A novel recombinant human thrombopoietin for treating prolonged isolated thrombocytopenia after allogeneic stem cell transplantation

Patients with prolonged isolated thrombocytopenia (PT) after allogeneic stem cell transplantation (allo-SCT) are known to have a poor prognosis. However, there is no standard treatment for PT. The present study aimed to investigate the potential effect of a novel recombinant human thrombopoietin (rhTPO) in a cohort of patients with PT following allo-SCT. A total of 24 patients with PT (including delayed platelet engraftment and secondary failure of platelet recovery) were treated with rhTPO from July 1, 2016 to May 31, 2017. rhTPO injections were administered at 300 IU/kg/d for 28 consecutive days or until platelet counts were ≥ 50 × 10⁹/L, independent of platelet transfusion. Response was defined as platelet recovery to ≥ 20 × 10⁹/L for seven consecutive days without transfusion support during or within 7 days of the end of rhTPO treatment. All patients completed the 28 days of treatment, and none were withdrawn due to adverse effects. The overall response was 45.8%, which was significantly higher than historical data (12.2%, p < 0.001). The median response time was 12 (7–25) days from the initiation of rhTPO treatment. A response to rhTPO was associated with megakaryocytes in the bone marrow (positive vs. negative, 81.8 vs. 22.2%; p = 0.022). Among 11 patients exhibiting a response to rhTPO, the median number of megakaryocytes in bone marrow was increased significantly (10 vs. 2; p = 0.036) after rhTPO treatment. In conclusion, the results of this preliminary study suggest that rhTPO may represent a therapeutic option, with a response of 45.8% for patients with PT after allo-SCT, and especially for those with megakaryocytes in the bone marrow. However, this should be further confirmed in randomized prospective clinical trials.