Open Label Trial on the Safety and Efficacy of Sym001 in the Treatment of Immune Thrombocytopenic Purpura (ITP)

Inclusion Criteria: * Confirmed presence of thrombocytopenia with platelet count \< 30,000/mm3 at the pre-dose visit. * History of isolated ITP * RhD-positive serology. * Previous treatment and response to first line therapy for ITP Exclusion Criteria: * Known clinical picture suggestive of other causes of thrombocytopenia, especially systematic lupus erythematosus,antiphospholipid syndrome, Evans syndrome, immunodeficiency states, lymphoproliferative disorders, liver disease,ingestion of drugs such as quinidine/quinine, heparin and sulfonamides and hereditary thrombocytopenia confirmed by relevant laboratory findings. * Suspected infection with HIV, Hepatitis C, H. pylori. * Clinical splenomegaly * History of abnormal bone marrow examination. * Ongoing haemorrhage corresponding to a grade 3 or 4 on the WHO bleeding scale. * Underlying haemolytic condition * History of splenectomy. * Subject is pregnant, breast feeding or intends to become pregnant.