 Pre-clinical and clinical evaluations show that PRTX- 100 has biological activity that may lead to improved platelet levels where these are decreased due to immunological pathologies and that PRTX-100 has an acceptable safety profile. In vivo treatment with PRTX-100 has been shown to raise platelet counts in a mouse model of immune thrombocytopenia ITP. The primary objective of the study is to assess the efficacy of PRTX-100 in terms of platelet response in patients with chronicpersistent ITP. 