Search for metabolites of ecteinascidin 743, a novel, marine-derived, anti-cancer agent, in man

Marine Compounds, Mitochondria, and Malignancy: A Therapeutic Nexus

The marine environment is important yet generally underexplored. It contains new sources of functional constituents that can affect various pathways in food processing, storage, and fortification. Bioactive secondary metabolites produced by marine microorganisms may have significant potential applications for humans. Various components isolated from disparate marine microorganisms, including fungi, microalgae, bacteria, and myxomycetes, showed considerable biological effects, such as anticancer, antioxidant, antiviral, antibacterial, and neuroprotective activities. Growing studies are revealing that potential anticancer effects of marine agents could be achieved through the modulation of several organelles. Mitochondria are known organelles that influence growth, differentiation, and death of cells via influencing the biosynthetic, bioenergetic, and various signaling pathways related to oxidative stress and cellular metabolism. Consequently, mitochondria play an essential role in tumorigenesis and cancer treatments by adapting to alterations in environmental and cellular conditions. The growing interest in marine-derived anticancer agents, combined with the development and progression of novel technology in the extraction and cultures of marine life, led to revelations of new compounds with meaningful pharmacological applications. This is the first critical review on marine-derived anticancer agents that have the potential for targeting mitochondrial function during tumorigenesis. This study aims to provide promising strategies in cancer prevention and treatment.

Pharmacogenetic Study of Trabectedin-Induced Severe Hepatotoxicity in Patients with Advanced Soft Tissue Sarcoma

Hepatotoxicity is an important concern for nearly 40% of the patients treated with trabectedin for advanced soft tissue sarcoma (ASTS). The mechanisms underlying these liver damages have not yet been elucidated but they have been suggested to be related to the production of reactive metabolites. The aim of this pharmacogenetic study was to identify genetic variants of pharmacokinetic genes such as CYP450 and ABC drug transporters that could impair the trabectedin metabolism in hepatocytes. Sixty-three patients with ASTS from the TSAR clinical trial (NCT02672527) were genotyped by next-generation sequencing for 11 genes, and genotype-toxicity association analyses were performed with R package SNPassoc. Among the results, ABCC2 c.1249A allele (rs2273697) and ABCG2 intron variant c.-15994T (rs7699188) were associated with an increased risk of severe cytolysis, whereas ABCC2 c.3563A allele had a protective effect, as well as ABCB1 variants rs2032582 and rs1128503 (p-value < 0.05). Furthermore, CYP3A5*1 rs776746 (c.6986A > G) increased the risk of severe overall hepatotoxicity (p = 0.012, odds ratio (OR) = 5.75), suggesting the implication of metabolites in the hepatotoxicity. However, these results did not remain significant after multiple analysis correction. These findings need to be validated on larger cohorts of patients, with mechanistic studies potentially being able to validate the functional consequences of these variants.

Analysis of anticancer drugs: a review

In the last decades, the number of patients receiving chemotherapy has considerably increased. Given the toxicity of cytotoxic agents to humans (not only for patients but also for healthcare professionals), the development of reliable analytical methods to analyse these compounds became necessary. From the discovery of new substances to patient administration, all pharmaceutical fields are concerned with the analysis of cytotoxic drugs. In this review, the use of methods to analyse cytotoxic agents in various matrices, such as pharmaceutical formulations and biological and environmental samples, is discussed. Thus, an overview of reported analytical methods for the determination of the most commonly used anticancer drugs is given.

Phase I and pharmacokinetic study of trabectedin 3-hour infusion every three weeks in patients with advanced cancer and alteration of hepatic function

Maximum tolerated dose (MTD), recommended dose (RD), and pharmacokinetics (PK) were evaluated for trabectedin 3-h every-3-weeks schedule in 33 cancer patients stratified according to liver dysfunction degree as per baseline alkaline phosphatase (AP). Stratification was as follows: stratum I [upper limit of normal (ULN) < AP ≤ 1.5 × ULN; n = 16], stratum II [1.5 × ULN < AP ≤ 2.5 × ULN; n = 12], and stratum III [AP >2.5 × ULN; n = 5] (bilirubin <2.5 × ULN for all 3 strata). In each stratum, patients were treated in sequential cohorts at escalating doses. Dose-limiting toxicities (DLTs) were grade 3 transaminase increases not recovering baseline values on day 21, febrile neutropenia/grade 4 neutropenia lasting >5 days and AP increase more than twice over baseline. The MTD and RD for stratum I (mild baseline AP) was 1.3 mg/m(2). Recruitment was stopped early in strata II/III (moderate/severe baseline AP) without reaching the MTD due to slow accrual and difficulty in finding patients. Biochemical parameters other than AP (bilirubin, AST or ALT) were similar between strata. No relevant PK differences were found between strata. In conclusion, the MTD and RD (1.3 mg/m(2)) were confirmed only for stratum I. Stratification criteria based on baseline AP apparently did not segregate the patients according to their liver dysfunction degree. Antitumor activity was found in patients with pretreated ovarian cancer.

Wide-spectrum characterization of trabectedin: biology, clinical activity and future perspectives

Ecteinascidin-743 (trabectedin, Yondelis®; PharmaMar, Madrid, Spain), a 25-year-old antineoplastic alkylating agent, has recently shown unexpected and interesting mechanisms of action. Trabectedin causes perturbation in the transcription of inducible genes (e.g., the multidrug resistance gene MDR1) and interaction with DNA repair mechanisms (e.g., the nucleotide excision repair pathway) owing to drug-related DNA double strand breaks and adduct formation. Trabectedin was the first antineoplastic agent from a marine source (namely, the Caribbean tunicate Ecteinascidia turbinata) to receive marketing authorization. This article summarizes the mechanisms of action, the complex metabolism, the main toxicities, the preclinical and clinical evidences of its antineoplastic effects in different types of cancer and, finally, the future perspectives of this promising drug.

Disposition and toxicity of trabectedin (ET-743) in wild-type and mdr1 gene (P-gp) knock-out mice

Trabectedin is a novel anticancer drug active against soft tissue sarcomas. Trabectedin is a substrate for P-glycoprotein (P-gp), which is encoded by mdr1a/1b in rodents. Plasma and tissue distribution, and excretion of [(14)C]-trabectedin were evaluated in wild-type and mdr1a/1b(-/-) mice. In parallel, we investigated the toxicity profile of trabectedin by serial measurements of blood liver enzymes and general pathology. [(14)C]-trabectedin was extensively distributed into tissues, and rapidly converted into a range of unknown metabolic products. The excretion of radioactivity was similar in both genotypes. The plasma clearance of unchanged trabectedin was not reduced when P-gp was absent, but organs under wild type circumstances protected by P-gp showed increased trabectedin concentrations in mdr1a/1b(-/-) mice. Although hepatic trabectedin concentrations were not increased when P-gp was absent, mdr1a/1b(-/-) mice experienced more severe liver toxicity. P-gp plays a role in the in vivo disposition and toxicology of trabectedin.

Metabolism of trabectedin (ET-743, Yondelis™) in patients with advanced cancer

PURPOSE

Trabectedin (ET-743, Yondelis) is a novel anti-cancer drug currently undergoing phase II-III evaluation, that has shown remarkable activity in pre-treated patients with soft tissue sarcoma. Despite extensive pharmacokinetic studies, the human disposition and metabolism of trabectedin remain largely unknown. We aimed to determine the metabolic profile of trabectedin and to identify its metabolites in humans.

METHODS

We analysed urine and faeces (the major excretory route) from eight cancer patients after a 3 or 24 h intravenous administration of [14C]trabectedin. Using liquid chromatography with tandem quadrupole mass spectrometric detection (LC-MS/MS) and radiochromatography with off-line radioactivity detection by liquid scintillation counting (LC-LSC), we characterised the metabolic profile in 0-24 h urine and 0-120 h faeces.

RESULTS

By radiochromatography, a large number of trabectedin metabolites were detected. Incubation with beta-glucuronidase indicated the presence of a glucuronide metabolite in urine. Trabectedin, ET-745, ET-759A, ETM-259, ETM-217 (all available as reference compounds) and a proposed new metabolite coined ET-731 were detected using LC-MS/MS. The inter-individual differences in radiochromatographic profiles were small and did not correlate with polymorphisms in drug-metabolising enzymes (CYP2C9, 2C19, 2D6, 2E1, 3A4, GST-M1, P1, T1 and UGT1A1 2B15) as determined by genotyping.

CONCLUSIONS

Trabectedin is metabolically converted to a large number of compounds that are excreted in both urine and faeces. In urine and faeces we have confirmed the presence of trabectedin, ET-745, ET-759A, ETM-259, ETM-217 and ETM-204. In addition we have identified a putative new metabolite designated ET-731. Future studies should be aimed at further identification of possible metabolites and assessment of their activity.

In vitro characterization of the human biotransformation and CYP reaction phenotype of ET-743 (Yondelis®, Trabectidin®), a novel marine anti-cancer drug

ET-743 is a potent marine anti-cancer drug and is currently being investigated in phase I and II clinical trials, e.g. in combination with other anti-cancer agents. To assess the biotransformation and CYP reaction phenotype and their potential implications for human pharmacology and toxicology, the in vitro metabolism of ET-743 was characterized using incubations with human liver preparations, cytochrome P450 (CYP) and uridine diphosphoglucuronosyl transferase (UGT) supersomes.CYP supersomes and liver microsomes showed that ET-743 was metabolized mainly by CYP3A4, but also by CYP2C9, 2C19, 2D6, and 2E1. ET-743 showed the highest affinity for CYP3A4 and the highest maximal metabolic rate for CYP2D6 among the CYPs shown to metabolize ET-743. In addition, the Km value of ET-743 in female microsomes was significantly lower compared to male microsomes, while the Vmax values did not differ. ET-743 glucuronidation, catalyzed by UGT2B15, was observed in microsomes and S9 fraction. In addition, conjugation by glutathione-S-transferase and no sulphation was observed for ET-743 in cytosol and S9 fraction. ET-743 was more extensively metabolized when CYP activity was combined with phase II enzymes UGT and glutathione-S-transferase (GST), indicating that CYP, UGT, and GST simultaneously metabolize ET-743 in the S9 fraction. These results provide evidence that CYP3A4 has a major role in the metabolism of ET-743 in vitro with additional involvement of CYP2C9, 2C19, 2D6, and 2E1. Furthermore, ET-743 is conjugated by UGT and GST. This information could be important for interpretation of the pharmacokinetic data of clinical trials and prediction of drug-drug interactions.

In-vitro cytotoxicity of ET-743 (Trabectedin, Yondelis), a marine anti-cancer drug, in the Hep G2 cell line: influence of cytochrome P450 and phase II inhibition, and cytochrome P450 induction

ET-743 is a marine anti-cancer drug and is currently in phase I trials in which the effect of combination therapies will be investigated. Its dose-limiting toxicity in patients is hepatotoxicity. In-vitro studies have shown that ET-743 is mainly metabolized by cytochrome P450 (CYP) 3A4, but also by 2C9, 2C19, 2D6 and 2E1, and the phase II enzymes uridine diphosphoglucuronosyl transferase and glutathione-S-transferase. Based on this metabolic profile, there is a risk of drug-drug interactions possibly influencing the hepatotoxicity of ET-743. Therefore, the effect of CYP and phase II activity on the cytotoxicity of ET-743 was investigated in vitro in a human cell line model system. The effect of different CYP and phase II inhibitors and CYP inducers on ET-743 cytotoxicity was studied after 48 and 120 h of treatment in Hep G2 cells using different assays. Furthermore, the toxicity of ET-743 metabolites was investigated. Potent cytotoxic activity of ET-743 after 120 h treatment was observed, which could be increased in combination with the CYP inhibitors metyrapone (3A4), phenanthrene (substrate for 2E1, 3A4), piperonyl butoxide (3A), proadifen (2C9, 2E1, 3A4), ritonavir (3A4), and warfarin (2C9, 2C19). No effect on the cytotoxicity of ET-743 was observed in combination with phase II enzyme inhibition and CYP induction. CYP metabolites of ET-743 were less toxic compared with ET-743. These findings indicate that combination therapy of ET-743 with CYP inhibitors, e.g. other anti-cancer drugs, could lead to changes in the hepatotoxicity of ET-743 and are therefore of clinical importance.

Trabectedin (YondelisTM, formerly ET-743), a mass balance study in patients with advanced cancer

Trabectedin (Yondelis, formerly ET-743) is an anti-cancer drug currently undergoing phase II development. Despite extensive pharmacokinetic studies, the human disposition and excretory pathways of trabectedin remain largely unknown. Our objective was to determine the mass balance of trabectedin in humans. To this aim, we intravenously administered [(14)C]trabectedin to 8 cancer patients, followed by collection of whole blood, urine and faeces samples. A 24-h infusion was administered to 2 patients, whereas the other 6 patients received a 3-h infusion. Levels of total radioactivity and unchanged trabectedin were determined and used for calculation of pharmacokinetic parameters. No schedule dependency of pharmacokinetic parameters was observed apart from C(max). Plasma and whole blood concentrations of [(14)C]trabectedin related radioactivity were comparable. Only 8% of the plasma exposure to [(14)C]trabectedin related compounds is accounted for by trabectedin, indicating the importance of metabolism in trabectedin elimination. Trabectedin displays a large volume of distribution (+/-1700 L), relative to total radioactivity (+/-220 L). [(14)C]trabectedin related radioactivity is mainly excreted in the faeces (mean: 55.5% of the dose). Urinary excretion accounts for 5.9% of the dose on average resulting in a mean overall recovery of 61.4% (3-h administration schedule). The excretion of unchanged trabectedin is very low both in faeces and in urine (< 1% of dose). In conclusion, trabectedin is extensively metabolised and principally excreted in the faeces.

Structure elucidation of aplidine metabolites formed in vitro by human liver microsomes using triple quadrupole mass spectrometry

The cyclic depsipeptide aplidine is a new anti-cancer drug of marine origin. Four metabolites of this compound were found after incubation with pooled human microsomes using gradient high-performance liquid chromatography with ultraviolet detection. After chromatographic isolation, the metabolites have been identified using nano-electrospray triple quadrupole mass spectrometry. A highly specific sodium-ion interaction with the cyclic structure opens the depsipeptide ring, and cleavage of the amino acid residues gives sequence information when activated by collision-induced dissociation in the second quadrupole. The aplidine molecule could undergo the following metabolic reactions: hydroxylation at the isopropyl group (metabolites apli-h 1 and apli-h 2); C-dealkylation at the N(Me)-leucine group (metabolite apli-da); hydroxylation at the isopropyl group and C-dealkylation at the N(Me)-leucine group (metabolite apli-da/h), and C-demethylation at the threonine group (metabolite apli-dm). The identification of these metabolites formed in vitro may greatly aid the elucidation of the metabolic pathways of aplidine in humans.

Hepatotoxicity and metabolism of trabectedin: a literature review

Trabectedin is a promising anticancer drug currently undergoing phase II evaluation. In preclinical studies, trabectedin was found to cause hepatotoxicity and in patients it reversibly increases plasma levels of liver enzymes. On the basis of preclinical work, it was suggested that metabolism of trabectedin contributed to the pharmacological effects of trabectedin, including hepatotoxicity in rats and increases in liver enzymes in humans. Our aim was to review the current literature on the metabolism of trabectedin and its role in the increases in liver enzymes and hepatotoxicity. We conclude that the trabectedin metabolic profile appears to predict the reversible nature of hepatotoxicity. The rat may not be the best species to investigate trabectedin hepatotoxicity because both trabectedin metabolic profile and reversibility of hepatotoxicity differs from humans. Humans and monkeys display a similar metabolic profile of trabectedin and in both species hepatotoxicity is reversible. Trabectedin is a drug with predictable hepatotoxic effects. Monitoring of plasma levels of liver enzymes ensures safe use of trabectedin in the clinic. Future investigations must be aimed at elucidating the mechanism of trabectedin hepatotoxicity.

Preclinical and clinical results with the natural marine product ET-743

ET-743 (Yondelis, trabectedin) is a natural marine product with antitumour properties derived from the tunicate Ecteinascidia turbinata. ET-743 binds to the N2 position of guanine in the minor groove of DNA with some degree of sequence specificity, altering the transcription regulation of induced genes. Cells that are deficient in nucleotide excision repair, hypersensitive to UV rays, cisplatin and conventional alkylating agents, are resistant to ET-743. This is a unique property of ET-743 and is of potential importance for the drug activity when administered alone or in combination with other drugs. ET-743 showed striking antitumour activity against sensitive and resistant human xenografts. The dose-limiting toxicities in animal models, hepatobiliary events, were of concern, but the pattern of the reversibility noted in monkeys and the evidence of a positive therapeutic index in tumour-bearing nude mice prompted its clinical development. The Phase I programme investigated different schedules of administration, with the dose-limiting toxicities being neutropenia and fatigue. As anticipated in the preclinical models, reversible non-cumulative transaminitis was a prevalent finding from one-third of the maximum tolerated dose level; long-lasting objective responses in pretreated resistant patients were noted, including consistent efficacy data in mesenchymal tumours. The Phase II data for ET-743 administered as a single agent has established a clinical role for the compound in advanced pretreated soft tissue sarcoma and a promising potential in pretreated ovarian and breast cancer. ET-743 combined with other drugs (i.e., cisplatin, paclitaxel or doxorubicin) showed more than additive effects in several preclinical systems and initial clinical results (e.g., a combination of ET-743 with cisplatin) appear to confirm the preclinical findings. In summary, ET-743 is a new drug with a novel mode of action, which has demonstrated activity in human tumours resistant to the available anticancer drugs. Further comparative studies are needed to define the role of ET-743 alone or in combination in cancer chemotherapy.

Dietary agent indole-3-carbinol protects female rats against the hepatotoxicity of the antitumor drug ET-743 (trabectidin) without compromising efficacy in a rat mammary carcinoma

ET-743, an experimental antitumor drug with promising activity in sarcoma, breast and ovarian carcinoma, is currently under phase 2 clinical evaluation. It is hepatotoxic in animals and patients. We tested the hypothesis that indole-3-carbinol (I3C), the hydrolysis product of glucosinolates occurring in cruciferous vegetables, may protect against ET-743-induced hepatotoxicity in the female Wistar rat, the animal species with the highest sensitivity toward the adverse hepatic effect of this drug. Hepatotoxicity was adjudged by measurement of plasma levels of bilirubin, alkaline phosphatase (ALP) and aspartate aminotransferase (AST) and by liver histopathology. The effect of I3C on the kinetics of ET-743 in rat plasma and liver was investigated by high-pressure liquid chromatography. The effect of I3C on the antitumor efficacy of ET-743 was explored in rats bearing the 13762 mammary carcinoma. ET-743 (40 microg/kg i.v.) alone caused an elevation of plasma bilirubin, ALP and AST levels and degeneration and patchy focal necrosis of bile duct epithelial cells. Addition of I3C to the diet (0.5%) for 6 days prior to ET-743 administration almost completely abolished manifestations of hepatotoxicity. In contrast, a dietary concentration of 0.1% I3C did not protect, nor did dietary diindolylmethane (0.2%), an acid-catalyzed condensation product of I3C. Ingestion by rats of I3C for 6 days prior to ET-743 (40 microg/kg i.v.) decreased plasma but not hepatic concentrations of ET-743 compared to animals that received ET-743 alone. I3C did not interfere with the antitumor efficacy of ET-743. The results suggest that ingestion of I3C may counteract the unwanted effect of ET-743 in the liver. I3C should be investigated as a hepatoprotectant in patients who receive ET-743 therapy.

Yondelis (trabectedin, ET-743): the development of an anticancer agent of marine origin

Yondelis (trabectedin, ET-743) is a novel antitumor agent derived from a marine source, the Caribbean tunicate Ecteinascidia turbinata. Preclinical studies demonstrated activity at low concentrations against a variety of tumors. The mechanism by which ET-743 exerts its antitumor activity has not been completely elucidated yet. Binding to the minor groove of DNA which causes a bend towards the major groove has been demonstrated. Furthermore, ET-743 interferes with DNA binding proteins and transcription factors. Clinical studies have been initiated as phase I dose-finding studies at four different treatment regimens. Dose-limiting toxicities were hematological, including neutropenia and thrombocytopenia. Furthermore, significant liver toxicity was observed, especially as a rise in transaminase levels. Antitumor activity in phase I and phase II trials was studied in multiple tumor types, including soft tissue sarcomas, melanomas and breast cancer. ET-743 is currently being extensively investigated in advanced soft tissue sarcomas. The present review describes the development of ET-743, highlighting chemical properties, mode of action, metabolism and preclinical and clinical studies.

Clinical pharmacology of the novel marine-derived anticancer agent Ecteinascidin 743 administered as a 1- and 3-h infusion in a phase I study

Ecteinascidin 743 (ET-743) is an anticancer agent derived from the Caribbean tunicate Ecteinascidia turbinata. In the present article, the pharmacokinetics and pharmacodynamics of ET-743 are described within a phase I study. Forty patients with solid tumors initially received ET-743 as a 1-h i.v. infusion every 21 days at nine dose levels (50-1100 microg/m(2)). The maximal tolerated dose (MTD) was 1100 microg/m(2), with thrombocytopenia and fatigue as dose-limiting toxicities (DLTs). As this MTD was substantially lower than in parallel phase I studies, dose escalation continued using a prolonged, 3-h infusion. Thirty-two patients were entered at five dose levels (1000-1800 microg/m(2)). The MTD was 1800 microg/m(2) with pancytopenia and fatigue as DLTs. The recommended phase II dose was 1650 microg/m(2) given over 3 h at which 12 patients were treated. Pharmacokinetic monitoring was performed for both treatment schedules. Non-compartmental pharmacokinetic parameters at the recommended dose with the 3-h infusion were (mean value+/-SD): clearance 87+/-30 l/h and mean elimination half-life 26+/-7 h. Pharmacokinetics were linear at the dose range tested with this schedule. The percentage decrease in platelets, white blood cells and neutrophils correlated with the area under the plasma concentration versus time curve (AUC), dose and maximal plasma concentration (C(max)). Hepatic toxicity increased with dose, AUC and C(max). Administration of 1650 microg/m(2) ET-743 over 3 h seemed clinically feasible; pharmacokinetics were linear with this schedule. Hepatic and hematological toxicities correlated with exposure to ET-743.