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At least 163 records · Page 9Linked to original sources
PubMed2002

A phase I and pharmacokinetic study of ecteinascidin-743 on a daily x 5 schedule in patients with solid malignancies.

PURPOSE: The purpose of this study was to (a) assess the feasibility of administering ecteinascidin-743 (ET-743), a novel DNA minor-groove disrupting agent of marine origin, administered as a daily i.v. infusion for 5 days every 3 weeks; (b) recommend a dose for Phase II studies; (c) characterize its pharmacokinetic behavior; and (d) seek preliminary evidence of anticancer activity. EXPERIMENTAL DESIGN: Patients with advanced solid malignancies were treated with escalating doses of ET-743 as a daily 1-h i.v. infusion for 5 days every 3 weeks. Plasma and urine were sampled on both days 1 and 5 of the first course. Pharmacokinetic parameters were related to the principal toxicities. RESULTS: Forty-two patients were treated with 118 courses of ET-743 at doses ranging from 6 to 380 microg/m(2)/day. Elevations in hepatic transaminases were common at ET-743 dose levels > or =216 microg/m(2)/day, resolved rapidly, and were never dose limiting nor cumulative. Instead, hematological toxicity was the principal toxicity that precluded dose escalation. The maximum tolerated dose of ET-743 that could be administered repetitively was 325 microg/m(2)/day. Antitumor activity was noted in three patients with leiomyosarcoma and primary peritoneal and ovarian carcinomas. The pharmacokinetics of ET-743 were dose independent, and drug accumulation over the 5 days of treatment was modest, with the ratio of the area under the plasma-versus-time curve on day 5 to that on day 1 averaging 2.05. The volume of distribution at steady state was large (mean, 1037 liters/m(2)), and the mean terminal half life on day 5 was 26.81 h. CONCLUSIONS: The maximum tolerated dose of ET-743 that can be administered repetitively is 325 microg/m(2)/day daily x 5 every 3 weeks, which is recommended for disease-directed clinical trials. The acceptable toxicity profile of ET-743 on the divided-dose schedule evaluated in this trial, as well as the generally superior antitumor activity associated with divided-dose schedules in preclinical studies, provides a rationale for further evaluation of ET-743 on this administration schedule.

Adult↗
PubMed2002

Ecteinascidin-743 inhibits activated but not constitutive transcription.

Ecteinascidin-743 (ET-743) is a promising chemotherapeutic agent currently in Phase III clinical trials. Previous studies indicated a novel spectrum of activity for this agent, including transcriptional inhibition. Initially hypothesized to target a single transcription factor (NF-Y), we now show that ET-743 is a more general inhibitor of activated transcription. Induction of the Sp1-regulated p21 gene by Trichostatin A (TSA) was blocked by ET-743 at concentrations that had minimal effect on uninduced (constitutive) expression. Moreover, ET-743 blocked induction of Gal4 fusion proteins by TSA without affecting activation mediated by the fusion proteins in the absence of the inducer. Finally, microarray analysis of SW620 cells treated with TSA and/or ET-743 indicated that activation of TSA-responsive promoters was blocked by ET-743 with little affect on nonresponsive promoters. These results, taken together with previous reports, leads us to suggest a mechanism whereby ET-743 is a novel, potent, and general inhibitor of activated but not uninduced transcription.

Antineoplastic Agents, Alkylating↗
PubMed2002

Hepatobiliary damage and changes in hepatic gene expression caused by the antitumor drug ecteinascidin-743 (ET-743) in the female rat.

Ecteinascidin-743 (ET-743) is a novel marine-derived anticancer drug with clinical activity in soft tissue sarcoma and ovarian cancer. Reversible transaminitis and subclinical cholangitis have frequently been described in patients who receive ET-743. To facilitate understanding of this adverse effect and help design suitable therapeutic rescue strategies, we characterized the hepatic effects of ET-743 in rats. Female rats received ET-743 (single dose, 40 microg/kg) i.v., and liver changes were assessed from 6 h up to 3 months after dosing by histopathology, immunohistochemistry, electron microscopy, hepatic and plasma biochemistry, and DNA microarray analysis. At 24 h posttreatment and beyond, livers displayed degeneration and patchy focal necrosis of bile duct epithelial cells associated with mild inflammation followed by fibrosis. Sporadic and focal zones of hepatic necrosis and hemorrhage were observed from day 2 onward, although the majority of hepatocytes appeared normal as judged by electron microscopy. Pathological alterations persisted up to 3 months after dosing. Plasma levels of total bilirubin were elevated up to 7-fold over those in untreated rats from day 2 onward and returned to control values by day 24. Activities of alkaline phosphatase and aspartate aminotransferase in plasma were elevated for 2 and 3 months, respectively. Activities of the hepatic microsomal drug-metabolizing enzymes cytochrome P-450 A1/2, CYP2E1, and CYP3A2 were decreased. DNA microarray analysis of livers from ET-743-treated animals showed a dramatic increase in the expression of ATP binding cassette transport genes Abcb1a and Abcb1b, which impart resistance to anticancer drugs, and of Cdc2a and Ccnd1, the rodent homologues of human cell cycle genes CDC2 and cyclin D1, respectively. The cell cycle gene expression changes mirrored ET-743-induced increases in liver weight and Ki-67 labeling of liver nuclei. The results suggest that the toxicity exerted by ET-743 in the rat liver is a consequence of biliary rather than hepatocellular damage and that it is accompanied by a wave of mitogenic activity, which may be driven by the transcriptional increase in Cdc2a expression.

Animals↗
PubMed2002

Safety and efficacy of ET-743: the French experience.

Initial evidence of clinical benefit with ecteinascidin-743 (ET-743) in patients with sarcoma was provided during a Phase I pharmacokinetic study in which 52 patients received ET-743 at doses of 50-1800 micrograms/m2 as a 24 h continuous infusion every 3 weeks. Neutropenia and thrombocytopenia were the dose-limiting toxicities; liver toxicity (a severe but transient and reversible increase in transaminase concentrations) was not treatment limiting. In conjunction with results obtained with ET-743 in a compassionate-use program, these indications of activity in heavily pretreated patients with sarcoma prompted initiation of a French multicenter Phase II study of ET-743 in this population. From February 1999 to January 2001, 54 patients with advanced anthracycline-pretreated soft-tissue sarcoma (STS) received ET-743 at a dose of 1500 micrograms/m2 every 3 weeks by continuous 24 h infusion. The main histological subtype was leiomyosarcoma (37%); the majority of primary tumors were visceral (24%) or uterine (19%) sarcomas. In this Phase II population (> or = 25% negative prognostic or predictive factors of response to chemotherapy; > or = 50% anthracycline- and ifosfamide-resistant), safety data were comparable to those obtained in the Phase I and compassionate-use studies. Asymptomatic and reversible neutropenia and transaminitis (grade 3/4) were the most frequent toxicities (approximately 60% of patients); febrile neutropenia was infrequent (< 10%). No mucositis, alopecia, cardiac or neurotoxicity was observed. Two severe cases of rhabdomyolysis occurred. Side effects were non-cumulative, reversible and manageable. Of 52 evaluable patients, three (6%) achieved a long-lasting (8-13 months) partial response, four (8%) achieved a minor response (25-50% tumor reduction) and 22 (42%) achieved disease stabilization. With a 13-month median follow-up, median survival was almost 11 months. Progression-free survival at 6 months was 26.5% and the overall survival rate at 12 months was almost 50%. The response rate was uninfluenced by tumor metastatic site, size or anthracycline sensitivity status. These results, combined with the lack of cumulative toxicity, confirm the role of ET-743 in the treatment of advanced STS.

Antineoplastic Agents, Alkylating↗
PubMed2002

A clinical armamentarium of marine-derived anti-cancer compounds.

The sea, covering 70% of the Earth's surface, offers a considerably broader spectrum of biological diversity than terra firma. Containing approximately 75% of all living organisms, the marine environment offers a rich source of natural products with potential therapeutic application. Marine organisms have evolved the enzymatic capability to produce potent chemical entities that make them promising sources of innovative cytotoxic compounds. Prominent in the identification and development of novel anti-cancer agents from marine sources is the Spanish biotechnology company, PharmaMar, which currently has a large number of oncology products in late preclinical and clinical development. These include: ecteinascidin-743 (ET-743), a marine-derived antitumor agent isolated from the Caribbean tunicate, Ecteinascidia turbinata; aplidine (Aplidin), a cyclopeptide cytotoxic agent derived from the Mediterranean tunicate, Aplidium albicans; kahalalide F, a depsipeptide isolated from the Hawaiian mollusc, Elysia rufescens; and ES-285, a molecule isolated from the mollusc, Spisula polynyma. Many of these innovative compounds have novel mechanisms of anti-tumor action that have yet to be fully elucidated.

Animals↗
PubMed2002

ET-743: more than an innovative mechanism of action.

Ecteinascidin-743 (ET-743), an anti-tumor agent derived from the marine tunicate, Ecteinascidia turbinata, is active against various solid tumor cell lines, including soft tissue sarcoma, breast, ovarian, non-small-cell lung and prostate cancers and melanoma, and has a broad spectrum of anti-cancer activity in vivo. For reasons as yet unclear, sarcoma cell lines are exquisitely sensitive to ET-743. The drug has a unique mechanism of action that makes it a novel anti-tumor agent. ET-743 is a DNA-binding agent that covalently interacts with the minor groove of the DNA double helix to bend the molecule towards the major groove. Defects in DNA repair pathways have paradoxical effects on the anti-tumor activity of ET-743: loss of mismatch repair does not affect its toxicity; loss of DNA-dependent protein kinase activity enhances its toxicity; defects in transcription-coupled nucleotide excision repair confer resistance to ET-743. As a DNA repair capability appears to be necessary for at least one mechanism of ET-743-mediated cytotoxicity, the drug may interact with the DNA repair machinery to induce lethal strand breaks. One of the most novel aspects of ET-743 is its effect on RNA polymerase II-mediated gene transcription. ET-743 selectively inhibits activation of the multidrug resistance gene, while leaving constitutive gene expression relatively unaffected. Preliminary studies of other genes and transcriptional inducers indicate that ET-743 may be a more general inhibitor of activated, but not basal, transcription.

Antineoplastic Agents, Alkylating↗
PubMed2002

ET-743: the US experience in sarcomas of soft tissues.

Ecteinascidin-743 (ET-743) has shown promise as a new and effective treatment for soft-tissue sarcomas. Two independent, multicenter, Phase II studies have been performed in the USA for patients with unresectable soft-tissue sarcomas (either chemotherapy-naïve or pretreated patients). The patients received ET-743 at a dose of 1500 micrograms/m2 as a 24 h continuous intravenous infusion every 3 weeks on an outpatient basis. Assessments were conducted every 6 weeks until documented progressive disease, unacceptable toxicity, or withdrawal. Responses were assessed in accordance with conventional oncological criteria and toxicities were graded using the National Cancer Institute common toxicity criteria. A total of 72 patients were enrolled: 36 patients to each study. Confirmed objective response rates were 14% (95% confidence interval (CI) 5 to 30%) and 8% (95% CI 2 to 23%) in chemotherapy-naïve and pretreated patients, respectively. In chemotherapy-naïve patients, 12-month progression-free and overall survival rates were 18% (95% CI 4 to 32%) and 49% (95% CI 20 to 78%), respectively. For patients with progressive disease despite prior conventional chemotherapy, 12-month progression-free and overall survival rates were 11% (95% CI 2 to 24%) and 55% (95% CI 35 to 75%), respectively. The median duration of response was 11 months. The durability of major responses in a subset of patients was impressive, as was the number of patients who achieved disease stabilization without showing objective response. Overall, ET-743 had a favorable safety profile. The most common grade 3-4 toxicities included neutropenia and transiently increased transaminase concentrations. ET-743 did not cause alopecia, mucositis, cardiotoxicity or neurotoxicity. The side effects were reversible, non-cumulative and manageable. There were no treatment-associated deaths. In conclusion, ET-743 is an active chemotherapeutic agent that can induce objective responses and clinical benefit in a subset of patients with metastatic or advanced soft-tissue sarcoma.

Antineoplastic Agents, Alkylating↗
PubMed2002

Rat and human liver cytochrome P-450 isoform metabolism of ecteinascidin 743 does not predict gender-dependent toxicity in humans.

Ecteinascidin 743 (ET743, NSC648766) is a marine natural product with potent in vivo activity in human xenograft models. Hepatotoxicity was the most prominent toxicity in preclinical studies and was greater in female rats than in male rats. To assess the potential implications for human toxicities, the in vitro metabolism of ET743 was characterized using rat and human preparations. NADPH-dependent ET743 metabolism was greater with male rat liver microsomal preparations than with preparations from female rats and was induced by pretreatment of rats with phenobarbital and dexamethasone but not by pretreatment with 3-methylcholanthrene. Rat and human microsomal metabolism of ET743 was reduced in the presence of chemical CYP3A inhibitors or antirat CYP3A2 antiserum and to a much lesser extent by CYP2E, CYP2C, and CYP2A inhibitors. In human liver panel studies, ET743 disappearance was highly correlated with CYP3A activities and to a lesser extent with CYP2C activities. ET743 was metabolized by a number of cDNA-expressed rat P-450 isoforms, including male-predominant CYP2A2 and CYP3A2. ET743 was metabolized by cDNA-expressed human CYP3A4 and to a much lesser extent by CYP2C9, CYP2D6, and CYP2E1 preparations. Three oxidative metabolites were detected in cDNA-expressed isoform incubations, including the N-demethylated metabolite ET729 and two additional products characterized by laser capture-mass spectrometry analyses. The plasma pharmacokinetics and biliary excretion of ET743 were characterized in rats. There were no gender-dependent differences in half-life or total body clearance values. Although very modest, the biliary excretion of ET743 in male rats (0.48%) was greater than in female rats (0.28%). In contrast, the biliary excretion of the cytotoxic N-demethylated metabolite ET729 was 5-fold greater in the female rat (1.05% of dose) than in the male rat (0.19% of dose). Biliary excretion of ET729 may contribute to the hepatic toxicity in rats. These data are consistent with a major role for CYP3A isoforms in ET743 rat and human metabolism. Although there are conflicting data in the literature, expression of CYP3A isoforms in human tissues and elimination of CYP3A substrates have not been shown to vary substantially by gender. There are no indications that the other CYP isoforms implicated in ET743 metabolism are expressed differently in males and females. Thus, although it is not possible to rule out gender differences in ET743 human toxicities, our data do not predict major gender-dependent differences in the toxicity of ET743 based on metabolism.

Animals↗
PubMed2002

Sequence-dependent synergistic cytotoxicity of ecteinascidin-743 and paclitaxel in human breast cancer cell lines in vitro and in vivo.

Ecteinascidin 743 (ET-743) is a potent antitumor agent from the Caribbean tunicate Ecteinascidia turbinata and is presently in clinical trials for human cancers. The aim of this study was to assess the nature of the interaction between ET-743 and other antineoplastic agents using the combination index method of Chou and Talalay to better understand how ET-743 might be used clinically. We examined the cytotoxic effect of ET-743 combined with six other antineoplastic agents on human breast cancer cell lines, MX-1, MCF7, and P-glycoprotein overexpressing MCF7/DXR to different schedules. Pretreatment with paclitaxel for 24 h before ET-743 was the most effective combination regimen in all three breast cancer cell lines. Furthermore, sequential treatment with paclitaxel followed by ET-743 increased the antitumor effects in nude mice bearing MX-1 mammary carcinoma xenografts without increasing toxicity. These results suggest that the combination of ET-743 and paclitaxel should be assessed in clinical trials for the treatment of breast cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2002

Effectiveness of Ecteinascidin-743 against drug-sensitive and -resistant bone tumor cells.

PURPOSE: The identification of new drugs is strongly needed for bone tumors.Ecteinascidin-743 (ET-743), a highly promising antitumor agent isolated from the marine tunicate Ecteinascidia turbinata, is currently under Phase II clinical investigation in Europe and the United States for treatment of soft tissue sarcoma. In this study, we analyzed the preclinical effectiveness of this drug in osteosarcoma and Ewing's sarcoma. EXPERIMENTAL DESIGN: The effects of ET-743 were evaluated against a panel of human osteosarcoma and Ewing's sarcoma cell lines characterized by different drug responsiveness and compared with the effects of standard anticancer agents. In addition, combination treatments with ET-743 and the other standard chemotherapy agents for sarcoma were analyzed to highlight the best drug-to-drug interaction RESULTS: A potent activity of ET-743 was clearly observed against both drug-sensitive and drug-resistant (multidrug-resistant, methotrexate- and cisplatin-resistant) bone tumor cells at concentrations that are easily achievable in patients (pM to nM range). Ewing's sarcoma cells appeared to be particularly sensitive to the effects of this drug. The analysis of the effects of ET-743 on cell cycle, apoptosis, and differentiation indicated that both osteosarcoma and Ewing's sarcoma cells had a slower progression through the different phases of the cell cycle after treatment with ET-743. However, the drug was able to induce a massive apoptosis in Ewing's sarcoma but not in osteosarcoma cells. In the latter neoplasm, ET-743 showed a differential effect, as indicated by the significant increase in the expression and activity of alkaline phosphatase, a marker of osteoblastic differentiation. Concurrent exposure of cells to ET-743 and other chemotherapeutic agents resulted in greater than additive interactions when doxorubicin and cisplatin were used, whereas subadditive effects were observed with methotrexate, vincristine, and actinomycin D. CONCLUSIONS: Overall, these results encourage the inclusion of this drug in the treatment of patients with bone tumors, although a careful design of new regimens is required to identify the best therapeutic conditions.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2002

Overcoming multidrug drug resistance in P-glycoprotein/MDR1-overexpressing cell lines by ecteinascidin 743.

Ecteinascidin 743 (Et-743) is a novel anticancer agent forming covalent guanine adducts at specific sites in the DNA minor groove. Et-743 has a unique mechanism of action because it kills cancer cells by poisoning transcription-coupled nucleotide excision repair. Recent studies suggested a complex relationship between P-glycoprotein (P-gp)/MDR1 and Et-743. On one hand, Et-743 was reported to down-regulate the MDR1 promoter in vitro. On the other hand, P-gp overexpression was hypothesized to contribute to Et-743 resistance in an ovarian cell line. The present study was performed to further investigate the relationship between P-gp/MDR1 and the activity of Et-743. First, we found no P-gp/MDR1 overexpression (mRNA and protein levels) in two independently generated Et-743-resistant human colon carcinoma cell lines (HCT116/ER5 and SW480/ER0.5). Secondly, we found no cross-resistance to Et-743 in two well-characterized P-gp/MDR1-overexpressing cell lines (KB-8-5 and KB-C-2). Third, Et-743 pretreatment enhanced the cytotoxicity and the cellular accumulation of doxorubicin and vincristine in P-gp/MDR1-overexpressing KB-8-5/KB-C-2 cell lines. Fourth, we observed P-gp/MDR1 down-regulation by Et-743 in KB-C-2 cells. These results indicate that Et-743 does not select for the emergence of a P-gp phenotype in all cell lines made resistant to Et-743 and that P-gp overexpression is not sufficient to confer resistance to Et-743. Furthermore, Et-743 is an effective agent in P-gp-overexpressing cells. Et-743 can potentiate the activity of other chemotherapeutic agents by down-regulating P-gp/MDR1, suggesting that the combination of Et-743 and chemotherapeutic agents that are substrates for P-gp/MDR1 may be valuable in the clinic.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

[Perspectives on the oncologist pharmacopoeia].

MGI114, ET743, BBR3464, ZD0473, ZD9331, BN80915, J107088, F11782, XR11576, BMS247550, PS341, UCN01, ISIS 3521, STI571, ZD1839, IMC-C225, OSI774, SU5416, DNA minor and major grooves, chimeric proteins, ribonucleotide reductase, topoisomerases, tubuline, proteasome, protein kinase C, bcr-abl, EGF or VEGF tyrosine kinase receptors are code names (somewhat barbarian) and targets for new drugs which will complement the therapeutic arsenal of the twenty-first century oncologist. This review provides a survey their clinical advances.

Angiogenesis Inhibitors↗
PubMed2003

[Development of marine-derived anti-cancer compounds].

The marine environment offers a rich source of natural products with potential therapeutic application. Marine organisms have evolved the enzymatic capability to produce potent chemical entities that make them promising sources of innovative cytotoxic compounds. Prominent in the identification and development of novel anti-cancer agents from marine sources is the Spanish biotechnology company, Pharma Mar, which currently has a large number of oncology products in late preclinical and clinical development. These include: Ecteinascidin-743 (ET-743), Aplidin, Kahalalide F and ES-285. Many of these innovative compounds have novel mechanisms of anti-tumor action that have yet to be fully elucidated.

Animals↗
PubMed2003

Marked activity of irofulven toward human carcinoma cells: comparison with cisplatin and ecteinascidin.

PURPOSE: To characterize the activities of irofulven, a novelanticancer agent derived from the mushroom natural productilludin S toward human cancer cells. EXPERIMENTAL DESIGN: We have determined the activity spectrum of irofulven toward a human tumor cell panel comprised of 10 different tumor types in comparison with cisplatin and ET-743. We have also evaluated the influence of major resistance mechanisms, such as expression of multidrug resistance-associated drug efflux pumps, cisplatin resistance, loss of p53 function, and absence of mismatch repair on the cytotoxic activity of irofulven. RESULTS: The activity spectrum of irofulven is clearly different from that of ET-743 and cisplatin. Irofulven shows excellent cytotoxicity toward the majority of human carcinoma cell lines tested, but lesser activity toward sarcoma and leukemia cell lines. The cytotoxic activity of irofulven was particularly pronounced toward head and neck, non-small cell lung, colon, and ovary carcinoma cells, as well as toward malignant glioma cell lines. In addition, irofulven displayed good activity toward poorly differentiated, androgen-independent prostate cancer cells and cell lines expressing high levels of the detoxifying enzymes glutathione S-transferase and gamma-glutamyl cysteine synthetase. The cytotoxicity of irofulven was not affected by loss of p53 or mismatch repair function, and the drug was not a substrate for multidrug transporters, such as the P-glycoprotein and multidrug resistance protein 1. CONCLUSIONS: Irofulven has an unusual activity spectrum with strong activity toward tumor cells of epithelial origin. Furthermore, irofulven is not or only marginally affected by resistance mechanisms limiting the efficacy of other alkylating agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

Complete protection by high-dose dexamethasone against the hepatotoxicity of the novel antitumor drug yondelis (ET-743) in the rat.

Yondelis (ET-743) is a promising antitumor drug with hepatotoxic properties in animals and humans. Here the hypothesis was tested that dexamethasone can ameliorate manifestations of yondelis-induced hepatotoxicity in the female Wistar rat, which is the animal species with the highest sensitivity toward the adverse hepatic effect of yondelis. Hepatotoxicity was adjudged by measurement of plasma levels of alkaline phosphatase, aspartate aminotransferase, and bilirubin, and by liver histopathology. Yondelis (40 micro g/kg i.v.) alone caused a dramatic elevation of plasma alkaline phosphatase, aspartate aminotransferase, and bilirubin levels, and degeneration and patchy focal necrosis of bile duct epithelial cells. Pretreatment of rats with dexamethasone (5-20 mg/kg, p.o.) 24 h before yondelis ameliorated or abrogated the biochemical and histopathological manifestations of yondelis-induced liver changes. In contrast, when dexamethasone was administered simultaneously with yondelis, its toxicity was not reduced. Pretreatment with dexamethasone (10 mg/kg) also reversed the gene expression changes induced by yondelis in rat liver. However, dexamethasone pretreatment did not interfere with the antitumor efficacy of yondelis in rats bearing the 13762 mammary carcinoma or in four murine models. Dexamethasone (10 mg/kg) administered 24 h before yondelis decreased hepatic levels of yondelis dramatically compared with those obtained after administration of yondelis alone, whereas yondelis plasma levels after the drug combination were not markedly different from those in rats on yondelis alone. The results suggest that pretreatment with high-dose dexamethasone effectively protects rats against yondelis-mediated hepatic damage by decreasing hepatic exposure to yondelis, perhaps linked to induction of metabolism by cytochrome P450 enzymes. Pretreatment with high-dose dexamethasone should be investigated in patients who receive yondelis to ameliorate its unwanted effect on the liver.

Animals↗
PubMed2001

Transcription of the multidrug resistance gene MDR1: a therapeutic target.

Two decades ago, the overexpression of P-glycoprotein (Pgp) was first demonstrated to mediate the energy-dependent efflux of a variety of chemotherapeutic agents from tumor cells, resulting in the development of multidrug resistance (MDR). Not surprisingly, this discovery triggered an ongoing search for agents that would inhibit Pgp function, with the hope that by doing so the MDR phenotype could be reversed. As our understanding of Pgp function and pharmacokinetics has increased, this quest has become more urgent, as well as more complex.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2004

[Progress in the studies on antitumor natural product ecteinascidin-743].

The alkaloid ecteinascidin-743, isolated from the marine tunicate Ecteinascidia turbinata, binds to DNA and induces cytotoxic effects in several tumors. The drug is being codeveloped by Pharma Mar and Ortho Biotech. In May 2001 and October 2003, it was granted orphan drug status by the European Commission for soft tissue sarcoma and ovarian cancer, respectively. This paper reviews its research progress, including chemical synthesis, in vitro studies and mechanism of action, antitumor activity in vivo, toxicity, pharmacokinetics, and clinical studies.

Animals↗
PubMed2005

A phase I and pharmacokinetic study of ecteinascidin-743 (Yondelis) in children with refractory solid tumors. A Children's Oncology Group study.

PURPOSE: To determine the dose-limiting toxicity (DLT) and the maximum tolerated dose of ecteinascidin-743 (ET-743, Yondelis) in children with refractory solid tumors, to establish the recommended dose for pediatric phase II trials, and to characterize the pharmacokinetics of ET-743 in children. EXPERIMENTAL DESIGN: ET-743 was administered as a 3-hour i.v. infusion every 21 days. The starting dose was 1,100 microg/m(2) with planned dose escalation of 200 microg/m(2) increments. Pharmacokinetic sampling was done during the first treatment course. RESULTS: Twelve evaluable patients received a total of 29 courses. One grade 4 DLT (prolonged grade 4 neutropenia) was noted at the first dose level. At the second dose level (1,300 microg/m(2)), there were two DLTs (reversible grade 4 elevations of hepatic transaminase); hence the maximum tolerated dose was defined as 1,100 microg/m(2). Overall, reversible hepatic toxicity, manifested as grade 3 or 4 elevations in hepatic transaminase, occurred in more than 50% of the patients. No grade 3 or 4 thrombocytopenia was reported at either dose level and only one episode of isolated creatine phosphokinase grade 4 elevation was observed. One complete response was documented after six courses in a patient with metastatic Ewing sarcoma. The pharmacokinetics of ET-743 in 8 children was characterized by a terminal disposition phase with a mean half-life of 43.8 +/- 18.4 hours, a total body clearance of 28.2 +/- 10.5 L/h/m(2), and a 959 +/- 807 L/m(2) steady-state apparent volume of distribution. CONCLUSION: ET-743 is safe. The phase II recommended dose of ET-743 administered as a 3-hour i.v. infusion following premedication with dexamethasone is 1,100 microg/m(2).

Adolescent↗