Reciprocal absence of cross-resistance between eltrombopag and romiplostim in two patients with refractory immune thrombocytopenic purpura.

Abstract

The recent availability in clinical practice of thrombopoietin (TPO) receptor agonists, which are effective in increasing platelet counts with relatively low toxicity1, has lead to important advances in the therapeutic management of immune thrombocytopenic purpura (ITP). There are two TPO-receptor agonists, the non-peptide eltrombopag and the peptide romiplostim. Both TPO-receptor agonists are able to rescue the platelet count by stimulating the TPO receptor on progenitors of megakaryocytes and inducing their proliferation and maturation. These agents have different pharmacological profiles and mechanisms of action1 and are approved and recommended by international ITP consensus guidelines2,3 for the treatment of resistant/relapsed disease. Both these thrombopoietic agents require maintenance dosing and continuous treatment in order to maintain the response. Indeed, if the administration of these drugs is interrupted for any reason, the platelet count falls rapidly. The absence of cross-resistance between the two drugs, likely due to their different mechanisms of action, has been reported4–8. In this regard, here we report two cases with symmetrically opposite therapeutic responses to these thrombomimetic drugs in patients who failed to benefit from previous treatment with one or the other agent.