Open-Label, Pilot Study of Romiplostim for Thrombocytopenia After Autologous Hematopoietic Cell Transplantation.

There are no standard treatments to prevent or hasten the recovery from severe conditioning-regimen-induced thrombocytopenia occurring after autologous hematopoietic cell transplantation (autoHCT). We conducted an open-label, single-arm pilot study of romiplostim, a thrombopoietin receptor agonist, to enhance platelet recovery in patients with multiple myeloma or lymphoma undergoing autoHCT. All patients were treated with weekly romiplostim starting day +1 after autoHCT until the platelet count was >50 x 109/L without transfusion. Compared to contemporary retrospective data from romiplostim-naïve patients (N=853), romiplostim-treated patients (N=59) had a similar median number of days of grade 4 thrombocytopenia or days requiring transfusions, time to platelet engraftment, and number of platelets transfusions during the autoHCT. However, romiplostim-treated patients had enhanced platelet recovery to normal values beginning at about day +15. In matched cohort multivariable analyses, romiplostim treatment was associated with a higher platelet count by an average of 40 x 109/L [95% CI (14, 67), P=0.003] and 118 x 109/L [95% CI (84, 152), P<0.001] at days +21 and +30, respectively, compared to no romiplostim. Only 1 adverse event was deemed possibly attributable to romiplostim, a low-risk pulmonary embolism in a patient with multiple myeloma. In conclusion, romiplostim showed promising activity and safety after autoHCT, but the improvement in platelet counts occurred later than the goal of shortening the duration and depth of the platelet nadir. This trial was registered at www.clinicaltrials.gov (NCT04478123).