On December 14, 2018, the U.S. Food and Drug Administration (FDA) approved romiplostim (Nplate) for pediatric patients one year of age and older with immune thrombocytopenia (ITP) for at least six months who have had an insufficient response to corticosteroids, immunoglobulins, or splenectomy.
Approval was based on two double-blind, placebo-controlled clinical trials in pediatric patients one year and older with ITP for at least six months duration. In one study (NCT01444417), patients whose disease was refractory or relapsed after at least one prior ITP therapy were randomized (2:1) to receive romiplostim (n=42) or placebo (n=20). Durable platelet response (at least six weekly platelet counts ≥ 50 × 109/L during weeks 18 through 25 of treatment) was achieved in 22 patients (52%) who received romiplostim and two (10%) on the placebo arm.
Overall platelet response, defined as a durable or a transient platelet response, was achieved in 30 (71%) and four (20%) patients, respectively. Patients who received romiplostim had platelet counts ≥ 50 x 109/L for a median of 12 weeks, compared to one week in patients who received placebo. The results for all three endpoints were statistically significant, with p-values all less than 0.05.
In the other study (NCT00515203), patients diagnosed with ITP at least six months prior to enrollment were randomized (3:1) to receive romiplostim (n=17) or placebo (n=5). Fifteen patients who received romiplostim achieved a platelet count ≥ 50 x 109/L for two consecutive weeks and an increase in platelet count of ≥ 20 × 109/L above baseline for two consecutive weeks during the treatment period (88%, 95% CI: 64%, 99%). No patient receiving placebo achieved either endpoint.
In pediatric patients, the most common adverse reactions (≥ 25%) include contusion, upper respiratory tract infection, and oropharyngeal pain.
The recommended initial romiplostim dose for pediatric patients is one mcg/kg based on actual body weight and administered as a weekly subcutaneous injection. Dose should be adjusted in increments of one mcg/kg until the patient achieves a platelet count ≥ 50 x 109/L. Reassessment of body weight is recommended every 12 weeks.
FDA granted this application orphan product designation. A description of FDA expedited programs is in the Guidance for Industry: Expedited Programs for Serious Conditions-Drugs and Biologics.
Healthcare professionals should report all serious adverse events suspected to be associated with the use of any medicine and device to FDA’s MedWatch Reporting System or by calling 1-800-FDA-1088.
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