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

Impact of relative dose intensity of trabectedin with pegfilgrastim support: a single-centre retrospective study

Relative dose intensity (RDI) has been associated with improved survival in patients with advanced solid tumours. However, there is no evidence regarding RDI in patients under long-term treatment with trabectedin for adult advanced soft tissue sarcoma (STS). Pegfilgrastim use was associated with chemotherapy dose intensity maintenance in patients with various cancers. We retrospectively evaluated the RDI in patients with STS receiving trabectedin. The patients were grouped based on whether trabectedin administration was supported by pegfilgrastim. RDI was obtained for 114 of the 140 included patients. Chemotherapy cycles that included filgrastim were excluded. Patients treated with and without pegfilgrastim had similar RDI rates (77.1% ± 17.6% vs 78.8% ± 16.4%; P = 0.485). Moreover, we found no association between patients receiving ≥4 trabectedin cycles and the use of pegfilgrastim. These results suggested that trabectedin dose delays or reductions should be considered before administering prophylactic pegfilgrastim.

Trabectedin in Cancers: Mechanisms and Clinical Applications

Trabectedin, a tetrahydroisoquinoline alkaloid, is the first marine antineoplastic agent approved with special anticancer mechanisms involving DNA binding, DNA repair pathways, transcription regulation and regulation of the tumor microenvironment. It has favorable clinical applications, especially for the treatment of patients with advanced soft tissue sarcoma, who failed in anthracyclines and ifosfamide therapy or could not receive these agents. Currently, trabectedin monotherapy regimen and regimens of combined therapy with other agents are both widely used for the treatment of malignancies, including soft tissue sarcomas, ovarian cancer, breast cancer, and non-small-cell lung cancer. In this review, we summarized the basic information and some updated knowledge on trabectedin, including its molecular structure, metabolism in various cancers, pharmaceutical mechanisms, clinical applications, drug combination, and adverse reactions, along with prospections on its possibly more optimal use in cancer treatment.

Total synthesis of the isoquinolinium metabolite ETM-204 of Trabectidin

Ecteinascidin-743 (Trabectidin, Trabectedin®, Yondelis®) is a synthetically obtained pharmaceutical drug originally isolated from a marine tunicate. Trabectedin is used for the chemotherapy of soft-tissue sarcoma and ovarian cancer. The isoquinolinium metabolite ETM-204 has been found in biotransformation and degradation studies of Trabectedin. We report the first total synthesis of ETM-204 and its full spectroscopic characterization confirming the postulated structure. Central elements of the 12-step synthesis starting from 2-methyl-6-nitrophenol are a Cu-mediated conversion of an iodoarene to a phenol, a Skattebøl-formylation, and a modified Pomeranz–Fritsch cyclization to assemble the isoquinoline ring. The pH-dependence of its visual absorbance could be clarified.

Graphic abstract

Human Family 1-4 cytochrome P450 enzymes involved in the metabolic activation of xenobiotic and physiological chemicals: an update

This is an overview of the metabolic activation of drugs, natural products, physiological compounds, and general chemicals by the catalytic activity of cytochrome P450 enzymes belonging to Families 1-4. The data were collected from > 5152 references. The total number of data entries of reactions catalyzed by P450s Families 1-4 was 7696 of which 1121 (~ 15%) were defined as bioactivation reactions of different degrees. The data were divided into groups of General Chemicals, Drugs, Natural Products, and Physiological Compounds, presented in tabular form. The metabolism and bioactivation of selected examples of each group are discussed. In most of the cases, the metabolites are directly toxic chemicals reacting with cell macromolecules, but in some cases the metabolites formed are not direct toxicants but participate as substrates in succeeding metabolic reactions (e.g., conjugation reactions), the products of which are final toxicants. We identified a high level of activation for three groups of compounds (General Chemicals, Drugs, and Natural Products) yielding activated metabolites and the generally low participation of Physiological Compounds in bioactivation reactions. In the group of General Chemicals, P450 enzymes 1A1, 1A2, and 1B1 dominate in the formation of activated metabolites. Drugs are mostly activated by the enzyme P450 3A4, and Natural Products by P450s 1A2, 2E1, and 3A4. Physiological Compounds showed no clearly dominant enzyme, but the highest numbers of activations are attributed to P450 1A, 1B1, and 3A enzymes. The results thus show, perhaps not surprisingly, that Physiological Compounds are infrequent substrates in bioactivation reactions catalyzed by P450 enzyme Families 1-4, with the exception of estrogens and arachidonic acid. The results thus provide information on the enzymes that activate specific groups of chemicals to toxic metabolites.

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.

Population-Pharmacokinetic and Covariate Analysis of Lurbinectedin (PM01183), a New RNA Polymerase II Inhibitor, in Pooled Phase I/II Trials in Patients with Cancer

BACKGROUND AND OBJECTIVES

Lurbinectedin is an inhibitor of RNA polymerase II currently under clinical development for intravenous administration as a single agent and in combination with other anti-tumor agents for the treatment of several tumor types. The objective of this work was to develop a population-pharmacokinetic model in this patient setting and to elucidate the main predictors to guide the late stages of development.

METHODS

Data from 443 patients with solid and hematologic malignancies treated in six phase I and three phase II trials with lurbinectedin as a single agent or combined with other agents were included in the analysis. The potential influence of demographic, co-treatment, and laboratory characteristics on lurbinectedin pharmacokinetics was evaluated.

RESULTS

The final population-pharmacokinetic model was an open three-compartment model with linear distribution and linear elimination from the central compartment. Population estimates for total plasma clearance, and apparent volume at steady state were 11.2 L/h and 438 L, respectively. Inter-individual variability was moderate for all parameters, ranging from 20.9 to 51.2%. High α-1-acid glycoprotein and C-reactive protein, and low albumin reduced clearance by 28, 20, and 20%, respectively. Co-administration of cytochrome P450 3A inhibitors reduced clearance by 30%. Combinations with other anti-tumor agents did not modify the pharmacokinetics of lurbinectedin significantly.

CONCLUSION

The population-pharmacokinetic model indicated neither a dose nor time dependency, and no clinically meaningful pharmacokinetic differences were found when co-administered with other anticancer agents. A chronic inflammation pattern characterized by decreased albumin and increased C-reactive protein and α-1-acid glycoprotein levels led to high lurbinectedin exposure. Co-administration of cytochrome P450 3A inhibitors increased lurbinectedin exposure.

Severe Rhabdomyolysis during Treatment with Trabectedin in Combination with a Herbal Drug in a Patient with Metastatic Synovial Sarcoma: A Case Report

Rhabdomyolysis is defined as dissolution of striped muscle characterized by leakage of intracellular muscle components into the circulation, which can ultimately lead to renal failure with a possible fatal outcome. This is an uncommon side effect of trabectedin which is used in second-line therapy of metastatic sarcoma after anthracycline and ifosfamide failure. Here, we describe a case of reversible rhabdomyolysis in a male patient with recurrent metastatic synovial sarcoma of the hand, with marked ¹⁸F-FDG uptake into his skeletal muscles, after 4 cycles of trabectedin, and who at the same time was taking an alternative medicine (bioflavonoids) suspected of triggering this adverse event.

Marine-Derived Pharmaceuticals - Challenges and Opportunities

Marine biosphere is the largest one of the earth and harbors an enormous number of different organisms. Living conditions differ fundamentally from those in terrestrial environment. The production of specific secondary metabolites is an important adaption mechanism of marine organisms to survive in the sea. These metabolites possess biological activities which make them interesting as possible drugs for human. The review presents sources, chemistry, production and pharmacology of FDA approved marine derived pharmaceuticals arranged according to their therapeutic indication. Four of the presently seven approved drugs are used for the treatment of cancer. Each another one is applicated for treatment of viral diseases, chronic pain and to lower triglyceride level in blood. Some other products are of interest in diagnostic and as experimental tools. Besides, this article describes challenges in drug development from marine sources, especially the supply problem.

Irreversible hepatotoxicity after administration of trabectedin to a pleiomorphic sarcoma patient with a rare ABCC2 polymorphism: a case report

We describe here the case of a 60-year old male patient treated for an extensive local progression of a pleiomorphic sarcoma on the right tibial crest with second-line trabectedin. Two cycles were administrated before a major liver toxicity was retrieved, with both cytolytic and cholestatic hepatitis quickly associated with irreversible jaundice. The radiological, histological, chemistry and pharmacogenetic investigations led us to diagnose chronic hepatobiliary toxicity with portal fibrosis, cholangiolitis damages and chronic hepatopathy. The patient had a deficient variant genotype of ABCC2 (c.-24TT, c.4488CT and c.4544GA), which has been suggested to play a role in excretion of toxic metabolites of trabectedin. This case report is, to our knowledge, the first description of trabectedin‘s irreversible liver toxicity in a human patient. Supported by a thorough review of the literature, this hepatitis is thought to have resulted from a multihit process involving genetic variants of ABC proteins and comedication.

Herbal-drug interaction induced rhabdomyolysis in a liposarcoma patient receiving trabectedin

BACKGROUND

Rhabdomyolysis is an uncommon side effect of trabectedin which is used for the second line therapy of metastatic sarcoma after anthracycline and ifosfamide failure. This side effect may be due to pharmacokinetic interactions caused by shared mechanisms of metabolism involving the cytochrome P450 (CYP) system in the liver. Here, for the first time in literature, we describe the unexpected onset of heavy toxicity, including rhabdomyolysis, after the fourth course of trabectedin in a patient with retroperitoneal liposarcoma who at the same time was taking an alternative herbal medicine suspected of triggering this adverse event.

CASE PRESENTATION

This is the case of a 56 year old Caucasian man affected by a relapsed de-differentiated liposarcoma who, after the fourth cycle of second-line chemotherapy with trabectedin, complained of sudden weakness, difficulty walking and diffuse muscle pain necessitating complete bed rest. Upon admission to our ward the patient showed grade (G) 4 pancytopenia and a marked increase in liver lytic enzymes, serum levels of myoglobin, creatine phosphokinase (CPK) and lactate dehydrogenase. No cardiac or kidney function injuries were present. Based on these clinical and laboratory features, our conclusive diagnosis was of rhabdomyolysis induced by trabectedin.The patient did not report any trauma or muscular overexertion and no co-morbidities were present. He had not received any drugs during treatment with trabectedin, but upon further questioning the patient informed us he had been taking a folk medicine preparation of chokeberry (Aronia melanocarpa) daily during the last course of trabectedin and in the 2 subsequent weeks.One week after hospitalization and cessation of intake of chokeberry extract, CPK and other markers of myolysis slowly returned to standard range, and the patient noted a progressive recovery of muscle strength.The patient was discharged on day 14 when a blood transfusion and parenteral hydration gradually lowered general toxicity. Progressive mobilization of the patient was obtained as well as a complete normalization of the laboratory findings.

CONCLUSIONS

The level of evidence of drug interaction leading to the adverse event observed in our patient was 2 (probable). Thus our case underlines the importance of understanding rare treatment-related toxicities such as trabectedin-induced rhabdomyolysis and the possible role of the drug-drug interactions in the pathogenesis of this rare side effect. Furthermore, this report draws attention to a potential problem of particular concern, that of nutritional supplements and complementary and alternative drug interactions. These are not widely recognized and can cause treatment failure.

A comprehensive safety analysis confirms rhabdomyolysis as an uncommon adverse reaction in patients treated with trabectedin

PURPOSE

This analysis determined the incidence of serious rhabdomyolysis events reported during trabectedin treatment since the first phase I clinical trial in April 1996 up to September 2010.

METHODS

Search was done in the Yondelis(®) Pharmacovigilance and Clinical Trials databases using a list of terms according to the Medical Dictionary for Regulatory Activities (MedDRA, v. 13.1), followed by a medical review of all cases retrieved. Total estimated sample was 10,841 patients: 2,789 from clinical trials; 3,926 from compassionate use programs; and 4,126 treated in the marketplace. Two groups were identified: (1) rhabdomyolysis and (2) clinically relevant creatine phosphokinase (CPK) increases without acute renal failure (ARF). Descriptive analysis included demographic, clinical/laboratory data, and contributing/confounding factors. Potential predictive factors were evaluated by multivariate stepwise logistic regression analysis. Possible changes of pharmacokinetics (PK) in patients with rhabdomyolysis were explored using a population PK model.

RESULTS

The global incidence of rhabdomyolysis was 0.7%, and most cases occurred in Cycle 2 of treatment. The incidence of fatal cases was 0.3%. None of the variables evaluated to detect potential risk factors of rhabdomyolysis were predictive. Additionally, CPK increases (without ARF) were detected in 0.4% of patients as an incidental finding with good prognosis.

CONCLUSIONS

Rhabdomyolysis is an uncommon event during trabectedin treatment. Multivariate analyses did not show any potential factor that could be predictive or represent a significantly higher risk of developing rhabdomyolysis. Nevertheless, close patient monitoring and adherence to drug administration guidelines may help to limit the incidence of this event.

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.

Metabolism-mediated drug interactions associated with ritonavir-boosted tipranavir in mice

Tipranavir (TPV) is the first nonpeptidic protease inhibitor used for the treatment of drug-resistant HIV infection. Clinically, TPV is coadministered with ritonavir (RTV) to boost blood concentrations and increase therapeutic efficacy. The mechanism of metabolism-mediated drug interactions associated with RTV-boosted TPV is not fully understood. In the current study, TPV metabolism was investigated in mice using a metabolomic approach. TPV and its metabolites were found in the feces of mice but not in the urine. Principal component analysis of the feces metabolome uncovered eight TPV metabolites, including three monohydroxylated, three desaturated, one dealkylated, and one dihydroxylated. In vitro study using human liver microsomes recapitulated five TPV metabolites, all of which were suppressed by RTV. CYP3A4 was identified as the primary enzyme contributing to the formation of four TPV metabolites (metabolites II, IV, V, and VI), including an unusual dealkylated product arising from carbon-carbon bond cleavage. Multiple cytochromes P450 (2C19, 2D6, and 3A4) contributed to the formation of a monohydroxylated metabolite (metabolite III). In vivo, RTV cotreatment significantly inhibited eight TPV metabolic pathways. In summary, metabolomic analysis revealed two known and six novel TPV metabolites in mice, all of which were suppressed by RTV. The current study provides solid evidence that the RTV-mediated boosting of TPV is due to the modulation of P450-dependent metabolism.

Phase I and pharmacokinetic study of trabectedin as a 1- or 3-hour infusion weekly in patients with advanced solid malignancies

PURPOSE

This study was designed to determine the safety, tolerability, and pharmacokinetics, and to seek preliminary evidence of anticancer activity of trabectedin, a novel marine-derived DNA minor grove binder, when administered as a 1-hour or 3-hour i.v. infusion for 3 consecutive weeks every 4 weeks in patients with advanced solid malignancies. The study also sought to determine the maximum tolerated dose (MTD) levels of trabectedin on these schedules, as well as to recommend doses for disease-directed studies.

EXPERIMENTAL DESIGN

A total of 32 and 31 patients were treated in sequential cohorts with trabectedin on the 1-hour schedule (doses ranging from 0.46 to 0.80 mg/m(2)) and on the 3-hour schedule (doses ranging from 0.30 to 0.65 mg/m(2)).

RESULTS

Neutropenia, transient elevations in hepatic transaminases and creatine phosphokinase, and fatigue precluded dose escalation above 0.70 mg/m(2) (1-hour schedule) and 0.65 mg/m(2) (3-hour schedule), which were determined to be the MTD levels, respectively. The pharmacokinetics of trabectedin on both schedules were characterized by a high clearance rate, a long terminal half-life, and a large volume of distribution. A patient with soft tissue sarcoma had partial response, and several soft tissue sarcoma patients had prolonged (> or =6 months) stable disease.

CONCLUSIONS

The MTD levels of trabectedin given weekly for 3 weeks every 4 weeks is 0.61 mg/m(2) as a 1-hour infusion and 0.58 mg/m(2) as a 3-hour infusion. The manageable toxicities at the MTDs, preliminary evidence of antitumor activity, pharmacokinetic profile, and the unique mechanistic aspects of trabectedin warrant further disease-directed evaluations on weekly schedules.

Marine pharmacology in 2005-2006: antitumour and cytotoxic compounds

During 2005 and 2006, marine pharmacology research directed towards the discovery and development of novel antitumour agents was reported in 171 peer-reviewed articles. The purpose of this article is to present a structured review of the antitumour and cytotoxic properties of 136 marine natural products, many of which are novel compounds that belong to diverse structural classes, including polyketides, terpenes, steroids and peptides. The organisms yielding these bioactive marine compounds included invertebrate animals, algae, fungi and bacteria. Antitumour pharmacological studies were conducted with 42 structurally defined marine natural products in a number of experimental and clinical models which further defined their mechanisms of action. Particularly potent in vitro cytotoxicity data generated with murine and human tumour cell lines were reported for 94 novel marine chemicals with as yet undetermined mechanisms of action. Noteworthy is the fact that marine anticancer research was sustained by a global collaborative effort, involving researchers from Australia, Belgium, Benin, Brazil, Canada, China, Egypt, France, Germany, India, Indonesia, Italy, Japan, Mexico, the Netherlands, New Zealand, Panama, the Philippines, Slovenia, South Korea, Spain, Sweden, Taiwan, Thailand, United Kingdom (UK) and the United States of America (USA). Finally, this 2005-2006 overview of the marine pharmacology literature highlights the fact that the discovery of novel marine antitumour agents continued at the same active pace as during 1998-2004.

Pharmacokinetics in drug discovery

The aim of this current review is to summarize the present status of pharmacokinetics in Drug Discovery. The review is structured into four sections. The first section is a general overview of what we understand by pharmacokinetics and the different LADMET aspects: Liberation, Absorption, Distribution, Metabolism, Excretion, and Toxicity. The second section highlights the different computational or in silico approaches to estimate/predict one or several aspects of the pharmacokinetic profile of a discovery lead compound. The third section discusses the most commonly used in vitro methodologies. The fourth and last section examines the various approaches employed towards the pharmacokinetic assessment of discovery molecules; including all the LADME processes, discussing the different mathematical methodologies available to establish the PK profile of a test compound; what the main differences are and what should be the criteria for using one or another mathematical approach. The major conclusion of this review is that the use of the appropriate preclinical assays has a key role in the long-term viability of a pharmaceutical company since applying the right tools early in discovery will play a key role in determining the company's ability to discover novel safe and effective therapeutics to patients as quickly as possible.

Trabectedin : a review of its use in the management of soft tissue sarcoma and ovarian cancer

Trabectedin (Yondelis); ET-743) is an antineoplastic agent that was originally derived from the Caribbean marine tunicate Ecteinascidia turbinata and is now produced synthetically. It binds to the minor groove of DNA, disrupting the cell cycle and inhibiting cell proliferation. Intravenous trabectedin administered once every 3 weeks is approved as monotherapy in Europe for use in patients with advanced soft tissue sarcoma (STS) after failure of standard therapy with anthracyclines or ifosfamide, or who are unsuited to receive these agents. It also has orphan drug status in STS in the US and in ovarian cancer in the US and Europe, and is under investigation as combination therapy in patients with recurrent ovarian cancer. In clinical trials, trabectedin showed efficacy in the treatment of patients with advanced or metastatic STS, especially those with leiomyosarcoma or liposarcoma, as well as in women with platinum-sensitive advanced or recurrent ovarian cancer. In addition, its tolerability profile was generally manageable. The introduction of trabectedin expands the currently limited range of effective treatment options for patients with advanced or metastatic STS; trabectedin also has the potential to be a beneficial treatment for advanced or recurrent ovarian cancer.

Modulation of trabectedin (ET-743) hepatobiliary disposition by multidrug resistance-associated proteins (Mrps) may prevent hepatotoxicity

Trabectedin is a promising anticancer agent, but dose-limiting hepatotoxicity was observed during phase I/II clinical trials. Dexamethasone (DEX) has been shown to significantly reduce trabectedin-mediated hepatotoxicity. The current study was designed to assess the capability of sandwich-cultured primary rat hepatocytes (SCRH) to predict the hepato-protective effect of DEX against trabectedin-mediated cytotoxicity. The role of multidrug resistance-associated protein 2 (Mrp2; Abcc2) in trabectedin hepatic disposition also was examined. In SCRH from wild-type Wistar rats, cytotoxicity was observed after 24-h continuous exposure to trabectedin. SCRH pretreated with additional DEX (1 microM) exhibited a 2- to 3-fold decrease in toxicity at 100 nM and 1000 nM trabectedin. Unexpectedly, toxicity in SCRH from Mrp2-deficient (TR(-)) compared to wild-type Wistar rats was markedly reduced. Depletion of glutathione from SCRH using buthionine sulfoximine (BSO) mitigated trabectedin toxicity associated with 100 nM and 1000 nM trabectedin. Western blot analysis demonstrated increased levels of CYP3A1/2 and Mrp2 in SCRH pretreated with DEX; interestingly, Mrp4 expression was increased in SCRH after BSO exposure. Trabectedin biliary recovery in isolated perfused livers from TR(-) rats was decreased by approximately 75% compared to wild-type livers. In conclusion, SCRH represent a useful in vitro model to predict the hepatotoxicity of trabectedin observed in vivo. The protection by DEX against trabectedin-mediated cytotoxicity may be attributed, in part, to enhanced Mrp2 biliary excretion and increased metabolism by CYP3A1/2. Decreased trabectedin toxicity in SCRH from TR(-) rats, and in SCRH pretreated with BSO, may be due to increased basolateral excretion of trabectedin by Mrp3 and/or Mrp4.

In vitro characterization of the human biotransformation pathways of aplidine, a novel marine anti-cancer drug

Aplidine is a potent marine anti-cancer drug and is currently being investigated in phase II clinical trials. However, the enzymes involved in the biotransformation of aplidine and thus its pharmacokinetics are not known yet. To assess the biotransformation pathways of aplidine and their potential implications for human pharmacology and toxicology, the in vitro metabolism of aplidine was characterized using incubations with human plasma, liver preparations, cytochrome P450 (CYP) and uridine diphosphoglucuronosyl transferase (UGT) supersomes in combination with HPLC analysis and cytotoxicity assays with cell lines. Aplidine was metabolised by carboxyl esterases in human plasma. Using CYP supersomes and liver microsomes, it was shown that aplidine was metabolised mainly by CYP3A4 and also by CYP2A6, 2E1 and 4A11. Four metabolites were observed after incubation with human liver microsomes, one formed by CYP2A6 (C-demethylation) and three by CYP3A4 (hydroxylation and/or C-dealkylation). No conjugation was observed in human liver S9 fraction. However, the aplidine metabolites formed by CYP were further conjugated by the phase II enzymes UGT, GST and SULT. In accordance with the findings in microsomes and CYP supersomes, a significant effect of specific CYP2A6, 2E1, 3A4 and 4A11 inhibitors on the cytotoxicity of aplidine in Hep G2 and IGROV-1 cells could be observed. These results provide evidence that CYP3A4 has a major role in metabolising aplidine in vitro with additional involvement of CYP2A6, 2E1, and 4A11. Further, the metabolites formed by CYPs can be conjugated by UGT, SULT and GST. These findings could help interpret the in vivo pharmacokinetics of aplidine.

Population Pharmacokinetic Meta-Analysis of Trabectedin (ET-743,??Yondelis??) in Cancer Patients

OBJECTIVE

To characterise the population pharmacokinetics of trabectedin (ET-743, Yondelis(R)) in cancer patients.

METHODS

A total of 603 patients (945 cycles) receiving intravenous trabectedin as monotherapy at doses ranging from 0.024 to 1.8 mg/m(2) and given as a 1-, 3- or 24-hour infusion every 21 days; a 1- or 3-hour infusion on days 1, 8 and 15 of a 28-day cycle; or a 1-hour infusion daily for 5 consecutive days every 21 days were included in the analysis. An open four-compartment pharmacokinetic model with linear elimination, linear and nonlinear distribution to the deep and shallow peripheral compartments, respectively, and a catenary compartment off the shallow compartment was developed to best describe the index dataset using NONMEM V software. The effect of selected patient covariates on trabectedin pharmacokinetics was investigated. Model evaluation was performed using goodness-of-fit plots and relative error measurements for the test dataset. Simulations were undertaken to evaluate covariate effects on trabectedin pharmacokinetics.

RESULTS

The mean (SD) trabectedin elimination half-life was approximately 180 (61.4) hours. Plasma accumulation was limited when trabectedin was given every 3 weeks. Systemic clearance (31.5 L/h, coefficient of variation 51%) was 19.2% higher in patients receiving concomitant dexamethasone. The typical values of the volume of distribution at steady state for male and female patients were 6070L and 5240L, respectively. Within the range studied, age, body size variables, AST, ALT, alkaline phosphatase, lactate dehydrogenase, total bilirubin, creatinine clearance, albumin, total protein, Eastern Cooperative Oncology Group performance status and presence of liver metastases were not statistically related to trabectedin pharmacokinetic parameters. The pharmacokinetic parameters of trabectedin were consistent across the infusion durations and dose regimens evaluated.

CONCLUSIONS

The integration of trabectedin pharmacokinetic data demonstrated linear elimination, dose-proportionality up to 1.8 mg/m(2) and time-independent pharmacokinetics. The pharmacokinetic impact of dexamethasone and sex covariates is probably limited given the moderate to large interindividual pharmacokinetic variability of trabectedin. The antiemetic and hepatoprotective effects are still a valid rationale to recommend dexamethasone as a supportive treatment for 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.