The US Food and Drug Administration (FDA) has approved romiplostim (NPLATE, Amgen Inc) for the treatment of pediatric patients aged 1 year and older with immune thrombocytopenia (ITP) for a minimum of 6 months and who have had an insufficient response to corticosteroids, immunoglobulins, or splenectomy.
Two double-blind placebo-controlled clinical trials served as the basis for the approval.
One study (NCT01444417) included patients with refractory or relapsed disease who were administered at least 1 prior ITP therapy. Participants were randomized (2:1) to be administered romiplostim (n=42) or placebo (n=20). On the placebo arm, 22 patients (52%) who were administered romiplostim and 2 (10%) achieved durable platelet response (at least 6 weekly platelet counts ≥ 50 × 109/L during weeks 18 through 25 of treatment).
Defined as a durable or a transient platelet response, overall response rate was achieved in 30 (71%) and 4 (20%) patients, respectively. Compared to 1 week in patients who received placebo, patients who were administered romiplostim had platelet counts ≥ 50 x 109/L for a median of 12 weeks. With p-values all less than .05, all 3 endpoints reflected statistically significant results.
Another study included patients diagnosed with ITP at least 6 months prior to enrollment. Participants were randomized (3:1) to be administered romiplostim (n=17) or placebo (n=5). During the treatment period, 15 patients who were administered romiplostim achieved a platelet count ≥ 50 x 109/L for 2 consecutive weeks and an increase in platelet count of ≥ 20 × 109/L above baseline for 2 consecutive weeks. The endpoint was not achieved by any patient.
Contusion, upper respiratory tract infection, and oropharyngeal pain included the most common adverse reactions (≥ 25%) in pediatric patients.
Romiplostim is recommended to be administered as a weekly subcutaneous injection based on actual body weight (1 mcg/kg). Until the patient achieves a platelet count ≥ 50 x 109/L, the dose should be adjusted in increments of 1 mcg/kg. Twelve weeks is the recommended time for a reassessment of body weight.
Immune thrombocytopenia is a rare bleeding disorder in which the blood platelets are mistakenly attacked by the body’s immune system. Pediatric patients can develop ITP following viral infections in some cases.