Comparative cardiotoxicity of idarubicin and doxorubicin using the isolated perfused rat heart model

Anthracycline derivatives inhibit cardiac CYP2J2

Anthracycline chemotherapeutics are highly effective, but their clinical usefulness is hampered by adverse side effects such as cardiotoxicity. Cytochrome P450 2J2 (CYP2J2) is a cytochrome P450 epoxygenase in human cardiomyocytes that converts arachidonic acid (AA) to cardioprotective epoxyeicosatrienoic acid (EET) regioisomers. Herein, we performed biochemical studies to understand the interaction of anthracycline derivatives (daunorubicin, doxorubicin, epirubicin, idarubicin, 5-iminodaunorubicin, zorubicin, valrubicin, and aclarubicin) with CYP2J2. We utilized fluorescence polarization (FP) to assess whether anthracyclines bind to CYP2J2. We found that aclarubicin bound the strongest to CYP2J2 despite it having large bulky groups. We determined that ebastine competitively inhibits anthracycline binding, suggesting that ebastine and anthracyclines may share the same binding site. Molecular dynamics and ensemble docking revealed electrostatic interactions between the anthracyclines and CYP2J2, contributing to binding stability. In particular, the glycosamine groups in anthracyclines are stabilized by binding to glutamate and aspartate residues in CYP2J2 forming salt bridge interactions. Furthermore, we used iterative ensemble docking schemes to gauge anthracycline influence on EET regioisomer production and anthracycline inhibition on AA metabolism. This was followed by experimental validation of CYP2J2-mediated metabolism of anthracycline derivatives using liquid chromatography tandem mass spectrometry fragmentation analysis and inhibition of CYP2J2-mediated AA metabolism by these derivatives. Taken together, we use both experimental and theoretical methodologies to unveil the interactions of anthracycline derivatives with CYP2J2. These studies will help identify alternative mechanisms of how anthracycline cardiotoxicity may be mediated through the inhibition of cardiac P450, which will aid in the design of new anthracycline derivatives with lower toxicity.

Treatment outcome of doxorubicin versus idarubicin in adult acute myeloid leukemia

Purpose

The present study aimed to compare treatment outcome of idarubicin versus doxorubicin in combination with Ara-C as induction therapy for untreated AML patients.

Patients and methods

This retrospective study included 143 patients with de novo AML. All patients received full dose of standard induction therapy (3 + 7) using anthracyclines (doxorubicin or idarubicin) and cytarabine.

Results

The studied groups had comparable CR. No significant differences were noted between the studied groups regarding DFS and OS. The DXR group had significantly lower cost in comparison to IDA group.

Conclusions

Idarubicin doesn't have a clear advantage over doxorubicin in treatment of AML.

Co-Treatments of Edible Curcumin from Turmeric Rhizomes and Chemotherapeutic Drugs on Cytotoxicity and FLT3 Protein Expression in Leukemic Stem Cells

This study aims to enhance efficacy and reduce toxicity of the combination treatment of a drug and curcumin (Cur) on leukemic stem cell and leukemic cell lines, including KG-1a and KG-1 (FLT3+ LSCs), EoL-1 (FLT3+ LCs), and U937 (FLT3- LCs). The cytotoxicity of co-treatments of doxorubicin (Dox) or idarubicin (Ida) at concentrations of the IC10-IC80 values and each concentration of Cur at the IC20, IC30, IC40, and IC50 values (conditions 1, 2, 3, and 4) was determined by MTT assays. Dox-Cur increased cytotoxicity in leukemic cells. Dox-Cur co-treatment showed additive and synergistic effects in several conditions. The effect of this co-treatment on FLT3 expression in KG-1a, KG-1, and EoL-1 cells was examined by Western blotting. Dox-Cur decreased FLT3 protein levels and total cell numbers in all the cell lines in a dose-dependent manner. In summary, this study exhibits a novel report of Dox-Cur co-treatment in both enhancing cytotoxicity of Dox and inhibiting cell proliferation via FLT3 protein expression in leukemia stem cells and leukemic cells. This is the option of leukemia treatment with reducing side effects of chemotherapeutic drugs to leukemia patients.

Network integration and modelling of dynamic drug responses at multi-omics levels

Uncovering cellular responses from heterogeneous genomic data is crucial for molecular medicine in particular for drug safety. This can be realized by integrating the molecular activities in networks of interacting proteins. As proof-of-concept we challenge network modeling with time-resolved proteome, transcriptome and methylome measurements in iPSC-derived human 3D cardiac microtissues to elucidate adverse mechanisms of anthracycline cardiotoxicity measured with four different drugs (doxorubicin, epirubicin, idarubicin and daunorubicin). Dynamic molecular analysis at in vivo drug exposure levels reveal a network of 175 disease-associated proteins and identify common modules of anthracycline cardiotoxicity in vitro, related to mitochondrial and sarcomere function as well as remodeling of extracellular matrix. These in vitro-identified modules are transferable and are evaluated with biopsies of cardiomyopathy patients. This to our knowledge most comprehensive study on anthracycline cardiotoxicity demonstrates a reproducible workflow for molecular medicine and serves as a template for detecting adverse drug responses from complex omics data.

Using a network propagation approach with integrated multi-omic data, Selevsek et al. develop a reproducible workflow for identifying drug toxicity effects in cellular systems. This is demonstrated with the analysis of anthracycline cardiotoxicity in cardiac microtissues under the effect of multiple drugs.

A computational study of Anthracyclines interacting with lipid bilayers: Correlation of membrane insertion rates, orientation effects and localisation with cytotoxicity

Anthracyclines interact with DNA and topoisomerase II as well as with cell membranes, and it is these latter interactions that can cause an increase in their cytotoxic activity. In the present study a detailed computational analysis of the initial insertion, orientation and nature of the interaction occurring between Anthracyclines and two different lipid bilayers (unsaturated POPC and saturated DMPC) is explored through molecular dynamics (MD) simulations; four Anthracyclines: Doxorubicin (DOX), Epirubicin (EPI), Idarubicin (IDA) and Daunorubicin (DAU) were examined. The results indicate that the increased cytotoxicity of DOX, in comparison to the other three analogues, is correlated with its ability to diffuse at a faster rate into the bilayers. Additionally, DOX exhibited considerably different orientational behaviour once incorporated into the bilayer and exhibited a higher propensity to interact with the hydrocarbon tails in both lipids indicating a higher probability of transport to the other leaflet of the bilayer.

Network and Pathway Analysis of Toxicogenomics Data

Toxicogenomics is the study of the molecular effects of chemical, biological and physical agents in biological systems, with the aim of elucidating toxicological mechanisms, building predictive models and improving diagnostics. The vast majority of toxicogenomics data has been generated at the transcriptome level, including RNA-seq and microarrays, and large quantities of drug-treatment data have been made publicly available through databases and repositories. Besides the identification of differentially expressed genes (DEGs) from case-control studies or drug treatment time series studies, bioinformatics methods have emerged that infer gene expression data at the molecular network and pathway level in order to reveal mechanistic information. In this work we describe different resources and tools that have been developed by us and others that relate gene expression measurements with known pathway information such as over-representation and gene set enrichment analyses. Furthermore, we highlight approaches that integrate gene expression data with molecular interaction networks in order to derive network modules related to drug toxicity. We describe the two main parts of the approach, i.e., the construction of a suitable molecular interaction network as well as the conduction of network propagation of the experimental data through the interaction network. In all cases we apply methods and tools to publicly available rat in vivo data on anthracyclines, an important class of anti-cancer drugs that are known to induce severe cardiotoxicity in patients. We report the results and functional implications achieved for four anthracyclines (doxorubicin, epirubicin, idarubicin, and daunorubicin) and compare the information content inherent in the different computational approaches.

Incident adverse events following therapy for acute promyelocytic leukemia

The use of all-trans retinoic acid (ATRA) combined with arsenic trioxide (ATO) with or without cytotoxic chemotherapy is highly effective in acute promyelocytic leukemia (APL) but incident chronic adverse events (AEs) after initiation of therapy are not well understood. We retrospectively analyzed adult patients with newly diagnosed APL from 2004 through 2014 to identify incident AEs following treatment and contributing risk factors. Cardiac and neurologic AEs were more common and characterized in detail. Cardiac AEs such as the development of coronary artery disease (CAD), arrhythmias, and heart failure had a cumulative incidence of 6.4% (CI95 1.8–11.1%), 2.9% (CI95 0.0–6.4%), 5.8% (CI95 1.2–10.3%) at 4 years from diagnosis, respectively. In multivariate analyses of factors influencing heart failure, the presence of clinical or radiographic CAD (HR 4.25; P = 0.011) or troponin elevation prior to completion of therapy (HR 8.86; P = 0.0018) were associated with increased heart failure incidence, but not anthracycline use or dose. Neurological AEs were common following therapy; at 4 years, the cumulative incidence of vision changes was 12.4% (CI95 6.0–18.7%), peripheral neuropathy 10.3% (CI95 4.5–16.1%), and memory or cognitive change 7.6% (CI95 2.5–12.7%). We did not identify any association between specific therapies and the development of cardiac and neurologic AEs. APL is a highly curable leukemia; further efforts are needed to address incident chronic AEs, with particular focus on cardiac and neurological care.

Cardioprotective Effect of Grape Seed Extract on Chronic Doxorubicin-Induced Cardiac Toxicity in Wistar Rats

Purpose: The aim of the present study was to determine the ability of grape seed extract (GSE) as a powerful antioxidant in preventing adverse effect of doxorubicin (DOX) on heart function. Methods: Male rats were divided into three groups: control, DOX (2 mg/kg/48h, for 12 days) and GSE (100 mg/kg/24h, for 16 days) plus DOX. Left ventricular (LV) function and hemodynamic parameters were assessed using echocardiography, electrocardiography and a Millar pressure catheter. Histopathological analysis and in vitro antitumor activity were also evaluated. Results: DOX induced heart damage in rats through decreasing the left ventricular systolic and diastolic pressures, rate of rise/decrease of LV pressure, ejection fraction, fractional shortening and contractility index as demonstrated by echocardiography, electrocardiography and hemodynamic parameters relative to control group. Our data demonstrated that GSE treatment markedly attenuated DOX-induced toxicity, structural changes in myocardium and improved ventricular function. Additionally, GSE did not intervene with the antitumor effect of DOX. Conclusion: Collectively, the results suggest that GSE is potentially protective against DOX-induced toxicity in rat heart and maybe increase therapeutic index of DOX in human cancer treatment.

Identification of novel biomarkers for doxorubicin-induced toxicity in human cardiomyocytes derived from pluripotent stem cells

Doxorubicin is a chemotherapeutic agent indicated for the treatment of a variety of cancer types, including leukaemia, lymphomas, and many solid tumours. The use of doxorubicin is, however, associated with severe cardiotoxicity, often resulting in early discontinuation of the treatment. Importantly, the toxic symptoms can occur several years after the termination of the doxorubicin administration. In this study, the toxic effects of doxorubicin exposure have been investigated in cardiomyocytes derived from human embryonic stem cells (hESC). The cells were exposed to different concentrations of doxorubicin for up to 2 days, followed by a 12 day recovery period. Notably, the cell morphology was altered during drug treatment and the cells showed a reduced contractile ability, most prominent at the highest concentration of doxorubicin at the later time points. A general cytotoxic response measured as Lactate dehydrogenase leakage was observed after 2 days’ exposure compared to the vehicle control, but this response was absent during the recovery period. A similar dose-dependant pattern was observed for the release of cardiac specific troponin T (cTnT) after 1 day and 2 days of treatment with doxorubicin. Global transcriptional profiles in the cells revealed clusters of genes that were differentially expressed during doxorubicin exposure, a pattern that in some cases was sustained even throughout the recovery period, suggesting that these genes could be used as sensitive biomarkers for doxorubicin-induced toxicity in human cardiomyocytes. The results from this study show that cTnT release can be used as a measurement of acute cardiotoxicity due to doxorubicin. However, for the late onset of doxorubicin-induced cardiomyopathy, cTnT release might not be the most optimal biomarker. As an alternative, some of the genes that we identified as differentially expressed after doxorubicin exposure could serve as more relevant biomarkers, and may also help to explain the cellular mechanisms behind the late onset apoptosis associated with doxorubicin-induced cardiomyopathy.

Polypeptide conjugates of D-penicillamine and idarubicin for anticancer therapy

We investigated anticancer therapy with a novel combination of D-penicillamine (D-pen) and Idarubicin (Ida) in a synthetic dual drug conjugate (DDC). D-pen and Ida were covalently linked to poly(α)-L-glutamic acid (PGA) via reducible disulfide and acid-sensitive hydrazone bonds, respectively. The DDCs showed cell uptake and sustained release of the bound drugs in conditions mimicking the intracellular release media (10mM glutathione and pH 5.2). The in-vitro cytotoxicity of DDCs was comparable to unconjugated Ida in several sensitive and resistant cancer cell lines and correlated with the rate of cell uptake. In a single equivalent-dose pharmacokinetic study, DDCs enhanced the drug exposure by 7-fold and prolonged the plasma circulation half-life (t(1/2)) by 5-fold over unconjugated Ida. The therapeutic index of DDCs was 2-3-fold higher than unconjugated drugs. DDCs caused 89% tumor growth inhibition compared to 60% by unconjugated Ida alone and led to significant enhancement in the median survival (17%) of athymic nu/nu mice bearing NCI-H460 tumor xenografts.

Thiol Oxidation Induced by Oxidative Action of Adriamycin

To clarify the mechanism of the cardiotoxic action of adriamycin (ADM), the participation of free radicals from ADM in cardiotoxicity was investigated through the protective action of glutathione (GSH) or by using electron spin resonance (ESR). Oxidation of ADM by horseradish peroxidase and H2O2 (HRP-H2O2) was blocked by GSH concentration dependently. Inactivation of creatine kinase (CK) induced during interaction of ADM with HRP-H2O2 was also protected by GSH. Other anthracycline antitumor drugs that have a p-hydroquinone structure in the B ring also inactivated CK, and GSH inhibited the inactivation of CK. These results suggest that ADM was activated through oxidation of the p-hydroquinone in the B ring by HRP-H2O2. Although ESR signals of the oxidative ADM B ring semiquinone were not detected, glutathionyl radicals were formed during the interaction of ADM with HRP-H2O2 in the presence of GSH. ADM may be oxidized to the ADM B ring semiquinone and then reacts with the SH group. However, ESR signals of ADM C ring semiquinone, which was reductively formed by xanthine oxidase (XO) and hypoxanthine (HX) under anaerobic conditions, were not diminished by GSH, but they completely disappeared with ferric ion. These results indicate that oxidative ADM B ring semiquinones oxidized the SH group in CK, but reductive ADM C ring semiquinone radicals may participate in the oxidation of lipids or DNA and not of the SH group.

Prominent cardioprotective effects of third generation beta blocker nebivolol against anthracycline-induced cardiotoxicity using the model of isolated perfused rat heart

Nebivolol is a cardioselective beta-blocker (BB) currently used for the treatment of hypertension. It has mild vasodilating properties attributed to its interaction with the L-arginine/nitric oxide pathway, a property not shared by other BBs. Carvedilol is a nonselective ss-adrenergic receptor antagonist that also blocks alpha1-adrenergic receptors and is a potent antioxidant. Anthracyclines (ANTs), daunorubicin and doxorubicin, are commonly used in the treatment of several tumours, but their cardiac toxicity prevents their use at maximum myelotoxic doses, representing an important problem. In this study, we have evaluated the role of these BBs administered in combination with ANTs (daunorubicin and doxorubicin) on a reduction in cardiac toxicity. The combination of BB and ANTs has reduced the release of GSSG and GSH; in particular, co-treatment with nebivolol to ANTs has shown a significant reduction. The total integrated creatine kinase and troponin T activities were improved by BB and ANTs co-treatment. A significant reduction of their release was observed when hearts were treated with nebivolol. Cardiac tissue activity of gluthatione reductase was not significant and similar among experimental groups. In contrast, gluthatione peroxidise, Mn-superoxide dismutase and nitrite/nitrate release were increased after co-treatment with nebivolol. Finally, three parameters have been used to evaluate the cardiac toxicity of ANTs: the left ventricular pressure developed under a constant perfusion pressure (LVDP), the rate of variation of this parameter during systole (contractility) (LV/dt)max and during diastole (relaxation) (LV(dP/dt)min. Combination with BB has shown a reduction in cardiac toxicity; in particular, nebivolol has exerted the most significant cardioprotective effect.

A comparison of the effect of anticancer drugs, idarubicin and adriamycin, on soluble chromatin

The biological activity of an anticancer agent is related to its physicochemical interaction with biological receptors. In the present study we have investigated and compared the affinity and mode of action of two potent anticancer drugs, adriamycin and idarubicin on soluble chromatin using ultraviolet/visible and fluorescence spectroscopy, hydroxyapatite (HAP) chromatography and gel electrophoresis techniques. The results show that addition of various concentrations of drugs to chromatin solution individually, reduced both absorbance and fluorescence emission intensity of chromatin and precipitated it in a dose dependent manner, however, the extent of reduction was different for two drugs used. This effect was also observed on the histone gel patterns of the drug treated samples revealing that the chromatin is less affected by idarubicin compared to adriamycin implying higher aggregation of chromatin with the former. As hydroxyapatite chromatograms show, histone H1 represented the highest drug binding activity. The results suggest that although adriamycin and idarubicin are both grouped anthracycline antibiotic anticancer drugs, they differ considerably on their binding affinity to cellular chromatin.

Long-term and short-term models for studying anthracycline cardiotoxicity and protectors

The clinical importance of the cardiotoxicity of anthracyclines requires the availability of preclinical models able to predict the cardiotoxicity of novel anthracycline analogs in reference to doxorubicin or of cardioprotectors aimed at circumventing the deleterious effects of these drugs. The reference model has been defined long ago and has proven its validity. Weanling rabbits given weekly injections of doxorubicin for 4 months developed a cardiomyopathy, which can be assessed from a clinical and pathological point of view. Models in other animals such as rats or mice were similarly implemented, also with long-term exposures to the drug, resulting in cardiac failure and severe pathological alterations, which could be graded for comparison. Starting from the evidence that the damage caused by anthracyclines on cardiomyocytes was immediate after each injection and that the functional efficiency of the myocardium should be affected long before the morphological alterations become detectable, we developed a short-term model studying the cardiac performances of isolated perfused hearts of rats that had been treated within 12 days by repetitive administrations of the molecule(s) to be tested. This model provided the data expected from clinical experience: epirubicin appeared less cardiotoxic than doxorubicin; liposomal formulations appeared less cardiotoxic than free drug formulations; dexrazoxane strongly protected against doxorubicin cardiotoxicity. We were then able to show that paclitaxel could potentialize doxorubicin cardiotoxicity, but that docetaxel did not so; or that a high dose of dexrazoxane brought significantly higher protection than a conventional dose. Based upon these contributions, we can encourage the use of the short-term model of isolated perfused rat heart to screen the preclinical cardiotoxicity of anthracycline molecules, formulations and combinations.

Preclinical assessment of anthracycline cardiotoxicity in laboratory animals: predictiveness and pitfalls

Doxorubicin is one of the most prescribed anticancer drugs, due to its important activity in hematological malignancies as in solid tumors. However, its important cardiac toxicity still limits its long-term use and prevents from reaching optimal benefits. Numerous ways have been proposed to avoid cardiac toxicity, such as protracted infusions or special formulations, development of less cardiotoxic analogues and of cardioprotectors. There is a need for preclinical models able to screen rapidly these various approaches and to provide rational bases for clinical trials. The first model is the long-term rabbit model. Weanling rabbits given weekly injections of doxorubicin for 4 months developed a cardiomyopathy which was obvious from a clinical (cardiac failure) and from a pathological point of view. This model has been widely used afterwards for the discovery of cardioprotective molecules. Models in other animals such as rats or mice were similarly implemented, also with long-term exposures to the drug, resulting in cardiac failure and severe pathological alterations which could be graded for comparison. Starting from the evidence that the damage caused by anthracyclines on cardiomyocytes was immediate after each injection and that the functional efficiency of the myocardium should be affected by the anthracyclines long before the morphological alterations become detectable, we developed a short-term model studying the cardiac performances of isolated perfused hearts of rats that had been treated within 12 days by repetitive administrations of the molecule(s) to be tested. This model appeared easy to implement and provided the data expected from clinical experience: epirubicin appeared less cardiotoxic than doxorubicin; liposomal formulations appeared less cardiotoxic than free drug formulations; dexrazoxane strongly protected against doxorubicin cardiotoxicity. We were then to show that paclitaxel could potentiate doxorubicin cardiotoxicity, but that docetaxel did not so; or that a high dose of dexrazoxane brought significantly higher protection than a conventional dose. Based upon these various contributions, we can encourage the use of the short-term model of isolated perfused rat heart to screen the preclinical cardiotoxicity of anthracycline molecules, formulations and combinations.

Insights in the glycosylation steps during biosynthesis of the antitumor anthracycline cosmomycin: characterization of two glycosyltransferase genes

Glycosylation pattern in cosmomycins is a distinctive feature among anthracyclines. These antitumor compounds possess two trisaccharide chains attached at C-7 and C-10, each of them with structural variability, mainly at the distal deoxysugar moieties. We have characterized a 14-kb chromosomal region from Streptomyces olindensis containing 13 genes involved in cosmomycin biosynthesis. Two of the genes, cosG and cosK, coding for glycosyltransferase were inactivated with the generation of five new derivatives. Structural elucidation of these compounds showed altered glycosylation patterns indicating the capability of both glycosyltransferases of transferring deoxysugars to both sides of the aglycone and the flexibility of CosK with respect to the deoxysugar donor. A model is proposed for the glycosylation steps during cosmomycins biosynthesis.

Experimental study of dexrazoxane–anthracycline combinations using the model of isolated perfused rat heart

We have studied the protective effect of dexrazoxane on the cardiac toxicity induced by the anthracyclines currently used in clinics, doxorubicin, epirubicin, daunorubicin and idarubicin, with special emphasis on determining the optimal dose of dexrazoxane. This was performed using the model of isolated perfused rat heart after 12-day combination treatment of anthracyclines used at equi-cardiotoxic doses, and dexrazoxane used at 10-fold or 20-fold the anthracycline dose. We have shown in this study that dexrazoxane by itself was not cardiotoxic, and was able to significantly reduce anthracycline cardiac toxicity without increasing the general toxicity induced by these drugs. Using dexrazoxane at 20 times the anthracycline dose provided a better cardioprotection than using it at 10 times the anthracycline dose; at the higher dexrazoxane dose, the functional cardiac parameters (developed pressure, contractility and relaxation) were not different from those recorded in control animals.

Protecting against anthracycline-induced myocardial damage: a review of the most promising strategies

Over the last 40 years, great progress has been made in treating childhood and adult cancers. However, this progress has come at an unforeseen cost, in the form of emerging long-term effects of anthracycline treatment. A major complication of anthracycline therapy is its adverse cardiovascular effects. If these cardiac complications could be reduced or prevented, higher doses of anthracyclines could potentially be used, thereby further increasing cancer cure rates. Moreover, as the incidence of cardiac toxicity resulting in congestive heart failure or even heart transplantation dropped, the quality and extent of life for cancer survivors would improve. We review the proposed mechanisms of action of anthracyclines and the consequences associated with anthracycline treatment in children and adults. We summarise the most promising current strategies to limit or prevent anthracycline-induced cardiotoxicity, as well as possible strategies to prevent existing cardiomyopathy from worsening.

Pharmacology of anticancer drugs in the elderly population

Modifications to bodily functions and physiology are known to occur with age. These changes can have a considerable impact on the pharmacokinetic processes of absorption, distribution, metabolism and excretion and the pharmacodynamic properties of administered drugs. For many drugs with a high therapeutic index, this will be clinically unimportant, but for anticancer drugs, which usually have a low therapeutic index, these pharmacological changes can lead to dramatic consequences, such as excessive drug concentrations and unacceptable toxicity, or subtherapeutic drug concentrations and ineffective treatment. Despite the increased susceptibility of the elderly to these changes, doses are rarely adapted on the basis of pharmacokinetics and pharmacodynamics, with the exception of changes secondary to altered renal function. Until recently, only a few large prospective randomised trials have provided evidence-based data for dose adaptations in elderly patients. However, with increasing knowledge of the pharmacokinetics of anticancer drugs, advances in the knowledge of pharmacokinetic behaviour with aging, and documented efficacy and toxicity data in the elderly population, it is possible to highlight aspects of prescribing anticancer drugs in the elderly. In general, and for most drugs, age itself is not a contraindication to full-dose chemotherapy. The main limiting factors are comorbidity and poor functional status, which may be present in a significant number of the elderly population. Elderly patients with cancer are part of the daily practice of oncologists, but currently clinicians can often only estimate whether dose modification is advantageous for the elderly. This review attempts to elucidate the factors that can influence the pharmacokinetics of anticancer drugs frequently used in the elderly, and the clinical or biochemical parameters that form the basis for dose adjustments with age.

New oral drugs in older patients: a review of idarubicin in elderly patients

Idarubicin (IDA) is a structural analogue of daunorubicin with the same mechanism of action. Unlike the other currently available anthracyclines, it has a significant oral bioavailability, which makes it particularly attractive for the treatment of elderly patients. IDA resulted at least as effective as daunorubicin for acute nonlymphocytic leukemia and additional data are in analysis as far as lymphomas and breast cancer are concerned. Adverse effects are mainly hematological, while hair loss, mucositis and cardiotoxicity are less frequently reported with IDA than with other anthracyclines. The pharmacokinetics, activity, adverse effects and new modalities of oral administration are reviewed.

Pharmacological factors influencing anticancer drug selection in the elderly

Persons over the age of 65 years are the fastest growing segment of the US population. In the next 30 years this segment will represent more than 20% of the population. Fifty percent of all cancers occur in this age group and therefore the total cancer burden is expected to rise. Data are becoming available that will better guide the use of chemotherapy in the older patient population. Studies are presented discussing pharmacokinetic data on a number of chemotherapeutic agents with an emphasis on those that have entered clinical practice over the past few years. Many of these agents seem to have a beneficial therapeutic index, particularly in regard to older patients. Aging can affect the pharmacokinetics of chemotherapy in a number of ways. Absorption is only modified minimally by age. The greater concern with the use of oral drugs is patient compliance. Volume of distribution is affected by changes in body composition, anaemia and decreased plasma albumin concentration. There are many drugs in which renal excretion plays an important role. Decline in glomerular filtration is a consistent phenomenon with aging. Drug metabolism is primarily affected by changes in the P450 system and coadministration of drugs which also interact with this important enzyme system. The selection of chemotherapy in the elderly is frequently determined by degree of comorbidity and the patients' functional status. These factors are critical and can often determine response and toxicity. This article discusses the changes that occur with antimetabolites, camptothecins, anthracyclines, taxanes, platinum compounds, epipodophyllotoxins and vinca alkaloids. There has also been an increasing trend toward the use of oral chemotherapy. Factors that must be considered in selecting chemotherapeutic agents include limitations of saturability of absorption, patient compliance and the pharmacokinetic and pharmacodynamic changes that occur in older patients. Interpatient variability and age-related changes in drug metabolism are discussed. Careful attention to the physiological changes with age and dose adjustments necessary for end-organ dysfunction (renal, hepatic) are needed to ensure the safe administration of chemotherapy. In this article specific diseases are discussed (breast, colon, ovarian and non-small lung cancers) with recommendations for drug selection in adjuvant chemotherapy and the treatment of metastatic disease. Future studies will need to incorporate these various factors to properly evaluate chemotherapy in older patients. Research and educational initiatives targeted to this population will need to be a priority.

Free Radicals Mediate Cardiac Toxicity Induced by Adriamycin

Anthracycline antibiotics, including adriamycin (ADM), are widely used to treat various human cancers, but their clinical use has been limited because of their cardiotoxicity. ADM is especially toxic to heart tissue. The mechanisms responsible for the cardiotoxic effect of ADM have been very/extremely controversial. This review focuses on the participation of free radicals generated by ADM in the cardiotoxic effect. ADM is reduced to a semiquinone radical species by microsomal NADPH-P450 reductase and mitochondrial NADH dehydrogenase. In the presence of oxygen, the reductive semiquinone radical species produces superoxide and hydroxyl radicals. Generally, lipid peroxidation proceeds by mediating the redox of iron. ADM extracts iron from ferritin to form ADM-Fe3+, which causes lipid peroxidation of membranes. These events may lead to disturbance of the membrane structure and dysfunction of mitochondria. However, superoxide dismutase and hydroxyl radical scavengers have little effect on lipid peroxidation induced by ADM-Fe3+. Alternatively, ADM is oxidatively activated by peroxidases to convert to an oxidative semiquinone radical, which participates in inactivation of mitochondrial enzymes or including succinate dehydrogenase and creatine kinase. Here, we discuss the activation of ADM and the role of reductive and oxidative ADM semiquinone radicals in the cardiotoxic effect of this antibiotic.

Pharmacology of antineoplastic agents in older cancer patients

Persons over the age of 65 years are the fastest growing segment of the United States population. In the next 30 years it will comprise over 20% of the population. Fifty percent of all cancers occur in this age group and therefore there will be an expected rise in the total cancer burden. Data is becoming available which will better guide the use of chemotherapy in the older patient population. Studies will be presented discussing pharmacokinetic data on a number of chemotherapeutic agents with an emphasis on those which have entered practice over the past few years. Many of these agents seem to have a beneficial therapeutic index, particularly in regard to older patients. There has also been an increasing trend toward the use of oral chemotherapy. Factors that must be considered in choosing chemotherapy include limitations of saturability of absorption, patient compliance and the pharmacokinetic and pharmacodynamic changes which occur in older patients. Interpatient variability and age related changes in drug metabolism are discussed. Careful attention to the physiologic changes with age, and dose adjustments necessary for end organ dysfunction (renal, hepatic) are needed to ensure the safe administration of chemotherapy.

Modeling the metabolism of idarubicin to idarubicinol in rat heart: effect of rutin and phenobarbital

Since the severe cardiotoxicity of anthracyclines has been attributed to the intramyocardial formation of C-13 alcohol metabolites, the kinetics of cardiac metabolite formation and disposition as well as the effect of carbonyl reductase inhibitors are of specific interest. This study was designed to investigate the effect of rutin and phenobarbital on the pharmacokinetics of idarubicin (IDA) and its conversion to idarubicinol (IDOL) in the single-pass perfused rat heart. After infusion of IDA (0.5 mg) during 1min, the venous outflow concentrations of IDA and IDOL were measured up to 80 min in the presence and absence of rutin and phenobarbital. A kinetic model was developed to help to interpret the concentration profiles in terms of compartmentation of IDOL formation and to estimate parameters quantitatively descriptive of the transport and biotransformation processes. Rutin and phenobarbital significantly reduced the residual amount of IDOL in heart to 64 and 47% of control, respectively. Pharmacokinetic modeling of the data revealed that IDOL is generated in two different compartments, besides the tissue compartment characterized by saturable uptake, also the compartment that accounts for the quasi-instantaneous initial distribution process is involved. The efflux rate constant of IDOL, k(21,IDOL,) was much smaller than that of IDA. Rutin and phenobarbital significantly reduced IDOL production. Additionally, phenobarbital competitively inhibited the saturable uptake of both IDA and IDOL (increase in apparent Michaelis constants). Reanalysis of data obtained in previous experiments showed that P-glycoprotein inhibitors (verapamil and amiodarone) reduced IDOL uptake in a similar way as already shown for IDA. The present study further supports the utility of pharmacokinetic modeling in identifying sites of drug interactions within the heart.

Inactivation of mitochondrial succinate dehydrogenase by adriamycin activated by horseradish peroxidase and hydrogen peroxide

Although human cancers are widely treated with anthracycline drugs, these drugs have limited use because they are cardiotoxic. To clarify the cardiotoxic action of the anthracycline drug adriamycin (ADM), the inhibitory effect on succinate dehydrogenase (SDH) by ADM and other anthracyclines was examined by using pig heart submitochondrial particles. ADM rapidly inactivated mitochondrial SDH during its interaction with horseradish peroxidase (HRP) in the presence of H(2)O(2) (HRP-H(2)O(2)). Butylated hydroxytoluene, iron-chelators, superoxide dismutase, mannitol and dimethylsulfoxide did not block the inactivation of SDH, indicating that lipid-derived radicals, iron-oxygen complexes, superoxide and hydroxyl radicals do not participate in SDH inactivation. Reduced glutathione was extremely efficient in blocking the enzyme inactivation, suggesting that the SH group in enzyme is very sensible to ADM activated by HRP-H(2)O(2). Under anaerobic conditions, ADM with HRP-H(2)O(2) caused inactivation of SDH, indicating that oxidized ADM directly attack the enzyme, which loses its activity. Other mitochondrial enzymes, including NADH dehydrogenase, NADH oxidase and cytochrome c oxidase, were little sensitive to ADM with HRP-H(2)O(2). SDH was also sensitive to other anthracycline drugs except for aclarubicin. Mitochondrial creatine kinase (CK), which is attached to the outer face of the inner membrane of muscle mitochondria, was more sensitive to anthracyclines than SDH. SDH and CK were inactivated with loss of red color of anthracycline, indicating that oxidative activation of the B ring of anthracycline has a crucial role in inactivation of enzymes. Presumably, oxidative semiquinone or quinone produced from anthracyclines participates in the enzyme inactivation.

Pharmacokinetic considerations of oral chemotherapy in elderly patients with cancer

Persons over the age of 65 years are the fastest growing segment of the US population. In the next 30 years they will comprise over 20% of the population. Fifty per cent of all cancers occur in this age group and therefore there will be an expected rise in the total cancer burden. There has been an increasing trend over the past 20 years toward the use of oral chemotherapy. This change has been encouraged by the need to decrease the costs of chemotherapy administration, patient preferences and quality of life issues. Factors that must be considered with oral chemotherapy administration include limitations of saturability of absorption, patient compliance and pharmacokinetic/pharmacodynamic changes which occur in elderly patients. Interpatient variability and drug metabolism, particularly age-related changes in drug metabolism are being studied. The cytochrome P450 system has been intensively studied because of its importance with regard to chemotherapeutic drugs. This article reviews these issues and provides details regarding specific drugs including temozolomide, thalidomide, topotecan, the fluoropyrimidines, etoposide, hydroxycarbamide (hydroxyurea), tamoxifen, and alkylating drugs. Complementary and alternative therapies are also discussed.

Transient dilated cardiomyopathy in a newborn exposed to idarubicin and all-trans-retinoic acid (ATRA) early in the second trimester of pregnancy

Acute promyelocytic leukemia was diagnosed in a 28-year-old pregnant woman at 13 gestational weeks. She was immediately started on idarubicin and all-trans-retinoic acid (ATRA) and achieved remission after her fourth cycle of treatment. Serial fetal ultrasonograms throughout pregnancy did not reveal any intrauterine growth retardation or other obvious malformations. The mother delivered a term (36.7 gestational weeks), 2720-gram female neonate. The infant was admitted to the intermediate care nursery for observation due to transient mild respiratory distress during the peripartum period. Because of right ventricular hypertrophy on an electrocardiogram, an echocardiogram was performed on the first day of life which showed moderate dilation of the right atrium and right ventricle with mildly depressed function, two small secundum atrial septal defects, and a small patent ductus arteriosus. The neonate remained hemodynamically stable and no arrhythmias were detected. The remainder of the hospital course was uneventful. When reassessed 1-1/2 months later, she was doing well and did not show any signs of congestive heart failure. A repeat echocardiogram at that time demonstrated complete resolution of the right heart enlargement and closure of the ductus arteriosus with persistence of the small and hemodynamically insignificant secundum atrial septal defects.

Anthracycline drug targeting: cytoplasmic versus nuclear--a fork in the road

The anthracycline antibiotics doxorubicin (Adriamycin; DOX) and daunorubicin (DNR) continue to be essential components of first-line chemotherapy in the treatment of a variety of solid and hematopoietic tumors. The overall efficacies of DOX and DNR are, however, impeded by serious dose-limiting toxicities, including cardiotoxicity, and the selection of multiple mechanisms of cellular drug resistance. These limitations have necessitated the development of newer anthracyclines whose structural and functional modifications circumvent these impediments. In this review, we will present recent strategies in anthracycline design and assess their potential therapeutic merits. Current anthracycline design has diverged to target either cytoplasmic or nuclear sites. Nuclear targets have been broadened to include not only topoisomerase II (topo II) inhibition through ternary complex stabilization and catalytic inhibition, but also topoisomerase I (topo I) inhibition and transcriptional inhibition. In contrast, cytoplasmic targeting focuses on anthracycline binding to protein kinase C (PKC) regulatory domain with consequent modulation of activity.

Chemotherapy in the elderly: pharmacologic considerations

BACKGROUND

The aging of the population has focused interest on the care of elderly cancer patients. A better understanding of the effects of chemotherapeutic agents on older patients with cancer will help to determine the appropriate use of chemotherapy for this age group.

METHODS

The authors review recent studies and present pharmacokinetic data on several chemotherapeutic agents, particularly those that have recently become available.

RESULTS

Agents such as gemcitabine, vinorelbine, the taxanes, anthracyclines, platinum compounds, topoisomerase I and II inhibitors, and the oral fluoropyrimidines appear to have a beneficial therapeutic index in elderly patients.

CONCLUSIONS

Careful attention to the physiologic changes associated with aging, along with dose adjustments for end-organ dysfunction (eg, renal and hepatic), is necessary to ensure the safe administration of antitumor chemotherapy to the elderly.