Thrombopoietic Agents in Immune Thrombocytopenia
Purpura, Thrombocytopenic, Idiopathic
Immune thrombocytopenia (ITP) is a disease characterized by accelerated platelet destruction and suboptimal platelet production. The latter concept has led to the exploration of new therapeutic options by focusing on the stimulation of platelet production as opposed to the traditional approach of immune suppression. Thrombopoietic agents act by stimulating the thrombopoietin receptor on the hematopoietic cells leading to stem cell differentiation, megakaryocyte proliferation, and platelet production. The last decade has witnessed the birth of second-generation thrombopoietic agents. Romiplostim and eltrombopag are the two agents that have been recently licensed. In randomized controlled trials, these agents have demonstrated unequivocal superiority over placebo in the treatment of ITP in splenectomized and in nonsplenectomized patients-an effect that seems to be durable while treatment continues and at an acceptable short-/intermediate-term safety profile. These agents represent a new therapeutic option in refractory ITP and in chronic ITP when splenectomy is contraindicated or needs to be deferred. However, the scope of therapeutic indications is expected to expand should long-term safety be confirmed in the ongoing studies. Several other agents are currently being investigated and are in preclinical and clinical development programs.