 Following informed consent, subjects will undergo baseline evaluation with a history, physical exams, blood work, and disease assessment. Subjects will be assigned a dose of PR104 based on a Bayesian model maintained at the Statistical department at MD Anderson Cancer Center. The model will be updated with both toxicity and efficacy data as it is generated for each subject. New subjects will receive the currently predicted best dose for their respective subset based on prior treatment, age and duration of prior response. 