Eltrombopag and romiplostim are thrombopoietin receptor agonists (TPO-RAs) marketed for immune thrombocytopenia (ITP). Thrombotic events have been reported with both drugs. This study was aimed at assessing whether there is a signal for differential risks of thrombosis between these two TPO-RAs.

We carried out a disproportionality analysis in the World Health Organization global individual case safety report (ICSR) database (VigiBase(®)). We selected all ICSRs with exposure to a TPO-RA between January 2011 and December 2014. We searched for exposures to eltrombopag or romiplostim in thrombosis reports as compared with other ICSRs, and we calculated adjusted reporting odds ratios (aRORs).

We identified 5850 ICSRs, including 764 cases of thrombosis. In multivariate analyses, there was a signal for an increased risk of thrombosis (venous or arterial; aROR 1.72, 95 % confidence interval [CI] 1.47-2.02), venous thrombosis (aROR 1.88, 95 % CI 1.53-2.31), arterial thrombosis (aROR 1.54, 95 % CI 1.18-2.00), ischaemic stroke (aROR 1.65, 95 % CI 1.13-2.42) and myocardial infarction (aROR 1.50, 95 % CI 1.05-2.13) with eltrombopag as compared with romiplostim. Restriction to ICSRs reported by physicians led to similar results. However, worldwide dispensing data for romiplostim and eltrombopag were not accessible, so the rates of thrombosis with both drugs were not normalized by the daily defined doses and the generalizability of the results is limited.

This study suggests the presence of a signal for an increased risk of thrombosis with eltrombopag compared with romiplostim. These results must be confirmed and quantified by large aetiological pharmacoepidemiological studies.