The use of romiplostim in long-term treatment of immune thrombocytopenia (ITP) was shown to be effective and without new safety concerns in a 3-year trial involving children with ITP. Study results were recently published in the journal Blood Advances.
Romiplostim is a thrombopoietin receptor agonist. Long-term efficacy and safety of romiplostim in children with ITP was assessed in an open-label phase 3b trial (ClinicalTrials.gov Identifier: NCT02279173).
In this single-arm, multicenter trial, eligible patients were under 18 years of age who were at least 1 year old had been diagnosed with ITP 6 or more months prior to screening. Romiplostim was given subcutaneously, titrated up to a maximum dose of 10 mg/kg, with a goal of maintaining platelet counts within the range of 50 to 200 x 109/L.
The study had a primary endpoint of the percentage of time with platelet response (with a platelet count of ≥50 x 109/L) from weeks 2 to 24 of treatment and without ITP rescue medication for 4 weeks prior. Bone marrow evaluations were also performed in some patients.
There were 203 patients in the study who had received at least 1 dose of romiplostim, with a median age of 10.0 years. Patients received a median average weekly dose of 6.9 mg/kg of romiplostim and underwent a median treatment duration of 155.9 weeks per patient.
The rate of discontinuation was 46.8%, and this was attributed to a lack of efficacy in 21.2% of patients. Platelet response was achieved in 88.2% of patients overall at any time during the treatment period. Within the first 6 months, platelet responses were reached a median of 50.0% (interquartile range [IQR], 16.7%-83.3%) of the time during treatment.
Across the overall treatment period, this rate rose to 78.2% (IQR, 26.7%-90.4%) of the time. The mean time to onset of sustained response was 57.1 weeks, and 5.4% of patients achieved a sustained platelet response.
Rescue medication was used by 29.6% of patients during the treatment period, most commonly involving corticosteroids or immunoglobulins. Splenectomy was performed in 3 patients during the study, representing 1.6% of patients who had not undergone this procedure by the beginning of the study.
Treatment-related adverse events (AEs) were reported in 27.6% of the patient population. Serious treatment-related AEs were reported in 3.9% of patients, and these led to discontinuation in each case, with neutralizing antibody positivity being the most common among these.
There were bleeding events in 69.5% of patients, the rate of which reportedly decreased with time, and grade 3 or higher bleeding events were reported in 9.9% of patients. Increased reticulin was reported in 5 of 27 evaluable patients in year 1 and in 17 of 36 evaluable patients in year 2.
“In conclusion, the findings reported here 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,” the study investigators wrote in their report.
Disclosures: Some authors have declared affiliations with or received grant support from the pharmaceutical industry. Please refer to the original study for a full list of disclosures.
Grainger J, Bussel J, Tarantino M, et al. A single-arm, long-term efficacy and safety study of subcutaneous romiplostim in children with immune thrombocytopenia. Blood Adv. 2023;7(3):396-405. doi:10.1182/bloodadvances.2021006014