Safety and Efficacy of Romiplostim in Patients With Lower-Risk Myelodysplastic Syndrome and Thrombocytopenia

Purpose To assess the safety and efficacy of romiplostim, a peptibody that increases platelet production, for treatment of thrombocytopenic patients with myelodysplastic syndromes (MDS). Patients and Methods Eligible patients had lower-risk MDS (International Prognostic Scoring System low or intermediate 1), a mean baseline platelet count <= 50 x 10(9)/L, and were only receiving supportive care. Patients received three injections of 300, 700, 1,000, or 1,500 mu g romiplostim at weekly intervals. After evaluation of platelet response at week 4, patients could continue to receive romiplostim in a treatment extension phase for up to 1 year. Results All 44 patients who enrolled completed the treatment phase; 41 patients continued into the extension phase. Median platelet counts increased throughout the study, from fewer than 30 x 10(9)/L at baseline to 60, 73, 38, and 58 x 10(9)/L at week 4 for the 300-, 700-, 1,000-, and 1,500-mu g dose cohorts, respectively. A durable platelet response (per International Working Group 2000 criteria for 8 consecutive weeks independent of platelet transfusions) was achieved by 19 patients (46%). The incidence of bleeding events and platelet transfusions was less common among patients who achieved a durable platelet response than those who did not (4.3 v 39.3 per 100 patient-weeks). Forty-three patients (98%) reported one or more adverse events. Treatment-related serious adverse events were reported in five patients (11%), all of whom were in the 1,500-mu g dose cohort. Two patients progressed to acute myeloid leukemia during the study. No neutralizing antibodies to either romiplostim or endogenous thrombopoietin were seen. Conclusion Romiplostim appeared well-tolerated in this study and may be a useful treatment for patients with MDS and thrombocytopenia.