Multicenter, prospective study to evaluate the efficacy of biweekly romiplostim administration in patients with immune thrombocytopenia

Multicenter, prospective study was conducted to evaluate the efficacy of biweekly romiplostim in maintaining platelet ≥30 × 10⁹/L for at least 4 weeks. Treatment was started with a weekly injection (1 mcg/kg), and the dose was escalated until a titrated dose was achieved that maintained a platelet 50–200 × 10⁹/L for four consecutive weeks. Patients were scheduled to a biweekly schedule, and returned to a weekly schedule if platelets fell to <30 × 10⁹/L. Eighteen patients were enrolled (median platelet, 14 × 10⁹/L). After the first weekly schedule, ten of eighteen (55.6 %) attained a median titrated dose of 3 mcg/kg and proceeded to the first biweekly schedule. However, all failed to maintain a platelet ≥30 × 10⁹/L for at least 4 weeks, and returned to a second weekly schedule, where eight of the ten achieved a titrated dose (median, 5 mcg/kg) and moved to a second schedule of biweekly romiplostim. Three of the eight (37.5 %) showed platelet ≥30 × 10⁹/L for 4, 8, and 10 weeks, but all eight patients eventually experienced a drop in platelets. Lengthening the dose interval of romiplostim to greater than a week is not feasible to maintain stable platelet count.