Subcutaneous romiplostim leads to favorable long-term platelet response rates among children with immune thrombocytopenic purpura (ITP), according to a poster presentation at the 23rd Congress of the European Hematology Association (EHA).

For these phase 1/2 and 3 studies, 203 children with ITP who had received romiplostim 1 to 10 μg/kg subcutaneously for 3 years or less were evaluated. Eligible patients had a median age of 10 years, received ITP diagnosis at least 6 months prior, were previously treated for ITP, and had screening platelet counts of 30×109/L or lower or uncontrolled bleeding. Bone marrow biopsies were evaluated at baseline and at 1 or 2 years, and/or at the end of treatment.

Interim data showed that after a median treatment duration of 53 weeks, the median percentage of time with a platelet response — defined as a platelet count of at least 50×109/L and no use of any rescue medications in the past 4 weeks — in the first 6 months was 50%. The platelet response rate was 88% over the course of the study, and median platelet counts exceeded 50×109/L starting from week 12.

The median average weekly dose throughout the study was 6.9 μg/kg, with median weekly doses of 9.0 μg/kg and 10.0 μg/kg at 1 and 2 years, respectively.

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Overall, 64 patients discontinued therapy; the most common causes were lack of efficacy (38), patient request (7), and adverse events (AEs; 7).

Forty-one (20%) patients had serious AEs, including epistaxis (5% of patients) and decreased platelet counts (3% of patients). Other treatment-related AEs included headaches, abdominal pain, presyncope, and neutralizing antibodies. Grade 3 or worse bleeding was observed in 8% of patients, and 2 patients had grade 4 bleeding events.

Reference

Grainger J, Bussel J, Tarantino M, et al. A single-arm, open-label, long-term efficacy and safety study of subcutaneous (SC) romiplostim in children with immune thrombocytopenia (ITP). Poster presentation at: 23rd Congress of EHA; June 14-17, 2018; Stockholm, Sweden.