5. A mean platelet count of < 30,000/μL, with no individual platelet count > 35,000/μL; or for those subjects receiving a constant dose of permitted treatments for ITP: a mean platelet count < 50,000/μL, with no count greater than 55,000/μL. (Note: The mean platelet count must be determined based on 2 platelet counts including one obtained within ≤ 7 days of first PRTX-100 dose and the other within ≤ 30 days of the first dose of PRTX-100.)