A Study for Participants Who Participated in Prior Clinical Studies of ASTX727 (Standard Dose)

Main Extension Study: Participants will attend clinic visits on Day 1 of each 28-day cycle to undergo study procedures and to be given ASTX727 tablets for Days 1-5 of that dose cycle. Participants should continue to receive the same ASTX727 dose and regimen they were receiving in the last cycle of the parent study in which they were originally enrolled. Subsequent treatment delays and/or dose reductions are at the discretion of the investigator as guided by the dose adjustment guidelines of the parent study protocol. Food Effect Substudy: Participants received ASTX727 once daily on Days 1 through 5 followed by a 23-day treatment-free period in a 28-day cycle (Cycle 1). Participants received either a high-calorie, high-fat breakfast meal (Arm A) or a low-calorie/low-fat breakfast meal (Arm B) predose on Day 4. Participants in Arms A and B received ASTX727 on Days 1, 2, 3, and 5 in the fasted condition. Participants may continue treatment with ASTX727 in Cycle 2 onwards in the ASTX727-06 study at the Investigator's discretion, where they continued to receive ASTX727. This substudy consists of a 21-day Screening Period, a 1-cycle (28 days) Treatment Period, and a 30-day (+7 days) Safety Follow-up Period (only if the participant discontinues from the ASTX727-06 food effect substudy and does not continue to receive ASTX727 in the ASTX727-06 study).