Romiplostim treatment for children with immune thrombocytopenia: Results of an integrated database of five clinical trials.

ABSTRACT

BACKGROUND: Treatment for chronic immune thrombocytopenia (cITP) in children is largely limited to immunosuppressive agents. Thrombopoietin receptor agonists (TRAs) have been used to treat cITP in adults for over a decade. The objective of this integrated analysis was to examine the safety and efficacy of the TRA romiplostim in children with ITP. METHODS: We examined efficacy and safety in children with ITP across five romiplostim trials final data from two double-blind placebo-controlled trials and two open-label extensions, and interim data from an ongoing single-arm trial. RESULTS: Patients (n = 24 initially placebo; n = 262 initially romiplostim) had a median age of 10.0 years (Q1 6.0, Q3 13.0), ITP duration of 1.9 years (Q1 1.0, Q3 4.0), and baseline platelet count of 14.3 × 109 /L (Q1 7.5, Q3 23.0). Among 282 patients receiving romiplostim, median treatment duration was 65 weeks (range 8-471 weeks) and median weekly dose was 6.6 µg/kg (range 0.1-9.7 µg/kg). Overall, 89% of romiplostim-treated patients had platelet responses. Nineteen patients (7%) maintained treatment-free responses for ≥6 months while withholding all ITP therapy. Grade 3 and 4 adverse events of bleeding occurred in 10% and <1% of romiplostim-treated patients, respectively. Twenty-five percent of patients had a serious adverse event, most commonly epistaxis (6%). Seven patients (2%) had neutralizing antibodies against romiplostim postbaseline and none had neutralizing antibodies against endogenous thrombopoietin. Efficacy and safety results appeared similar between children with ITP for ≤12 months and >12 months at baseline. CONCLUSIONS: Across five pediatric clinical trials, romiplostim was well tolerated. Most patients had a platelet response; some maintained responses for at least 6 months while withholding all ITP therapy.