Moving towards a new era in the management of chronic immune thrombocytopenia

Immune thrombocytopenia (ITP) is an organ-specific autoimmune disease in which a low concentration of plasma thrombopoietin (TPO) contributes to the thrombocytopenia. Functional thrombopoietin deficiency in response to thrombocytopenia is central to the pathophysiology of chronic ITP. Decreased platelet production in ITP patients has been described only in recent years, however. Following the development of TPO-mimetics, it has become clear that the augmentation of thrombopoiesis is a key therapeutic target. TPO mimetics are novel effective treatments providing durable platelet responses in ITP. Two agents have reached clinical practice, the 'peptibody' romiplostim (Nplate(R)) approved for treatment of thrombocytopenia in patients with chronic ITP in Europe, Canada, Australia and the USA and the non-peptide TPO mimetic, eltrombopag (Promacta(R)), approved in the USA. This review summarises the background to the development of these agents and presents an update on data from randomised phase III trials and open-label studies. These novel drugs provide a noteworthy treatment option for patients with chronic ITP, in whom thrombocytopenia and bleeding risk have not been controlled by standard treatments. The first candidates for treatment in clinical practice are undoubtedly refractory patients with lack of response to other therapies or at continued risk for bleeding despite treatment. Appropriate inclusion of TPO mimetics into the treatment paradigm will most likely have a positive impact on the long-term outcome of ITP and allow carefully monitored patients to remain well controlled, with good tolerability for prolonged periods.