Long-term use of the thrombopoietin-mimetic romiplostim in children with severe chronic immune thrombocytopenia (ITP).

Bussel JB, Hsieh L, Buchanan GR, Stine K, Kalpatthi R, Gnarra DJ, Ho RH, Nie K, Eisen M
Pediatr Blood Cancer. 2015 62 (2): 208-213

PMID: 25345874 · PMCID: PMC4309514 · DOI:10.1002/pbc.25136

BACKGROUND - Treatment of chronic severe pediatric ITP is not well studied. In a phase 1/2 12-16-week study, 15/17 romiplostim-treated patients achieved platelet counts ≥50 × 10 /L, and romiplostim treatment was well tolerated. In a subsequent open-label extension (≤109 weeks), 20/22 patients received romiplostim; all achieved platelet counts >50 × 10 /L. Twelve patients continued in a second extension (≤127 weeks). Longitudinal data from start of romiplostim treatment through the two extensions were evaluated to investigate the safety and efficacy of long-term romiplostim treatment in chronic severe pediatric ITP.

PROCEDURE - Patients received weekly subcutaneous romiplostim, adjusted by 1 µg/kg/week to maintain platelet counts (50-200 × 10 /L, maximum dose 10 µg/kg). Bone marrow examinations were not required.

RESULTS - At baseline, patients were median age 10.0 years; median ITP duration 2.4 years; median platelet count 13 × 10 /L; 73% were male; and 36% had prior splenectomy. Median romiplostim treatment duration was 167 weeks (Q1, Q3: 78,227 weeks), and median average weekly dose was 5.4 µg/kg (Q1, Q3: 4.3, 8.0 µg/kg). Seven patients discontinued treatment: four withdrew consent, two were noncompliant, and one received alternative therapy. None withdrew because of adverse events (AEs). After the first 12 weeks, median platelet counts remained >50 × 10 /L. Eight (36.4%) patients received rescue medication, and 14 (63.6%) used concurrent ITP therapy. Seven patients (31.8%) reported serious AEs, and two (9.1%) reported life-threatening AEs (both thrombocytopenia); there were no serious AEs attributed to treatment and no fatalities.

CONCLUSIONS - Long-term romiplostim treatment in this small cohort increased and maintained platelet counts for over 4 years in children with ITP with good tolerability and without significant toxicity. Pediatr Blood Cancer 2015;62:208-213. © 2014. The Authors. Pediatr Blood & Cancer published by Wiley Periodicals, Inc.

© 2014 The Authors. Pediatric Blood & Cancer published by Wiley Periodicals, Inc.

MeSH Terms (17)

Adolescent Blood Platelets Child Child, Preschool Chronic Disease Female Humans Infant Longitudinal Studies Male Platelet Count Purpura, Thrombocytopenic, Idiopathic Receptors, Fc Receptors, Thrombopoietin Recombinant Fusion Proteins Thrombopoietin Treatment Outcome

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