clinical benefit rate (CBR) of GSK3326595 in monotherapy and Part 2 will be expanded to study GSK3326595 in combination with 5-Azacitidine which will be composed of a dose escalation phase followed by dose expansion cohort of GSK3326595.

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.