Pharmacogenomic Markers of Targeted Therapy Toxicity in Patients with Metastatic Renal Cell Carcinoma

Background: Targeted therapy (TT) in metastatic renal cell carcinoma (mRCC) may be associated with a high rate of toxicity that undermines treatment efficacy and patient quality of life. Polymorphisms in genes involved in the pharmacokinetic pathways of TTs may predict toxicity.

Objective: To investigate whether selected single-nucleotide polymorphisms (SNPs) in three core genes involved in the metabolism and transport of sunitinib and the mTOR inhibitors everolimus and temsirolimus are associated with adverse events (AEs).

Design, setting, and participants: Germline DNA was extracted from blood or normal kidney tissue from mRCC patients of Caucasian ethnicity in two cohorts treated with either sunitinib (n=159) or mTOR inhibitors (n=62). Six SNPs in three candidate genes (CYP3A4: rs2242480, rs4646437, and rs2246709; CYP3A5: rs15524; and ABCB1: rs2032582 and rs1045642) were analyzed.

Outcome measurements and statistical analysis: Primary endpoints were grade ≥3 AEs for all patients; grade ≥3 hypertension in the sunitinib cohort, and any grade pneumonitis in the mTOR inhibitors cohort. A logistic regression model was used to assess the association between SNPs and AEs, with adjustment for relevant clinical factors.

Results and limitations: In total, 221 samples were successfully genotyped for the selected SNPs. In the sunitinib cohort, the CYP3A4 rs464637 AG variant was associated with a lower risk of high-grade AEs (odds ratio 0.27, 95% confidence interval 0.08-0.88; p=0.03), but no SNPs were associated with hypertension. In the mTOR inhibitor cohort, none of the selected SNPs was associated with analyzed toxicities.

Conclusions: We observed an association between CYP3A4 polymorphisms and toxicity outcomes in mRCC patients treated with sunitinib, but not with everolimus or temsirolimus. Our findings are exploratory in nature, and further validation in independent and larger cohorts is needed.

Patient summary: We found that variants of CYP3A4, a gene involved in drug metabolism, are associated with sunitinib toxicity. This information may help in better selection of patients for targeted therapies in metastatic renal cell carcinoma.