In the latest article in our Clinical Therapeutics review series, a young woman with immune thrombocytopenia (ITP) who has been treated with a thrombopoietin-receptor agonist presents for advice regarding long-term treatment. The agents in this therapeutic class, romiplostim and eltrombopag, are effective in increasing platelet counts.
Immune thrombocytopenia is a disorder that is characterized by immune-mediated platelet destruction and impaired platelet production resulting in a platelet count of less than 100,000 per cubic millimeter and varying degrees of bleeding risk.
• Does platelet count correlate with bleeding risk in patients with primary immune thrombocytopenia?
Bleeding in immune thrombocytopenia is rare in patients who have a platelet count of more than 50,000 per cubic millimeter. The bleeding risk at lower platelet counts varies greatly from none to very severe, although spontaneous, life-threatening or fatal bleeding is generally confined to patients with a platelet count of less than 10,000 to 20,000 per cubic millimeter.
• What is the initial approach to managing patients with primary immune thrombocytopenia?
Initial treatment for immune thrombocytopenia is generally a course of glucocorticoids, intravenous immune globulin, or both. The only second-line treatment that has been shown to produce sustained increases in the platelet count is splenectomy. Rituximab is widely used as a second-line agent, although the median duration of response with this agent is only 10.5 months.
Morning Report Questions
Q: What is the efficacy of the thrombopoietin-receptor agonists, romiplostim?
A: Romiplostim is administered subcutaneously once weekly. In an ongoing open-label extension study involving 292 patients treated with romiplostim, 94.5% achieved a platelet count of at least 50,000 per cubic millimeter during the study.
Q: What is the efficacy of the thrombopoietin-receptor agonist, eltrombopag?
A: Eltrombopag is given orally daily. In an ongoing open-label extension study involving 299 patients who completed a previous eltrombopag study, 87% of patients achieved a platelet count of at least 50,000 per cubic millimeter during treatment.