If you have been found to be eligible to take part in this study and you agree, you will be assigned to a dose level of azacitidine based on when you join this study. Up to 7 dose levels of azacitidine will be tested. At least 3 participants will be enrolled at each dose level. The first group of participants will receive the lowest dose level. Each new group will receive a higher dose than the group before it, if no intolerable side effects were seen. This will continue until the highest tolerable dose of azacitidine is found.