Rare Disease Report

FDA Green Lights Romiplostim for Pediatric Patients with Immune Thrombocytopenia

DECEMBER 14, 2018
Krista Rossi
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.
 

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