Kehua Wu

Dose-Finding and Pharmacokinetic Study to Optimize the Dosing of Irinotecan According to the UGT1A1 Genotype of Patients With Cancer

PURPOSE The risk of severe neutropenia from treatment with irinotecan is related in part to UGT1A1*28, a variant that reduces the elimination of SN-38, the active metabolite of irinotecan. We aimed to identify the maximum-tolerated dose (MTD) and dose-limiting toxicity (DLT) of irinotecan in patients with advanced solid tumors stratified by the *1/*1, *1/*28, and *28/*28 genotypes. PATIENTS AND METHODS Sixty-eight patients received an intravenous flat dose of irinotecan every 3 weeks. Forty-six percent of the patients had the *1/*1 genotype, 41% had the *1/*28 genotype, and 13% had the *28/*28 genotype. The starting dose of irinotecan was 700 mg in patients with the *1/*1 and *1/*28 genotypes and 500 mg in patients with the *28/*28 genotype. Pharmacokinetic evaluation was performed at cycle 1. RESULTS In patients with the *1/*1 genotype, the MTD was 850 mg (four DLTs per 16 patients), and 1,000 mg was not tolerated (two DLTs per six patients). In patients with the *1/*28 genotype, the MTD was 700 mg (five DLTs per 22 patients), and 850 mg was not tolerated (four DLTs per six patients). In patients with the *28/*28 genotype, the MTD was 400 mg (one DLT per six patients), and 500 mg was not tolerated (three DLTs per three patients). The DLTs were mainly myelosuppression and diarrhea. Irinotecan clearance followed linear kinetics. At the MTD for each genotype, dosing by genotype resulted in similar SN-38 areas under the curve (AUCs; r(2) = 0.0003; P = .97), but the irinotecan AUC was correlated with the actual dose (r(2) = 0.39; P < .001). Four of 48 patients with disease known to be responsive to irinotecan achieved partial response. CONCLUSION The UGT1A1*28 genotype can be used to individualize dosing of irinotecan. Additional studies should evaluate the effect of genotype-guided dosing on efficacy in patients receiving irinotecan.

Two Drug Interaction Studies of Sirolimus in Combination with Sorafenib or Sunitinib in Patients with Advanced Malignancies

Purpose: Sirolimus is the prototypical mTOR inhibitor. Sorafenib and sunitinib are small molecule inhibitors of multiple kinases including VEGF receptor (VEGFR) kinases. These agents have different mechanisms of action, providing a strong rationale for combination. Experimental Design: Patients with advanced cancer were assigned to receive either sirolimus or the VEGFR inhibitor alone for a 2-week lead-in period, followed by combination therapy. The primary end point of each trial was to determine whether a drug interaction exists between sirolimus and either sorafenib or sunitinib, as defined by a difference in Cmax for each drug alone compared with its Cmax during combination therapy. Results: The sorafenib and sunitinib trials enrolled 34 and 23 patients, respectively. There were no clinically significant differences in Cmax for any of the drugs alone compared with the Cmax during combination therapy. Toxicity profiles were similar to those expected for each drug alone. One patient with adrenal cortical cancer had a partial response to sirolimus and sunitnib. Conclusions: Sirolimus can be safely combined with sorafenib or sunitinib. Our trial design is feasible and informative in screening for potential drug–drug interactions, using a relatively small number of patients and limited pharmacokinetic sampling. Clin Cancer Res; 17(7); 1956–63. ©2011 AACR.

Personalized targeted therapy for lung cancer.

Lung cancer has long been recognized as an extremely heterogeneous disease, since its development is unique in every patient in terms of clinical characterizations, prognosis, response and tolerance to treatment. Personalized medicine refers to the use of markers to predict which patient will most likely benefit from a treatment. In lung cancer, the well-developed epidermal growth factor receptor (EGFR) and the newly emerging EML4-anaplastic lymphoma kinase (ALK) are important therapeutic targets. This review covers the basic mechanism of EGFR and EML4-ALK activation, the predictive biomarkers, the mechanism of resistance, and the current targeted tyrosine kinase inhibitors. The efficacy of EGFR and ALK targeted therapies will be discussed in this review by summarizing the prospective clinical trials, which were performed in biomarker-based selected patients. In addition, the revolutionary sequencing and systems strategies will also be included in this review since these technologies will provide a comprehensive understanding in the molecular characterization of cancer, allow better stratification of patients for the most appropriate targeted therapies, eventually resulting in a more promising personalized treatment. The relatively low incidence of EGFR and ALK in non-Asian patients and the lack of response in mutant patients limit the application of the therapies targeting EGFR or ALK. Nevertheless, it is foreseeable that the sequencing and systems strategies may offer a solution for those patients.

Genetic factors affecting gene transcription and catalytic activity of UDP-glucuronosyltransferases in human liver

The aim of this study was to discover cis- and trans-acting factors significantly affecting mRNA expression and catalytic activity of human hepatic UDP-glucuronosyltransferases (UGTs). Transcription levels of five major hepatic UGT1A (UGT1A1, UGT1A3, UGT1A4, UGT1A6 and UGT1A9) and five UGT2B (UGT2B4, UGT2B7, UGT2B10, UGT2B15 and UGT2B17) genes were quantified in human liver tissue samples (n = 125) using real-time PCR. Glucuronidation activities of 14 substrates were measured in 47 livers. We genotyped 167 tagSNPs (single-nucleotide polymorphisms) in UGT1A (n = 43) and UGT2B (n = 124), as well as the known functional UGT1A1*28 and UGT2B17 CNV (copy number variation) polymorphisms. Transcription levels of 15 transcription factors (TFs) known to regulate these UGTs were quantified. We found that UGT expression and activity were highly variable among the livers (median and range of coefficient of variations: 135%, 74-217% and 52%, 39-105%, respectively). CAR, PXR and ESR1 were found to be the most important trans-regulators of UGT transcription (median and range of correlation coefficients: 46%, 6-58%; 47%, 9-58%; and 52%, 24-75%, respectively). Hepatic UGT activities were mainly determined by UGT gene transcription levels. Twenty-one polymorphisms were significantly (FDR-adjusted P < 0.05) associated with mRNA expression and/or activities of UGT1A1, UGT1A3 and UGT2B17. We found novel SNPs in the UGT2B17 CNV region accounting for variability in UGT2B17 gene transcription and testosterone glucuronidation rate, in addition to that attributable to the UGT2B17 CNV. Our study discovered novel pharmacogenetic markers and provided detailed insight into the genetic network regulating hepatic UGTs.

Phase I Studies of Sirolimus Alone or in Combination with Pharmacokinetic Modulators in Advanced Cancer Patients

Purpose: Sirolimus is the eponymous inhibitor of the mTOR; however, only its analogs have been approved as cancer therapies. Nevertheless, sirolimus is readily available, has been well studied in organ transplant patients, and shows efficacy in several preclinical cancer models. Experimental Design: Three simultaneously conducted phase I studies in advanced cancer patients used an adaptive escalation design to find the dose of oral, weekly sirolimus alone or in combination with either ketoconazole or grapefruit juice that achieves similar blood concentrations as its intravenously administered and approved prodrug, temsirolimus. In addition, the effect of sirolimus on inhibition of p70S6 kinase phosphorylation in peripheral T cells was determined. Results: Collectively, the three studies enrolled 138 subjects. The most commonly observed toxicities were hyperglycemia, hyperlipidemia, and lymphopenia in 52%, 43%, and 41% of subjects, respectively. The target sirolimus area under the concentration curve (AUC) of 3,810 ng-h/mL was achieved at sirolimus doses of 90, 16, and 25 mg in the sirolimus alone, sirolimus plus ketoconazole, and sirolimus plus grapefruit juice studies, respectively. Ketoconazole and grapefruit juice increased sirolimus AUC approximately 500% and 350%, respectively. Inhibition of p70 S6 kinase phosphorylation was observed at all doses of sirolimus and correlated with blood concentrations. One partial response was observed in a patient with epithelioid hemangioendothelioma. Conclusion: Sirolimus can be feasibly administered orally, once weekly with a similar toxicity and pharmacokinetic profile compared with other mTOR inhibitors and warrants further evaluation in studies of its comparative effectiveness relative to recently approved sirolimus analogs. Clin Cancer Res; 18(17); 4785–93. ©2012 AACR.

Next-generation sequencing for lung cancer

Lung cancer is biologically aggressive and is the leading cause of cancer-related deaths. The development of lung cancer is unique in each patient according to clinical characterizations, prognosis, response and tolerance to treatment. Traditional capillary-based single-gene sequencing by a first-generation technique (known as Sanger sequencing) has been replaced by next-generation sequencing (NGS) since it allows massive parallel sequencing with lower cost and higher throughput. The NGS approach has made remarkable advances compared with traditional methods. We expect these methodologies to comprehensively interpret the global landscape of cancer and provide more information to fulfill the needs of personalized medicine. This review covers a brief introduction and summary on various NGS technologies, applications and important findings by NGS in lung cancer advances, including further discoveries in previously known target genes (EGFR, ALK and KRAS), the identification of additional lung cancer mutations and the global coordination of cancer genome studies.

A phase I study of sirolimus and bevacizumab in patients with advanced malignancies.

BACKGROUND We performed a single institution, phase I study of sirolimus and bevacizumab, in order to determine the dose limiting toxicity (DLT) and recommended phase II doses. PATIENTS AND METHODS Eligible patients had previously treated advanced malignancies and were enrolled in three cohorts. Sirolimus 90 mg PO weekly (45 mg on days 1 and 2) was combined with bevacizumab 7.5mg/kg (cohort #1) or bevacizumab 15 mg/kg (cohort #2) IV q3weeks. Sirolimus 4 mg PO daily was combined with bevacizumab 15 mg/kg IV q3weeks (cohort #3). RESULTS Twenty-eight patients enrolled. The most common tumour types were colorectal (21%), head/neck (14%), and renal cell (11%). No DLTs were observed in cohorts #1 (4 patients) and #2 (12 patients), while two DLTs (grade 3 confusion and grade 3 fatigue) were observed in the first six patients in cohort #3 (12 patients). The most common grade 3 toxicities were fatigue (18%), hypertension (14%) and anorexia (11%). There were no responses, but one patient has had stable disease for 78 weeks. CONCLUSIONS The combination of sirolimus and bevacizumab at full doses is tolerable in the majority of patients. The availability and cost of sirolimus compared with other mTOR inhibitors make this an attractive agent to combine with bevacizumab.

Evaluation of food effect on pharmacokinetics of vismodegib in advanced solid tumor patients

Purpose: Vismodegib, an orally bioavailable small-molecule Smoothened inhibitor, is approved for treatment of advanced basal cell carcinoma (BCC). We conducted a pharmacokinetic study of vismodegib in patients with advanced solid tumors to explore the effects of food on drug exposure. Experimental Design: In part I, patients were randomized to fasting overnight (FO), a high fat meal (HF), or a low fat meal (LF) before a single dose of vismodegib 150 mg. Plasma concentrations of vismodegib were determined by a validated liquid chromatography-tandem mass spectrometry assay. Primary endpoints were Cmax and area under the curve (AUC0–168). In part II, patients randomized to FO or HF in part I took vismodegib 150 mg daily after fasting; those randomized to LF took it after a meal. Primary endpoints after two weeks were Cmax and AUC0–24. Results: Sixty (22 FO, 20 HF, 18 LF) and 52 (25 fasting, 27 fed) patients were evaluable for primary endpoints in parts I and II, respectively. Mean Cmax and AUC0–168 after a single dose were higher in HF than FO patients [ratios of geometric means (90% CI) = 1.75 (1.30, 2.34) and 1.74 (1.25, 2.42), respectively]. There were no significant differences in Cmax or AUC0–24 between fasting and fed groups after daily dosing. The frequencies of drug-related toxicities were similar in both groups. Conclusions: A HF meal increases plasma exposure to a single dose of vismodegib, but there are no pharmacokinetic or safety differences between fasting and fed groups at steady-state. Vismodegib may be taken with or without food for daily dosing. Clin Cancer Res; 19(11); 3059–67. ©2013 AACR.

Estimation of Renal Cell Carcinoma Treatment Effects From Disease Progression Modeling

To improve future drug development efficiency in renal cell carcinoma (RCC), a disease‐progression model was developed with longitudinal tumor size data from a phase III trial of sorafenib in RCC. The best‐fit model was externally evaluated on 145 placebo‐treated patients in a phase III trial of pazopanib; the model incorporated baseline tumor size, a linear disease‐progression component, and an exponential drug effect (DE) parameter. With the model‐estimated effect of sorafenib on RCC growth, we calculated the power of randomized phase II trials between sorafenib and hypothetical comparators over a range of effects. A hypothetical comparator with 80% greater DE than sorafenib would have 82% power (one‐sided α = 0.1) with 50 patients per arm. Model‐based quantitation of treatment effect with computed tomography (CT) imaging offers a scaffold on which to develop new, more efficient, phase II trial end points and analytic strategies for RCC.

Nonlinear population pharmacokinetics of sirolimus in patients with advanced cancer.

Sirolimus, the prototypical inhibitor of the mammalian target of rapamycin, has substantial antitumor activity. In this study, sirolimus showed nonlinear pharmacokinetic characteristics over a wide dose range (from 1 to 60 mg/week). The objective of this study was to develop a population pharmacokinetic (PopPK) model to describe the nonlinearity of sirolimus. Whole blood concentration data, obtained from four phase I clinical trials, were analyzed using a nonlinear mixed‐effects modeling (NONMEM) approach. The influence of potential covariates was evaluated. Model robustness was assessed using nonparametric bootstrap and visual predictive check approaches. The data were well described by a two‐compartment model incorporating a saturable Michaelis–Menten kinetic absorption process. A covariate analysis identified hematocrit as influencing the oral clearance of sirolimus. The visual predictive check indicated that the final pharmacokinetic model adequately predicted observed concentrations. The pharmacokinetics of sirolimus, based on whole blood concentrations, appears to be nonlinear due to saturable absorption.