Ecteinascidin-743 (ET-743): early test or effective treatment in soft tissue sarcomas?
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Ecteinascidin-743 (ET-743) for chemotherapy-naive patients with advanced soft tissue sarcomas: multicenter phase II and pharmacokinetic study.
PURPOSE: To evaluate the response rate, toxicity profile, and pharmacokinetics of ecteinascidin-743 (ET-743) as first-line therapy in patients with unresectable advanced soft tissue sarcoma (STS). PATIENTS AND METHODS: Thirty-six patients with STS were enrolled onto the study between September 1999 and August 2000. Patients were treated with 1.5 mg/m2 of ET-743 given as a 24-hour continuous intravenous (IV) infusion every 21 days. Pharmacokinetic sampling was performed in 23 patients. RESULTS: One complete and five partial responses were achieved in 35 assessable patients for an overall response rate of 17.1% (95% CI, 6.6% to 33.6%). In addition, one patient had a minor response, leading to an overall clinical benefit of 20%. Neutropenia and transaminitis were the main grade 3 to 4 toxicities, which occurred in 33% and 36% of the patients. The estimated 1-year progression-free and overall survival rates were 21% (95% CI, 11% to 41%) and 72% (95% CI, 59% to 88%), respectively. Total body clearance (L/h) was not significantly correlated with body-surface area (r = -0.28; P = .21). Mild hepatic impairment or the extent of prior cytotoxic therapy does not seem to contribute significantly to the high interpatient variability (49%) in the clearance of this drug. Severity of treatment-related toxicity was not correlated with pharmacokinetic variables. CONCLUSION: ET-743 demonstrates clinical activity as first-line therapy against STS with acceptable toxicity. Additional studies to establish empirical dosing guidelines may be necessary to improve the safety of the drug in patients with varying degrees of hepatic dysfunction and definitively establish the role of ET-743 for patients with these malignancies.
Adult↗
A practical synthesis of the ABC ring model of ecteinascidins.
A practical synthesis of 1,2,3,4,5,6-hexahydro-1,5-imino-10-hydroxy-9-methoxy-3,8,11-trimethyl-3- benzazocin-4-one (3) as an ABC ring model compound of ecteinascidin 743 and safracins from 3-hydroxy-4-methoxy-5-methylbenzaldehyde (7) is described. The overall yield in 15 steps is 27%.
Dioxoles↗
Developing therapeutic pharmaceuticals for the treatment of soft-tissue sarcomas.
Recent progress in the therapy of sarcomas is highlighted by the rapid development and approval of the molecularly targeted therapy imatinib mesylate (STI571, Gleevec) for advanced gastrointestinal stromal tumours. Several other agents are in various stages of clinical development with far less rewarding results based on the preliminary data available. Amongst these, the encouraging ones include the nucleoside analogue gemcitabine and gemcitabine/docetaxel combination with some selective activity in sarcomas of gynaecological origin. The marine compound ecteinascidin-743 (ET743) has been studied in two different schedules (24-h and 3-h infusions) with some interesting biological activity worthy of further investigation. Identification of new agents with activity in this diverse group of diseases is extremely important.
Antineoplastic Agents↗
ET-743: a novel agent with activity in soft tissue sarcomas.
Ecteinascidin-743 (ET-743) is a natural product derived from the marine tunicate Ectenascidia turbinate. ET-743 binds in the minor groove of DNA, blocks transcription factors activity, and traps protein from the nucleotide excision repair system, thus blocking cells in G2-M phase. ET-743 demonstrated cytotoxic activity at very low concentrations against sarcoma cell lines in pre-clinical studies. In several phase II clinical studies in patients with advanced sarcoma failing conventional doxorubicin- and ifosfamide-based chemotherapy, ET-743 delivered by continuous intravenous 24-hour infusion at a dose of 1,500 microg/m2 every 21 days yielded 8% overall response and 30%-40% stabilization rates for a clinical benefit rate close to 40%. Interestingly, long-term stabilizations over more than 3 years have been described. In vivo, ET-743 has a specific toxicity profile, the major toxicity of this product being hepatic, through biliary duct destruction, and hematologic. ET-743 has also been evaluated in first-line treatment for these patients. Finally, due to its original mode of action and the lack of cross-resistance with other chemotherapy agents, ET-743 was tested in a preclinical model in combination with other drugs. Synergy was reported in vitro with doxorubicin and cisplatin; phase I combination studies are in progress.
Antineoplastic Combined Chemotherapy Protocols↗
Unique features of the mode of action of ET-743.
This paper describes the current knowledge of the primary mode of action of a natural product, ecteinascidin 743 (ET-743), derived from the marine tunicate Ecteinascidia turbinata. ET-743 was initially selected for preclinical development because of its potent antitumor activity observed against several human solid tumor types. In vitro, the drug is cytotoxic in the nanomolar range, and in the case of some very sensitive cell lines, in the picomolar range. The large potency differences observed among several solid tumor types indicate that this compound possesses some tumor selectivity, but the molecular basis of these differential effects remains to be elucidated. The present studies were undertaken to evaluate the mechanism of action of ET-743 in this context. The available information on ET-743 binding to DNA and its effects on transcriptional regulation point to a unique behavior of this drug, as it independently affects specific gene transcription in a promoter-dependent way. In addition, ET-743 shows a peculiar pattern of selectivity in cells with different defects in their DNA-repair pathways. These results highlight a unique property of ET-743, possibly explaining why it possesses antitumor activity against tumors that are refractory to standard anticancer drugs, all of which certainly act by mechanisms that are different from that of ET-743.
Antineoplastic Agents, Alkylating↗
A phase II and pharmacokinetic study of ecteinascidin 743 in patients with gastrointestinal stromal tumors.
PURPOSE: To assess the efficacy, tolerability, and pharmacokinetics of ecteinascidin 743 (ET-743) in patients with advanced gastrointestinal stromal tumors (GISTs). PATIENTS AND METHODS: The study was confined to adult patients with radiographically measurable GISTs. ET-743 was administered as a 24-hour continuous i.v. infusion at a dose of 1.5 mg/m(2) repeated every 3 weeks. Pharmacokinetic blood sampling was performed during the first cycle of therapy. Tumors were restaged after every second cycle of therapy. RESULTS: A total of 20 patients was enrolled in the study, 19 of whom were treated with 47 cycles of ET-743 (median 2, range 1-10). Severe toxicities were limited to reversible grade 3 transaminitis in 10 patients and grade 3 fatigue in one patient. There were no objective responses, and disease stabilization occurred in two patients lasting for periods of 4 and 10 months. The 1-year survival rate was 71.1%. Mean +/- standard deviation values of the maximum plasma concentration and total plasma clearance were 1.1 +/- 0.4 ng/ml and 44 +/- 16 l/h/m(2), respectively, for 19 of the 20 patients. CONCLUSION: This study is the first report of a prospective phase II trial to evaluate a cytotoxic agent in patients with GISTs. This study underscores the primary resistance of GISTS to chemotherapy and stands in stark contrast to the encouraging results recently achieved with STI571. The lack of response may be associated with a therapeutically ineffective exposure to the drug based upon the lower incidence of severe toxicities and greater clearance than described in phase I and II trials of ET-743.
Adult↗
Cytotoxic agents in the era of molecular targets and genomics.
Cancer treatment is evolving due to the development of molecularly targeted agents and the utilization of pharmacogenomics and pharmacogenetics to identify patients who are at an increased risk for toxicity or may be uniquely responsive to cytotoxic therapies. By identifying polymorphisms in the human genome that confer changes in the ability to metabolize or activate cancer agents, a more patient-specific treatment approach can be initiated. Molecularly targeted therapies such as PS-341, flavopiridol, Iressa, and anti-vascular endothelial growth factor antibodies may help to overcome resistance to cytotoxic therapies by lowering the apoptotic threshold and increasing cytotoxicity. Using molecularly targeted agents in combination with traditional cytotoxic agents may increase the percentage of patients who achieve disease stabilization and prolonged survival. With the development of genetic tools and genotyping of tumor and patient prior to initiating treatment, antitumor efficacy may be increased with a substantial reduction in toxicity.
Antineoplastic Agents, Alkylating↗
ET-743.
ET-743 is a novel antineoplastic DNA-binding agent derived from the marine tunicate Ecteinascidia turbinata. It has significant cytotoxic activity against soft tissue sarcomas (STS). It also has in vitro activity against melanoma, breast, ovarian, colon, renal, non-small cell lung and prostate carcinomas. The drug has unique mechanism of action which includes in vitro inhibition of transcription-dependent nucleotide excision repair pathways and inhibition of cell cycle progression leading to p53-independent apoptosis. It also selectively inhibits transcriptional activation of multidrug-resistance (MDR1) gene in human sarcoma cells in vivo. The efficacy of ET-743 has been investigated in patients with advanced STS in three multicentre phase II clinical trials. Patients receiving ET-743 as second- or third-line treatment had partial tumour response rates of 6 to 8%. Patients receiving ET-743 as first-line chemotherapy had a partial response rate of 18%. Forty-two to 50% of all patients in these trials achieved stable disease. All responses were durable up to 14 months. A pooled analysis of the three multicentre phase II trials showed the following: median overall survival time of 10.2 months, 1-year survival rate of 40% and 6-month progression-free rate of 27.2%. ET-743 is generally well tolerated. The most common adverse events in clinical trials were non-cumulative haematological and hepatic toxicities. Transient and reversible elevation of hepatic transaminases, nausea, vomiting and asthenia were common but seldom severe and never treatment-limiting. Mucositis, alopecia and cardiac or neurotoxicities were not observed.
Antineoplastic Agents, Alkylating↗
Effect of ecteinascidin-743 on the interaction between DNA binding proteins and DNA.
Ecteinascidin-743 (ET-743) is a tetrahydroisoquinoline alkaloid isolated from Ecteinascidia turbinata, a tunicate growing in mangrove roots in Caribbean. It has been shown to bind in the minor groove of DNA forming covalent adducts by reaction of the N2 of guanine with the carbinolamine moiety. We investigated ET-743 ability to inhibit the binding of different transcription factors to their consensus sequences by using gel shift assays. We have selected three types of factors: (i) oncogene products such as MYC, c-MYB and Maf; (ii) transcriptional activators regulated during the cell cycle as E2F and SRF; and (iii) general transcription factors such as TATA binding protein (TBP), Sp1 and NF-Y. We observed no inhibition of the binding of Sp1, Maf, MYB and MYC. Inhibition of DNA binding was observed for TBP, E2F, SRF at ET-743 concentrations ranging from 50 to 300 microM. The inhibition of binding of NF-Y occurs at even lower concentrations (i.e. 10-30 microM) when the recombinant subunits of NF-Y are preincubated with the drug, indicating that the inhibition of NF-Y binding does not require previous ET-743 DNA binding. Since NF-Y is a trimer containing two subunits with high resemblance to histones H2B and H2A, we have investigated the effect of ET-743 on nucleosome reconstitution. ET-743 caused a decrease of the nucleosomal band at 100 nM, with the complete disappearance of the band at 3-10 microM. These data suggest that the mode of action of this novel anticancer drug is related to its ability to modify the interaction between some DNA binding proteins and DNA.
Animals↗
Pharmacokinetics and pharmacodynamics of the novel marine-derived anticancer agent ecteinascidin 743 in a phase I dose-finding study.
Ecteinascidin (ET) 743 is an anticancer agent derived from the Caribbean tunicate Ecteinascidia turbinata. Preclinical studies revealed activity of ET-743 against different tumor types. A Phase I clinical trial was designed with ET-743 to identify the maximum tolerated dose and dose-limiting toxicities (DLTs). Furthermore, the pharmacokinetics of ET-743 and relationships with pharmacodynamics were evaluated. Adult patients with solid, resistant tumors received ET-743 as a 24-h i.v. infusion every 21 days. Blood samples were obtained during the first treatment course and in several consecutive courses. Noncompartmental pharmacokinetic analysis was performed. Relationships between pharmacokinetics and hepatic and hematological toxicities were explored. Fifty-two patients were treated at nine dose levels (50-1800 microg/m2). The DLTs, neutropenia and thrombocytopenia, were experienced at 1800 microg/m2. Twenty-five patients were treated at the recommended Phase II dose of 1500 microg/m2. At this dose, the mean value +/- SD for total body clearance was 59 +/- 31 liters/h, and the mean t(1/2) was 89 +/- 41 h. Pharmacokinetics were linear over the dose range tested. Prior exposure to ET-743 did not alter the pharmacokinetics in subsequent courses. The percentage of decrease in WBC count and absolute neutrophil count was correlated to the area under the plasma concentration versus time curve (AUC). Hepatic toxicity, defined as rise in alanine aminotransferase and aspartate aminotransferase, increased with dose and AUC but was reversible and not dose limiting. In conclusion, ET-743 administered as a 24-h i.v. infusion at a dose of 1500 microg/m2 is clinically feasible; severe thrombocytopenia and neutropenia are the DLTs.
Adult↗
Ecteinascidin 743 induces protein-linked DNA breaks in human colon carcinoma HCT116 cells and is cytotoxic independently of topoisomerase I expression.
Ecteinascidin 743 (Et743; NSC 648766) is a potent antitumor agent presently in clinical trials. Et743 selectively alkylates guanine N2 from the minor groove of duplex DNA and bends the DNA toward the major groove. This differentiates Et743 from other DNA-alkylating agents presently in the clinic. To date, the cellular effects of Et743 have not been elucidated. Recently, Et743 DNA adducts have been found to suppress gene expression selectively and to induce topoisomerase I (top1) cleavage complexes in vitro and top1-DNA complexes in cell culture. In the present study, we characterized the DNA damage and the cell cycle response induced by Et743 in human colon carcinoma HCT116 cells. Alkaline elution experiments demonstrated that micromolar concentrations of Et743 produced comparable frequencies of DNA-protein cross-links and DNA single-strand breaks. The single-strand breaks were protein-cross-linked and were not associated with detectable DNA double-strand breaks. By contrast with camptothecin, these lesions persisted for several hours after drug removal and were not formed at 4 degrees C. Et743 treatment induced transient p53 elevation, dose-dependent cell cycle accumulation in G2-M and in G1- and S-phase, and inhibition of DNA synthesis. The sensitivity of camptothecin-resistant mouse leukemia P388/ CPT45 cells, which fail to express detectable top1, was similar to the sensitivity of wild-type P388 cells, suggesting that top1 is not a critical target for the antiproliferative activity of Et743.
Antineoplastic Agents, Alkylating↗
Phase I and pharmacokinetic study of ecteinascidin 743 administered as a 72-hour continuous intravenous infusion in patients with solid malignancies.
Ecteinascidin 743 (ET-743) is a cytotoxic tetrahydroisoquinoline alkaloid that covalently binds to DNA in the minor groove. The in vitro chemosensitivity of cancer cells to ET-743 is markedly enhanced by prolonging the duration of exposure to the drug. A Phase I study of ET-743 given as a 72-h continuous i.v. infusion every 21 days was performed. Characteristics of the 21 adult patients with refractory solid tumors enrolled in the study were as follows: (a) 12 men; (b) 9 women; (c) median age, 59 years; (d) Eastern Cooperative Oncology Group performance status < or = 1, 20 patients; and (e) two prior regimens of chemotherapy, 7 patients. Dose limiting toxicity (DLT) was defined by typical criteria, except that grade 3 transaminitis did not constitute a DLT. There were no DLTs in the six patients evaluated at the first two dose levels of 600 and 900 microg/m2. Reversible grade 4 transaminitis occurred in two of nine patients after treatment with the first cycle of therapy at the third dose level of 1200 microg/m2. Another patient experienced grade 4 rhabdomyolysis, renal failure requiring hemodialysis, grade 4 neutropenia, and grade 3 thrombocytopenia during the second cycle of therapy with this dose. The maximum tolerated dose was 1200 microg/m2, and an additional six patients were enrolled at an intermediate dose level of 1050 microg/m2. This well-tolerated dose was established as the recommended Phase II dose. The disposition of ET-743 was distinctly biexponential, and a departure from linear pharmacokinetic behavior was evident at the 1200-microg/m2 dose level. Pharmacokinetic parameters determined at 1050 microg/m2 were (mean +/- SD): maximum plasma concentration, 318 +/- 147 pg/ml; initial disposition phase half-life, 9.0 +/- 10.3 min; terminal phase half-life, 69.0 +/- 56.7 h; and total plasma clearance, 28.4 +/- 22.5 liters/h/m2. Prolonged systemic exposure to concentrations of the agent that are cytotoxic in vitro were achieved. Toxicity of the drug is clearly schedule-dependent, because increasing the duration of infusion from 3 or 24 h to 72 h results in decreased myelosuppression and comparable hepatotoxicity. Although there were no objective responses to therapy, clear evidence of antitumor activity was observed in a patient with epithelioid mesothelioma, as confirmed by positron emission tomography studies. A Phase II trial to assess the efficacy of ET-743 against this highly refractory neoplasm has been initiated on the basis of this observation. The therapeutically optimal administration schedule remains to be established, inasmuch as there have been indications of activity against a variety of tumors during Phase I studies when the drug was infused over times ranging from 1 to 72 h. Characterizing the pharmacokinetics of ET-743 during the course of Phase II trials and Phase I combination studies is recommended to assure that this promising new anticancer drug can be used with an acceptable margin of safety.
Adult↗
Sensitivity of soft tissue sarcoma cell lines to chemotherapeutic agents: identification of ecteinascidin-743 as a potent cytotoxic agent.
The cytotoxic effects of ecteinascidin-743(ET-743), a novel marine natural product, were evaluated and compared with that of clinically used anticancer agents methotrexate, doxorubicin, etoposide, and paclitaxel in eight human soft tissue sarcoma (STS) cell lines. HT-1080, a fibrosarcoma cell line, and HS-42, a malignant mesodermal cell line, were the most sensitive of the cell lines to methotrexate, doxorubicin, etoposide, and paclitaxel. Other cell lines (IC50s) varied considerably and were more resistant to these agents. ET-743 was more potent than any of these agents, with IC50s in the pM range in all of the cell lines. Cytotoxicity of ET-743 was dose- and time-related (4-72 h exposure). Cytotoxic concentrations of ET-743 produced a S/G2 block in all of the cell lines tested. Three colon adenocarcinoma cell lines, HCT-8, HT-29, and HCT-116, and one breast cancer cell line, MCF-7, were 1-2 logs less sensitive to ET-743 than the STS cell lines. Cell lines were also characterized as to expression of oncogenes and tumor suppressor genes to attempt to correlate sensitivity of these cell lines to ET-743 and other chemotherapeutic agents. All of the cell lines except M8805, a malignant fibrous histiocytoma cell line, had mutations in p53 and/or overexpressed the MDM2 protein. Only HS-18, a liposarcoma cell line, lacked expression of the retinoblastoma protein. None of the cell lines had detectable expression of P-glycoprotein as measured by immunohistochemistry. ET-743 is an extremely potent cytotoxic agent against human STS cell lines and is being evaluated as an antitumor agent in this disease.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
Sequence-dependent enhancement of cytotoxicity produced by ecteinascidin 743 (ET-743) with doxorubicin or paclitaxel in soft tissue sarcoma cells.
Ecteinascidin 743 (ET-743) is a potent antitumor agent from the Caribbean tunicate Ecteinascidin turbinata and is presently in clinical trials for human cancers. To better understand how ET-743 might be used clinically, the present study used SRB assays to examine the cytotoxicity resulting from combining ET-743 with three other antineoplastic agents: doxorubicin (DXR), trimetrexate, and paclitaxel in different administration schedules in two soft tissue sarcoma cell lines, HT-1080 and HS-18, in vitro. Concurrent exposure of ET-743 with DXR resulted in synergistic interactions in both cell lines. Addition of ET-743 for 24 h before DXR was the most effective cytotoxic regimen against both cell lines. Morphological study by fluorescence microscopy revealed that combination treatment of both cells with ET-743 and DXR induced apoptosis. Exposure to paclitaxel before ET-743 was also an effective regimen. These results encourage studies of the combination of ET-743 and DXR in the treatment of soft tissue sarcoma, because each of these agents have activity in this disease.
Antineoplastic Agents↗
[High-dose chemotherapy in soft tissue sarcomas of adults].
Few cytotoxic agents are active for the treatment of soft tissue sarcomas of adults: drugs active in monotherapy are doxorubicin, ifosfamide, dacarbazine and ET743. In patients with advanced stage soft tissue sarcomas (ASTS), a dose-response relationship has been established for doxorubicin and ifosfamide. Intensive combination chemotherapy regimens at conventional doses (MAID, or AI) yield higher objective response rates than monochemotherapy regimens, ranging between 25% and 44%, but failed improve survival rates as comparted to less intensive regimens. Recently, several phase I or II studies have investigated the use of high dose chemotherapy regimens as consolidation therapy in ASTS in response to conventional regimens. HDCT regimens have been reported to yield response rates ranging between 18% and 66%. Some of these patients with ASTS achieved long term complete remission, in particular in the subgroup of patients in complete remission after conventional chemotherapy in advanced phase. Phase III studies are required to confirm that survival may be improved by HDCT in subgroups of patients with ASTS.
Antineoplastic Combined Chemotherapy Protocols↗
ET-743 (PharmaMar/NCI/Ortho Biotech).
Ecteinascidin-743 (ET-743), a tetrahydroisoquinoline alkaloid isolated from the Caribbean tunicate, Ecteinascidia turbinata, is under development by PharmaMar (the pharmaceutical subsidiary of Zeltia), the National Cancer Institute (NCI) and Ortho Biotech, as a potential treatment for several tumor types including breast cancer, lung cancer, ovarian cancer and melanoma. It appears to function by DNA minor groove alkylation, which induces topoisomerase I-mediated protein-linked DNA strand breakage [322446]. ET-743 is an analog of ET-729 [169825]. As of February 1999, it was in phase II trials [326363], [326268], [375811] and, in August 2001, PharmaMar expected phase II trials for breast, ovarian and non-small cell lung cancer to be completed by August 2002 [423408]. In June 2001, the EMEA awarded ET-743 Orphan Drug status for the treatment of soft tissue sarcoma [412446]. The orphan medicinal product designation is designed to expedite the registration of pharmaceuticals for life-threatening or debilitating conditions with low prevalence (< 5 per 10,000 in the EU), for which no satisfactory treatment exists. The designation offers the sponsor several incentives, such as centralized procedure review of the Marketing Authorization Application and, upon approval, ten-year marketing exclusivity throughout Europe for the therapeutic indication for which it was granted. PharmaMar is also collaborating with the European Organization for Research and Treatment of Cancer (EORTC); PharmaMar has obtained the worldwide rights to ET-743, amongst other ecteinascidins, from the University of Illinois [177268]. In August 2001, Dresdner Kleinwort Wasserstein predicted total sales, for all ET-743's indications, of $1 million in 2002, rising through $1106 million in 2007 to $2725 million in 2011 [423408].
Animals↗