Thrombopoietic agents for the treatment of persistent and chronic immune thrombocytopenia in children.

Objectives: To determine the safety, tolerability, or efficacy of 2 licensed thrombopoietic agents in children with persistent and chronic immune thrombocytopenia (ITP).

Study Design: Retrospective analysis approved by the institutional review board of children with ITP not on-study who received thrombopoietin (TPO) therapy; 21 received romiplostim (11 at Children's Hospital of Orange County, 10 at Weill Cornell Medical Center) and 12 received eltrombopag (all at Weill Cornell Medical Center). Primary response measures were platelet counts ≥ 50 × 10(9)/L or ≥ 20 × 10(9)/L above baseline for 2 consecutive weeks and 50% of platelet counts ≥ 50 × 10(9)/L. Duration of treatment and adverse events, including bone marrow myelofibrosis (MF) consensus grades, were tabulated.

Results: Twenty-seven of 33 (82%) patients responded to TPO agents, 18 of 21 to romiplostim, and 9 of 12 to eltrombopag, after an average of 3.6 previous ITP therapies. These 27 patients had platelet counts ≥ 50 × 10(9)/L and ≥ 20 × 10(9)/L above baseline for 2 consecutive weeks; 26 had 50% of platelet counts ≥ 50 × 10(9)/L. Duration of romiplostim use ranged from 6 to 44 months (11/18 ongoing) and of eltrombopag 23 to 53 months (7/12 ongoing). One patient on eltrombopag experienced a provoked deep-vein thrombosis at site of ankle fracture. No other serious drug-related adverse events occurred. Among 24 bone marrows, 10 after greater than 2 years of therapy, 23 were normal (MF grades 0-1); 1 was MF-2.

Conclusion: Retrospective analysis of off-study use of TPO agents in children with mainly chronic ITP showed increases in platelet counts in more than 4 of 5 children. The long-term use of TPO agents, up to 53 months, without tachyphylaxis supports their efficacy. These agents appear safe, effective, and tolerable in children with chronic ITP.