This research study involves receiving a study drug referred to as PRT543. This study is a Phase 1 study and this is the first study in humans using the study drug. You are being invited to participate in either dose escalation or dose expansion depending on which portion of the study is open when you join. The purpose of dose escalation is to test the safety of the study drug, at different dose levels and to find out what effects, good and/or bad, the study drug has on you and your type of cancer. The information collected from you and from other patients in the study when taking different dose levels will be used to decide the most appropriate dose of the study drug that should be used in dose expansion and for other studies which may be completed in the future.