After frontline treatment with corticosteroids fails to elicit a response in patients with chronic immune thrombocytopenia (cITP), the choice between rituximab or thrombopoietin receptor agonists (TPO-RAs) is unclear. In a study presented at the 2019 ASH Annual Meeting, lead investigator Natalia Ruiz-Negrón, PharmD, from the University of Utah in Salt Lake City, and researchers attempted to provide guidance in this decision, comparing outcomes after rituximab or TPO-RA treatment in more than 30,000 U.S. veterans diagnosed with cITP.
The investigators conducted a historical cohort study using data from the U.S. Veteran’s Health Administration to identify 31,501 veterans (mean age = 67.9 years) diagnosed with cITP.
Between 2011 and 2017, a total of 244 patients began treatment with a TPO-RA and 185 began treatment with rituximab after failure of corticosteroids. There were “no significant differences between the groups among all baseline characteristics,” including platelet measures, comorbidities, and concomitant medications, the researchers reported.
Overall, patients who received TPO-RAs were 27% less likely to have long-term complications with treatment (i.e., infections, thromboembolic events, and cancer), excluding death, compared with those who received rituximab (hazard ratio [HR] = 0.73; 95% CI 0.62-0.85; p<0.001). As seen in the TABLE, rituximab-treated patients had a significantly higher risk of developing pneumonia, septicemia, deep vein thrombosis, pulmonary embolism, and myocardial infarction. However, the risk of death did not differ significantly between the treatment groups (HR=1.00; 95% CI 0.81-1.24; p=0.969).
While these findings suggest that TPO-RAs have a lower risk of complications than rituximab, the implications of these data are limited by the lack of information about avatrombopag, another TPO-RA approved for cITP, which was approved by the U.S. Food and Drug Administration in June 2019. In addition, the study population was overwhelmingly male (93%), so it is unclear if these results are applicable to women with cITP.
Study authors report relationships with Novartis, the manufacturer of eltrombopag.
|TABLE. Adjusted Risks of Complications and Mortality Outcomes in cITP-Diagnosed U.S. Veterans Receiving TPO-RAs or Rituximab|
|Complications||TPO-RA vs. Rituximab|
|Adjusted HR (95% CI)||p Value|
|Any complication (excluding death)||0.73 (0.62-0.85)||<0.001|
|Any thromboembolic event||0.61 (0.48-0.78)||<0.001|
|Any cancer||0.86 (0.69-1.06)||0.158|
|cITP = chronic immune thrombocytopenia; TPO-RAs = thrombopoietin receptor agonists; HR = hazard ratio; DVT = deep vein thrombosis; PE = pulmonary embolism; MI = myocardial infarction|