Optimization of Romiplostim Administration in ITP Treatment
In their newly published review article, authors from several American institutions summarize findings on the role of romiplostim in the treatment of immune thrombocytopenia (ITP) and its efficacy and safety. Among other things, they provide the latest data on its early administration as early as 3 months after the onset of the disease, discuss the possibility of achieving remission without the need for further treatment, and also address practical aspects of therapy.
Immune Thrombocytopenia and Treatment Options
Immune thrombocytopenia (ITP) is an autoimmune disease caused by excessive destruction of platelets and their insufficient production. Many patients have minimal symptoms (bruising), but some experience severe bleeding, including intracranial bleeding. The goal of ITP treatment is to reduce bleeding and maintain a sufficient number of platelets to preserve hemostasis.
Therapeutic options include corticosteroids (CS), IV immunoglobulins, anti-D immunoglobulin, rituximab, thrombopoietin receptor agonists (TPO-RA: romiplostim, eltrombopag, and avatrombopag), fostamatinib, other immunosuppressants, and splenectomy. According to current recommendations, pharmacotherapy is preferable to surgical treatment for ITP persisting ≥ 3 months, and TPO-RA should be started as early as 3 months after disease onset. The guidelines also emphasize the need to limit the duration of CS administration.
Romiplostim in ITP Therapy
Romiplostim is an Fc-peptide fusion protein (peptibody) that increases platelet production by activating the TPO receptor pathway on megakaryocytes and their precursors. Like other TPO-RAs, it is recommended for patients with ITP who are dependent on CS or unresponsive to CS. Romiplostim increases platelet count in a dose-dependent manner, with an average effective weekly dose of approximately 5 μg/kg. A response can be expected within 1–3 weeks in 99% of patients, including those who have undergone splenectomy (at the same dose). About half of the patients treated with romiplostim achieve remission without the need for ongoing treatment. Predictors of this outcome include ITP duration < 1 year, lower required maximum dose of romiplostim, higher platelet count after 2 months of treatment, and prior splenectomy.
Treatment Safety
Clinical data suggest that romiplostim is appropriate for adult patients with newly diagnosed ITP and for children and adults with persistent ITP. Romiplostim treatment is not associated with an increased risk of thromboembolic events, regardless of age. The long-term safety of this drug has been evaluated in numerous studies. Neutralizing antibodies developed in 0.4% of adults and 2.5% of pediatric patients and did not exhibit cross-reactivity with endogenous TPO nor did they affect the treatment response.
Self-Injection Option
Many patients prefer self-injecting romiplostim. For properly selected adult patients with a platelet count > 50 × 109/L that remains stable for at least 4 weeks without dose adjustment, self-administration after training is associated with similar efficacy and safety as administration by healthcare professionals.
Practical Aspects of Administration
Based on the latest available data on romiplostim administration in patients with ITP lasting < 1 year, this drug is indicated for ITP treatment in adults who have shown inadequate response to previous treatment and in children over 1 year old who have had ITP diagnosed for ≥ 6 months. The dose is adjusted based on platelet count determined 1× weekly with the aim of achieving and maintaining a count of ≥ 50 × 109/L. A sudden decrease in platelet count in an otherwise stable patient should prompt comprehensive reevaluation.
Romiplostim should be discontinued if there is no increase in platelet count sufficient to prevent clinically significant bleeding after 4 weeks of the maximum dose 10 μg/kg/week. Upon gradual discontinuation of romiplostim (for any reason), platelet count should be monitored at least 1× weekly and for at least 2 weeks after stopping the drug.
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Source: Kuter D. J., Tarantino M. D., Lawrence T. Clinical overview and practical considerations for optimizing romiplostim therapy in patients with immune thrombocytopenia. Blood Rev 2021 Sep; 49: 100811, doi: 10.1016/j.blre.2021.100811.
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