 An initial cohort of 10 patients will be enrolled. Based on the efficacy outcome at least 3 out of 10 patients responding and safety outcome no significant adverse event associated with study drug a second cohort of 10 patients will be treated. Patients in the second cohort who are considered responders i.e., have had at least a 3 point reduction in the 18 point PDAI scoring system or who are in remission PDAI7 are eligible to receive open-label AST-120 for as long as response is maintained up to a maximum of 52 weeks. If, at any time, the patient relapses PDAI7 for patients who were in remission, or an increase in PDAI such that at least a 3 point reduction is not maintained for responders, open-label treatment will be discontinued and the patient will be removed from the study. Patients will also discontinue open-label treatment and be removed from the study if warranted by treatment-emergent safety concerns or if, in the opinion of the investigator, it is in the patients best interest to discontinue the study. 