Population pharmacokinetics of carboplatin, etoposide and melphalan in children: a re-evaluation of paediatric dosing formulas for carboplatin in patients with normal or mild impairment of renal function

Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) methods for the therapeutic drug monitoring of cytotoxic anticancer drugs: An update

In the era of precision medicine, there is increasing evidence that conventional cytotoxic agents may be suitable candidates for therapeutic drug monitoring (TDM)- guided drug dosage adjustments and patient's tailored personalization of non-selective chemotherapies. To that end, many liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) assays have been developed for the quantification of conventional cytotoxic anticancer chemotherapies, that have been comprehensively and critically reviewed. The use of stable isotopically labelled internal standards (IS) of cytotoxic drugs was strikingly uncommon, accounting for only 48 % of the methods found, although their use could possible to suitably circumvent patients' samples matrix effects variability. Furthermore, this approach would increase the reliability of cytotoxic drug quantification in highly multi-mediated cancer patients with complex fluctuating pathophysiological and clinical conditions. LC-MS/MS assays can accommodate multiplexed analyses of cytotoxic drugs with optimal selectivity and specificity as well as short analytical times and, when using stable-isotopically labelled IS for quantification, provide concentrations measurements with a high degree of certainty. However, there are still organisational, pharmacological, and medical constraints to tackle before TDM of cytotoxic drugs can be more largely adopted in the clinics for contributing to our ever-lasting quest to improve cancer treatment outcomes.

Generation of evidence-based carboplatin dosing guidelines for neonates and infants

BACKGROUND

To optimally dose childhood cancer patients it is essential that we apply evidence-based dosing approaches. Carboplatin is commonly dosed to achieve a cumulative target exposure (AUC) in children, with target AUC values of 5.2-7.8 mg/ml.min defined. To achieve these exposures patients are dosed at 6.6 mg/kg/day or 4.4 mg/kg for patients <5 kg. The current study uses real world clinical pharmacology data to optimise body weight-based doses to effectively target AUCs of 5.2-7.8 mg/ml.min in infants.

METHODS

Carboplatin exposures were determined across 165 treatment cycles in 82 patients ≤10 kg. AUC and clearance values were determined by Bayesian modelling from samples collected on day 1. These parameters were utilised to assess current dosing variability, determine doses required to achieve target AUC values and predict change in AUC using the modified dose.

RESULTS

No significant differences in clearance were identified between patients <5 kg and 5-10 kg. Consequently, for patients <5 kg, 4.4 mg/kg dosing was not sufficient to achieve a target AUC of 5.2 mg/ml.min, with <55% of patients within 25% of this target. Optimised daily doses for patients ≤10 kg were 6 mg/kg and 9 mg/kg for cumulative carboplatin target exposures of 5.2 and 7.8 mg/ml.min, respectively.

CONCLUSIONS

Adoption of these evidence-based carboplatin doses in neonates and infants will reduce drug exposure variability and positively impact treatment.

Approaches to handling missing or "problematic" pharmacology data: Pharmacokinetics

Missing or erroneous information is a common problem in the analysis of pharmacokinetic (PK) data. This may present as missing or inaccurate dose level or dose time, drug concentrations below the analytical limit of quantification, missing sample times, or missing or incorrect covariate information. Several methods to handle problematic data have been evaluated, although no single, broad set of recommendations for commonly occurring errors has been published. In this tutorial, we review the existing literature and present the results of our simulation studies that evaluated common methods to handle known data errors to bridge the remaining gaps and expand on the existing knowledge. This tutorial is intended for any scientist analyzing a PK data set with missing or apparently erroneous data. The approaches described herein may also be useful for the analysis of nonclinical PK data.

In vitro Toxico-genomics of Etoposide Loaded Gelatin Nanoparticles and Its in-vivo Therapeutic Potential: Pharmacokinetics, Biodistribution and Tumor Regression in Ehrlich Ascites Carcinoma (EAC) Mice Model

Globally, breast cancer is the foremost cause of mortality among women detected with cancer, with 21% diagnosed in India alone. Etoposide loaded gelatin nanoparticles (EGNP) were prepared and its physical characterization (size:150nm±0.241; zeta potential −29.32 mV) was done along with in-vitro studies to assess biotoxicity, intracellular ROS, cell cycle arrest and death caused by EGNPs. We report the molecular pathways induced by EGNP in-vitro, pharmacokinetics, biodistribution and tumor regression in-vivo in Balb/c mice.Gene expression profiling of Bax, Bcl2, p53, Caspase-3, RIPK1, RIPK3 and ß-actin as internal control were done by RT-PCR wherein Etoposide and EGNP treated MCF-7 cells showed higher expressions of apoptotic genes-Bax, p53, caspase-3, lower expression of anti-apoptotic gene-Bcl2 when compared to control. Enhanced expression of necroptosis-RIPK1 were observed, while RIPK3 was insignificant. Since, RIPK1 regulates necroptosis and apoptosis, expression of apoptotic markers confirmed apoptotic molecular mechanisms. Negligible hemolysis of Gelatin nanoparticles (GNP), and EGNP at selected dosages confirmed biocompatibility. In vivo pharmacokinetics and biodistribution were done by 99Tc-labelled nanoparticles indicating increased circulation of EGNPs, allowing accumulation at the tumor site by Enhanced permeability and retention (EPR) phenomena. Tumor regression indicates the efficacy of EGNP by reducing the tumor burden when compared to void GNP and Etop per se, resulting in increased life span. High biocompatibility and bio-efficacy of EGNPs prove their therapeutic potential in cancer treatment.

Diversity of dose-individualization and therapeutic drug monitoring practices of platinum compounds: a review

Introduction: Platinum-derived drugs are commonly used for the treatment of solid tumors. The differences in chemical structures of these molecules lead to different pharmacological properties, in terms of indication, efficacy, and toxicity. Their pharmacokinetics (PK) differ according to their respective renal elimination and have led to many studies investigating their dose optimization. Area covered: This review attempts to summarize and compare PK and pharmacodynamics of cisplatin, carboplatin, and oxaliplatin, with an emphasis on differences of dose calculations and opportunities for therapeutic drug monitoring (TDM) in various patient populations. Expert opinion: Although cisplatin and carboplatin can be considered as analogs since they share the same DNA interacting properties, the slower hydrolysis of the latter results in a better safety profile. Carboplatin is the only drug in oncology to be administrated according to a target area under the curve of concentration versus time, considering that its PK variability is almost fully explained by renal function, not by body size. This enables individual dosing based on predicted carboplatin clearance (along with patients renal characteristics) or on actual clearance with TDM, especially in a high-dose protocol.

Over a decade of experience with carboplatin therapeutic drug monitoring in a childhood cancer setting in the United Kingdom

The widely used platinum agent carboplatin represents a good example of an anticancer drug where clear relationships between pharmacological exposure and clinical response and toxicity have previously been shown. Within the setting of childhood cancer, there are defined groups of patients who present a particular challenge when dosing with carboplatin, including neonates and infants, those who are anephric, and poor prognosis patients receiving high-dose chemotherapy. For these groups, nonstandard chemotherapy dosing regimens are currently utilised, often with different approaches between clinical study protocols and between treatment centres. For the treatment of these patient populations in the UK, there is now significant experience in carrying out therapeutic drug monitoring, aiming to consistently achieve target drug exposures, maximise drug efficacy and minimise treatment-related side effects. An ongoing clinical trial is currently providing information on drug exposure for a wide range of anticancer agents in these hard to treat patient populations. In addition to supporting dosing decisions for individual patients, the collection and analysis of these data may allow the development of future dosing regimens. For example, current reduced dosing approaches for neonates and infants based on age or body weight, may well be better replaced by regimens based on a sound pharmacological rationale. The successful use of adaptive carboplatin dosing in childhood cancer should encourage the development of therapeutic drug monitoring approaches more widely in an oncology setting.

Pharmacotherapy in Children and Adolescents: Oncology

Pharmacotherapy in paediatric oncology is a difficult task. It is challenging to determine the optimal dose in children of different age groups. In addition, anticancer drugs display severe side effects reducing the quality of life. Late effects like secondary tumours and cardiotoxicity can be apparent years after treatment and must be taken into account when planning treatment schedules. Classical cytoreducing agents are still of great importance in treating children with leukaemia and solid tumours. In addition, drugs developed by rational drug design (targeted drugs) are a very important part of many treatment protocols, and newer drugs are emerging in several types of cancer. Unfortunately, there is only limited experience with newer drugs in children, because new drugs are mostly developed for adults. Complicated therapy regimens require a solid knowledge of the pharmacology of the drugs applied. This chapter attempts to introduce some pharmacological knowledge for the most important anticancer drugs in children with a focus on side effects and age-specific considerations.

Population pharmacokinetics of carboplatin, etoposide and melphalan in children: a re-evaluation of paediatric dosing formulas for carboplatin in patients with normal or mild impairment of renal function

AIMS

Carboplatin dosage is calculated by using the estimated glomerular filtration rate (GFR) to achieve a target plasma area under the plasma concentration-time curve (AUC). The aims of the present study were to investigate factors that influence the pharmacokinetics of carboplatin in children with high-risk neuroblastoma, and whether target exposures for carboplatin were achieved using current treatment protocols.

METHODS

Data on children receiving high-dose carboplatin, etoposide and melphalan for neuroblastoma were obtained from two study sites [European International Society for Paediatric Oncology (SIOP) Neuroblastoma study, Children's Hospital at Westmead; n = 51]. A population pharmacokinetic model was built for carboplatin to evaluate various dosing formulas. The pharmacokinetics of etoposide and melphalan was also investigated. The final model was used to simulate whether target carboplatin AUC (16.4 mg ml^-1 ·min) would be achieved using the paediatric Newell formula, modified Calvert formula and weight-based dosing.

RESULTS

Allometric weight was the only significant, independent covariate for the pharmacokinetic parameters of carboplatin, etoposide and melphalan. The paediatric Newell formula and modified Calvert formula were suitable for achieving the target AUC of carboplatin for children with a GFR <100 ml min^-1 1.73 m^-2 but not for those with a GFR ≥100 ml min^-1 1.73 m^-2 . A weight-based dosing regimen of 50 mg kg^-1 achieved the target AUC more consistently than the other formulas, regardless of renal function.

CONCLUSIONS

GFR did not appear to influence the pharmacokinetics of carboplatin after adjusting pharmacokinetic parameters for weight. This model-based approach validates the use of weight-based dosing as an appropriate alternative for carboplatin in children with either mild renal impairment or normal renal function.