The Food and Drug Administration has approved romiplostim (Nplate) for pediatric patients aged 1 year and older who have had immune thrombocytopenia (ITP) for at least 6 months and have had an insufficient response to corticosteroids, immunoglobulins, or splenectomy.
The FDA based the approval on two trials in pediatric patients 1 year and older with ITP for at least 6 months duration.
In the first trial, 62 patients were randomized 2:1 to receive romiplostim or placebo; differences in durable platelet response, overall platelet response, and duration of response were all statistically significant, with P values less than .05.
Durable platelet response (at least 6 weekly platelet counts greater than or equal to 50 × 109/L during weeks 18 through 25 of treatment) was achieved in 22 patients (52%) who received romiplostim and 2 (10%) who received placebo. Overall platelet response was achieved in 30 (71%) and 4 (20%) patients, respectively. Patients who received romiplostim had platelet counts greater than or equal to 50 x 109/L for a median of 12 weeks, compared with 1 week in patients who received placebo, the FDA said in a.
In the second randomized trial, 22 patients were randomized 3:1 to receive romiplostim or placebo; 15 patients in the romiplostim arm achieved a platelet count greater than or equal to 50 x 109/L for 2 consecutive weeks and an increase in platelet count of greater than or equal to 20 × 109/L above baseline for 2 consecutive weeks during the treatment period (88%; 95% confidence interval, 64%-99%), compared with 0 patients in the placebo arm.
The most common adverse reactions observed in children receiving romiplostim include contusion, upper respiratory tract infection, and oropharyngeal pain.
The recommended initial romiplostim dose for pediatric patients is 1 mcg/kg based on actual body weight and administered as a weekly subcutaneous injection. Dose should be adjusted in increments of 1 mcg/kg until the patient achieves a platelet count greater than or equal to 50 x 109/L. Body weight should be reassessed every 12 weeks, according to the FDA announcement.