Use of Thrombopoietin Receptor Agonists in Prolonged Thrombocytopenia after Hematopoietic Stem Cell Transplantation

Prolonged thrombocytopenia after hematopoietic stem cell transplantation (HSCT) is a strong risk factor for transplantation-related morbidity and mortality, and no standard treatment guideline exists. Thrombopoietin receptor agonists (TPO-RAs), eltrombopag and romiplostim, increases the platelet production, and are being increasingly used in various conditions with thrombocytopenia. In this review, we present an overview of these TPO-RAs and review their efficacy and safety in prolonged post-HSCT thrombocytopenia. Through a systematic literature search, we identified 25 reports describing their use for this indication. Thirteen reports (8 case series and 5 case reports) described the use of eltrombopag in 78 patients with prolonged isolated thrombocytopenia (PIT) and 43 patients with secondary failure of platelet recovery (SFPR). A consistent and durable response with a rise in platelet counts >50 × 10 9/L for 7 consecutive days without platelet transfusion was seen in 85 of 121 patients (overall response rate [ORR], 70%). The responders included 56 patients with PIT (ORR for PIT, 72%) and 29 patients with SFPR (ORR for SFPR, 67%). No serious grade 3 or 4 adverse effects were reported. Similarly, 12 reports (6 case series and 6 case reports) described the use of romiplostim in prolonged post-HSCT thrombocytopenia (in 17 patients with PIT and 32 patients with SFPR). Response with the increment of platelet count was described in 40 out of 49 patients (ORR, 82%). Among the responders, 10 patients had PIT (ORR for PIT, 59%) and 30 patients had SFPR (ORR for SFPR, 94%). Our data show that TPO-RAs have an overall favorable response rate for both PIT and SFPR with a reasonable safety profile. However, given the lack of control groups, study heterogeneity, and the potential publication bias, these results should be interpreted with caution.