Model-based assessment of pharmacokinetic changes of sunitinib, tacrolimus, and everolimus in a patient with metastatic renal cell carcinoma after renal transplantation

Abstract The safety of the coadministration of sunitinib with tacrolimus and everolimus with regard to therapeutic drug monitoring has not been demonstrated. Here, we report a patient who showed high sunitinib concentrations, in addition to pharmacokinetic changes in tacrolimus and everolimus after sunitinib therapy. A living-donor renal transplant patient treated with tacrolimus and everolimus was diagnosed with pulmonary and pleural metastases of renal cell carcinoma. The patient received sunitinib therapy (37.5 mg/day, 2 weeks on and 1 week off). This patient exhibited a high total sunitinib concentration (sunitinib, 105.8 ng/mL; N-desethyl sunitinib, 27.9 ng/mL) on day 10 postinitiation and experienced grade 3 diarrhea. The observed sunitinib concentrations were a little higher than those reported in the 421C>A polymorphism of the ATP-binding cassette subfamily G member 2 gene carrier. The observed concentrations of both tacrolimus and everolimus gradually decreased compared with the Bayesian-predicted values after the onset of sunitinib therapy, and the doses of tacrolimus and everolimus were increased. Careful therapeutic drug monitoring of sunitinib, tacrolimus, and everolimus concentrations is necessary during combination therapy, especially after episodes of diarrhea.