Doxorubicin cardiotoxicity may be caused by its metabolite, doxorubicinol

Examining tissue-level changes in doxorubicin accumulation and nitric oxide formation in skeletal muscle and tumours in a mouse model of breast cancer

Doxorubicin is a commonly used chemotherapy that rapidly accumulates in skeletal muscle and disrupts nitric oxide (NO) formation. However, studies investigating these effects have largely been performed in tumour-free models, therefore it remains unknown whether intramuscular accumulation and disruptions to NO content persist during tumour growth. Female C57bl/6 mice (n = 8/group) were randomly assigned to true control, doxorubicin control, tumour only, or tumour plus doxorubicin groups. Tumours were grown for 21, 24, or 28 days using E0771 cells. Doxorubicin was administered as a single 10 mg/kg intraperitoneal dose on day 21. Doxorubicin accumulation was similar in muscle with and without tumours present. Doxorubicinol, a metabolite of doxorubicin, was elevated (p < 0.05) in 24-day tumour + doxorubicin compared to doxorubicin alone. NO was similar across all groups in muscle; however, tumour NO was 15-fold higher at day 21 compared to 24, or 28 days (p < 0.05). The results confirm that doxorubicin is sequestered in skeletal muscle when a tumour is present, which may impact bioavailability. Tumour growth transiently increased intramuscular doxorubicinol, potentially exacerbating the toxicity of the drug. Earlier stage tumour growth appeared to profoundly elevate NO, which could suggest temporal angiogenesis and vasodilation to facilitate growth.

Influence of Polymorphisms in Pharmacokinetics-Related Genes on the Areas Under the Plasma Concentration-Time Curves of Doxorubicin and Doxorubicinol in Patients with Diffuse Large B-Cell Lymphoma Receiving CHOP Therapy

BACKGROUND AND OBJECTIVES

Doxorubicin (DOX) and its metabolite doxorubicinol (DOXol) are drugs with large differences in pharmacokinetics (PK) between patients. In this study, we investigated the effects of polymorphisms in PK-related genes on the areas under the plasma concentration-time curves (AUCs) of DOX and DOXol.

METHODS

This study included 43 patients diagnosed with non-Hodgkin lymphoma undergoing the first round of CHOP therapy. The AUCs of DOX and DOXol were calculated using the linear trapezoidal rule based on the plasma concentrations in blood sampled from 1.5 to 25.5 h after the start of administration. Genotyping was performed for genes encoding carbonyl reductase (CBR1, CBR3), aldo-keto reductase (AKR1C3), and transporters (ABCB1, ABCG2).

RESULTS

Although the dose of DOX was adjusted for body surface area for each patient, the coefficients of variation for the AUCs of DOX and DOXol were substantial. Serum albumin was identified as an independent factor significantly influencing the dose-adjusted AUC of DOX (AUC/D; R2 = 0.116, P = 0.015). Additionally, body mass index was identified as an independent factor significantly influencing the AUC/D of DOXol and the DOX-DOXol AUC ratio (DOXol/DOX; R2 = 0.181, P = 0.003 and R2 = 0.134, P = 0.009, respectively). Nonetheless, no significant differences in PK parameters were observed among polymorphisms in PK-related genes.

CONCLUSIONS

Our findings suggested that polymorphisms in CBR1, CBR3, AKR1C3, ABCB1, and ABCG2 were unlikely to be reliable predictors of cumulative plasma exposure to DOX and DOXol. Therefore, mitigating the risk of cumulative plasma exposure to DOX and DOXol through PK approaches may require the development of novel therapeutic drug monitoring strategies. Supplementary file1 (MP4 3804 KB).

Diosmin-loaded chitosan nanoparticles mitigate doxorubicin-evoked cardiotoxicity in rats by featuring oxidative imbalance mechanism, NF-κB, and Bcl-2/Bax pathways

Cardiotoxicity is doxorubicin's primary side effect. Its cardiac toxicity has been attributed to the generation of free radicals. The present work was designed to understand the potential underlying pathways behind the cardioprotective action of diosmin (Dio) and Dio-loaded chitosan nanoparticles (DCNPs) against doxorubicin (Dox)-mediated cardiotoxicity. Male rats were allocated into five groups: control, Dio (100 mg/kg), Dox (12 mg/kg), Dio + Dox (100 mg/kg + 12 mg/kg), and DCNPs+Dox (100 mg/kg DCNPs/orally+12 mg/kg Dox/IP). Notably, in response to Dox, a significant increase of cardiac biomarkers with a decrease in Na+/K+-ATPase activity was detected. The cardiac inflammatory and pro-apoptotic protein levels were elevated with decreased cardiac interleukin-10 and Bcl-2 levels when the rats were subjected to Dox. Also, the cardiac expression of the fibrotic marker MMP-9 was increased. Moreover, Dox raised malondialdehyde and nitric oxide levels, accompanied by minimizing antioxidant status. Also, Dox-treated rats showed cardiac histopathological impairment compared to the control. The oral administration of Dio or DCNPs enhanced the activity of antioxidant enzymes and diminished inflammatory cytokines and apoptotic markers in the Dox-exposed rats. In summary, these findings indicate that DCNPs exhibit significant cardioprotective effectiveness against Dox-mediated toxicity by suppressing various mechanisms, such as redox status, the NF-κB pathway, and apoptosis.

Endothelial c-Myc and Doxorubicin-Induced Metabolic Alterations: A Multi-Organ Optical Imaging Study

SIGNIFICANCE

Endothelial c-Myc plays a critical role in redox homeostasis, with its deletion potentially exacerbating oxidative stress, particularly, during chemotherapy.

AIM

To assess the metabolic impact of endothelial c-Myc knockout (KO) and Doxorubicin (DOXO) treatment on kidneys, hearts, and livers using 3D optical cryo-imaging.

APPROACH

Redox ratios (NADH/FAD) were analyzed in control (CT) and KO mice treated with DOXO or saline to evaluate mitochondrial function and oxidative states.

RESULTS

KO tissues showed significant reductions in redox ratios, indicating an oxidized state, with kidneys exhibiting up to a 51.42% decrease. DOXO treatment further exacerbated oxidative stress in KO tissues, while CT groups demonstrated protective effects.

CONCLUSIONS

Endothelial c-Myc is crucial for redox balance and protection against chemotherapy-induced oxidative damage, offering insights for targeted therapeutic strategies.

Recent developments of topoisomerase inhibitors: Clinical trials, emerging indications, novel molecules and global sales

The nucleic acid topoisomerases (TOP) are an evolutionary conserved mechanism to solve topological problems within DNA and RNA that have been historically well-established as a chemotherapeutic target. During investigation of trends within clinical trials, we have identified a very high number of clinical trials involving TOP inhibitors, prompting us to further evaluate the current status of this class of therapeutic agents. In total, we have identified 233 unique molecules with TOP-inhibiting activity. In this review, we provide an overview of the clinical drug development highlighting advances in current clinical uses and discussing novel drugs and indications under development. A wide range of bacterial infections, along with solid and hematologic neoplasms, represent the bulk of clinically approved indications. Negative ADR profile and drug resistance among the antibacterial TOP inhibitors and anthracycline-mediated cardiotoxicity in the antineoplastic TOP inhibitors are major points of concern, subject to continuous research efforts. Ongoing development continues to focus on bacterial infections and cancer; however, there is a degree of diversification in terms of novel drug classes and previously uncovered indications, such as glioblastoma multiforme or Clostridium difficile infections. Preclinical studies show potential in viral, protozoal, parasitic and fungal infections as well and suggest the emergence of a novel target, TOP IIIβ. We predict further growth and diversification of the field thanks to the large number of experimental TOP inhibitors emerging.

Fertility protection during chemotherapy treatment by boosting the NAD(P)+ metabolome

Chemotherapy induced ovarian failure and infertility is an important concern in female cancer patients of reproductive age or younger, and non-invasive, pharmacological approaches to maintain ovarian function are urgently needed. Given the role of reduced nicotinamide adenine dinucleotide phosphate (NADPH) as an essential cofactor for drug detoxification, we sought to test whether boosting the NAD(P)+ metabolome could protect ovarian function. We show that pharmacological or transgenic strategies to replenish the NAD+ metabolome ameliorates chemotherapy induced female infertility in mice, as measured by oocyte yield, follicle health, and functional breeding trials. Importantly, treatment of a triple-negative breast cancer mouse model with the NAD+ precursor nicotinamide mononucleotide (NMN) reduced tumour growth and did not impair the efficacy of chemotherapy drugs in vivo or in diverse cancer cell lines. Overall, these findings raise the possibility that NAD+ precursors could be a non-invasive strategy for maintaining ovarian function in cancer patients, with potential benefits in cancer therapy.

Population pharmacokinetics of TLD-1, a novel liposomal doxorubicin, in a phase I trial

STUDY OBJECTIVES

TLD-1 is a novel pegylated liposomal doxorubicin (PLD) formulation aiming to optimise the PLD efficacy-toxicity ratio. We aimed to characterise TLD-1's population pharmacokinetics using non-compartmental analysis and nonlinear mixed-effects modelling.

METHODS

The PK of TLD-1 was analysed by performing a non-compartmental analysis of longitudinal doxorubicin plasma concentration measurements obtained from a clinical trial in 30 patients with advanced solid tumours across a 4.5-fold dose range. Furthermore, a joint parent-metabolite PK model of doxorubicinentrapped, doxorubicinfree, and metabolite doxorubicinol was developed. Interindividual and interoccasion variability around the typical PK parameters and potential covariates to explain parts of this variability were explored.

RESULTS

Medians  ± standard deviations of dose-normalised doxorubicinentrapped+free Cmax and AUC0-∞ were 0.342 ± 0.134 mg/L and 40.1 ± 18.9 mg·h/L, respectively. The median half-life (95 h) was 23.5 h longer than the half-life of currently marketed PLD. The novel joint parent-metabolite model comprised a one-compartment model with linear release (doxorubicinentrapped), a two-compartment model with linear elimination (doxorubicinfree), and a one-compartment model with linear elimination for doxorubicinol. Body surface area on the volumes of distribution for free doxorubicin was the only significant covariate.

CONCLUSION

The population PK of TLD-1, including its release and main metabolite, were successfully characterised using non-compartmental and compartmental analyses. Based on its long half-life, TLD-1 presents a promising candidate for further clinical development. The PK characteristics form the basis to investigate TLD-1 exposure-response (i.e., clinical efficacy) and exposure-toxicity relationships in the future. Once such relationships have been established, the developed population PK model can be further used in model-informed precision dosing strategies.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov-NCT03387917-January 2, 2018.

TLD-1, a novel liposomal doxorubicin, in patients with advanced solid tumors: Dose escalation and expansion part of a multicenter open-label phase I trial (SAKK 65/16)

BACKGROUND

TLD-1 is a novel liposomal doxorubicin that compared favorably to conventional doxorubicin liposomal formulations in preclinical models. This phase I first-in-human study aimed to define the maximum tolerated dose (MTD), recommended phase 2 dose (RP2D), safety and preliminary activity of TLD-1 in patients with advanced solid tumors.

PATIENTS AND METHODS

We recruited patients with advanced solid tumors who failed standard therapy and received up to 3 prior lines of palliative systemic chemotherapy. TLD-1 was administered intravenously every 3 weeks up to a maximum of 9 cycles (6 for patients with prior anthracyclines) from a starting dose of 10 mg/m2, according to an accelerated titration design followed by a modified continual reassessment method.

RESULTS

30 patients were enrolled between November 2018 and May 2021. No dose-limiting toxicities (DLT) were observed. Maximum administered dose of TLD-1 was 45 mg/m2, RP2D was defined at 40 mg/m2. Most frequent treatment-related adverse events (TRAE) of any grade included palmar-plantar erythrodysesthesia (PPE) (50% of patients), oral mucositis (50%), fatigue (30%) and skin rash (26.7%). Most common G3 TRAE included PPE in 4 patients (13.3%) and oral mucositis in 2 (6.7%). Overall objective response rate was 10% in the whole population and 23.1% among 13 patients with breast cancer; median time-to-treatment failure was 2.7 months. TLD-1 exhibit linear pharmacokinetics, with a median terminal half-life of 95 h.

CONCLUSIONS

The new liposomal doxorubicin formulation TLD-1 showed a favourable safety profile and antitumor activity, particularly in breast cancer. RP2D was defined at 40 mg/m2 administered every 3 weeks. (NCT03387917).

Doxorubicin conjugates: a practical approach for its cardiotoxicity alleviation

INTRODUCTION

Doxorubicin (DOX) emerges as a cornerstone in the arsenal of potent chemotherapeutic agents. Yet, the clinical deployment of DOX is tarnished by its proclivity to induce severe cardiotoxic effects, culminating in heart failure and other consequential morbidities. In response, a panoply of strategies has undergone rigorous exploration over recent decades, all aimed at attenuating DOX's cardiotoxic impact. The advent of encapsulating DOX within lipidic or polymeric nanocarriers has yielded a dual triumph, augmenting DOX's therapeutic efficacy while mitigating its deleterious side effects.

AREAS COVERED

Recent strides have spotlighted the emergence of DOX conjugates as particularly auspicious avenues for ameliorating DOX-induced cardiotoxicity. These conjugates entail the fusion of DOX through physical or chemical bonds with diminutive natural or synthetic moieties, polymers, biomolecules, and nanoparticles. This spectrum encompasses interventions that impinge upon DOX's cardiotoxic mechanism, modulate cellular uptake and localization, confer antioxidative properties, or refine cellular targeting.

EXPERT OPINION

The endorsement of DOX conjugates as a compelling stratagem to mitigate DOX-induced cardiotoxicity resounds from this exegesis, amplifying safety margins and the therapeutic profile of this venerated chemotherapeutic agent. Within this ambit, DOX conjugates stand as a beacon of promise in the perpetual pursuit of refining chemotherapy-induced cardiac compromise.

Comparative In Vitro Study of the Cytotoxic Effects of Doxorubicin's Main Metabolites on Cardiac AC16 Cells Versus the Parent Drug

Doxorubicin (DOX; also known as adriamycin) serves as a crucial antineoplastic agent in cancer treatment; however, its clinical utility is hampered by its' intrinsic cardiotoxicity. Although most DOX biotransformation occurs in the liver, a comprehensive understanding of the impact of DOX biotransformation and its' metabolites on its induced cardiotoxicity remains to be fully elucidated. This study aimed to explore the role of biotransformation and DOX's main metabolites in its induced cardiotoxicity in human differentiated cardiac AC16 cells. A key discovery from our study is that modulating metabolism had minimal effects on DOX-induced cytotoxicity: even so, metyrapone (a non-specific inhibitor of cytochrome P450) increased DOX-induced cytotoxicity at 2 µM, while diallyl sulphide (a CYP2E1 inhibitor) decreased the 1 µM DOX-triggered cytotoxicity. Then, the toxicity of the main DOX metabolites, doxorubicinol [(DOXol, 0.5 to 10 µM), doxorubicinone (DOXone, 1 to 10 µM), and 7-deoxydoxorubicinone (7-DeoxyDOX, 1 to 10 µM)] was compared to DOX (0.5 to 10 µM) following a 48-h exposure. All metabolites evaluated, DOXol, DOXone, and 7-DeoxyDOX caused mitochondrial dysfunction in differentiated AC16 cells, but only at 2 µM. In contrast, DOX elicited comparable cytotoxicity, but at half the concentration. Similarly, all metabolites, except 7-DeoxyDOX impacted on lysosomal ability to uptake neutral red. Therefore, the present study showed that the modulation of DOX metabolism demonstrated minimal impact on its cytotoxicity, with the main metabolites exhibiting lower toxicity to AC16 cardiac cells compared to DOX. In conclusion, our findings suggest that metabolism may not be a pivotal factor in mediating DOX's cardiotoxic effects.

In vitro evaluation of the reductive carbonyl idarubicin metabolism to evaluate inhibitors of the formation of cardiotoxic idarubicinol via carbonyl and aldo-keto reductases

The most important dose-limiting factor of the anthracycline idarubicin is the high risk of cardiotoxicity, in which the secondary alcohol metabolite idarubicinol plays an important role. It is not yet clear which enzymes are most important for the formation of idarubicinol and which inhibitors might be suitable to suppress this metabolic step and thus would be promising concomitant drugs to reduce idarubicin-associated cardiotoxicity. We, therefore, established and validated a mass spectrometry method for intracellular quantification of idarubicin and idarubicinol and investigated idarubicinol formation in different cell lines and its inhibition by known inhibitors of the aldo-keto reductases AKR1A1, AKR1B1, and AKR1C3 and the carbonyl reductases CBR1/3. The enzyme expression pattern differed among the cell lines with dominant expression of CBR1/3 in HEK293 and MCF-7 and very high expression of AKR1C3 in HepG2 cells. In HEK293 and MCF-7 cells, menadione was the most potent inhibitor (IC50 = 1.6 and 9.8 µM), while in HepG2 cells, ranirestat was most potent (IC50 = 0.4 µM), suggesting that ranirestat is not a selective AKR1B1 inhibitor, but also an AKR1C3 inhibitor. Over-expression of AKR1C3 verified the importance of AKR1C3 for idarubicinol formation and showed that ranirestat is also a potent inhibitor of this enzyme. Taken together, our study underlines the importance of AKR1C3 and CBR1 for the reduction of idarubicin and identifies potent inhibitors of metabolic formation of the cardiotoxic idarubicinol, which should now be tested in vivo to evaluate whether such combinations can increase the cardiac safety of idarubicin therapies while preserving its efficacy.

Protective effect of coenzyme Q10 against doxorubicin-induced cardiotoxicity: Scoping review article

Introduction

Doxorubicin (dox) is classified as an antineoplastic antibiotic which is known as adriamycin from the anthracycline group. Due to the release of free radicals and lipid peroxidation which can cause acute cardiotoxicity. Coenzyme Q10 is found in many cells of the body, it is an antioxidant that reduces oxidative stress and lipid peroxidation.

Aim

This scoping review aims to evaluate the cardioprotective effect of coenzyme Q10 in doxorubicin-induced cardiotoxicity in animals.

Methods

This review was done based on Arksey and O'Malley's methodology, reviewing published articles from October 1978 and September 2023.

Results

14 out of 11,303 articles were included from the initial search, (10 out of 14 articles found that coenzyme Q10 protect has a protection effect against doxorubicin-induced cardiotoxicity).

Conclusion

The results of this review found coenzyme Q10 protects against doxorubicin cardiotoxicity. It is a promising supplement that could be used to prevent cardiotoxicity induced by doxorubicin in cancer patients.

Metabolism investigation of the peptide-drug conjugate LN005 in rats using UHPLCHRMS

LN005, as a peptide-drug conjugate (PDC), is a conjugate of the homing peptide VAP and doxorubicin (DOX). The exceptional targeting ability of the homing peptide VAP is directed toward glucose-regulated protein (GRP78), a highly expressed protein primarily found in the endoplasmic reticulum of various solid tumors. However, there are limited reports regarding the metabolism of peptide-drug conjugates (PDCs), and the in vivo metabolism of LN005 has yet to be investigated. After intravenous injection of 18 mg/kg LN005 in SD rats, biological samples including plasma, urine, fecal, and bile samples, were collected and analyzed by ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). A total of 11 possible metabolites of LN005 were identified. Unchanged LN005 was found to be the main component in rat blood and urine, accounting for 46.46% and 63.79% of the total peak areas, respectively. M1057 was the most abundant metabolite in feces, accounting for 57.65% of the total peak area. Only one metabolite, M398, was identified in rat bile. The metabolism of LN005 is closely related to DOX, and the primary metabolic pathways involved oxidative deamination or hydrolysis, reductive glycosidic cleavage, hydrolytic glycosidic cleavage, and dehydrogenation.

Molecular assessment of drug-phospholipid interactions consequent to cancer treatment: a study of anthracycline-induced cardiotoxicity

Cardiotoxicity limits the use of anthracyclines as potent chemotherapeutics. We employ classical molecular dynamics to explore anthracycline interactions with a realistic myocardial membrane and compare to an ideal membrane widely used in literature. The interaction of these two membranes with four anthracyclines; doxorubicin, epirubicin, daunorubicin, and idarubicin are studied. Careful analysis was conducted on three forms of each drug; pristine, primary metabolite, and cationic salt. By examining the molecular residence time near the membrane's surface, the average number of molecule/membrane hydrogen bonds, the immobilization of the molecules near the membrane, and the location of those molecules relative to the mid-plane of the membrane we found out that salt forms exhibit the highest cardiotoxic probability, followed by the metabolites and pristine forms. Additionally, all forms have more affinity to the upper layer of the realistic myocardial membrane. Meanwhile, an ideal membrane consisting of a single type of phospholipids is not capable of capturing the specific interactions of each drug form. These findings confirm that cardiotoxic mechanisms are membrane-layer and drug-form dependent.

Lercanidipine alleviates doxorubicin-induced lung injury by regulating PERK/CHOP and Bax/Bcl 2/Cyt c pathways

Doxorubicin (DOX), which is used to treat various cancers and hematological malignancies, has limited therapeutic application due to its toxicity in tissues and organs. These toxic effects occur through alterations in intracellular calcium regulation, elevated cell stress and oxidative damage, and increased apoptosis. Lercanidipine (LRD) is a long-acting antihypertensive calcium channel blocker with anti-inflammatory, anti-apoptotic, and antioxidant effects. The aim of this study was to investigate the effect of LRD on DOX-induced lung toxicity. Four groups (control, DOX, DOX + 0.5 LRD, and DOX + 2 LRD) totaling 32 rats were established. TNF-α levels in the lung tissues were detected by immunohistochemistry, and the tissues were subjected to histopathological examination. In determining oxidative stress, total antioxidant status (TAS) and total oxidative stress (TOS) were determined using spectrophotometry, and the oxidative stress index (OSI) value was calculated. The mRNA relative expression levels of the genes were evaluated by RT-qPCR. It was determined that inflammatory and oxidative stress markers and pro-apoptotic gene levels were increased and anti-apoptotic gene levels were decreased in the lung tissues of the DOX-administered group. In addition, histopathological changes were significantly increased. Although it was not statistically significant, inflammation, oxidative stress, and apoptosis were reduced, as were other histopathological indicators, in the group that received LRD (0.5 mg/kg). Inflammation, oxidative stress, and apoptosis were found to be statistically reduced and corroborated by histological findings in the group given LRD (2 mg/kg). In conclusion, it was determined that LRD had an ameliorative effect on DOX-induced lung toxicity in an experimental animal model.

Protective effect of Pueraria lobata leaves on doxorubicin-induced myocardial infarction in experimental Wistar rats

The present study intended to explore the preventive effects of Pueraria lobata leaves against doxorubicin (DOX)-induced myocardial infarction (MI) in Wistar rats. The rats were separated into four groups, with each group containing six rats. Group I control rats; group II received DOX-alone in six equivalent injections for 2 weeks; group III received DOX as abovementioned with P. lobata oral administration for 2 weeks; group IV received P. lobata alone for 2 weeks. At the end of the experiment, postcervical dislocation and MI induced by DOX were determined on the basis of the variations in the animal body and heart weight and further instabilities in cardiac marker enzymes aspartate transaminase, lactate dehydrogenase, creatine kinase, creatine kinase-myoglobin binding, and cardiac troponin I in the serum. At the same time, for group III animals, which were exposed to P. lobata, all the above-denoted marker levels were maintained. Levels of some crucial heart-binding proteins like heart fatty acid binding protein, monocyte chemoattractant protein-1, and transforming growth factor beta were elevated in DOX-alone treated rats. Additionally, group III animals treated with P. lobata showed some preventive downregulated expressions of these binding proteins. Histopathological observations also revealed the preventive effect of P. lobata. Ultimately proteins tangled in the phosphoinositide 3-kinase/protein kinase B pathway were studied by Western blot. P. lobata treatment downregulated the inflammatory markers. The findings suggest that P. lobata exhibits cardioprotective effect on MI.

Vernonia amygdalina Ethanol Extract Protects against Doxorubicin-Induced Cardiotoxicity via TGFβ, Cytochrome c, and Apoptosis

Doxorubicin (DOX) has been extensively utilized in cancer treatment. However, DOX administration has adverse effects, such as cardiac injury. This study intends to analyze the expression of TGF, cytochrome c, and apoptosis on the cardiac histology of rats induced with doxorubicin, since the prevalence of cardiotoxicity remains an unpreventable problem due to a lack of understanding of the mechanism underlying the cardiotoxicity result. Vernonia amygdalina ethanol extract (VAEE) was produced by soaking dried Vernonia amygdalina leaves in ethanol. Rats were randomly divided into seven groups: K- (only given doxorubicin 15 mg/kgbw), KN (water saline), P100, P200, P400, P4600, and P800 (DOX 15 mg/kgbw + 100, 200, 400, 600, and 800 mg/kgbw extract); at the end of the study, rats were scarified, and blood was taken directly from the heart; the heart was then removed. TGF, cytochrome c, and apoptosis were stained using immunohistochemistry, whereas SOD, MDA, and GR concentration were evaluated using an ELISA kit. In conclusion, ethanol extract might protect the cardiotoxicity produced by doxorubicin by significantly reducing the expression of TGF, cytochrome c, and apoptosis in P600 and P800 compared to untreated control K- (p < 0.001). These findings suggest that Vernonia amygdalina may protect cardiac rats by reducing the apoptosis, TGF, and cytochrome c expression while not producing the doxorubicinol as doxorubicin metabolite. In the future, Vernonia amygdalina could be used as herbal preventive therapy for patient administered doxorubicin to reduce the incidence of cardiotoxicity.

In Silico and In Vitro Assessment of Carbonyl Reductase 1 Inhibition Using ASP9521-A Potent Aldo-Keto Reductase 1C3 Inhibitor with the Potential to Support Anticancer Therapy Using Anthracycline Antibiotics

Anthracycline antibiotics (ANT) are among the most widely used anticancer drugs. Unfortunately, their use is limited due to the development of drug resistance and cardiotoxicity. ANT metabolism, performed mainly by two enzymes-aldo-keto reductase 1C3 (AKR1C3) and carbonyl reductase 1 (CBR1)-is one of the proposed mechanisms generated by the described effects. In this study, we evaluated the CBR1 inhibitory properties of ASP9521, a compound already known as potent AKR1C3 inhibitor. First, we assessed the possibility of ASP9521 binding to the CBR1 catalytic site using molecular docking and molecular dynamics. The research revealed a potential binding mode of ASP9521. Moderate inhibitory activity against CBR1 was observed in studies with recombinant enzymes. Finally, we examined whether ASP9521 can improve the cytotoxic activity of daunorubicin against human lung carcinoma cell line A549 and assessed the cardioprotective properties of ASP9521 in a rat cardiomyocytes model (H9c2) against doxorubicin- and daunorubicin-induced toxicity. The addition of ASP9521 ameliorated the cytotoxic activity of daunorubicin and protected rat cardiomyocytes from the cytotoxic effect of both applied drugs. Considering the favorable bioavailability and safety profile of ASP9521, the obtained results encourage further research. Inhibition of both AKR1C3 and CBR1 may be a promising method of overcoming ANT resistance and cardiotoxicity.

Exercise and Doxorubicin Modify Markers of Iron Overload and Cardiolipin Deficiency in Cardiac Mitochondria

Doxorubicin (DOX) is a chemotherapeutic agent highly effective at limiting cancer progression. Despite the efficacy of this anticancer drug, the clinical use of DOX is limited due to cardiotoxicity. The cardiac mitochondria are implicated as the primary target of DOX, resulting in inactivation of electron transport system complexes, oxidative stress, and iron overload. However, it is established that the cardiac mitochondrial subpopulations reveal differential responses to DOX exposure, with subsarcolemmal (SS) mitochondria demonstrating redox imbalance and the intermyofibrillar (IMF) mitochondria showing reduced respiration. In this regard, exercise training is an effective intervention to prevent DOX-induced cardiac dysfunction. Although it is clear that exercise confers mitochondrial protection, it is currently unknown if exercise training mitigates DOX cardiac mitochondrial toxicity by promoting beneficial adaptations to both the SS and IMF mitochondria. To test this, SS and IMF mitochondria were isolated from sedentary and exercise-preconditioned female Sprague Dawley rats exposed to acute DOX treatment. Our findings reveal a greater effect of exercise preconditioning on redox balance and iron handling in the SS mitochondria of DOX-treated rats compared to IMF, with rescue of cardiolipin synthase 1 expression in both subpopulations. These results demonstrate that exercise preconditioning improves mitochondrial homeostasis when combined with DOX treatment, and that the SS mitochondria display greater protection compared to the IMF mitochondria. These data provide important insights into the molecular mechanisms that are in part responsible for exercise-induced protection against DOX toxicity.

Metformin and Dapagliflozin Attenuate Doxorubicin-Induced Acute Cardiotoxicity in Wistar Rats: An Electrocardiographic, Biochemical, and Histopathological Approach

Doxorubicin is a widely used anticancer drug whose efficacy is limited due to its cardiotoxicity. There is no ideal cardioprotection available against doxorubicin-induced cardiotoxicity. This study aimed to investigate the anticipated cardioprotective potential of metformin and dapagliflozin against doxorubicin-induced acute cardiotoxicity in Wistar rats. At the beginning of the experiment, cardiac screening of experimental animals was done by recording an electrocardiogram (ECG) before allocating them into the groups. Thereafter, a total of thirty healthy adult Wistar rats (150-200 g) were randomly divided into five groups (n = 6) and treated for eight days as follows: group I (normal control), group II (doxorubicin control), group III (metformin 250 mg/kg/day), group IV (metformin 180 mg/kg/day), and group V (dapagliflozin 0.9 mg/kg/day). On the 7th day of the treatment phase, doxorubicin 20 mg/kg was administered intraperitoneal to groups II, III, IV, and V. On the 9th day (immediately after 48 h of doxorubicin administration), blood was collected from anesthetized animals for glucose, lipid profile, CK-MB & AST estimation, and ECG was recorded. Later, animals were sacrificed, and the heart was dissected for histopathological examination. We found that compared to normal control rats, CK-MB, AST, and glucose were significantly increased in doxorubicin control rats. There was a significant reversal of doxorubicin-induced hyperglycemia in the rats treated with metformin 250 mg/kg compared to doxorubicin control rats. Both metformin (180 mg/kg and 250 mg/kg) and dapagliflozin (0.9 mg/kg) significantly altered doxorubicin-induced ECG changes and reduced the levels of cardiac injury biomarkers CK-MB and AST compared to doxorubicin control rats. Metformin and dapagliflozin protected the cellular architecture of the myocardium from doxorubicin-induced myocardial injury. Current study revealed that both metformin and dapagliflozin at the FDA-recommended antidiabetic doses mitigated doxorubicin-induced acute cardiotoxicity in Wistar rats. The obtained data have opened the perspective to perform chronic studies and then to clinical studies to precisely consider metformin and dapagliflozin as potential chemoprotection in the combination of chemotherapy with doxorubicin to limit its cardiotoxicity, especially in patients with comorbid conditions like type II diabetes mellitus.

Population pharmacokinetics of doxorubicin: A systematic review

Because of the high interindividual pharmacokinetic variability, several population pharmacokinetic (PopPK) models of doxorubicin (DOX) were developed to characterize factors influencing such variability. However, significant predictors for DOX pharmacokinetics identified using PopPK models varied across studies. Thus, this review aims to summarize PopPK models of DOX and its metabolites (if any) as well as significant covariates influencing DOX (and its metabolites) pharmacokinetic variability. A systematic search from PubMed, CINAHL Complete, Science Direct, and SCOPUS databases identified 503 studies. Of these, 16 studies met the inclusion criteria and were included in this review. DOX pharmacokinetics was described with two- or three-compartment models. Most studies found a significant increase in DOX clearance with an increase in body surface area from the median value of 1.8 m² . Moreover, this review identified that while a 10-year increase in patient age resulted in a decrease in DOX clearance in adults and the elderly, younger children had lower DOX clearance compared to older children. Further, low DOX exposure was observed in pregnant women, and thus dosage adjustment is required. Concerning model applicability, predictive performance assessment of these published models should be performed before implementing such models in clinical practice.

Aidi injection reduces doxorubicin-induced cardiotoxicity by inhibiting carbonyl reductase 1 expression

CONTEXT

Aidi injection (ADI), a traditional Chinese medicine antitumor injection, is usually combined with doxorubicin (DOX) for the treatment of malignant tumours. The cardiotoxicity of DOX is ameliorated by ADI in the clinic. However, the relevant mechanism is unknown.

OBJECTIVE

To investigate the effects of ADI on DOX-induced cardiotoxicity and its mechanism.

MATERIALS AND METHODS

ICR mice were randomly divided into six groups: control, ADI-L, ADI-H, DOX, DOX + ADI-L and DOX + ADI-H. DOX (i.p., 0.03 mg/10 g) was administered in the presence or absence of ADI (i.p., 0.1 or 0.2 mL/10 g) for two weeks. Heart pathology and levels of AST, LDH, CK, CK-MB and BNP were assessed. H9c2 cells were treated with DOX in the presence or absence of ADI (1, 4, 10%). Cell viability, caspase-3 activity, nuclear morphology, and CBR1 expression were then evaluated. DOX and doxorubicinol (DOXol) concentrations in heart, liver, kidneys, serum, and cells were analysed by UPLC-MS/MS.

RESULTS

High-dose ADI significantly reduced DOX-induced pathological changes and the levels of AST, LDH, CK, CK-MB and BNP to normal. Combined treatment with ADI (1, 4, 10%) improved the cell viability, and IC50 increased from 68.51 μM (DOX alone) to 83.47, 176.9, and 310.8 μM, reduced caspase-3 activity by 39.17, 43.96, and 61.82%, respectively. High-dose ADI inhibited the expression of CBR1 protein by 32.3%, reduced DOXol levels in heart, serum and H9c2 cells by 59.8, 72.5 and 48.99%, respectively.

DISCUSSION AND CONCLUSIONS

ADI reduces DOX-induced cardiotoxicity by inhibiting CBR1 expression, which provides a scientific basis for the rational use of ADI.

Serum Biomarkers for the Detection of Cardiac Dysfunction in Childhood Cancers Receiving Anthracycline-Based Treatment

Anthracyclines are routinely used in cancer chemotherapy in many childhood cancers. A serious adverse effect of doxorubicin chemotherapy is cardiotoxicity which may lead to congestive heart failure for long-term survivors years after treatment. Currently, echocardiography is used to control the heart function during anthracyclines therapy. B-type natriuretic peptide (BNP) and NT-proBNP as well as cardiac troponins have been proposed as clinical markers for subclinical anthracycline-induced cardiotoxicity. The BNP and pro-BNP can be easily measured in plasma and initial data indicate that the NT-proBNP could be sensitive predictor for the development of congestive heart failure.

Molecular mechanisms associated with the chemoprotective role of protocatechuic acid and its potential benefits in the amelioration of doxorubicin-induced cardiotoxicity: A review

Since its discovery in the 1960 s, doxorubicin (DOX) has constantly elicited the broadest spectrum of cancerocidal activity against human cancers. However, cardiotoxicity caused by DOX directly as well as its metabolites is a great source of concern over the continuous use of DOX in chemotherapy. While the exact mechanism of DOX-induced cardiotoxicity is yet to be completely understood, recent studies indicate oxidative stress, inflammation, and several forms of cell death as key pathogenic mechanisms that underpin the etiology of doxorubicin-induced cardiotoxicity (DIC). Notably, these key mechanistic events are believed to be negatively regulated by 3,4-dihydroxybenzoic acid or protocatechuic acid (PCA)-a plant-based phytochemical with proven anti-oxidant, anti-inflammatory, and anti-apoptotic properties. Here, we review the experimental findings detailing the potential ameliorative effects of PCA under exposure to DOX. We also discuss molecular insights into the pathophysiology of DIC, highlighting the potential intervention points where the use of PCA as a veritable chemoprotective agent may ameliorate DOX-induced cardiotoxicities as well as toxicities due to other anticancer drugs like cisplatin. While we acknowledge that controlled oral administration of PCA during chemotherapy may be insufficient to eliminate all toxicities due to DOX treatment, we propose that the ability of PCA to block oxidative stress, attenuate inflammation, and abrogate several forms of cardiomyocyte cell death underlines its great promise in the amelioration of DIC.

Harnessing Clinical Trial and Real-World Data Towards an Understanding of Sex Effects on Drug Pharmacokinetics, Pharmacodynamics and Efficacy

Increasing clinical data on sex-related differences in drug efficacy and toxicity has highlighted the importance of understanding the impact of sex on drug pharmacokinetics and pharmacodynamics. Intrinsic differences between males and females, such as different CYP enzyme activity, drug transporter expression or levels of sex hormones can all contribute to different responses to medications. However, most studies do not include sex-specific investigations, leading to lack of sex-disaggregated pharmacokinetic and pharmacodynamic data. Based available literature, the potential influence of sex on exposure-response relationship has not been fully explored for many drugs used in clinical practice, though population-based pharmacokinetic/pharmacodynamic modelling is well-placed to explore this effect. The aim of this review is to highlight existing knowledge gaps regarding the effect of sex on clinical outcomes, thereby proposing future research direction for the drugs with significant sex differences. Based on evaluated drugs encompassing all therapeutic areas, 25 drugs demonstrated a clinically meaningful sex differences in drug exposure (characterised by ≥ 50% change in drug exposure) and this altered PK was correlated with differential response.

Genetics of Anthracycline-Associated Cardiotoxicity

Anthracyclines are a major component of chemotherapies used in many pediatric and adult malignancies. Anthracycline-associated cardiotoxicity (ACT) is a dose-dependent adverse effect that has substantial impact on morbidity and mortality. Therefore, the identification of genetic variants associated with increased risk of ACT has the potential for significant clinical impact to improve patient care. The goal of this review is to summarize the current evidence supporting genetic variants associated with ACT, identify gaps and limitations in current knowledge, and propose future directions for incorporating genetics into clinical practice for patients treated with anthracyclines. We will discuss mechanisms of ACT that could be illuminated by genetics and discuss clinical applications for the cardiologist/cardio-oncologist.

Inhibition of human carbonyl reducing enzymes by plant anthrone and anthraquinone derivatives

Members of the aldo-keto reductase and short-chain dehydrogenase/reductase enzyme superfamilies catalyze the conversion of a wide range of substrates, including carbohydrates, lipids, and steroids. These enzymes also participate in the transformation of xenobiotics, inactivation of the cytostatics doxo- and daunorubicin, and play a role in the development of cancer. Therefore, inhibitors of such enzymes may improve therapeutic outcomes. Plant-derived compounds such as anthraquinones have been used for medicinal purposes for several centuries. In the current study, the inhibitory potential of selected anthrone and anthraquinone derivatives (from plants) was tested on six recombinant human carbonyl reducing enzymes (AKR1B1, AKR1B10, AKR1C3, AKR7A2, AKR7A3, CBR1) isolated from an Escherichia coli expression system. Overall, the least inhibition was observed with the anthrone derivative aloin, while IC50 values obtained with the anthraquinone derivatives (frangula emodin, aloe emodin, frangulin A, and frangulin B) and the aldo-keto reductase AKR1B10 were in the low micromolar range (3.5-16.6 μM). AKR1B1 inhibition was significantly weaker in comparison with AKR1B10 inhibition (IC50 values > 50 μM). The strongest inhibition was observed with the short-chain dehydrogenase/reductase CBR1. AKR7A2, AKR7A3, and AKR1C3 were not, or less inhibited by inhibitor concentrations of up to 50 μM. Analysis of the kinetic data suggests noncompetitive or uncompetitive inhibition mechanisms. The new inhibitors described here may serve as lead structures for the development of future drugs.

Cancer Chemotherapy-Induced Sinus Bradycardia: A Narrative Review of a Forgotten Adverse Effect of Cardiotoxicity

Cardiotoxicity is a common adverse effect of anticancer drugs (ACDs), including the so-called targeted drugs, and increases morbidity and mortality in patients with cancer. Attention has focused mainly on ACD-induced heart failure, myocardial ischemia, hypertension, thromboembolism, QT prolongation, and tachyarrhythmias. Yet, although an increasing number of ACDs can produce sinus bradycardia (SB), this proarrhythmic effect remains an underappreciated complication, probably because of its low incidence and severity since most patients are asymptomatic. However, SB merits our interest because its incidence increases with the aging of the population and cancer is an age-related disease and because SB represents a risk factor for QT prolongation. Indeed, several ACDs that produce SB also prolong the QT interval. We reviewed published reports on ACD-induced SB from January 1971 to November 2020 using the PubMed and EMBASE databases. Published reports from clinical trials, case reports, and recent reviews were considered. This review describes the associations between ACDs and SB, their clinical relevance, risk factors, and possible mechanisms of onset and treatment.

DEHP mediates drug resistance by directly targeting AhR in human breast cancer

Resistance to chemotherapy and hormonal therapy is a major clinical problem in breast cancer medicine, especially for cancer metastasis and recurrence. Di(2-ethylhexyl)phthalate (DEHP) affects drug resistance by an unknown mechanism of action. Here we analyzed breast cancer patients (N = 457) and found that Σ₄MEHP (the sum of MEHP, MEHHP, MECPP and MEOHP concentrations) in urine was significantly higher (P = 0.018) in the recurrent breast cancer group compared with non-recurrent patients. Σ₄MEHP-High was positively and significantly correlated with tumor stage (P = 0.005), lymph node status (P = 0.001), estrogen receptor status (P = 0.010), Her2/Neu status (P = 0.004), recurrence (P = 0.000) and tumor size (P = 0.002), as well as an independent prognostic marker (OR = 1.868; 95% CI = 1.424-2.451; P < 0.000) associated with poor survival rates based on a positive Her2/Neu status (P = 0.035). In addition, we found that DEHP inhibited paclitaxel and doxorubicin effects in breast cancer cell lines MCF-7 and MDA-MB-231 and in zebrafish and mouse tumor initiation models. DEHP induced trefoil factor 3 (TFF3) expression through the vinculin/aryl hydrocarbon receptor (AhR)/ERK signaling pathway and induced CYP2D6, CYP2C8 and CYP3A4 expression through the AhR genomic pathway to increase the epithelial-mesenchymal transition (EMT) and doxorubicin metabolism, respectably. DEHP mediated AhR-related alterations in estrogen receptor expression through the ubiquitination system, which decreased tamoxifen effects in AhR knockout mice. These findings suggest a novel therapeutic avenue by targeting AhR in drug-resistant and recurrent breast cancer.

One-dimensional scanning multiphoton imaging reveals prolonged calcium transient and sarcomere contraction in a zebrafish model of doxorubicin cardiotoxicity

Doxorubicin (DOX) is a potent chemotherapeutic agent known to induce cardiotoxicity. Here we applied one-dimensional scanning multiphoton imaging to investigate the derangement of cardiac dynamics induced by DOX on a zebrafish model. DOX changed the cell morphology and significantly prolonged calcium transient and sarcomere contraction, leading to an arrhythmia-like contractile disorder. The restoration phase of calcium transient dominated the overall prolongation, indicating that DOX perturbed primarily the protein functions responsible for recycling cytosolic calcium ions. This novel finding supplements the existing mechanism of DOX cardiotoxicity. We anticipate that this approach should help mechanistic studies of drug-induced cardiotoxicity or heart diseases.

Research progress on evodiamine, a bioactive alkaloid of Evodiae fructus: Focus on its anti-cancer activity and bioavailability (Review)

Evodiae fructus (Wu-Zhu-Yu in Chinese) can be isolated from the dried, unripe fruits of Tetradium ruticarpum and is a well-known traditional Chinese medicine that is applied extensively in China, Japan and Korea. Evodiae fructus has been traditionally used to treat headaches, abdominal pain and menorrhalgia. In addition, it is widely used as a dietary supplement to provide carboxylic acids, essential oils and flavonoids. Evodiamine (EVO) is one of the major bioactive components contained within Evodiae fructus and is considered to be a potential candidate anti-cancer agent. EVO has been reported to exert anti-cancer effects by inhibiting cell proliferation, invasion and metastasis, whilst inducing apoptosis in numerous types of cancer cells. However, EVO is susceptible to metabolism and may inhibit the activities of metabolizing enzymes, such as cytochrome P450. Clinical application of EVO in the treatment of cancers may prove difficult due to poor bioavailability and potential toxicity due to metabolism. Currently, novel drug carriers involving the use of solid dispersion techniques, phospholipids and nanocomplexes to deliver EVO to improve its bioavailability and mitigate side effects have been tested. The present review aims to summarize the reported anti-cancer effects of EVO whilst discussing the pharmacokinetic behaviors, characteristics and effective delivery systems of EVO.

Liver-Heart on chip models for drug safety

Current pre-clinical models to evaluate drug safety during the drug development process (DDP) mainly rely on traditional two-dimensional cell cultures, considered too simplistic and often ineffective, or animal experimentations, which are costly, time-consuming, and not truly representative of human responses. Their clinical translation thus remains limited, eventually causing attrition and leading to high rates of failure during clinical trials. These drawbacks can be overcome by the recently developed Organs-on-Chip (OoC) technology. OoC are sophisticated in vitro systems capable of recapitulating pivotal architecture and functionalities of human organs. OoC are receiving increasing attention from the stakeholders of the DDP, particularly concerning drug screening and safety applications. When a drug is administered in the human body, it is metabolized by the liver and the resulting compound may cause unpredicted toxicity on off-target organs such as the heart. In this sense, several liver and heart models have been widely adopted to assess the toxicity of new or recalled drugs. Recent advances in OoC technology are making available platforms encompassing multiple organs fluidically connected to efficiently assess and predict the systemic effects of compounds. Such Multi-Organs-on-Chip (MOoC) platforms represent a disruptive solution to study drug-related effects, which results particularly useful to predict liver metabolism on off-target organs to ultimately improve drug safety testing in the pre-clinical phases of the DDP. In this review, we focus on recently developed liver and heart on chip systems for drug toxicity testing. In addition, MOoC platforms encompassing connected liver and heart tissues have been further reviewed and discussed.

Next generation risk assessment (NGRA): Bridging in vitro points-of-departure to human safety assessment using physiologically-based kinetic (PBK) modelling - A case study of doxorubicin with dose metrics considerations

Using the chemical doxorubicin (DOX), the objective of the present study was to evaluate the impact of dose metrics selection in the new approach method of integrating physiologically-based kinetic (PBK) modelling and relevant human cell-based assays to inform a priori the point of departure for human health risk. We reviewed the literature on the clinical consequences of DOX treatment to identify dosing scenarios with no or mild cardiotoxicity observed. Key concentrations of DOX that induced cardiomyocyte toxicity in vitro were derived from studies of our own and others. A human population-based PBK model of DOX was developed and verified against pharmacokinetic data. The model was then used to predict plasma and extracellular and intracellular heart concentrations of DOX under selected clinical settings and compared with in vitro outcomes, based on several dose metrics: C_max (maximum concentration) or AUC (area under concentration-time curve) in free or total form of DOX. We found when using in vitro assays to predict cardiotoxicity for DOX, AUC is a better indicator. Our study illustrates that when appropriate dose metrics are used, it is possible to combine PBK modelling with in vitro-derived toxicity information to define margins of safety and predict low-risk human exposure levels.

Role of Oxidative Stress in the Mechanisms of Anthracycline-Induced Cardiotoxicity: Effects of Preventive Strategies

Anthracycline-induced cardiotoxicity (AIC) persists as a significant cause of morbidity and mortality in cancer survivors. Although many protective strategies have been evaluated, cardiotoxicity remains an ongoing threat. The mechanisms of AIC remain unclear; however, several pathways have been proposed, suggesting a multifactorial origin. When the central role of topoisomerase 2β in the pathophysiology of AIC was described some years ago, the classical reactive oxygen species (ROS) hypothesis shifted to a secondary position. However, new insights have reemphasized the importance of the role of oxidative stress-mediated signaling as a common pathway and a critical modulator of the different mechanisms involved in AIC. A better understanding of the mechanisms of cardiotoxicity is crucial for the development of treatment strategies. It has been suggested that the available therapeutic interventions for AIC could act on the modulation of oxidative balance, leading to a reduction in oxidative stress injury. These indirect antioxidant effects make them an option for the primary prevention of AIC. In this review, our objective is to provide an update of the accumulated knowledge on the role of oxidative stress in AIC and the modulation of the redox balance by potential preventive strategies.

Evaluation of PNU-159682 antibody drug conjugates (ADCs)

PNU-159682 is a highly potent secondary metabolite of nemorubicin belonging to the anthracycline class of natural products. Due to its extremely high potency and only partially understood mechanism of action, it was deemed an interesting starting point for the development of a new suite of linker drugs for antibody drug conjugates (ADCs). Structure activity relationships were explored on the small molecule which led to six linker drugs being developed for conjugation to antibodies. Herein we describe the synthesis of novel PNU-159682 derivatives and the subsequent linker drugs as well as the corresponding biological evaluations of the small molecules and ADCs.

Is there scope for better individualisation of anthracycline cancer chemotherapy?

Anthracyclines are used to treat solid and haematological cancers, particularly breast cancers, lymphomas and childhood cancers. Myelosuppression and cardiotoxicity are the primary toxicities that limit treatment duration and/or intensity. Cardiotoxicity, particularly heart failure, is a leading cause of morbidity and mortality in cancer survivors. Cumulative anthracycline dose is a significant predictor of cardiotoxicity risk, suggesting a role for anthracycline pharmacokinetic variability. Population pharmacokinetic modelling in children has shown that doxorubicin clearance in the very young is significantly lower than in older children, potentially contributing to their higher risk of cardiotoxicity. A model of doxorubicin clearance based on body surface area and age offers a patient-centred dose-adjustment strategy that may replace the current disparate initial-dose selection tools, providing a rational way to compensate for pharmacokinetic variability in children aged <7 years. Population pharmacokinetic models in adults have not adequately addressed older ages, obesity, hepatic and renal dysfunction, and potential drug-drug interactions to enable clinical application. Although candidate gene and genome-wide association studies have investigated relationships between genetic variability and anthracycline pharmacokinetics or clinical outcomes, there have been few clinically significant reproducible associations. Precision-dosing of anthracyclines is currently hindered by lack of clinically useful pharmacokinetic targets and models that predict cumulative anthracycline exposures. Combined with known risk factors for cardiotoxicity, the use of advanced echocardiography and biomarkers, future validated pharmacokinetic targets and predictive models could facilitate anthracycline precision dosing that truly maximises efficacy and provides individualised early intervention with cardioprotective therapies in patients at risk of cardiotoxicity.

Unraveling heterogeneity of the clinical pharmacogenomic guidelines in oncology practice among major regulatory bodies

Pharmacogenomics (PGx) implementation in clinical practice is steadily increasing. PGx uses genetic information to personalize medication use, which increases medication efficacy and decreases side effects. The availability of clinical PGx guidelines is essential for its implementation in clinical settings. Currently, there are few organizations/associations responsible for releasing those guidelines, including the Clinical Pharmacogenetics Implementation Consortium, Dutch Pharmacogenetics Working Group, the Canadian Pharmacogenomics Network for Drug Safety and the French National Network of Pharmacogenetics. According to the US FDA, oncology medications are highly correlated to PGx biomarkers. Therefore, summarizing the PGx guidelines for oncology drugs will positively impact the clinical decisions for cancer patients. This review aims to scrutinize side-by-side available clinical PGx guidelines in oncology.

Electromembrane extraction of anthracyclines from plasma: Comparison with conventional extraction techniques

Electromembrane extraction (EME) of the polar zwitterionic drugs, anthracyclines (ANT, doxorubicin, daunorubicin and its metabolite daunorubicinol), from rabbit plasma was investigated. The optimized EME was compared to conventional sample pretreatment techniques such as protein precipitation (PP) and liquid-liquid extraction (LLE), mainly in terms of extraction reliability, recovery and matrix effect. In addition, phospholipids profile in the individual extracts was evaluated. The extracted samples were analyzed using UHPLC-MS/MS with electrospray ionization in positive ion mode. The method was validated within the concentration range of 0.25-1000 ng/mL for all tested ANT. Compared with PP and LLE, the EME provided high extraction recovery (more than 80% for all ANT) and excellent sample clean-up (matrix effect were 100 ± 10% with RSD values lower than 4% for all ANT). Furthermore, only negligible amounts of phospholipids were detected in the EME samples. Finally, practical applicability of EME was proved by analysis of plasma samples taken from a pilot in vivo study in rabbits. Consistent results were obtained when using both EME and LLE to extract the plasma prior to the analysis, which further confirmed high reliability of EME. This study clearly showed that EME is a simple, rapid, repeatable technique for extraction of ANT from plasma and it is an up to date alternative to routine conventional extraction techniques.

Interactions of antileukemic drugs with daunorubicin reductases: could reductases affect the clinical efficacy of daunorubicin chemoregimens?

Although novel anticancer drugs are being developed intensively, anthracyclines remain the gold standard in the treatment of acute myeloid leukaemia (AML). The reductive conversion of daunorubicin (Dau) to less active daunorubicinol (Dau-ol) is an important mechanism that contributes to the development of pharmacokinetic anthracycline resistance. Dau is a key component in many AML regimes, in which it is combined with many drugs, including all-trans-retinoic acid (ATRA), cytarabine, cladribine and prednisolone. In the present study, we investigated the influence of these anticancer drugs on the reductive Dau metabolism mediated by the aldo-keto reductases AKR1A1, 1B10, 1C3, and 7A2 and carbonyl reductase 1 (CBR1). In incubation experiments with recombinant enzymes, cladribine and cytarabine did not significantly inhibit the activity of the tested enzymes. Prednisolone inhibited AKR1C3 with an IC₅₀ of 41.73 µM, while ATRA decreased the activity of AKR1B10 (IC₅₀ = 78.33 µM) and AKR1C3 (IC₅₀ = 1.17 µM). Subsequent studies showed that AKR1C3 inhibition mediated by ATRA exhibited tight binding (Ki^app = 0.54 µM). Further, the combination of 1 µM ATRA with different concentrations of Dau demonstrated synergistic effects in HCT116 and KG1a human cells expressing AKR1C3. Our results suggest that ATRA-mediated inhibition of AKR1C3 can contribute to the mechanisms that are hidden beyond the beneficial clinical outcome of the ATRA-Dau combination.

Gut microbiota in reductive drug metabolism

Gut bacteria are predominant microorganisms in the gut microbiota and have been recognized to mediate a variety of biotransformations of xenobiotic compounds in the gut. This review is focused on one of the gut bacterial xenobiotic metabolisms, reduction. Xenobiotics undergo different types of reductive metabolisms depending on chemically distinct groups: azo (-NN-), nitro (-NO₂), alkene (-CC-), ketone (-CO), N-oxide (-NO), and sulfoxide (-SO). In this review, we have provided select examples of drugs in six chemically distinct groups that are known or suspected to be subjected to the reduction by gut bacteria. For some drugs, responsible enzymes in specific gut bacteria have been identified and characterized, but for many drugs, only circumstantial evidence is available that indicates gut bacteria-mediated reductive metabolism. The physiological roles of even known gut bacterial enzymes have not been well defined.

Pharmacokinetics and population pharmacokinetics in pediatric oncology

Pharmacokinetic research has become increasingly important in pediatric oncology as it can have direct clinical implications and is a crucial component in individualized medicine. Population pharmacokinetics has become a popular method especially in children, due to the potential for sparse sampling, flexible sampling times, computing of heterogeneous data, and identification of variability sources. However, population pharmacokinetic reports can be complex and difficult to interpret. The aim of this article is to provide a basic explanation of population pharmacokinetics, using clinical examples from the field of pediatric oncology, to facilitate the translation of pharmacokinetic research into the daily clinic.

Carbonyl Reductase 1 Plays a Significant Role in Converting Doxorubicin to Cardiotoxic Doxorubicinol in Mouse Liver, but the Majority of the Doxorubicinol-Forming Activity Remains Unidentified

Doxorubicin is a widely used cancer therapeutic, but its effectiveness is limited by cardiotoxic side effects. Evidence suggests cardiotoxicity is due not to doxorubicin, but rather its metabolite, doxorubicinol. Identification of the enzymes responsible for doxorubicinol formation is important in developing strategies to prevent cardiotoxicity. In this study, the contributions of three murine candidate enzymes to doxorubicinol formation were evaluated: carbonyl reductase (Cbr) 1, Cbr3, and thioredoxin reductase 1 (Tr1). Analyses with purified proteins revealed that all three enzymes catalyzed doxorubicin-dependent NADPH oxidation, but only Cbr1 and Cbr3 catalyzed doxorubicinol formation. Doxorubicin-dependent NADPH oxidation by Tr1 was likely due to redox cycling. Subcellular fractionation results showed that doxorubicin-dependent redox cycling activity was primarily microsomal, whereas doxorubicinol-forming activity was exclusively cytosolic, as were all three enzymes. An immunoclearing approach was used to assess the contributions of the three enzymes to doxorubicinol formation in the complex milieu of the cytosol. Immunoclearing Cbr1 eliminated 25% of the total doxorubicinol-forming activity in cytosol, but immunoclearing Cbr3 had no effect, even in Tr1 null livers that overexpressed Cbr3. The immunoclearing results constituted strong evidence that Cbr1 contributed to doxorubicinol formation in mouse liver but that enzymes other than Cbr1 also played a role, a conclusion supported by ammonium sulfate fractionation results, which showed that doxorubicinol-forming activity was found in fractions that contained little Cbr1. In conclusion, the results show that Cbr1 accounts for 25% of the doxorubicinol-forming activity in mouse liver cytosol but that the majority of the doxorubicinol-forming activity remains unidentified. SIGNIFICANCE STATEMENT: Earlier studies suggested carbonyl reductase (Cbr) 1 plays a dominant role in converting chemotherapeutic doxorubicin to cardiotoxic doxorubicinol, but a new immunoclearing approach described herein shows that Cbr1 accounts for only 25% of the doxorubicinol-forming activity in mouse liver cytosol, that two other candidate enzymes-Cbr3 and thioredoxin reductase 1-play no role, and that the majority of the activity remains unidentified. Thus, targeting Cbr1 is necessary but not sufficient to eliminate doxorubicinol-associated cardiotoxicity; identification of the additional doxorubicinol-forming activity is an important next challenge.

Toxic Mechanisms of the Heart: A Review*

Toxic injury is one of the many ways by which the functional integrity of the heart may become compromised. Any of the subcellular elements may be the target of toxic injury, including all of the various membranes and organelles. Understanding the mechanisms underlying cardiotoxicity may lead to treatment of the toxicity or to its prevention. Doxorubicin and its analogs are very important cancer chemotherapeutic agents that can cause cardiotoxicity. Other agents which are cardiotoxic and which have profound public health implications include the alkaloid emetine in ipecac syrup, cocaine, and ethyl alcohol. The most important cardiotoxic mechanisms proposed for doxorubicin include oxidative stress with its resultant damage to myocardial elements, changes in calcium homeostasis, decreased ability to produce ATP, and systemic release of cardiotoxic humoral mediators from tissue mast cells. Each of the first 3 mechanisms can lead to each of the other 2, and the causal relationships between all of these mechanisms are not clear. New evidence suggests that doxorubicinol, one of the metabolites of doxorubicin may be the moiety responsible for cardiotoxicity. Several other potential mechanisms also have been proposed for doxorubicin. Emetine in ipecac syrup is the first aid treatment of choice for many acute toxic oral ingestions and the alkaloid, itself, is used to treat amebiasis. Cardiotoxicity occurs following chronic exposure, such as occurs therapeutically in amebiasis and with ipecac abuse by bulemics. A number of mechanisms are proposed for emetine cardiotoxicity, but the current mechanistic literature is quite scarce. Cocaine abuse recently has caught the public interest, in particular because of the drug-related sudden deaths of certain athletes. Cocaine can cause hypertension, arrhythmias, and reduced coronary blood flow, each of which can contribute to its lethality. However, it may be possible that cocaine sudden death episodes are more related to hyperthermia and convulsive seizures, rather than to cardiovascular toxicity. Chronic alcohol use leads to dilated cardiomyopathy and failure as part of the general physical degeneration that occurs with alcoholism. Several mechanisms are proposed for the cardiomyopathy, but only 2 things seem clear. The cardiotoxicity is due to an intrinsic effect of alcohol, rather than to malnutrition or co-toxicity, and abstinence is the only effective treatment for the cardiomyopathy. Recent articles indicate that very moderate use of alcohol may be beneficial and protect against cardiovascular-related morbidity. One explanation for these findings seems to be that the non-drinking groups, against whom the moderate drinking comparisons were made, were enriched in former drinkers with significant alcohol-related cardiovascular pathology.

Protective effect of curcumin nanoparticles against cardiotoxicity induced by doxorubicin in rat

The present study designed to investigate the protective effect of curcumin nanoparticles (CUR-NPs) on the cardiotoxicity induced by doxorubicin. Rats were divided into four groups; control, rats treated daily with CUR-NPs (50 mg/kg) for 14 days, rats treated with an acute dose of doxorubicin (20 mg/kg) and rats treated daily with CUR-NPs for 14 days injected with doxorubicin on the 10th day. After electrocardiogram (ECG) recording from rats at different groups, rat decapitation was carried out and the heart of each rat was excised out to measure the oxidative stress parameters; lipid peroxidation (MDA), nitric oxide (NO) and reduced glutathione (GSH) and the activities of Na,K,ATPase and acetylcholinesterase (AchE). In addition, the levels of dopamine (DA), norepinephrine (NE) and serotonin (5-HT) were determined in the cardiac tissues. Lactate dehydrogenase (LDH) activity was measured in the serum. The ECG recordings indicated that daily pretreatment with CUR- NPs has prevented the tachycardia (i.e. increase in heart rate) and ameliorated the changes in ST wave and QRS complex induced by doxorubicin. In addition, CUR-NPs prevented doxorubicin induced significant increase in MDA, NO, DA, AchE and LDH and doxorubicin induced significant decrease in GSH, NE, 5-HT and Na,K,ATPase. According to the present findings, it could be concluded that CUR-NPs have a protective effect against cardiotoxicity induced by doxorubicin. This may shed more light on the importance of CUR-NPs pretreatment before the application of doxorubicin therapy.

Insights into Doxorubicin-induced Cardiotoxicity: Molecular Mechanisms, Preventive Strategies, and Early Monitoring

Doxorubicin (DOX) is one of the most effective anticancer drugs to treat various forms of cancers; however, its therapeutic utility is severely limited by its associated cardiotoxicity. Despite the enormous amount of research conducted in this area, the exact molecular mechanisms underlying DOX toxic effects on the heart are still an area that warrants further investigations. In this study, we reviewed literature to gather the best-known molecular pathways related to DOX-induced cardiotoxicity (DIC). They include mechanisms dependent on mitochondrial dysfunction such as DOX influence on the mitochondrial electron transport chain, redox cycling, oxidative stress, calcium dysregulation, and apoptosis pathways. Furthermore, we discuss the existing strategies to prevent and/or alleviate DIC along with various techniques available for therapeutic drug monitoring (TDM) in cancer patients treated with DOX. Finally, we propose a stepwise flowchart for TDM of DOX and present our perspective at curtailing this deleterious side effect of DOX.