Long-term therapy with romiplostim is safe and effective in children with primary immune thrombocytopenia (ITP), and could offer benefits to some beyond the standard 6 months’ treatment, an open-label trial has concluded.
The Phase IIIb study, published in Blood Advances, assessed the safety and efficacy of romiplostim (Nplate; Amgen) in children aged between 1 and 18 years old who had had ITP for six months or more and platelet counts less than 30×109/L.
In the trial, children were give weekly subcutaneous romiplostin (1 μg/kg titrated to 10 μg/kg) to maintain platelet levels within the 50–200×109/L range. Median treatment duration was around 3 years, and median average weekly dose was 6.9 μg/kg.
Nearly half (46.8%) discontinued, with just over a fifth (21.2%) because of a lack of treatment efficacy.
With regard to efficacy, results showed that overall 88.2% of patients had a platelet response at any time during treatment. Platelet responses were achieved a median of 50.0% of the time during the first 6 months, but this increased to 78.2% for the 36-month treatment period.
A sustained response, defined as consecutive counts of at least ≥50×109/L without ITP medications for 24 weeks or more, was achieved by 5.4% of patients.
According to the data, 29.6% were given rescue medicine during the treatment, including glucocorticoids (88.3%) and immunoglobulins (73.3%), and use tended to be higher in younger patients. However, use of rescue medication fell during the first weeks of treatment and remained stable thereafter, the authors noted.
On the safety side, treatment-related adverse events (AEs) were observed in 27.6% of patients, and were serious in 3.9%. Neutralising antibodies occurred in four patients, and bleeding was recorded in 69.5% of patients, with epistaxis the most common, occurring in 39.4%.
The authors concluded that their findings suggest that long-term romiplostim use in children with ITP “is efficacious and has a good overall safety profile, confirming previous studies showing that romiplostim is an effective treatment for children with ITP for ≥6 months.”
They also noted that the median romiplostim dose required to achieve a platelet response in the study was 6.9 µg/kg, further research “is required to determine if some pediatric patients may benefit from an initial higher starting dose and how to determine who those patients are.”
Also, while it had been expected that most patients would achieve a response within the first six months of treatment, “the continued improvements in platelet responses and bleeding events seen after 6 months on treatment suggest that certain patients benefit from longer treatment,” they added