A Comparison of the Pharmacokinetics and Pharmacodynamics of Docetaxel between African-American and Caucasian Cancer Patients: CALGB 9871

Efficacy and safety of nanosomal docetaxel lipid suspension based chemotherapy in metastatic ovarian carcinoma: A retrospective study

The aim of the current study was to assess the efficacy and safety of nanosomal docetaxel lipid suspension (NDLS) based chemotherapy in patients with metastatic epithelial ovarian carcinoma. In the present multicenter study, the medical records of patients who received NDLS (60-75 mg/m²; 3-weekly cycles) based chemotherapy for metastatic epithelial ovarian cancer in routine clinical care were retrospectively evaluated. Patients were followed-up from September 2014 until September 2018. The efficacy endpoints were the overall response rate (ORR) and disease control rate measured in accordance with the Response Evaluation Criteria in Solid Tumours 1.1. Overall survival (OS) and safety were also evaluated. Of the 13 patients evaluated, 46.2% (6/13) received NDLS-based first-line chemotherapy and 53.8% (7/13) patients received second-line chemotherapy [platinum-sensitive, 57.1% (4/7); platinum-resistant, 42.9% (3/7)]. The ORRs were 60.0% (3/5) and 57.1% (4/7) for patients receiving first- and second-line chemotherapy, respectively. The estimated median OS for patients receiving NDLS-based first-line chemotherapy was 17.4 months (follow-up duration, 4.3-49.4 months). The estimated median OS was 26.1 months (follow-up duration, 5.1-37.5 months) in patients with platinum-sensitive disease, whereas the OS was 14.8 months (follow-up duration, 3.5-14.8 months) in patients with platinum-resistant disease. No grade III/IV adverse events (AEs) were observed; ≥1 AE in grade I-II was reported in 84.6% (11/13) of patients. Overall, NDLS-based chemotherapy was efficacious and well-tolerated in the management of metastatic epithelial ovarian carcinoma.

Toxicity profile of taxanes in Tunisian cancer patients: A retrospective study of 90 cases

INTRODUCTION

Taxanes are widely used in medical oncology. The aim of our study was to report and analyze the toxicity features of these drugs in Tunisian patients and to determine their impact on treatment response.

METHODS

Our retrospective study concerned 90 patients treated by taxanes in a medical oncology unit, from January 2014 to January 2017. We collected their epidemiologic and anatomo-clinical data and we detailed toxicity features including types grades and impact on tumor response.

RESULTS

Median age was 46 years. 80% of patients had breast cancer. Tumors were metastatic in 23.3% of cases. Nail toxicity was observed in 100% of patients. Grade I-II digestive toxicity was observed in 54.4% of cases. Hematological toxicity was noted in 42.2% of patients and it reached grade III-IV in five patients. Neurological toxicity occurred in 31% of patients and was grade III-IV in 6 cases. Alopecia was observed in 60% of patients. Fatigue was noted in 57.8% of patients. Myalgia was observed in 42.2% of patients. Toxicity did not affect the response to treatment.

CONCLUSION

The taxanes' toxicity profile in Tunisian patients is characterized by more frequent digestive and nail toxicities and less frequent hematological toxicities, dose reduction and treatment delays than other populations.

Different treatment efficacies and side effects of cytotoxic chemotherapy

Differences in efficacy and toxicity between Asian and Caucasian patients with lung cancer treated with systemic chemotherapy is increasingly recognised. This is a major concern in the clinical setting as it influences outcomes and affect international harmonization of drug development. Interindividual variability of pharmacokinetics, where different genetic polymorphisms affect drug metabolism, transport, and receptor binding may account for the ethnic differences. Treatment efficacy and outcomes may also be explained by differences in diet and lifestyle, access to healthcare, cultural barriers and environmental exposure. Efforts made to design prospective studies investigating ethnic specific determinants to systemic therapy and individualise lung cancer treatment based on genetic makeup of patient are important.

Efficacy and safety of nanosomal docetaxel lipid suspension based chemotherapy in gastric and gastroesophageal junction adenocarcinoma

The current retrospective multicenter study evaluated the efficacy and safety of nanosomal docetaxel lipid suspension (NDLS; DoceAqualip) based chemotherapy in patients with gastric and gastroesophageal junction (GEJ) adenocarcinoma. The medical charts of patients with gastric and GEJ adenocarcinoma, who were treated with NDLS (50-75 mg/m²; 3 weekly cycles) based chemotherapy and followed-up from April 2014 to September 2018, were analyzed. The study endpoints included overall response rate (ORR) and disease control rate (DCR) in neoadjuvant and metastatic settings. Overall survival (OS) and safety were also evaluated. Of the 43 patients with gastric (n=39) and GEJ (n=4) adenocarcinoma, efficacy evaluation was available in 35 (neoadjuvant, 17/18 patients; metastatic, 18/25 patients). In the neoadjuvant setting, an ORR of 58.82% and a DCR of 94.11% were observed, whereas in the metastatic setting, the ORR was 77.77% and the DCR was 83.33%. In the neoadjuvant setting, at a follow-up ranging from 0.7 to 41.2 months, the median OS was not reached. In the metastatic setting, the median OS was 31.9 months at a follow-up ranging from 0.2 to 50.3 months. At least one adverse event (AE) was reported in 24 patients. Anemia, lymphopenia and thrombocytopenia were the most common hematological AEs, while nausea, vomiting and weakness were the most common non-hematological AEs. NDLS based treatment was well-tolerated without any new safety concerns. Overall, NDLS-based chemotherapy was effective and well-tolerated in the management of gastric and GEJ adenocarcinoma.

Clinical pharmacokinetics and drug exposure-toxicity correlation study of docetaxel based chemotherapy in Chinese head and neck cancer patients

Background

Area under time-concentration curve (AUC) of docetaxel is related with its toxicity and efficacy. The aim of this study is to investigate the target range of docetaxel AUC in Chinese head and neck cancer (HNC) patients.

Methods

Eligible HNC patients were enrolled and received at least 2 cycles of docetaxel-based chemotherapy. A simplified pharmacokinetic (PK) strategy (2 monitored samples) was developed to simulate docetaxel AUC using the nonlinear mixed-effect modelling program. Preliminary target range of AUC was pre-set as 2.5–3.7 µg·hr/mL according to pooled analysis from 8 previous studies. Fisher exact test was used to analyze the relationship between AUC with neutropenia and efficacy, and to verify the target range.

Results

Thirty-nine eligible patients were enrolled. Grade 3-4 and grade 4 neutropenia rate in 1^st cycle was 64% and 36%, respectively. AUC simulation by simplified PK strategy was acceptable compared to full sampling method from the analysis of archived 300 patients’ data, with −5.67% of mean prediction error (MPE). Median AUC of all patients was 2.58 µg·hr/mL (range from 1.28 to 9.39). A significant correlation (P=0.007) was detected between AUC and body surface area (BSA)-dosage, but BSA contributed only 18.3% of AUC inter-individual variability. Docetaxel AUC was significantly related with the severity (grade 3–4) of neutropenia (correlation of coefficient was 0.452, P=0.004). Fourteen patients (36%) were within the target AUC range. Patients with AUC above the target experienced more severe neutropenia (grade 3–4 rate 100% vs. 56%, P=0.036; grade 4 rate 86% vs. 25%, P=0.005). No significant difference of response rate was found between patients within the target or not.

Conclusions

A simplified samples PK strategy was developed for docetaxel AUC simulation. The target range of docetaxel AUC in Chinese HNC patients was suggested at 2.5–3.7 µg·hr/mL for reduced toxicity without compromising efficacy of docetaxel treatment.

Efficacy and Safety of Nanosomal Docetaxel Lipid Suspension-Based Chemotherapy in Sarcoma: A Multicenter, Retrospective Study

Objective

To evaluate the efficacy and safety of nanosomal docetaxel lipid suspension (NDLS, DoceAqualip) based chemotherapy in patients with sarcoma.

Methods

In this retrospective, multicenter (6 centers), observational study, we analyzed the medical charts of adult patients of either sex, who were treated with NDLS (75 mg/m² in 3-weekly cycles) based chemotherapy for the treatment of sarcoma. The efficacy outcomes were overall response rate (ORR: complete response (CR) + partial response (PR)) and disease control rate (DCR: CR + PR + stable disease (SD)) in patients who received NDLS-based chemotherapy in neoadjuvant and metastatic settings. Overall survival (OS) and safety were evaluated for all settings.

Results

Of 11 patients (neoadjuvant: 1, adjuvant: 3, and metastatic: 7) in this study, majority had leiomyosarcoma (63.6%, 7/11) followed by extraskeletal myxoid chondrosarcoma (EMC), high grade pleomorphic sarcoma of mandible, malignant fibrous histiocytoma of right thigh, and osteosarcoma of femur (9.1% each, 1/11 each). NDLS plus gemcitabine combination was used in 10 patients (90.9%), and NDLS plus cyclophosphamide was used in one patient with EMC (9.1%). Efficacy evaluation was performed for 7 patients (neoadjuvant: 1/1; metastatic: 6/7). Complete response was reported in one patient (soft tissue sarcoma of mandible) treated in neoadjuvant setting. In metastatic setting, ORR was 50% and DCR was 66.7% (CR: 16.7% (1/6), PR: 33.3% (2/6), SD: 16.7% (1/6)). At a median follow-up of 6.5 months (range: 0.06–20.2 months), median OS was not reached in neoadjuvant and adjuvant settings, but it was 15.8 months in metastatic setting. At least 1 AE was reported in 7 (63.6%) patients. Neutropenia, thrombocytopenia, lymphopenia, and anemia were the hematological AEs, whereas nausea, vomiting, and diarrhea were the most common nonhematological AEs. NDLS treatment was well tolerated without any new safety concerns.

Conclusion

Nanosomal docetaxel lipid suspension-based chemotherapy was efficacious and well tolerated in the treatment of sarcoma. Further prospective trials are needed to confirm the data.

Plasma alpha-1-acid glycoprotein as a potential predictive biomarker for non-haematological adverse events of docetaxel in breast cancer patients

CONTEXT

Rash and oral mucositis are major non-haematological adverse events (AEs) of docetaxel, in addition to fatigue, nausea, vomiting and diarrhoea, which restrict the use of the drug in cancer therapy. Alpha-1-acid glycoprotein (AAG) is an acute phase reactant glycoprotein and is a primary carrier of docetaxel in the blood. Docetaxel has extensive binding (>98%) to plasma proteins such as AAG, lipoproteins and albumin.

OBJECTIVE

To study the association between plasma AAG level and non-haematological AEs of docetaxel in Malaysian breast cancer patients of three major ethnic groups (Malays, Chinese and Indians).

MATERIALS AND METHODS

One hundred and twenty Malaysian breast cancer patients receiving docetaxel as single agent chemotherapy were investigated for AAG plasma level using enzyme-linked immunosorbent assay technique. Toxicity assessment was determined using Common Terminology Criteria of Adverse Events v4.0. The association between AAG and toxicity were then established.

RESULTS

There was interethnic variation of plasma AAG level; it was 182 ± 85 mg/dl in Chinese, 237 ± 94 mg/dl in Malays and 240 ± 83 mg/dl in Indians. It was found that low plasma levels of AAG were significantly associated with oral mucositis and rash.

CONCLUSIONS

This study proposes plasma AAG as a potential predictive biomarker of docetaxel non-haematological AEs namely oral mucositis and rash.

Metabolomics Analysis of Hormone-Responsive and Triple-Negative Breast Cancer Cell Responses to Paclitaxel Identify Key Metabolic Differences

To date, no targeted therapies are available to treat triple negative breast cancer (TNBC), while other breast cancer subtypes are responsive to current therapeutic treatment. Metabolomics was conducted to reveal differences in two hormone receptor-negative TNBC cell lines and two hormone receptor-positive Luminal A cell lines. Studies were conducted in the presence and absence of paclitaxel (Taxol). TNBC cell lines had higher levels of amino acids, branched-chain amino acids, nucleotides, and nucleotide sugars and lower levels of proliferation-related metabolites like choline compared with Luminal A cell lines. In the presence of paclitaxel, each cell line showed unique metabolic responses, with some similarities by type. For example, in the Luminal A cell lines, levels of lactate and creatine decreased while certain choline metabolites and myo-inositol increased with paclitaxel. In the TNBC cell lines levels of glutamine, glutamate, and glutathione increased, whereas lysine, proline, and valine decreased in the presence of drug. Profiling secreted inflammatory cytokines in the conditioned media demonstrated a greater response to paclitaxel in the hormone-positive Luminal cells compared with a secretion profile that suggested greater drug resistance in the TNBC cells. The most significant differences distinguishing the cell types based on pathway enrichment analyses were related to amino acid, lipid and carbohydrate metabolism pathways, whereas several biological pathways were differentiated between the cell lines following treatment.

Significant effect of age on docetaxel pharmacokinetics in Japanese female breast cancer patients by using the population modeling approach

PURPOSE

Docetaxel is frequently used in the treatment of a wide variety of solid tumors, including breast cancer. The aim of this study is to obtain the population pharmacokinetic parameters of docetaxel in Japanese female patients with breast cancer.

METHODS

Blood samples from 24 patients were collected sequentially before and after docetaxel infusion. Genomic DNA was isolated from the peripheral blood and genotyped for the selected polymorphisms in the candidate genes of drug transporters and metabolizing enzymes. The influence of patient characteristics on the pharmacokinetics of docetaxel was evaluated using the nonlinear-mixed-effect modeling program, NONMEM. As a basis for comparison, the pharmacokinetics of another taxane paclitaxel in 41 separate female patients with breast cancer was calculated.

RESULTS

A two-compartment model adequately described the pharmacokinetic profiles of docetaxel. The population mean estimates of the total body clearance for patients aged 58 years or less and the central volume of distribution for docetaxel were 32.6 L/h and 5.77 L, respectively. In patients over 58 years, the clearance was 24 % higher than that in the younger patients. No influences of the genotypes examined were noted on the clearance of docetaxel. The clearance of paclitaxel was not affected by patient age.

CONCLUSIONS

Patients over the age of 58 years showed significantly higher clearance of docetaxel than that in patients aged 58 years or less. Since the clearance of paclitaxel was not affected by the age, it is possible that the pharmacokinetic mechanisms of docetaxel might be specifically affected by age in females.

Inter-patient variability in docetaxel pharmacokinetics: A review

Docetaxel is a frequently used chemotherapeutic agent in the treatment of solid cancers. Because of the large inter-individual variability (IIV) in the pharmacokinetics (PK) of docetaxel, it is challenging to determine the optimal dose in individual patients in order to achieve optimal efficacy and acceptable toxicity. Despite the established correlation between systemic docetaxel exposure and efficacy, the precise factors influencing docetaxel PK are not yet completely understood. This review article highlights currently known factors that influence docetaxel PK, and focusses on those that are clinically relevant. For example, liver impairment should be taken into account when calculating docetaxel dosages as this may decrease docetaxel clearance. In addition, drug-drug interactions may be of distinct clinical importance when using docetaxel. Particularly, drugs strongly inhibiting CYP3A4 such as ketoconazole should not be concurrently administered without dose modification, as they may decrease the clearance of docetaxel. Gender, castration status, and menopausal status might be of importance as potential factors influencing docetaxel PK. The role of pharmacogenetics in predicting docetaxel PK is still limited, since no polymorphisms of clinical importance have yet been established.

Pharmacokinetics, dynamics and toxicity of docetaxel: Why the Japanese dose differs from the Western dose

Docetaxel (Taxotere®) has been one of the most important chemotherapeutic drugs for cancer treatment since 1996. Although a large number of clinical studies have been conducted in various cancer fields, there is a discrepancy in the standard dose between Japan and Western countries. This article reviews the pharmacokinetic, pharmacodynamic and toxicological profiles of docetaxel, and explains why there exists an ethnic difference in dose, and further discusses which direction we should go forward to solve this problem. The original recommended dose was 100 mg/m² every 3 weeks in US and European populations, while a Japanese phase I study suggested the recommended dose as 60 mg/m² every 3 weeks. A prospective population pharmacokinetic analysis of docetaxel conducted in both the USA/Europe and Japan, indicated an absence of ethnic difference in the pharmacokinetics. Both analyses demonstrated that docetaxel clearance is related to α1-acid glycoprotein level, hepatic function, age and body surface area. The relationship was observed between increasing docetaxel dose and increased tumor response rates across the dose range of 60 to 100 mg/m². The area under the serum concentration time curve (AUC) of docetaxel at the first cycle was significantly related to time to progression. Hematological toxicities were well correlated with the AUC of docetaxel, and severe hematological toxicities were more frequently observed in Japanese patients treated with 60 mg/m², compared to the US/European patients treated with 75–100 mg/m² dose. The Japanese population seems more susceptible to the toxicity of docetaxel. A docetaxel dose of 75 mg/m² is now standard not only in global trials but also in recent Japanese trials. Although the optimal dose of docetaxel is still unclear, we need to continue to seek the appropriate dose of docetaxel depending on patient status and the goals of chemotherapy.

Genetic variation: effect on prostate cancer

The crucial role of androgens in the development of prostate cancer is well established. The aim of this review is to examine the role of constitutional (germline) and tumor-specific (somatic) polymorphisms within important regulatory genes of prostate cancer. These include genes encoding enzymes of the androgen biosynthetic pathway, the androgen receptor gene, genes that encode proteins of the signal transduction pathways that may have a role in disease progression and survival, and genes involved in prostate cancer angiogenesis. Characterization of deregulated pathways critical to cancer cell growth have lead to the development of new treatments, including the CYP17 inhibitor abiraterone and clinical trials using novel drugs that are ongoing or recently completed [1]. The pharmacogenetics of the drugs used to treat prostate cancer will also be addressed. This review will define how germline polymorphisms are known affect a multitude of pathways, and therefore phenotypes, in prostate cancer etiology, progression, and treatment.

Race and ethnicity in cancer therapy: what have we learned?

Racial and ethnic disparities in the pathogenesis of common malignancies and outcomes from treatment remain a major health concern. Factors attributed to these disparities include differences in lifestyle, environment, genetics, and tumor biology. As we strive to personalize cancer therapy, it will be imperative that we understand the relative contributions of each factor so that we may apply this knowledge in choosing the best treatment for each individual, regardless of his or her racial or ethnic heritage.

The role of Multidrug Resistance-1 (MDR1) variants in response to atorvastatin among Jordanians

The MDR1 gene encodes for P-glycoprotein (P-gp), which is an efflux transporter at the cell membrane. The P-gp has wide substrate specificity for multiple medications including the lipid lowering drug, atorvastatin. In this study, we investigated the possible association between three common MDR1 gene polymorphisms (G2677T, C3435T, and C1236T), and the lipid lowering effect of atorvastatin among Jordanians. Lipid and lipoproteins were measured in blood samples collected from patients (n = 201) at baseline and during atorvastatin treatment. MDR1 polymorphisms were genotyped using polymerase chain reaction-restriction fragment length polymorphism. Both the TT genotype of G2677T and the TT genotype of the C3435T polymorphisms were associated with lower levels of low-density lipoproteins after atorvastatin treatment. However, the effects of atorvastatin on the levels of total cholesterol, triglycerides, and high-density lipoprotein, were not correlated with any of the genotypes in both polymorphisms. Finally, the C1236T polymorphism was not associated with the lipid lowering effect of atorvastatin. In conclusion, the MDR1 gene polymorphisms G2677T, and C3435T, but not C1236T were associated with the lipid lowering effect of atorvastatin among Jordanians.

Pharmacogenetics of taxanes: impact of gene polymorphisms of drug transporters on pharmacokinetics and toxicity

Interindividual variability in drug response and the emergence of adverse drug effects are the main causes of treatment failure in cancer therapy. Functional membrane drug transporters play important roles in altering pharmacokinetic profile, resistance to treatment, toxicity and patient survival. Pharmacogenetic studies of these transporters are expected to provide new approaches for optimizing therapy. Taxanes are approved for the treatment of various cancers. Circulating taxanes are taken up by SLCO1B3 into hepatocytes. The CYP450 enzymes CYP3A4, CYP3A5 and CYP2C8 are responsible for the conversion of taxanes into their metabolites. Ultimately, ABCB1 and ABCC2 will dispose the metabolites into bile canaliculi. Polymorphisms of genes encoding for proteins involved in the transport and clearance of taxanes reduce excretion of the drugs, leading to development of toxicity in patients. This review addresses current knowledge on genetic variations of transporters affecting taxanes pharmacokinetics and toxicity, and provides insights into future direction for personalized medicine.

The relationship of polymorphisms in ABCC2 and SLCO1B3 with docetaxel pharmacokinetics and neutropenia: CALGB 60805 (Alliance)

Docetaxel-related neutropenia was associated with polymorphisms in the drug transporters ABCC2 and SLCO1B3 in Japanese cancer patients. We hypothesized that this association is because of reduced docetaxel clearance, associated with polymorphisms in those genes. We studied 64 US cancer patients who received a single cycle of 75 mg/m of docetaxel monotherapy. We found that the ABCC2 polymorphism at rs-12762549 trended to show a relationship with reduced docetaxel clearance (P=0.048), but not with neutropenia. There was no significant association of the SLCO1B3 polymorphisms with docetaxel clearance or neutropenia. We conclude that the relationship between docetaxel-associated neutropenia and polymorphisms in drug transporters identified in Japanese patients was not confirmed in this cohort of US cancer patients.

Influence of polymorphic OATP1B-type carriers on the disposition of docetaxel

PURPOSE

Docetaxel is extensively metabolized by CYP3A4 in the liver but mechanisms by which the drug is taken up into hepatocytes remain poorly understood. We hypothesized that (i) liver uptake of docetaxel is mediated by the polymorphic solute carriers OATP1B1 and OATP1B3 and (ii) inherited genetic defects in this process may impair systemic drug elimination.

EXPERIMENTAL DESIGN

Transport of docetaxel was studied in vitro using various cell lines stably transfected with OATP1B1*1A (wild-type), OATP1B1*5 [c.521T>C (V174A); rs4149056], OATP1B3, or the mouse transporter Oatp1b2. Docetaxel clearance was evaluated in wild-type and Oatp1b2-knockout mice as well as in two cohorts of patients with multiple variant transporter genotypes (n = 213).

RESULTS

Docetaxel was found to be a substrate for OATP1B1, OATP1B3, and Oatp1b2 but was not transported by OATP1B1*5. Deficiency of Oatp1b2 in mice was associated with an 18-fold decrease in docetaxel clearance (P = 0.0099), which was unrelated to changes in intrinsic metabolic capacity in mouse liver microsomes. In patients, however, none of the studied common reduced function variants in OATP1B1 or OATP1B3 were associated with docetaxel clearance (P > 0.05).

CONCLUSIONS

The existence of at least two potentially redundant uptake transporters in the human liver with similar affinity for docetaxel supports the possibility that functional defects in both of these proteins may be required to confer substantially altered disposition phenotypes. In view of the established exposure-toxicity relationships for docetaxel, we suggest that caution is warranted if docetaxel has to be administered together with agents that potently inhibit both OATP1B1 and OATP1B3.

An update on ethnic differences in drug metabolism and toxicity from anti-cancer drugs

INTRODUCTION

Based on recent emerging evidence of inter-ethnic differences in drug response and toxicity, ethnic diversity in pharmacokinetics, pharmacogenomics and clinical outcomes are being increasingly investigated. Ultimately, this will promote improved understanding of inter-individual differences in the pharmacokinetics and tolerance of cytotoxic drugs.

AREAS COVERED

This article reviews potential explanations for the observed ethnic differences in treatment outcomes and provides clinical data to support this concept. A literature search was implemented on PubMed and PharmGKB to investigate the areas of ethnic differences in pharmacogenomics, pharmacogenetics and clinical outcomes of cancer therapies.

EXPERT OPINION

There has been a relative paucity of clinical evidence linking genetic polymorphisms of genes encoding drug-metabolizing enzymes to the pharmacokinetics, pharmacodynamics and tolerance of anti-cancer drugs. Future research should focus on studies using large sample sizes, in the hope that they will provide results of high clinical significance. Due to the potential for ethnic differences to impact on both toxicities and benefits of systemic cancer therapies, the development of new therapeutic agents should include patients from diverse geographical ancestries in each phase of drug development.

Part 2: pharmacogenetic variability in drug transport and phase I anticancer drug metabolism

Equivalent drug doses in anticancer chemotherapy may lead to wide interpatient variability in drug response reflected by differences in treatment response or in severity of adverse drug reactions. Differences in the pharmacokinetic (PK) and pharmacodynamic (PD) behavior of a drug contribute to variation in treatment outcome among patients. An important factor responsible for this variability is genetic polymorphism in genes that are involved in PK/PD processes, including drug transporters, phase I and II metabolizing enzymes, and drug targets, and other genes that interfere with drug response. In order to achieve personalized pharmacotherapy, drug dosing and treatment selection based on genotype might help to increase treatment efficacy while reducing unnecessary toxicity. We present a series of four reviews about pharmacogenetic variability in anticancer drug treatment. This is the second review in the series and is focused on genetic variability in genes encoding drug transporters (ABCB1 and ABCG2) and phase I drug-metabolizing enzymes (CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4, CYP3A5, DPYD, CDA and BLMH) and their associations with anticancer drug treatment outcome. Based on the literature reviewed, opportunities for patient-tailored anticancer therapy are presented.

NCT01110291: induction of CYP3A activity and lowered exposure to docetaxel in patients with primary breast cancer

PURPOSE

To study the CYP3A activity before and after docetaxel administration. Furthermore, it was investigated whether peroral midazolam could predict docetaxel exposure and adverse events.

METHODS

Twenty patients with primary high risk breast cancer were given docetaxel as a 1-h infusion 80 mg/m(2) in a 21-day cycle in 3 cycles followed by 3 cycles of cyclophosphamide, epirubicin and fluorouracil. CYP3A activity was assessed a day before and a day after docetaxel by 7.5 mg oral midazolam. All patients were given peroral dexamethasone a total dose of 45 mg, of which 15 mg was given before docetaxel infusion and 30 mg before the latter assessment of CYP3A activity. All except one patient were given 11-19 mg of intravenous dexamethasone before docetaxel infusion.

RESULTS

CYP3A activity was clearly induced when assessed a day after docetaxel administration as shown by lower midazolam AUC (P < 0.0001) and higher AUC ratio (1-OH-midazolam/midazolam, P = 0.018). The mean docetaxel AUC was about a half of that previously reported in the literature. Incidence of febrile neutropenia was smaller (15%) than reported in literature with comparable docetaxel doses and seemed to associate with slower metabolism. No correlation between pharmacokinetics of midazolam and docetaxel was found at baseline.

CONCLUSIONS

We show here a markedly reduced docetaxel exposure followed by CYP3A induction by, most likely, dexamethasone. Peroral midazolam seemed not to predict docetaxel exposure. Slow CYP3A-mediated metabolism might predispose patients to adverse events of docetaxel.

Effect of ABCB1 C3435T polymorphism on docetaxel pharmacokinetics according to menopausal status in breast cancer patients

Background:

It can be hypothesised that inherited polymorphisms in the drug-transporter ABCB1 gene may interfere with interindividual variations in drug response in breast cancer patients. Docetaxel is a substrate for ABCB1 whose function has been shown to be modulated by oestrogen and progesterone.

Methods:

Whether ABCB1 polymorphisms including T-129C, A61G, C1236T, G2677T/A and C3435T polymorphisms could account for variations in the disposition of docetaxel and whether menopausal status at the time of diagnosis might interact with this effect were analysed in women receiving neoadjuvant chemotherapy for breast cancer (n=86).

Results:

A highly significant association was observed, but restricted to premenopausal women (n=53), between the pharmacokinetics of docetaxel and C3435T polymorphism, as patients with CC genotype had lower mean values of the area under the plasma concentration-time curve (AUC) of docetaxel than patients with CT and TT genotypes (P<0.0001). Comparison between pre- and postmenopausal women with the same C3435T genotype yielded a significant difference in docetaxel AUC only for CC genotype (P<0.0001).

Conclusion:

These results suggest that C3435T polymorphism genotyping and menopausal status at the time of diagnosis might be useful when considering chemotherapy regimens including docetaxel in breast cancer patients.

Pharmacogenetics in breast cancer: focus on hormone therapy, taxanes, trastuzumab and bevacizumab

Breast cancer is the most common female cancer, with more than one million new patients diagnosed annually worldwide. The great heterogeneity, in terms of prognosis and outcome, within patients with the same clinical and pathological characteristics may limit the potential for personalized therapy. Most of the cytotoxic agents and new targeted agents have a narrow therapeutic index and the administration of an equal dose may result in a wide range of toxicities as well as to different antitumor efficacy. Inter-subject variability in drug toxicity and response is common during treatment, so that individualization of treatments is an important issue. Pharmacogenetics is the study of how inter-individual variations in the DNA sequence of specific genes may affect drug response and toxicity. This article highlights the clinical use of determination of polymorphisms of important human drug-metabolizing cytochrome P450s, ABCB1, IgG fragment C receptors and vascular endothelial growth factor, which are responsible of the large inter-individual variability in drug metabolism and clearance of the agents commonly used in breast cancer treatment, such as tamoxifen, aromatase inhibitors, taxanes, trastuzumab and bevacizumab.

Population-based differences in treatment outcome following anticancer drug therapies

Population-based differences in toxicity and clinical outcome following treatment with anticancer drugs have an important effect on oncology practice and drug development. These differences arise from complex interactions between biological and environmental factors, which include genetic diversity affecting drug metabolism and the expression of drug targets, variations in tumour biology and host physiology, socioeconomic disparities, and regional preferences in treatment standards. Some well-known examples include the high prevalence of activating epidermal growth factor receptor (EGFR) mutations in pulmonary adenocarcinoma among northeast (China, Japan, Korea) and parts of southeast Asia (excluding India) non-smokers, which predict sensitivity to EGFR kinase inhibitors, and the sharp contrast between Japan and the west in the management and survival outcome of gastric cancer. This review is a critical overview of population-based differences in the four most prevalent cancers in the world: lung, breast, colorectal, and stomach cancer. Particular attention is given to the clinical relevance of such knowledge in terms of the individualisation of drug therapy and in the design of clinical trials.

Emerging ethnic differences in lung cancer therapy

Although global clinical trials for lung cancer can enable the development of new agents efficiently, whether the results of clinical trials performed in one population can be fully extrapolated to another population remains questionable. A comparison of phase III trials for the same drug combinations against lung cancer in different countries shows a great diversity in haematological toxicity. One possible reason for this diversity may be that different ethnic populations may have different physiological capacities for white blood cell production and maturation. In addition, polymorphisms in the promoter and coding regions of drug-metabolising enzymes (e.g., CYP3A4 and UGT1A1) or in transporters (e.g., ABCB1) may vary among different ethnic populations. For example, epidermal growth factor receptor (EGFR) inhibitors are more effective in Asian patients than in patients of other ethnicities, a characteristic that parallels the incidence of EGFR-activating mutations. Interstitial lung disease associated with the administration of gefitinib is also more common among Japanese patients than among patients of other ethnicities. Although research into these differences has just begun, these studies suggest that possible pharmacogenomic and tumour genetic differences associated with individual responses to anticancer agents should be carefully considered when conducting global clinical trials.

Pharmacogenetic pathway analysis of docetaxel elimination

The purpose of this study was to evaluate the affinity of docetaxel for 14 transporter proteins and assess the functional significance of 17 variants in five genes involved in drug elimination. Among the transfected models investigated, OATP1B3 (SLCO1B3) was identified as the most efficient influx transporter for docetaxel. None of the observed genotypes (SLCO1B3, ABCB1, and ABCC2) was related with docetaxel clearance in 92 white patients (P > 0.17). However, the simultaneous presence of the CYP3A4*1B and CYP3A5*1A alleles was associated with a 64% increase in docetaxel clearance (P = 0.0015), independent of both sex and CYP3A activity (as determined using the erythromycin breath test). This haplotype was also associated with increased midazolam clearance in another population (P = 0.0198). An analysis of the CYP3A locus among CEPH-HapMap samples revealed that CYP3A4*1B is present exclusively among a subset of CYP3A5 expressors. Therefore, future studies should first stratify the population on the basis of CYP3A5 genotype and then compare CYP3A activity between individuals with and without the CYP3A4*1B allele.

Randomized phase II adjuvant trial of dose-dense docetaxel before or after doxorubicin plus cyclophosphamide in axillary node-positive breast cancer

PURPOSE

An anthracycline-based combination followed by, or combined with, a taxane is the sequence used in most adjuvant chemotherapy regimens. We hypothesized that administering the taxane before the anthracycline combination would be associated with fewer dose reductions and delays than the reverse sequence. To test this hypothesis, a randomized phase II multicenter adjuvant chemotherapy trial was performed.

PATIENTS AND METHODS

Fifty-six patients with axillary node-positive, nonmetastatic breast cancer were randomly assigned either to group A (docetaxel [DOC] 75 mg/m(2) intravenously [IV] every 14 days for four cycles followed by doxorubicin 60 mg/m(2) and cyclophosphamide 600 mg/m(2) [AC] IV every 14 days for four cycles); or to group B (AC followed by DOC) at the identical doses and schedule. Pegfilgrastim 6 mg subcutaneous injection was administered 1 day after the chemotherapy in all treatment cycles. The primary objective was to administer DOC without dose reductions or delays before or after AC and calculate the relative dose intensity (RDI) of DOC and AC.

RESULTS

The majority of toxicities were grade 0 to 2 irrespective of sequence. The RDI for DOC was 0.96 and 0.82, respectively, in groups A (DOC followed by AC) and B (AC followed by DOC), with more frequent dose reductions occurring in group B (46% v 18%). The RDI for AC was 0.95 and 0.98 in groups A and B, respectively.

CONCLUSION

The administration of DOC before AC results in fewer DOC dose reductions and a higher RDI than the reverse sequence. Larger trials evaluating the sequence of DOC before anthracyclines are justified.