Treatment of Essential Thrombocythemia with Anagrelide Is Associated with an Increased Risk of Worsened Kidney Function

Background and Purpose: When choosing a cytoreduction method for patients suffering from essential thrombocythemia (ET), it is important to know the safety profile of the medicine used. Few articles have been published about the effects of hydroxycarbamide (hydroxyurea, HU) and anagrelide (ANA) on renal function in ET patients. This study is the largest analysis of nephrotoxicity of cytoreductive drugs used in ET therapy so far, which additionally includes risk factors for the progression of kidney disease and coexisting genetic mutation. Experimental Approach: The retrospective study included 310 patients diagnosed with ET. Demographic data, comorbidities, Cr, and estimated glomerular filtration rate (eGFR) were all taken into account prior to diagnosis and after 6 months of HU and ANA treatment. Key Results: A statistically significant difference was found between Cr and eGFR levels at baseline and after 6 months of treatment (p < 0.001). The applied treatment (HU and ANA) had the greatest impact on kidney function. ANA significantly increased the risk of worsening renal function in contrary to hydroxycarbamide after 6 months of treatment (eGFR change: median +1 mL/min/1.73 m2 [interquartile range (IQR) (−4)–(+7)] in the HU group vss. median −13 mL/min/1.73 m2 [IQR (−18)–(−6)] in the ANA group, odds ratio [OR] 7.92 95% confidence interval [95% CI] [4.17–15.08], p < 0.001). Lowering of eGFR 2 occurred in 31 patients (31.0%) from the ANA group and 10 people (4.8%) treated with HU (p = 0.000). In 1 patient from the ANA group, >50% decrease in eGFR was observed. The chance for an increase in Cr levels was higher in people with pre-existing arterial hypertension (OR 1.92 CI = 95% [1.21–3.05], p = 0.006). Sex, type of mutation found (JAK2 V617F or CALR), and previous renal impairment did not affect renal function after 6 months of treatment. In addition, there was no difference in the efficacy of ET treatment between HU and ANA (p = 0.998). Conclusions and Implications: The observations indicate that ANA should be used in patients with ET with great caution and taking into account the risk of worsened kidney function.