Population pharmacokinetics of cisplatin in adult cancer patients

Sex Difference in Cisplatin-Induced Nephrotoxicity: Laboratory and Clinical Findings

Cisplatin (CP) as the most important anticancer drug has limited usage due to a lot of side effects such as nephrotoxicity. Additionally, nephrotoxicity is gender/sex-related. There is a variety of experimental studies in association with sex and CP-induced nephrotoxicity. Some studies have reported that female sex is resistant than male sex due to greater antioxidant defense and protective effects of estrogen in females. Other studies have indicated that males are less vulnerable than females due to CP high clearance. Also, various supplementations have revealed conflicting effects in males and females. It is uncovered that sex hormones have determinant roles on the conflicting effects. Some supplements could improve CP-induced nephrotoxicity, but several supplements intensified CP-induced nephrotoxicity, especially in female sex. On the other hand, major clinical studies introduced female gender as a risk factor of CP-induced nephrotoxicity. Although, rare studies evaluated the effect of various supplemental compounds on CP-induced nephrotoxicity in patients underwent CP therapy. Therefore, it requires further investigations to clarify the controversial subject of gender/sex and CP-induced nephrotoxicity in both clinic and laboratory.

Unexpected Enhancement of Cytotoxicity of Cisplatin in a Rat Kidney Proximal Tubular Cell Line Overexpressing Mitochondrial Glutathione Transport Activity

In previous studies, we identified the two principal transporters that mediate the uptake of glutathione (GSH) from cytoplasm into the mitochondrial matrix of rat kidney proximal tubular cells. We hypothesized that genetic modulation of transporter expression could markedly alter susceptibility of renal proximal tubular cells to a broad array of oxidants and mitochondrial toxicants. Indeed, we previously showed that overexpression of either of these transporters resulted in diminished susceptibility to several chemicals. In the present work, we investigated the influence of overexpression of the mitochondrial 2-oxoglutarate carrier (OGC) in NRK-52E cells on the cytotoxicity of the antineoplastic drug cisplatin. In contrast to previous results showing that overexpression of the mitochondrial OGC provided substantial protection of NRK-52E cells from injury due to several toxicants, we found a remarkable enhancement of cellular injury from exposure to cisplatin as compared to wild-type NRK-52E cells. Despite the oxidative stress that cisplatin is known to cause in the renal proximal tubule, the increased concentrations of mitochondrial GSH associated with OGC overexpression likely resulted in increased delivery of cisplatin to molecular targets and increased cellular injury rather than the typical protection observed in the previous work.

In Vitro Nephrotoxicity Studies of Established and Experimental Platinum-Based Compounds

Cisplatin is one of the most commonly used drugs for the treatment of various solid cancers. However, its efficacy is restricted by severe side effects, especially dose-limiting nephrotoxicity. New platinum-based compounds are designed to overcome this limitation. Previous investigations showed that the platinum(IV)–nitroxyl complex PN149 is highly cytotoxic in various tumor cell lines. In the present study, investigations with PN149 were extended to normal human kidney tubule epithelia. Coincident with higher intracellular platinum accumulation, the cytotoxicity of PN149 in the proximal tubule epithelial cell line ciPTEC was more pronounced compared to the established platinum chemotherapeutics cisplatin, carboplatin and oxaliplatin. Quantitative gene expression profiling revealed the induction of ROS-inducible and anti-oxidative genes, suggesting an oxidative stress response by PN149. However, in contrast to cisplatin, no pro-inflammatory response was observed. Genes coding for distinct DNA damage response factors and genes related to apoptosis were up-regulated, indicating the activation of the DNA damage response system and induction of the apoptotic cascade by PN149. Altogether, a comparable transcriptional response was observed for PN149 and the platinum chemotherapeutics. However, the lack of inflammatory activity, which is a possible cause contributing to toxicity in human renal proximal tubule epithelia, might indicate the reduced nephrotoxic potential of PN149.

Modeling chemotherapy induced neurotoxicity with human induced pluripotent stem cell (iPSC) -derived sensory neurons

Chemotherapy-induced peripheral neuropathy (CIPN) is a frequent, potentially irreversible adverse effect of cytotoxic chemotherapy often leading to a reduction or discontinuation of treatment which negatively impacts patients' prognosis. To date, however, neither predictive biomarkers nor preventive treatments for CIPN are available, which is partially due to a lack of suitable experimental models. We therefore aimed to evaluate whether sensory neurons derived from induced pluripotent stem cells (iPSC-DSN) can serve as human disease model system for CIPN. Treatment of iPSC-DSN for 24 h with the neurotoxic drugs paclitaxel, bortezomib, vincristine and cisplatin led to axonal blebbing and a dose dependent decline of cell viability in clinically relevant IC₅₀ ranges, which was not observed for the non-neurotoxic compounds doxorubicin and 5-fluorouracil. Paclitaxel treatment effects were less pronounced after 24 h but prominent when treatment was applied for 72 h. Global transcriptome analyses performed at 24 h, i.e. before paclitaxel-induced cell death occurred, revealed the differential expression of genes of neuronal injury, cellular stress response, and sterol pathways. We further evaluated if known neuroprotective strategies can be reproduced in iPSC-DSN and observed protective effects of lithium replicating findings from rodent dorsal root ganglia cells. Comparing sensory neurons derived from two different healthy donors, we found preliminary evidence that these cell lines react differentially to neurotoxic drugs as expected from the variable presentation of CIPN in patients. In conclusion, iPSC-DSN are a promising platform to study the pathogenesis of CIPN and to evaluate neuroprotective treatment strategies. In the future, the application of patient-specific iPSC-DSN could open new avenues for personalized medicine with individual risk prediction, choice of chemotherapeutic compounds and preventive treatments.

The Predictive Value of Low Skeletal Muscle Mass Assessed on Cross-Sectional Imaging for Anti-Cancer Drug Toxicity: A Systematic Review and Meta-Analysis

Low skeletal muscle mass (LSMM) is increasingly recognized for its predictive value for adverse events in cancer patients. In specific, the predictive value of LSMM has been demonstrated for anti-cancer drug toxicity in a variety of cancer types and anti-cancer drugs. However, due to the limited sample size and study populations focused on a single cancer type, an overall predictive value of LSMM for anti-cancer drug toxicity remains unknown. Therefore, this review aims to provide a comprehensive overview of the predictive value of LSMM and perform a meta-analysis to analyse the overall effect. A systematic search was conducted of MEDLINE, Scopus, EMBASE, and Cochrane. Inclusion criteria were skeletal muscle mass (SMM) evaluated with computed tomography (CT) or magnetic resonance imaging (MRI), articles published in English, SMM studied in humans, SMM measurement normalized for height, and patients did not receive an intervention to treat or prevent LSMM. A meta-analysis was performed using a random-effects model and expressed in odds ratio (OR) with 95% confidence interval (CI). Heterogeneity was assessed using χ² and I² statistics. The search yielded 907 studies. 31 studies were included in the systematic review. Sample sizes ranged from 21 to 414 patients. The occurrence of LSMM ranged from 12.2% to 89.0%. The most frequently studied cancer types were oesophageal, renal, colorectal, breast, and head and neck cancer. Patients with LSMM had a higher risk of severe toxicity (OR 4.08; 95% CI 2.48-6.70; p < 0.001) and dose-limiting toxicity (OR 2.24; 95% CI 1.28-3.92; p < 0.001) compared to patients without LSMM. To conclude, the predictive value of LSMM for anti-cancer drug toxicity can be observed across cancer types. This information increases the need for further research into interventions that could treat LSMM as well as the possibility to adapt treatment regimens based on the presence of LSMM.

Better survival in impaired renal function patients with metastatic non-small cell lung cancer treated by cisplatin-pemetrexed

PURPOSE

Cisplatin-pemetrexed is the first-line chemotherapy for advanced, metastatic non-squamous non-small cell lung cancer (NSCLC), but the risk of kidney toxicity limits the therapeutic schedule. We performed a retrospective study of patient survival at 1 year and glomerular filtration rate (GFR) outcomes in cisplatin-pemetrexed-treated NSCLC patients.

METHODS

Patients (P) treated for NSCLC between 2008 and 2014 were divided into two groups according to GFR at diagnosis: G1 (GFR ≥ 90 mL/min/1.73 m²) and G2 (GFR between 60 and 89 mL/min/1.73 m²). GFR were compared in the two groups at 3 and 12 months. The following statistical methods were used: multivariate generalized estimating equation model for GFR outcome, Kaplan-Meier method for patient survival rate, and Cox model for analysing survival criteria.

RESULTS

A total of 112 patients were included in the study (G1 = 87 P, G2 = 25 P). At 12 months, mean GFR significantly decreased by 28.4 mL/min/1.73 m² (- 22.3%, p = 0.001) in G1 and. 13.8 mL/min/1.73 m² (- 17.2%, p = 0.001) in G2. Median patient survival was 9.6 months (1.1-52.4) in G1 and 19.7 months (3.7-56.9) in G2. A better overall survival was significantly correlated with GFR between 60 and 89 mL/min/1.73 m² at diagnosis (p = 0.04), and higher cumulated doses of pemetrexed (p = 0.003) and cisplatin (p = 0.001).

CONCLUSION

The better survival rate in G2 and its correlation with pemetrexed and cisplatin treatments suggest that, until other therapeutic choices become available, a cautious increase in dosage could be investigated as a way to improve poor prognoses.

Role of SLC transporters in toxicity induced by anticancer drugs

INTRODUCTION

. Membrane transporters are integral to the maintenance of cellular integrity of all tissue and cell types. While transporters play an established role in the systemic pharmacokinetics of therapeutic drugs, tissue specific expression of uptake transporters can serve as an initiating mechanism that governs the accumulation and impact of cytotoxic drugs.

AREAS COVERED

. This review provides an overview of organic cation transporters as determinants of chemotherapy-induced toxicities. We also provide insights into the recently updated FDA guidelines for in vitro drug interaction studies, with a particular focus on the class of tyrosine kinase inhibitors as perpetrators of transporter-mediated drug interactions.

EXPERT OPINION

. Studies performed over the last few decades have highlighted the important role of basolateral uptake and apical efflux transporters in the pathophysiology of drug-induced organ damage. Increased understanding of the mechanisms that govern the accumulation of cytotoxic drugs has provided insights into the development of novel strategies to prevent debilitating toxicities. Furthermore, we argue that current regulatory guidelines provide inadequate recommendations for in vitro studies to identify substrates or inhibitors of drug transporters. Therefore, the translational and predictive power of FDA-approved drugs as modulators of transport function remains ambiguous and warrants further revision of the current guidelines.

Pemetrexed exposure predicts toxicity in advanced non-small-cell lung cancer: A prospective cohort study

BACKGROUND

We explored whether total exposure to pemetrexed predicts effectiveness and toxicity in advanced non-small-cell lung cancer (NSCLC). Furthermore, we investigated alternative dosing schedules.

METHODS

In this prospective cohort study, patients with advanced NSCLC receiving first- or second-line pemetrexed(/platinum) were enrolled. Plasma sampling was performed weekly (cyclePK) and within 24 h (24hPK) after pemetrexed administration. With population pharmacokinetic/pharmacodynamic modelling, total exposure to pemetrexed during cycle 1 (area under the curve during chemotherapy cycle 1 [AUC₁]) was estimated and related to progression-free survival (PFS)/overall survival (OS). We compared mean AUC₁ (mg·h/L) in patients with and without severe chemotherapy-related adverse events (AEs) during total treatment. Second, different dosing schedules were simulated to minimise the estimated variability (coefficient of variation [CV]) of AUC.

RESULTS

For 106 of 165 patients, concentrations of pemetrexed were quantified (24hPK, n = 15; cyclePK, n = 106). After adjusting for prognostic factors, sex, disease stage and World Health Organisation performance score, AUC₁ did not predict PFS/OS in treatment-naive patients (n = 95) (OS, hazard ratio [HR] = 1.05, 95% confidence interval [CI]: 1.00-1.11; PFS, HR = 1.03, 95% CI: 0.98-1.08). Patients with severe chemotherapy-related AEs (n = 55) had significantly higher AUC₁ values than patients without them (n = 51) (226 ± 53 vs 190 ± 31, p < 0.001). Compared with body surface area-based dosing (CV: 22.5%), simulation of estimated glomerular filtration rate (eGFR)-based dosing (CV 18.5%) and fixed dose of 900 mg with 25% dose reduction, if the eGFR<60 mL/min (CV: 19.1%), resulted in less interindividual variability of AUC.

CONCLUSIONS

Higher exposure to pemetrexed does not increase PFS/OS but is significantly associated with increased occurrence of severe toxicity. Our findings suggest that fixed dosing reduces interpatient pharmacokinetic variability and thereby might prevent toxicity, while preserving effectiveness.

Drug-induced expression of EpCAM contributes to therapy resistance in esophageal adenocarcinoma

Background

With a less than 5% overall survival rate, esophageal adenocarcinoma (EAC) is one of the leading causes of death in the United States. Epithelial cell adhesion molecule (EpCAM) is a cancer stem cell (CSC) marker that is expressed in various epithelial carcinomas, including EAC. Accumulating evidence indicates that CSC subpopulations can initiate cancer development and, in addition, drive metastasis, recurrence and drug resistance. It has also been reported that EpCAM up-regulation in EAC may lead to an aggressive behavior and, thus, an adverse clinical outcome. Here, we aimed to determine whether treatment with standard chemotherapeutic agents may induce EpCAM expression and, concomitantly, increases in malignant potential and drug resistance in EAC.

Methods

EpCAM expression was assessed in 20 primary human EAC/adjacent normal tissues, as well as in a human EAC-derived cell line (OE-19), in a pre-malignant Barrett’s Esophagus cell line (Bar-T) and in a benign esophageal cell line (HET 1-A), using immunohistochemistry, Western blotting and qRT-PCR, respectively. Drug-induced resistance was investigated in OE-19-derived spheres treated with (a combination of) adriamycin, cisplatin and 5-fluorouracil (ACF) using survival, adhesion and flow cytometric assays, respectively, and compared to drug resistance induced by standard chemotherapeutic agents (CTA). Finally, ACF treatment-surviving cells were evaluated for their tumor forming capacities both in vitro and in vivo using spheroid formation and xenograft assays, respectively.

Results

High EpCAM expression was observed in esophageal cancer tissues and esophageal cancer-derived cell lines, but not in adjacent benign esophageal epithelia and benign esophageal cell lines (HET 1-A and Bar-T). The OE-19 cell spheres were drug resistant and EpCAM expression was significantly induced in the OE-19 cell spheres compared to the non-sphere OE-19 cells. When OE-19 cell spheres were challenged with ACF, the EpCAM mRNA and protein levels were further up-regulated up to 48 h, whereas a decreased EpCAM expression was observed at 72 h. EpCAM down-regulation by RNA interference increased the ACF efficacy to kill OE-19 cells. Increased EpCAM expression coincided with the CSC marker CD90 and was associated with an aggressive growth pattern of OE-19 cell spheres in vivo.

Conclusions

From our data we conclude that an ACF-induced increase in EpCAM expression reflects the selection of a CSC subpopulation that underlies tumor development and drug resistance in EAC.

Therapeutic drug monitoring of cancer chemotherapy

Therapeutic drug monitoring is not routinely used for chemotherapy agents. There are Several reasons, but one major drawback is the lack of established therapeutic Concentration ranges. Combination chemotherapy makes the establishment of Therapeutic ranges for individual drugs difficult, the concentration-effect relationship for a single drug may not be the same as when that drug is used in a drug combination. Pharmacokinetic optimization protocols for many classes of cytotoxic compounds exist in specialized centers, and some of these protocols are now part of large multicentre trials. Nonetheless, TDM clearly has the potential to improve the clinical use of chemotherapy gents, most of which have very narrow therapeutic indices and highly variable pharmacokinetics. A substantial body of literature accumulating during the past 15 years demonstrates relationships between systemic exposure to various chemotherapy agents and their toxic or therapeutic effects. This article reviews TDM concepts in addition to tools based on pharmacokinetic modeling of chemotherapy agents. The administered dose of chemotherapy agents is sometimes adjusted individually using either a priori or a posteriori methods. These models can only be applied by using the same dose and schedule as the original study. Bayesian estimation offers more flexibility in blood sampling times and, owing to its precision and to the amount of information provided is the method of choice for ensuring that a given patient benefits from the desired systemic exposure. Moreover, the role and application of Pharmacogenetics as a tool for individualizing chemotherapy is discussed highlighting the agents and mechanisms that have been well studied and defined and their relevance to clinical practice. Finally, this paper address issues critical to the optimal use of TDM in a clinical setting, and the role of clinical pharmacist in this regard. In addition, it discusses future developments in this field that can contribute to improving cancer chemotherapy In terms of patient outcome and survival. J Oncol Pharm Practice (2007) 13: 207—221.

Epithelial cell adhesion molecule in human hepatocellular carcinoma cell lines: a target of chemoresistence

Background

The low survival rate of hepatocellular carcinoma (HCC) is partly attributable to its resistance to existing chemotherapeutic agents. Until now, there have been limited chemotherapeutic agents for liver cancer. Epithelial cell adhesion molecule (EpCAM) has been found to be over-expressed during stages of carcinogenesis and has been associated with poor overall survival in many cancers. The aim of this study was to evaluate EpCAM expression in HCC and evaluate the effects of EpCAM to established chemotherapy.

Methods

Three human hepatocellular carcinoma cell lines—HepG2, Hep3B and HuH-7—were pre- and post-treated with doxorubicin, 5-fluorouracil (5-FU) and cisplatin. Cell viability and EpCAM protein expression were measured by MTT assay and Western Blotting respectively. EpCAM positive cells were analyzed by flow cytometry. To evaluate the effects of doxorubicin efficacy on EpCAM positive cells, a small interfering RNA (siRNA) specific to EpCAM was transfected into the cells and treated with doxorubicin. Results: EpCAM was significantly down-regulated by doxorubicin treatment in all three HCC cell lines (P <0.05 or 0.01). EpCAM expression was down-regulated by the 5-FU and cisplatin in HepG2 cells, however the EpCAM expression was up-regulated by 5-FU and cisplatin in Hep3B cell line. EpCAM expression was down-regulated by 5-FU, and up-regulated by cisplatin in Huh-7 cell line. Flow cytometry assay showed doxorubicin exposure decreased EpCAM positive cell quantities in three HCC cell lines. EpCAM siRNA knock-down attenuated cell mortality after doxorubicin exposure.

Conclusion

All of these findings demonstrate that EpCAM is one of targets of chemoresistence.

Switching from body surface area-based to fixed dosing for the investigational proteasome inhibitor ixazomib: a population pharmacokinetic analysis

AIMS

This population pharmacokinetic analysis of the investigational oral proteasome inhibitor ixazomib assessed the feasibility of switching from body surface area (BSA)-based to fixed dosing, and the impact of baseline covariates on ixazomib pharmacokinetics.

METHODS

Data were pooled from 226 adult patients with multiple myeloma, lymphoma or solid tumours in four phase 1 studies, in which ixazomib dosing (oral/intravenous, once/twice weekly) was based on BSA. Population pharmacokinetic modelling was undertaken using nonmem version 7.2.

RESULTS

Ixazomib pharmacokinetics were well described by a three compartment model with first order absorption and linear elimination. Ixazomib was absorbed rapidly (Ka 0.5 h(-1)), with dose- and time-independent pharmacokinetics. Estimated absolute bioavailability and clearance were 60% and 2l h(-1), respectively. Although a small effect of BSA (range 1.3-2.6 m(2)) was observed on the peripheral volume of distribution (V4), reducing the corresponding inter-individual variability by 12.9%, there was no relationship between BSA and ixazomib clearance (the parameter that dictates total systemic exposure following fixed dosing). Consistently, based on simulations (n = 1000), median AUCs (including interquartile range) were similar after BSA-based (2.23 mg m(-2)) and fixed (4 mg) oral dosing with no trend in simulated AUC vs. BSA for fixed dosing (P = 0.42). No other covariates, including creatinine clearance (22-213.7 ml min(-1)) and age (23-86 years), influenced ixazomib pharmacokinetics.

CONCLUSIONS

This analysis supports a switch from BSA-based to fixed dosing, without dose modification for mild/moderate renal impairment or age, in future adult studies of ixazomib, simplifying dosing guidance and clinical development.

Anatomical and physiological basis for the allometric scaling of cisplatin clearance in dogs

Cisplatin is a platinum-containing cytotoxic drug indicated for the treatment of solid tumors in veterinary and human patients. Several of the algorithms used to standardize the doses of cytotoxic drugs utilize allometry, or the nonproportional relationships between anatomical and physiological variables, but the underlying basis for these relationships is poorly understood. The objective of this proof of concept study was to determine whether allometric equations explain the relationships between body weight, kidney weight, renal physiology, and clearance of a model, renally cleared anticancer agent in dogs. Postmortem body, kidney, and heart weights were collected from 364 dogs (127 juveniles and 237 adults, including 51 dogs ≥ 8 years of age). Renal physiological and cisplatin pharmacokinetic studies were conducted in ten intact male dogs including two juvenile and eight adult dogs (4-55 kg). Glomerular filtration rate (GFR), effective renal plasma flow, effective renal blood flow, renal cisplatin clearance, and total cisplatin clearance were allometrically related to body weight with powers of 0.75, 0.59, 0.61, 0.71, and 0.70, respectively. The similar values of these diverse mass exponents suggest a common underlying basis for the allometry of kidney size, renal physiology, and renal drug handling.

Conjunctive therapy of cisplatin with the OCT2 inhibitor cimetidine: influence on antitumor efficacy and systemic clearance

The organic cation transporter 2 (OCT2) regulates uptake of cisplatin in proximal tubules, and inhibition of OCT2 protects against severe cisplatin-induced nephrotoxicity. However, it remains uncertain whether potent OCT2 inhibitors, such as cimetidine, can influence the antitumor properties and/or disposition of cisplatin. Using an array of preclinical assays, we found that cimetidine had no effect on the uptake and cytotoxicity of cisplatin in ovarian cancer cells with high OCT2 mRNA levels (IGROV-1 cells). Moreover, the antitumor efficacy of cisplatin in mice bearing luciferase-tagged IGROV-1 xenografts was unaffected by cimetidine (P = 0.39). Data obtained in 18 patients receiving cisplatin (100 mg/m(2)) in a randomized crossover fashion with or without cimetidine (800 mg × 2) revealed that cimetidine did not alter exposure to unbound cisplatin, a marker of antitumor efficacy (4.37 vs. 4.38 µg·h/ml; P = 0.86). These results support the future clinical exploration of OCT2 inhibitors as specific modifiers of cisplatin-induced nephrotoxicity.

Constancy in Integrated Cisplatin Plasma Concentrations Among Pediatric Patients

The authors report on the variability in the integrated quantity of free (unbound) plasma cisplatin (area under curve of plasma concentration versus time, AUC). The AUC was measured in 19 patients receiving cisplatin doses proportional to body surface areas (BSA), 30 mg/m2 over 1 hour. The relative standard deviation (RSD, population standard deviation divided by mean value) for the maximum free plasma cisplatin concentration (Cmax, microM) was 0.338; for the half-life (t1/2, minute), 0.210; and for the AUC (microM minute), 0.320. Thus, BSA-based dosing gave significant variability in the AUC. We attempted to use (weight)a(height)b, seeking values of a and b that gave the smallest RSD in AUC, but only minimal improvement could be obtained by deviating from the BSA formula (a=b=0.5). However, dosing proportional to (weight)d(Cmax)f (with d approximately 3/4 and f approximately -1) reduced the RSD in AUC from approximately 1/3 to approximately 1/10. Dosing proportional to (weight)m (Cmax)n(t1/2)p (with m approximately 0.7, n approximately -1, and p approximately -1/2) reduced it further, to approximately 1/32. In contrast, using (weight)d(Cmax)f(age)g gave no improvement over (weight)d(Cmax)f. The authors conclude that the inconsistency in AUC can be reduced 10-fold with dosing proportional to the weight and the drug pharmacokinetic parameters [(weight0.7)/(Cmaxxt1/2(0.5))].

Associations between ABCC2 polymorphisms and cisplatin disposition and efficacy

ABCC2 (MRP2, cMOAT) expression has been implicated in cisplatin resistance in vitro. In mice, cisplatin disposition and toxicity were unaffected by Abcc2 knockout (Abcc2−/−). Moreover, in cancer patients (n = 237), cisplatin pharmacokinetics (P > 0.12) and efficacy (P > 0.41) were not associated with seven of the single-nucleotide polymorphisms (SNPs) in ABCC2. These SNPs were also not correlated with ABCC2 expression in the NCI60 panel (P > 0.26) or with cisplatin-induced cytotoxicity (P = 0.21). These findings highlight the importance of verifying drug-transporter interactions with in vitro tests in humans.

Proximal tubular secretion of creatinine by organic cation transporter OCT2 in cancer patients

PURPOSE

Knowledge of transporters responsible for the renal secretion of creatinine is key to a proper interpretation of serum creatinine and/or creatinine clearance as markers of renal function in cancer patients receiving chemotherapeutic agents.

EXPERIMENTAL DESIGN

Creatinine transport was studied in transfected HEK293 cells in vitro and in wild-type mice and age-matched organic cation transporter 1 and 2-deficient [Oct1/2(-/-)] mice ex vivo and in vivo. Clinical pharmacogenetic and transport inhibition studies were done in two separate cohorts of cancer patients.

RESULTS

Compared with wild-type mice, creatinine clearance was significantly impaired in Oct1/2(-/-) mice. Furthermore, creatinine inhibited organic cation transport in freshly isolated proximal tubules from wild-type mice and humans, but not in those from Oct1/2(-/-) mice. In a genetic association analysis (n = 590), several polymorphisms around the OCT2/SLC22A2 gene locus, including rs2504954 (P = 0.000873), were significantly associated with age-adjusted creatinine levels. Furthermore, in cancer patients (n = 68), the OCT2 substrate cisplatin caused an acute elevation of serum creatinine (P = 0.0083), consistent with inhibition of an elimination pathway.

CONCLUSIONS

Collectively, this study shows that OCT2 plays a decisive role in the renal secretion of creatinine. This process can be inhibited by OCT2 substrates, which impair the usefulness of creatinine as a marker of renal function.

Optimization of cisplatin doses in a testicular cancer patient with acute renal failure

Although testicular cancers are highly curable malignancies, conventional cisplatin based therapy often causes important toxicities, not often easily manageable. Nephrotoxicity occurs in almost all patients, and is potentialized in patients suffering from renal failure. Monitoring of residual levels of unbound platinum was used to define guidelines for cisplatin administration.

Monitoring of cisplatin was initiated in a patient treated for metastatic testicular cancer and acute renal failure. Reduced doses of cisplatin were first administered in conjunction with hemodialysis. Unbound and total platinum levels were determined by flameless atomic absorption spectrophotometry.

The data found allowed us to adapt and increase sequentially cisplatin doses, accordingly with the renal function. Full regimen doses were eventually administered when useful renal function returned. This simple approach may be useful in monitoring cisplatin administration during acute renal failure.

Pharmacokinetics and pharmacogenomics in esophageal cancer chemoradiotherapy

Esophageal cancer is one of the most lethal malignancies. Surgical resection of the tumor from the primary site has been the standard treatment, especially for localized squamous cell carcinoma, but considerable clinical efforts during the last decade have resulted in novel courses of treatment. These options include chemoradiotherapy, consisting of a continuous infusion of 5-fluorouracil (5-FU), cisplatin (CDDP), and concurrent radiation. Given the substantial inter- and/or intra-individual variation in clinical outcome, future improvements will likely require the incorporation of a novel anticancer drug, pharmacokinetically guided administration of CDDP or 5-FU, and identification of potential responders by patient genetic profiling prior to treatment. In this review, the latest information on incidence, risk factors, biomarkers, therapeutic strategies, and the pharmacokinetically guided or genotype-guided administration of CDDP and 5-FU is summarized for future individualization of esophageal cancer treatment.

Interaction of Cisplatin with the human organic cation transporter 2

PURPOSE

Cisplatin is predominantly eliminated in the urine through active secretion. As the solute carrier organic cation transporter 2 (OCT2) is highly expressed in the basolateral membrane of proximal tubules, we determined its contribution to cisplatin transport and assessed the relation of variation in the gene encoding OCT2 (SLC22A2) with the disposition of cisplatin.

EXPERIMENTAL DESIGN

Cell lines were transfected using the Flp-In 293 system with the full-length OCT2 cDNA, and platinum concentrations were measured using flameless atomic absorption spectrometry. Pharmacokinetic data were available from 106 cancer patients, and DNA was screened for eight nonsynonymous SLC22A2 variants using direct sequencing.

RESULTS

mRNA expression was 36-fold higher and uptake of the model substrate tetraethylammonium was significantly increased (P < 0.0001) in OCT2-transfected cells compared with empty vector-transfected controls. OCT2-mediated transport of cisplatin was saturable, and uptake was increased by approximately 4-fold (P < 0.0001) relative to control cells. Cisplatin inhibited OCT2-mediated transport of tetraethylammonium by up to 97%. The mean +/- SD systemic clearance of unbound cisplatin-derived platinum in the patient population was 29.2 +/- 8.39 L/h, and renal clearance was particularly variable. Only one single nucleotide polymorphism (Ala270Se; rs316019) was identified (minor allele frequency, 7.6%), and it was not found to be associated with any of the studied pharmacokinetic variables (P > 0.05).

CONCLUSION

These findings support the hypothesis that OCT2 is a key renal transporter involved in cisplatin elimination. However, known variants in SLC22A2 do not substantially contribute to explaining interindividual pharmacokinetic variability, suggesting that other mechanisms, controlling OCT2 expression, might be involved.

Therapeutic drug monitoring for dose individualization of Cisplatin in testicular cancer patients based upon total platinum measurement in plasma

Cisplatin (CDDP) is an anticancer agent widely used in testicular cancer, for which pharmacokinetic (PK)/pharmacodynamic relationships have usually been based upon measurement of its unbound fraction in plasma. Because it has been shown that free CDDP clearance can be related to patient's body surface area (BSA), dosage is mostly adjusted a priori using only this single parameter, with mixed results for accurately predicting CDDP exposure and reducing toxicities. In contrast, the authors present here an original, 5-day continuous infusion schedule, coupled to a daily Bayesian adaptive dosing with feedback strategy, based upon the rapid assay of total, rather than free, CDDP in plasma. Nineteen patients (66 therapeutic courses) were treated with platinum-based combinational therapy. Plasma samples were analyzed to allow real-time Bayesian estimation of individual PK parameters with subsequent prospective dose adjustment in order to reach a target Cmax (Cend) of 1.95 mg/L of total platinum. Performance of the Bayesian dosing method was evaluated by comparing target Cmax with achieved Cmax. The mean+/-SD Cmax achieved was 1.93+/-0.16 mg/L. No statistically significant difference was observed between experimental and target values (P>0.05, t test), and Cend achievement was done with an overall 6.6% precision, a performance to be compared with the initial 54% interpatient variability observed in CDDP clearance. A nonlinear mixed effect model population PK analysis was subsequently performed to identify retrospectively the covariates associated with PK parameters of total CDDP. It showed a good correlation (r=0.84, P=0.004) between total platinum clearance and therapeutic course number. A weaker correlation (r=0.59) was found between BSA and total CDDP clearance and, importantly, no additional relationship was established with BSA when successive therapeutic courses, and not only the first one, were considered. This highlights the critical importance of total drug accumulation on CDDP pharmacokinetics when several infusions are to be administered in a row and, therefore, the need for real-time dose individualization that takes into account the course number, rather than BSA. Finally, doses of CDDP administered during each course were significantly higher (+20%, P<0.01) than the ones classically normalized with BSA, thus leading to an overall greater drug exposure in the patients. It is noteworthy that despite these markedly higher doses, little severe toxicity was reported, and all of the patients presented in this study were still alive and disease free after a follow-up of up to 15 years.

Evaluation of an Alternate Dosing Strategy for Cisplatin in Patients With Extreme Body Surface Area Values

Purpose

The majority of cytotoxic drugs for adults are dosed based on body surface area (BSA), aiming to reduce interpatient variability in drug exposure. We prospectively studied the usefulness of BSA-based dosing of cisplatin in patients at extremes of BSA values.

Patients and Methods

Patients were randomly assigned to receive a fixed dose of cisplatin in course 1, and a BSA-adjusted dose in course 2, or vice versa. The fixed dose was based on the average BSA for males and females, while extremes were set at BSA values exceeding the average ± 1 standard deviation. Subsequently, we retrospectively analyzed data from a normal population.

Results

In 25 patients assessable for both courses, the use of a fixed dose of cisplatin resulted in reduced exposure to unbound platinum in patients at the upper extremes of BSA (P = .003) and higher exposures in patients at the lower extremes (P = .009), as compared with exposures following the BSA-adjusted dose. Although clearance was related to BSA (R2 = 0.44; P < .001), only a small reduction in interpatient variability in clearance after correction for BSA was achieved (20.8% v 17.1%). In the retrospective analysis, compared with the average patient, the clearance of unbound platinum in patients with a BSA value ≤ 1.65 m2 was 16% slower (P < .001), while an 18% faster clearance (P < .001) was observed in patients with a BSA value ≥ 2.05 m2.

Conclusion

Unless better predictors for platinum clearance are identified, fixed-dose regimens per BSA cluster (≤ 1.65 m2; 1.66 m2 to 2.04 m2; ≥ 2.05 m2) are recommended.