Personalizing Anti-Cancer Treatment from Genetic and Pharmacokinetic Perspective

Only recently, systemic anti-cancer treatment consisted of little more than chemotherapy, targeting mitosis in rapidly dividing cells such as cancer cells. Increasing biological insight has led to the development of more biology driven treatments, e.g. tyrosine kinase inhibitors and hormonal therapies. Still, not all patients benefit from anti-cancer treatment. This thesis comprises studies that aimed to personalize anti-cancer treatment based on intratumoral genetics and on pharmacokinetics of tyrosine kinase inhibitors

Individualization of Irinotecan Treatment: A Review of Pharmacokinetics, Pharmacodynamics, and Pharmacogenetics

Since its clinical introduction in 1998, the topoisomerase I inhibitor irinotecan has been widely used in the treatment of solid tumors, including colorectal, pancreatic, and lung cancer. Irinotecan therapy is characterized by several dose-limiting toxicities and large interindividual pharmacokinetic variability. Irinotecan has a highly complex metabolism, including hydrolyzation by carboxylesterases to its active metabolite SN-38, which is 100- to 1000-fold more active compared with irinotecan itself. Several phase I and II enzymes, including cytochrome P450 (CYP) 3A4 and uridine diphosphate glucuronosyltransferase (UGT) 1A, are involved in the formation of inactive metabolites, making its metabolism prone to environmental and genetic influences. Genetic variants in the DNA of these enzymes and transporters coul

Prospective Analysis in GIST Patients on the Role of Alpha-1 Acid Glycoprotein in Imatinib Exposure

Background: For imatinib, a relationship between systemic exposure and clinical outcome has been suggested. Importantly, imatinib concentrations are not stable and decrease over time, for which several mechanisms have been suggested. In this study, we investigated if a decrease in alpha-1 acid glycoprotein (AGP) is the main cause of the lowering in imatinib exposure over time. Methods: We prospectively measured imatinib trough concentration (Cmin) values in 28 patients with gastrointestinal stromal tumours, at 1, 3 and 12 months after the start of imatinib treatment. At the same time points, AGP levels were measured. Results: Overall, imatinib Cmin and AGP levels were correlated (r2 = 0.656; P < 0.001). However, AGP levels did not fluctuate significantly over time, nor did the change in AGP levels correlate with the change in the imatinib Cmin. Conclusion: We showed that systemic AGP levels are not likely to be a key player in the decrease in systemic imatinib exposure over time. As long as intra-individual changes in imatinib exposure remain unexplained, researchers should standardize the sampling times for imatinib in order to be able to assess the clinical applicability of therapeutic drug monitoring

The influence of single-nucleotide polymorphisms on overall survival and toxicity in cabazitaxel-treated patients with metastatic castration-resistant prostate cancer

Purpose: Cabazitaxel, used in patients with metastatic castration-resistant prostate cancer (mCRPC), is associated with adverse events which may require dose reductions or discontinuation of treatment. We investigated the potential association of single-nucleotide polymorphisms (SNPs) in genes encoding drug transporters and drug-metabolizing enzymes with cabazitaxel toxicity, overall survival (OS) and pharmacokinetics (PK). Methods: A total of 128 cabazitaxel-treated mCRPC patients, of whom prospectively collected data on toxicity and OS were available and 24 mCRPC patients with available cabazitaxel PK measurements, were genotyped using genomic DNA obtained from EDTA blood. The SLCO1B1 (388A > G; *1B; rs2306283 and 521 T > C; *5; rs4149056 and haplotype SLCO1B1*15), SLCO1B3 (334 T > G; rs4149117), CYP3A4 (*22; rs35599367), CYP3A5 (*3; rs776746), ABCB1 (3435C > T; rs1045642), and TUBB1 (57 + 87A > C; rs463312) SNPs were tested for their association with clinical and PK parameters by univariate/multivariate logistic regression, log-rank test, or Kruskal–Wallis test. Results: The SLCO1B1*15 haplotype was significantly associated with a lower incidence of leukopenia and neutropenia (p = 0.020 and p = 0.028, respectively). Patients harboring a homozygous variant for SLCO1B1*1B experienced higher rate ≥ grade 3 (p = 0.042). None of the SNPs were associated with pharmacokinetics or OS. Conclusions: In this study, SLCO1B1 (SLCO1B1*15 and SLCO1B1*1B) was associated with cabazitaxel-induced adverse events in mCRPC patients. As the associations were opposite to previous studies in other drugs and contradicted an underlying pharmacokinetic rationale, these findings are likely to be false-positive and would ideally be validated with even larger (pharmacokinetic) cohorts

Influence of OATP1B1 Function on the Disposition of Sorafenib-β-D-Glucuronide

The oral multikinase inhibitor sorafenib undergoes extensive UGT1A9-mediated formation of sorafenib-β-D-glucuronide (SG). Using transporter-deficient mouse models, it was previously established that SG can be extruded into bile by ABCC2 or follow a liver-to-blood shuttling loop via ABCC3-mediated efflux into the systemic circulation, and subsequent uptake in neighboring hepatocytes by OATP1B-type transporters. Here we evaluated the possibility that this unusual process, called hepatocyte hopping, is also operational in humans and can be modulated through pharmacological inhibition. We found that SG transport by OATP1B1 or murine Oatp1b2 was effectively inhibited by rifampin, and that this agent can significantly increase plasma levels of SG in wildtype mice, but not in Oatp1b2-deficient animals. In human subjects receiving sorafenib, rifampin acutely increased the systemic exposure to SG. Our study emphasizes the need to consider hepatic handling of xenobiotic glucuronides in the design of drug-drug interaction studies of agents that undergo extensive phase II conjugation

Influence of genetic variation in COMT on cisplatin-induced nephrotoxicity in cancer patients

Cisplatin is a chemotherapeutic agent widely used for multiple indications. Unfortunately, in a substantial set of patients treated with cisplatin, dose-limiting acute kidney injury (AKI) occurs. Here, we assessed the association of 3 catechol-O-methyltransferase (COMT) single nucleotide polymorphisms (SNPs) with increased cisplatin-induced nephrotoxicity. In total, 551 patients were genotyped for the 1947 G>A (Val158Met, rs4680), c.615 + 310 C>T (rs4646316), and c.616 – 367 C>T (rs9332377) polymorphisms. Associations between these variants and AKI grade ≥3 were studied. The presence of a homozygous variant of c.616-367C>T was associated with a decreased occurrence of AKI grade 3 toxicity (p = 0.014, odds ratio (OR) 0.201, 95% confidence interval (CI) (0.047–0.861)). However, we could not exclude the role of dehydration as a potential cause of AKI in 25 of the 27 patients with AKI grade 3, which potentially affected the results substantially. As a result of the low incidence of AKI grade 3 in this dataset, the lack of patients with a COMT variant, and the high number of patients with dehydration, the association between COMT variants and AKI does not seem clinically relevant

Granzyme B is correlated with clinical outcome after PD-1 blockade in patients with stage IV non-small-cell lung cancer

BACKGROUND: A minority of patients with advanced non-small-cell lung cancer (NSCLC) benefit from treatment with immune checkpoint inhibitors (ICIs). Ineffective effector function of activated T and NK cells may lead to reduced tumor cell death, even when these activated effector cells are released from their immune checkpoint brake. Hence, in this study we aimed to assess the association of baseline serum granzyme B, as well as germline variation of the GZMB gene, with clinical outcome to programmed cell death protein 1 (PD-1) blockade. METHODS: A total of 347 patients with stage IV NSCLC who started nivolumab treatment between June 2013 and June 2017 were prospectively included. Baseline serum and whole blood was available, allowing for protein quantification and targeted DNA sequencing. Clinical outcome was based on best overall response (BOR) according to Response Evaluation Criteria in Solid Tumors, V.1.1, progression-free survival (PFS), and overall survival (OS). RESULTS: Patients with low serum levels of granzyme B had worse PFS (HR: 1.96; 95% CI: 1.12 to 3.43; p=0.018) and worse OS (HR: 2.08; 95% CI: 1.12 to 3.87; p=0.021) than patients with high baseline serum levels. To validate the findings, germline variation of GZMB rs8192917 was assessed. Patients with homozygous and heterozygous variants of GZMB rs8192917 had worse BOR (OR: 1.60; 95% CI: 1.01 to 2.52; p=0.044) and worse PFS (HR: 1.38; 95% CI:1.02 to 1.87; p=0.036) than wild types. CONCLUSIONS: A low baseline serum level of granzyme B and germline variation of GZMB was associated with worse clinical outcome in NSCLC, emphasizing the relevance and additional value of monitoring germline genetic variations which mirror cytotoxic functions of T cells in ICI therapy. TRAIL REGISTRATION NUMBER: Dutch Trial Registry (NL6828)

Prognostic factors in men with metastatic castration-resistant prostate cancer treated with cabazitaxel

Background: Treatment selection for men with metastatic castration-resistant prostate cancer (mCRPC) has become increasingly challenging with the introduction of novel therapies at earlier disease stages. The purpose of this study was to identify prognostic factors for overall survival (OS) and PSA response in patients with mCRPC treated with cabazitaxel. Results: 224 mCRPC patients were included in the current analysis. In multivariable analysis, WHO performance status, baseline hemoglobin, alkaline phosphatase and albumin were all significantly associated with OS. Hemoglobin and alkaline phosphatase were significantly associated with PSA response. Conclusions: This study identified prognostic factors for OS and PSA response of men with mCRPC treated with cabazitaxel. In an increasingly complicated treatment landscape with several treatment options available our findings might serve to estimate the chance of survival of men qualifying for treatment with second-line chemotherapy in daily practice. Furthermore, these data can be used to risk-stratify patients in clinical trials. Methods: We performed a post-hoc analysis of a randomized phase II trial of mCRPC patients treated with cabazitaxel. Cox and logistic regression models were used to investigate the influence of clinical and biochemical variables on OS and PSA response. Nomograms were developed to estimate the chance of PSA response and OS

Influence of enzalutamide on cabazitaxel pharmacokinetics: A Drug–Drug interaction study in metastatic castration-resistant prostate cancer (mCRPC) patients

Purpose: In ongoing clinical research on metastatic castration-resistant prostate cancer (mCRPC) treatment, the potential enhanced efficacy of the combination of taxanes with AR-targeted agents, that is, enzalutamide and abiraterone, is currently being explored. Because enzalutamide induces the CYP3A4 enzyme and taxanes are metabolized by this enzyme, a potential drug–drug interaction needs to be investigated. Experimental Design: Therefore, we performed a pharmacokinetic cross-over study in mCRPC patients who were scheduled for treatment with cabazitaxel Q3W (25 mg/m2). Patients were studied for three consecutive cabazitaxel cycles. Enzalutamide (160 mg once daily) was administered concomitantly after the first cabazitaxel cycle, during 6 weeks. Primary endpoint was the difference in mean area under the curve (AUC) between the first (cabazitaxel monotherapy) and third cabazitaxel cycle, when enzalutamide was added. Results: A potential clinically relevant 22% (95% CI, 9%–34%; P ¼ 0.005) reduction in cabazitaxel exposure was found with concomitant enzalutamide use. The geometric mean AUC0–24h of cabazitaxel was 181 ngh/mL (95% CI, 150–219 ngh/mL) in cycle 3 and 234 ngh/mL (95% CI, 209–261 ngh/mL) in cycle 1. This combination did not result in excessive toxicity, whereas PSA response was promising. Conclusions: We found a significant decrease in cabazitaxel exposure when combined with enzalutamide. In an era of clinical trials on combination strategies for mCRPC, it is important to be aware of clinically relevant drug–drug interactions. Because recent study results support the use of a lower standard cabazitaxel dose of 20 mg/m2, the clinical relevance of this interaction may be substantial, because the addition of enzalutamide may result in subtherapeutic cabazitaxel exposure