Protalex, Inc. announced that following a planned interim analysis of data from the fourth dose cohort of its European Phase 1b study of PRTX-100 (PRTX-100-203 Study) in adults with persistent/chronic Immune Thrombocytopenia (ITP), the Company has initiated enrollment in the fifth and highest dose cohort of this dose-escalating study. The first patient in this final cohort was recently dosed in the United Kingdom at 24 micrograms/kg, the highest dose of PRTX-100 used in any clinical trial to date. One of the three patients treated in the fourth dose cohort (18 micrograms/kg) achieved a protocol defined platelet response. PRTX-100 has been granted Orphan Drug Designation in the U.S. and in Europe for the treatment of ITP. The 203 Study is a European open-label, dose escalating study that can enroll up to 30 patients in as many as five cohorts. Patients with chronic, persistent ITP are eligible for the 203 Study if they have received one prior ITP treatment and their platelet counts remain low. Each patient receives four weekly intravenous doses of PRTX-100 and is monitored for up to 48 weeks thereafter. The primary study endpoint of the 203 Study is to evaluate the safety of PRTX-100. Secondary endpoints include efficacy, immunogenicity, and pharmacokinetics.