Romiplostim brings benefit also to patients with ITP lasting less than 1 year
What is the role of second-line therapy, in this case romiplostim, in the management of adult ITP patients who have not yet reached the chronic phase of the disease?
Romiplostim in the treatment of ITP
The thrombopoietin receptor agonist romiplostim (TPO-RA) has been approved in patients with chronic immune thrombocytopenia (ITP) as a second-line treatment. First-line treatment involves corticosteroids with adjunctive therapy with intravenous immunoglobulins. To assess the benefit of romiplostim in patients with ITP lasting less than 1 year ("non-chronic" ITP), additional data were needed. This data was provided by a pooled analysis of 9 clinical studies conducted from 2002–2014.
Analysis methodology
The pooled analysis includes patients treated for ITP for less than 1 year (n = 311) or patients with chronic ITP (n = 726), in whom the first-line treatment failed and who subsequently received romiplostim (277 patients with disease duration ≤ 1 year; 634 patients with chronic ITP) or placebo or standard of care (n = 34 with disease duration ≤ 1 year; 92 with chronic ITP).
Platelet response was defined as achieving a platelet count of ≥ 50 × 109/l, excluding the 8-week period post-rescue medication administration. Rescue medication was administered to patients on romiplostim per the investigator's decision for the treatment or prevention of bleeding.
Sub-analysis by ITP duration
In the sub-analysis by ITP duration, it was shown that the incidence of platelet response in ≥ 75% of measurements was higher for romiplostim (in ITP duration < 1 year in 74% and in chronic ITP in 71% of participants) compared to placebo or standard of care (ITP duration < 1 year in 18% and in chronic ITP in 9% of patients).
Possibility of achieving ITP remission without further treatment
In patients followed for ≥ 9 months, it was documented that 16% of patients in the ITP ≤ 1 year group were able to discontinue romiplostim treatment and maintain platelet counts ≥ 50 × 109/l for ≥ 6 months without further treatment (so-called TFR – treatment-free remission). From the chronic ITP patients, 6% achieved remission without the need for treatment.
Risks of adverse effects
Regardless of ITP duration, a lower risk of serious adverse effects associated with romiplostim treatment compared to placebo/standard of care was documented. The incidence of serious adverse events in patients with an ITP duration ≤ 1 year was 51 vs. 90 events per 100 patient-years in the romiplostim group vs. placebo/standard care. In chronic ITP, a similar trend was observed (56 vs. 99 events/100 patient-years). The rate of thrombotic events was comparable in both arms.
Conclusion
This analysis demonstrated a similar safety profile of romiplostim compared to placebo/standard of care. On the other hand, treatment with romiplostim led to an increase in platelet counts in patients with both "non-chronic" ITP and chronic ITP. Additionally, a higher number of patients achieved ITP remission without the need for further treatment when they used romiplostim in the ITP indication for less than 1 year.
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Source: Kuter D. J., Newland A., Chong B. H. et al. Romiplostim in adult patients with newly diagnosed or persistent immune thrombocytopenia (ITP) for up to 1 year and in those with chronic ITP for more than 1 year: a subgroup analysis of integrated data from completed romiplostim studies. Br J Haematol 2019; 185 (3): 503–513, doi: 10.1111/bjh.15803.
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