Thrombopoietin Receptor Agonists for ITP

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Idiopathic thrombocytopenic purpura (ITP) is a disease of both increased platelet destruction in the peripheral blood and diminished platelet production, explains Keith McCrae, MD. The survival of a platelet in an individual with ITP may be 1 to 2 days, whereas a normal platelet typically survives 8 to 10 days.

Researchers have extracted antibodies from the serum and plasma of patients with ITP and incubated the samples with megakaryocytes, McCrae notes. These antibodies impair the function of the megakaryocytes, reducing their ability to make platelets.

Historical therapy, such as intravenous immunoglobulin and steroids, are designed to reduce platelet clearance, enhancing platelet lifespan. Newer agents, such as thrombopoietin receptor agonists, are thought to overcome the effects of the platelet antibodies, increasing platelet production.

Thrombopoietin agonists are FDA approved for second-line therapy and beyond, Ivy Altomare, MD, explains. These agents have an excellent role in patients with extremely refractory ITP. Altomare adds that these agents are equally as effective in individuals pre-splenectomy or post-splenectomy.

Although thrombopoietin agonists are highly effective in refractory patients, clinicians should not wait until patients are extremely refractory to try these agents, Altomare suggests. Ongoing research is investigating the upfront use of these agents. Although these studies have shown promising results, thrombopoietin agonists are not yet FDA approved or recommended in guidelines for upfront use.