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Long-term eltrombopag shows promise for chronic immune thrombocytopenia
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Eltrombopag maintained platelet counts for up to 3 years in a cohort of patients with chronic immune thrombocytopenia, according to study results.
Low platelet counts may cause bleeding in patients with chronic immune thrombocytopenia. Prior studies have indicated that eltrombopag (Promacta, GlaxoSmithKline), a thrombopoietin-receptor (TPO-R) agonist, may have the capacity to increase and maintain hemostatic platelet counts. However, those studies have only demonstrated this effect for treatment of 6 months or less.
The current study — conducted by Mansoor N. Saleh, MD, of Georgia Cancer Specialists and colleagues — was an interim analysis of the open-label EXTEND study, which included 299 patients treated with the drug for up to 3 years.
Results indicated that 80% of splenectomized patients and 88% of non-splenectomized patients achieved platelet levels of at least 50,000/mcL at least once during therapy.
Platelet levels of at least 50,000/mcL were maintained for a median of 73 of 104 cumulative study weeks. Platelet levels twice that of baseline levels were maintained for 109 of 156 cumulative study weeks, study results showed.
Bleeding symptoms occurred in 56% of patients at baseline, decreased to 20% at 2 years and then decreased to 11% at 3 years.
At enrollment, 33% (n=100) of patients were receiving concomitant treatments. Sixty-nine of those patients attempted to reduce those treatments. Of those 69 patients, 65% demonstrated a sustained reduction or permanent cessation of one or more concomitant therapies.
Thirteen percent of patients experienced at least one adverse event that caused withdrawal from the study. Four percent experienced thromboembolic events and 2% exceeded liver enzyme thresholds, both of which were protocol-defined withdrawal criteria.
However, the researchers did not observe new safety issues or increases in previously defined safety issues.
“The data of this analysis and future data on long-term treatment with eltrombopag — including those derived from two ongoing trials in pediatric chronic ITP — will help physicians decide in which patients and when in the course of the disease to introduce TPO-R agonists in patient treatment paradigms,” Saleh and colleagues wrote. “In addition, treatment algorithms need to be derived that include the TPO-R agonists and that maximize clinical benefit while minimizing risks.”
Perspective
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James N. George, MD
Saleh and colleagues report long-term outcomes of patients with ITP treated with the thrombopoietin-receptor (TPO-R) agonist eltrombopag (Promacta, GlaxoSmithKline). Since their approval in 2008, the TPO-R agonists eltrombopag and romiplostim (Nplate, Amgen) have provided effective management for patients who have failed other treatments for ITP. Their mechanism of action is to increase marrow platelet production, which is distinct from all other treatments for ITP, which decrease the accelerated platelet destruction. The current understanding of the TPO-R agonists is that treatment is required indefinitely. Because long-term treatment is anticipated, understanding long-term risks is critical.
In the report by Saleh and colleagues, some patients had adverse events, such as cataracts, abnormal liver function or thromboembolic events. However, most patients had no adverse events. Similarly, few long-term risks have been reported for romiplostim. Therefore, for patients who fail to achieve a durable remission with corticosteroids, splenectomy and/or rituximab (Rituxan, Genentech), TPO-R agonists are an effective and relatively safe option for long-term treatment.
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