Antitumor activity- and gene expression-based profiling of ecteinascidin Et 743 and phthalascidin Pt 650

Recent advances in the synthesis and activity of analogues of bistetrahydroisoquinoline alkaloids as antitumor agents

Ecteinascidin 743 (Et-743), also known by the trade name Yondelis®, is the pioneering marine natural product to be successfully developed as an antitumor drug. Moreover, it is the first tetrahydroisoquinoline natural product used clinically for antitumor therapy since Kluepfel, a Canadian scientist, discovered the tetrahydroisoquinoline alkaloid (THIQ) naphthyridinomycin in 1974. Currently, almost a hundred natural products of bistetrahydroisoquinoline type have been reported. Majority of these bistetrahydroisoquinoline alkaloids exhibit diverse pharmacological activities, with some family members portraying potent antitumor activities such as Ecteinascidins, Renieramycins, Saframycins, Jorumycins, among others. Due to the unique chemical structure and exceptional biological activity of these natural alkaloids, coupled with their scarcity in nature, research seeking to provide material basis for further bioactivity research through total synthesis and obtaining compound leads with medicinal value through structural modification, remains a hot topic in the field of antitumor drug R&D. Despite the numerous reviews on the total synthesis of bistetrahydroisoquinoline natural products, comprehensive reviews on their structural modification are apparently scarce. Moreover, structural modification of bioactive natural products to acquire lead compounds with improved pharmaceutical characteristics, is a crucial approach for innovative drug discovery. This paper presents an up-to-date review of both structural modification and activity of bistetrahydroisoquinoline natural products. It highlights how such alkaloids can be used as antitumor lead compounds through careful chemical modifications. This review offers valuable scientific references for pharmaceutical chemists engaged in developing novel antitumor agents based on such alkaloid modifications, as well as those with such a goal in future.

Design, synthesis, and biological evaluation of simplified tetrahydroisoquinoline analogs

A series of tetrahydroisoquinoline derivatives were prepared and their antitumor activity was studied against several human carcinoma cell lines, including Ketr3, BEL-7402, BGC-823, KB, HCT-8, MCF-7, HeLa, A2780, A549, and HT-1080. Compound 20, an analog of phthalascidin 650, exhibited good broad-spectrum antitumor activity in vitro. However, compounds 19 and 21, in which the side chains at C-22 are simplified, showed no obvious antitumor activity, indicating that the C-22 side chain of this type of compound has a greater impact on its activity. The difference in the in vivo activity between compound 20 and phthalascidin 650 also shows a significant effect of the substituents on the skeleton structure on the in vivo activity.

Renieramycin-type alkaloids from marine-derived organisms: Synthetic chemistry, biological activity and structural modification

Marine natural products are known for their diverse chemical structures and extensive bioactivities. Renieramycins, the member of tetrahydroisoquinoline family of marine natural products, arouse interests because of their strong antitumor activities and similar structures to the first marine antitumor agent ecteinascidin-743, approved by the European Union. According to the literatures, researches on the pharmacological activities of renieramycins mainly focus on their antitumor activities. In addition, by structural modification, derivatives of renieramycins show stronger antiproliferative activity and less accidental necrosis activity on cells. Nevertheless, the difficulties in extraction and separation hinder their further development. Hence, the synthetic chemistry work of renieramycins plays a key role in their further development. In this review, currently reported researches on the synthetic chemistry, pharmacological activities and structural modification of renieramycins are summarized, which will benefit future drug development and innovation.

Radiosensitizing effects of trabectedin on human A549 lung cancer cells and HT-29 colon cancer cells

Background and Purpose Trabectedin is a unique alkylating agent with promising effects against a range of solid tumors. In this study, we aimed to examine the cytotoxic and radiosensitizing effects of trabectedin on two human epithelial tumor cell lines in vitro, and its effects on DNA repair capacity. Methods Cancer cells (A549: human lung cancer cells, HT-29: colon cancer cells) were treated with either trabectedin alone for the determination of their growth, or in combination with radiation for the determination of their metabolic activity, proliferation, and clonogenic survival. Besides, the γH2AX foci assay was performed for the assessment of ionizing radiation-induced DNA damage and to evaluate the influence of trabectedin on DNA damage repair. Results Treatment with trabectedin resulted in a growth-inhibiting effect on both cell lines, with the IC₅₀ values remaining within a low nanomolar range. Analyses of metabolic activity confirmed a cytotoxic influence of trabectedin and a BrdU assay demonstrated an antiproliferative effect. When combined with radiation, incubation with trabectedin was found to enhance the radiosensitivity of the tumor cells. The γH2AX foci assay resulted in an increased number of DNA double-strand breaks (DSBs) in cells treated with trabectedin. Conclusion The results of this study underline the antitumor activity of trabectedin at low nanomolar concentrations. We demonstrated that trabectedin enhanced radiation response in human lung (A549) cancer cells and colon (HT-29) cancer cells. Further studies are necessary to examine trabectedin as a potential candidate for future applications in radiotherapy.

Developing Precisely Defined Drug-Loaded Nanoparticles by Ring-Opening Polymerization of a Paclitaxel Prodrug

Nanoparticles with high paclitaxel (PTX) loading and low systemic toxicity are prepared in scalable and versatile manner via one-step ring-opening polymerization of a prodrug monomer consisting of PTX that is appended to a cyclic carbonate through a hydrolysable ester linker. Initiating this monomer from a hydrophilic macroinitiator results in an amphiphilic diblock copolymer that spontaneously self-assembles into well-defined nanoparticles with tunable size.

Practical synthesis and cytotoxic evaluation of the pyrazino[1,2-b]-isoquinoline ring system

A multicomponent three-step synthesis of pyrazino[1-2b]isoquinolines is described. A preliminary cytotoxic screening against cancer cell lines was performed.

Characterization of antiproliferative potential and biological targets of a copper compound containing 4'-phenyl terpyridine

Several copper complexes have been assessed as anti-tumor agents against cancer cells. In this work, a copper compound [Cu(H2O){OS(CH3)2}L](NO3)2 incorporating the ligand 4'-phenyl-terpyridine antiproliferative activity against human colorectal, hepatocellular carcinomas and breast adenocarcinoma cell lines was determined, demonstrating high cytotoxicity. The compound is able to induce apoptosis and a slight delay in cancer cell cycle progression, probably by its interaction with DNA and induction of double-strand pDNA cleavage, which is enhanced by oxidative mechanisms. Moreover, proteomic studies indicate that the compound induces alterations in proteins involved in cytoskeleton maintenance, cell cycle progression and apoptosis, corroborating its antiproliferative potential.

Phase I study of the safety and pharmacokinetics of trabectedin with docetaxel in patients with advanced malignancies

PURPOSE

Combination therapy with trabectedin and docetaxel was evaluated in patients with advanced malignancies.

METHODS

In this open-label phase 1 study, docetaxel (60 or 75 mg/m(2); 1-h intravenous infusion) was given on day 1 of a 21-day cycle in combination with escalating doses of trabectedin (0.4-1.3 mg/m(2) by 3-h intravenous infusion, 1 h after docetaxel) and prophylactic granulocyte colony-stimulating factor (G-CSF). Maximum tolerated dose (MTD) as primary objective and safety, plasma pharmacokinetics, and antitumor activity as secondary objectives were assessed.

RESULTS

Patients (N = 49) received a median of four cycles of treatment. MTD was 1.3 mg/m(2) trabectedin and 60 mg/m(2) docetaxel for patients with limited and 1.1 mg/m(2) trabectedin and 60 mg/m(2) docetaxel for patients with unlimited prior chemotherapy. Dose-limiting toxicities (during cycle 1) included elevated alanine aminotransferase (ALT) and fatigue in patients with limited prior chemotherapy and elevated ALT and febrile neutropenia in those with unlimited prior chemotherapy. The most common drug-related adverse events were nausea (65 %), fatigue (63 %), and neutropenia (53 %). One patient achieved a complete response. Thirty patients had stable disease, and 11 had stable disease for ≥6 months. Pharmacokinetic results for trabectedin plus docetaxel were similar to those previously reported for the single agents.

CONCLUSION

In patients with previously treated, advanced malignancies, the combination of therapeutic doses of trabectedin and docetaxel showed clinical activity and was tolerable with prophylactic G-CSF, with no evidence of clinically important drug interactions.

Alkaloids from marine invertebrates as important leads for anticancer drugs discovery and development

The present review describes research on novel natural antitumor alkaloids isolated from marine invertebrates. The structure, origin, and confirmed cytotoxic activity of more than 130 novel alkaloids belonging to several structural families (indoles, pyrroles, pyrazines, quinolines, and pyridoacridines), together with some of their synthetic analogs, are illustrated. Recent discoveries concerning the current state of the potential and/or development of some of them as new drugs, as well as the current knowledge regarding their modes of action, are also summarized. A special emphasis is given to the role of marine invertebrate alkaloids as an important source of leads for anticancer drug discovery.

Trabectedin: novel insights in the treatment of advanced sarcoma

Soft tissue sarcomas are a heterogenous group of malignancies with relatively high mortality rates. The outlook for these patients has been poor, with only a few drugs showing measurable activity. Trabectedin is a new alkylating agent with significant activity in sarcomas, but particularly in liposarcomas and leiomyosarcomas, both as a single agent or in combination with other drugs. Phase I and II studies of trabectedin have shown measurable benefit. Currently there are several Phase III trials which have completed accrual to better study its use as a single agent or in combination therapy, although outcomes have not yet been reported. Trabectedin (Yondelis) is approved for the treatment of sarcomas by the EMEA, but is not yet approved by the FDA, pending the results of the currently maturing phase III trials.

Trabectedin as a single-agent treatment of advanced breast cancer after anthracycline and taxane treatment: a multicenter, randomized, phase II study comparing 2 administration regimens

BACKGROUND

The purpose of this study was to assess the efficacy and safety of trabectedin for advanced breast cancer.

PATIENTS AND METHODS

In an open-label, phase II, multicenter study, women with advanced breast cancer previously treated with ≤ 2 lines of chemotherapy for advanced disease, including both anthracyclines and taxanes, were randomized (1:1) to 3-hour infusions of trabectedin 1.3 mg/m(2) once every 3 weeks (1/3 treatment arm) or 0.58 mg/m(2) every week for 3 of 4 weeks (3/4 treatment arm). The primary end point was objective response. Secondary end points included time to progression (TTP), progression-free survival (PFS), and overall survival (OS).

RESULTS

Fifty-two women (median age, 50 years; median chemotherapy agents, 4) were enrolled. Relative trabectedin dose intensities were 81% and 76% in the 1/3 and 3/4 treatment arms, respectively. Objective response rates were 12% (3 of 25) and 4% (1 of 27), respectively. Stable disease was observed in 14 (56%) and 11 (41%) patients in the 1/3 and 3/4 treatment arms, respectively, with median durations of 3.5 and 3.7 months. Median TTP and PFS were higher in the 1/3 treatment arm (3.1 months each) than in the 3/4 treatment arm (2.0 months each). At a median follow-up of 7 months in both treatment arms, median OS was not reached in the 1/3 treatment arm and was 9.4 months in the 3/4 treatment arm. The most frequent drug-related adverse events in the 1/3 and 3/4 treatment arms, respectively, were alanine aminotransferase (ALT) level increases (68% vs. 63%), nausea (56% vs. 59%), and asthenia (56% vs. 48%). Neutropenia and increases in ALT levels were the most frequent grade 3/4 events. Both types of events were usually transient and reversible.

CONCLUSION

In the population studied, trabectedin showed a manageable safety profile for both regimens analyzed. There were higher objective response rates and a longer PFS in the 1/3 treatment arm compared with the 3/4 treatment arm.

Long-term outcome and effect of maintenance therapy in patients with advanced sarcoma treated with trabectedin: an analysis of 181 patients of the French ATU compassionate use program

BACKGROUND

The long term outcome of advanced sarcoma patients treated with trabectedin outside of clinical trials and the utility of maintenance treatment has not been reported.

METHODS

Between 2003 and 2008, patients with advanced sarcoma failing doxorubicin could be treated within a compassionate use program (ATU, Temporary Use Authorization) of trabectedin in France using the standard 3-weekly regimen. Data from 181 patients (55%) were collected from 11 centres and analyzed.

RESULTS

Trabectedin was given in first, second, third or fourth line in metastatic phase in 6%, 37%, 33% and 23% of patients respectively. With a median follow-up of 6 years, median PFS and OS were 3.6 months and 16.1 months respectively. The median number of cycles was 3 (range 1-19). Best response were partial response (PR, n = 18, 10%), stable disease (SD, n = 69, 39%) and progressive disease (PD, n = 83, 46%), non evaluable (NE, n = 9, 5%). Thirty patients (17%) had to be hospitalized for treatment- related side effects. Independent prognostic factors in multivariate analysis (Cox model) were myxoid LPS and line of trabectedin for PFS, and myxoid LPS and retroperitoneal sarcomas for OS. Patients in PR or SD after 6 cycles continuing treatment had a better PFS (median 5.3 vs 10.5 months, p = 0.001) and OS (median 13.9 vs 33.4 months, p = 0.009) as compared to patients who stopped after 6 cycles.

CONCLUSIONS

In this compassionate use program, trabectedin yielded similar or better PFS and OS than in clinical trials. Maintenance treatment beyond 6 cycles was associated with an improved survival.

Trabectedin has a low cardiac risk profile: a comprehensive cardiac safety analysis

PURPOSE

This analysis provides a cross-study evaluation of the cardiac safety of trabectedin.

METHODS

Drug-related cardiac adverse events (CAEs) were retrieved from phase I-III clinical trials, pharmacovigilance databases, and spontaneously reported cases. Left ventricular ejection fraction (LVEF) was monitored in combination phase I studies with doxorubicin or pegylated liposomal doxorubicin (PLD) and in a phase III trial (with PLD).

RESULTS

CAEs [grade 4 cardiac arrest with severe pancytopenia and sepsis (n = 1 patient), grade 4 atrial fibrillation (n = 2), and grade 1 tachycardia (n = 1)] occurred in 4/283 patients (1.4%) in 6 single-agent phase I trials. CAEs (grade 1 sinus tachycardia in a hypertensive patient and grade 1 ventricular dysfunction) occurred in 2/155 patients (1.3%) in 4 phase I combination trials. Results from 19 single-agent phase II trials showed CAEs in 20/1,132 patients (1.8%): arrhythmias (tachycardia/palpitations; n = 13; 1.1%) were the most common. A rather similar rate of symptomatic CAEs was observed in both arms of a phase III trial in recurrent ovarian cancer: 6/330 patients (1.8%; PLD) and 11/333 patients (3.3%; trabectedin/PLD). No clinically relevant LVEF changes occurred in phase I combination trials. In the phase III trial, LVEF decreases from baseline were similar: 9% of patients (PLD) and 7% (trabectedin/PLD), with no relevant symptoms. During postmarketing experience in soft tissue sarcoma (2,046 patients treated), 4 CAEs (2 cardiac arrest, 2 cardiac failure; ~0.2%) occurred in patients with preexisting conditions.

CONCLUSIONS

Trabectedin has a low incidence of CAEs, consisting mainly of arrhythmias. This extensive data review indicates a low cardiac risk profile for trabectedin.

Recent synthetic approaches to 6,15-iminoisoquino[3,2-b]3-benzazocine compounds

Saframycins, safracins, renieramycins, cribrostatins, and esteinascidins are 6,15-iminoisoquino[3,2-b]3-benzazocine compounds that constitute the largest subgroup among the antitumor antibiotics belonging to the tetrahydroisoquinoline family. Their structural complexity has led to widespread synthetic attention to obtain them in both racemic and enantiopure forms. Publication in 1996 of the first total synthesis of ecteinascidin 743 by Corey's group was an important milestone, but the development of preparative protocols for these structures has continued, offering new possibilities to exploit the biological activity of the above-mentioned natural products and their analogues. This minireview is intended to update this progress following a methodological rather than a chronological organization. Besides of a brief description of the different strategies evolved from retrosynthetic analyses, which have been organized according to the order of bonding events that will link the precursors, semisynthetic approaches and a brief account of the total syntheses of ecteinascidin 743, have been analyzed.

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.

Microarray-based transcriptional profiling of renieramycin M and jorunnamycin C, isolated from Thai marine organisms

Renieramycin M and jorunnamycin C, two isoquinolinequinone compounds differing only at the C-22 ester side chain, were evaluated for their cytotoxic effects on human colon (HCT116) and breast (MDA-MB-435) cancer cell lines. These two compounds displayed potent cancer cell growth inhibition, their IC(50) values reaching nanomolar order. To examine their effects on transcription, we carried out oligonucleotide microarray analysis with focus on the similarities and differences between the two compounds in terms of transcriptional profiles. We found that the down-regulation of PTPRK (protein tyrosine phosphatase receptor type K) can be considered as a biomarker responsive to the cytotoxic effects of this class of antitumor marine natural products.

Cytotoxicity mechanisms of pyrazino[1,2-b]isoquinoline-4-ones and SAR studies

The cytotoxicity showed by 1b, an interesting representant of the title compounds, for HT-29 human colon cancer cells (CI(50) value of 1.95 x 10(-7)M) has been related to the induced cell death at the G2 phase and not to DNA damage. This compound promotes the degradation of components of the G2/M checkpoint machinery, in particular cdc2, Cyclin B1 and Wee1, which represents a novel mechanism of cytotoxicity. Degradation of Wee1 seems to be mediated by proteasome activity but degradation of cdc2 has to occur through a different mechanism. The activity of 1b on G2 cell cycle components suggests that tumor cells that are arrested in G2/M by anticancer drugs like cisplatin could be targeted by compound 1b, increasing the apoptosis induction, and that their optimized analogs might be useful in the treatment of colon cancer through combination therapies with cisplatin or other anticancer drugs that affect the cytoskeleton integrity such as taxol and taxotere. SAR studies with compounds obtained by manipulation of the N(2) and C(4)-functional groups and the C(6)-chain of compound 1b have confirmed the importance of these structural features in the in vitro antitumor activity. Fused oxazolidine derivatives as compound 5 were inactive, and the lack of activity found in the replacement of the C(4)-lactam by a cyanoamine function, as in compounds 8-10, could be explained considering that their all-syn relative configuration makes them too stable to generate alkylating iminium species.

Zalypsis (PM00104) is a potent inducer of gamma-H2AX foci and reveals the importance of the C ring of trabectedin for transcription-coupled repair inhibition

Zalypsis (PM00104) is a novel tetrahydroisoquinoline alkaloid related to trabectedin [ecteinascidin 743 (Et743)]. Et743 and PM00104 have similar A and B rings but differ in their C rings. The present study shows that Et743 and PM00104 differ in at least two ways: in their DNA binding properties and nucleotide excision repair (NER) dependency for cellular targeting. DNase I footprinting shows that the two drugs bind DNA differentially. We also found that, in contrast to Et743, the antiproliferative activity of PM00104 does not depend on transcription-coupled NER. Accordingly, PM00104 induces gamma-H2AX foci with the same efficiency in NER-deficient or NER-proficient cells. Moreover, the formation of gamma-H2AX foci is replication dependent for PM00104, whereas it is both transcription and replication dependent in the case of Et743. These findings show the importance of the C ring structure of tetrahydroisoquinoline ecteinascidin derivatives for NER targeting. Finally, PM00104 exerts antiproliferative activity at nanomolar concentrations and induces gamma-H2AX response in two Ewing's sarcoma cell lines, suggesting that gamma-H2AX could serve as a pharmacodynamic biomarker for the clinical development of PM00104.

Chemistry of renieramycins. Part 8: synthesis and cytotoxicity evaluation of renieramycin M-jorunnamycin A analogues

Twenty-four ester analogues of renieramycin M (1m) were prepared from jorunnamycin A (3a), which was easily transformed from marine natural 1m in three steps. These analogues, along with 1m itself, cyanojorumycin (2b), and jorunnamycins A (3a) and C (3b), were evaluated in vitro for cytotoxicity by measuring IC(50) values through the 3-(4,5-dimethyltriazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay using human HCT116 colon carcinoma and MDA-MB-435 breast carcinoma cell lines. Nitrogen-containing heterocyclic ester derivatives 9a-f showed similar in vitro cytotoxicity to 1m, whereas the other derivatives were slightly less cytotoxic than 1m. 2'-Pyridinecarboxylic acid ester derivative (9c) exhibited a threefold increase in cytotoxicity relative to 1m.

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.

Trabectedin (ET-743) promotes differentiation in myxoid liposarcoma tumors

Differentiation is a complex set of events that can be blocked by rearrangements of regulatory genes producing fusion proteins with altered properties. In the case of myxoid liposarcoma (MLS) tumors, the causative abnormality is a fusion between the CHOP transcription factor and the FUS or EWS genes. CHOP belongs to and is a negative regulator of the large CAAT/enhancer binding protein family whose alpha, beta, and delta members are master genes of adipogenesis. Recent clinical data indicate a peculiar sensitivity of these tumors to the natural marine compound trabectedin. One hypothesis is that the activity of trabectedin is related to the inactivation of the FUS-CHOP oncogene. We find that trabectedin causes detachment of the FUS-CHOP chimera from targeted promoters. Reverse transcription-PCR and chromatin immunoprecipitation analysis in a MLS line and surgical specimens of MLS patients in vivo show activation of the CAAT/enhancer binding protein-mediated transcriptional program that leads to morphologic changes of terminal adipogenesis. The activity is observed in cells with type 1 but not type 8 fusions. Hence, the drug induces maturation of MLS lipoblasts in vivo by targeting the FUS-CHOP-mediated transcriptional block. These data provide a rationale for the specific activity of trabectedin and open the perspective of combinatorial treatments with drugs acting on lipogenic pathways.

Von Hippel-Lindau-coupled and transcription-coupled nucleotide excision repair-dependent degradation of RNA polymerase II in response to trabectedin

PURPOSE

Ecteinascidin 743 (Et743; trabectedin, Yondelis) has recently been approved in Europe for the treatment of soft tissue sarcomas and is undergoing clinical trials for other solid tumors. Et743 selectively targets cells proficient for TC-NER, which sets it apart from other DNA alkylating agents. In the present study, we examined the effects of Et743 on RNA Pol II.

EXPERIMENTAL DESIGN AND RESULTS

We report that Et743 induces the rapid and massive degradation of transcribing Pol II in various cancer cell lines and normal fibroblasts. Pol II degradation was abrogated by the proteasome inhibitor MG132 and was dependent on TC-NER. Cockayne syndrome (CS) cells and xeroderma pigmentosum (XP) cells (XPD, XPA, XPG, and XPF) were defective in Pol II degradation, whereas XPC cells whose defect is limited to global genome NER in nontranscribing regions were proficient for Pol II degradation. Complementation of the CSB and XPD cells restored Pol II degradation. We also show that cells defective for the VHL complex were defective in Pol II degradation and that complementation of those cells restores Pol II degradation. Moreover, VHL deficiency rendered cells resistant to Et743-induced cell death, a similar effect to that of TC-NER deficiency.

CONCLUSION

These results suggest that both TC-NER-induced and VHL-mediated Pol II degradation play a role in cell killing by Et743.

Phase I combination study of trabectedin and doxorubicin in patients with soft-tissue sarcoma

PURPOSE

To determine the dose of trabectedin plus doxorubicin with granulocyte colony-stimulating factor support associated with manageable neutropenia and acceptable dose-limiting toxicities (DLT) in patients with recurrent or persistent soft-tissue sarcoma.

METHODS

In this phase I, open-label, multicenter trial, patients previously treated with 0-1 prior chemotherapy regimens excluding doxorubicin, an Eastern Cooperative Oncology Group performance status 0-1, and adequate organ function received a 10- to 15-min i.v. infusion of doxorubicin 60 mg/m(2) immediately followed by a 3-h i.v. infusion of trabectedin 0.9 to 1.3 mg/m(2) on day 1 of a 3-week cycle. Because four of the first six patients experienced DLT-defining neutropenia during cycle 1, all subsequent patients received primary prophylactic granulocyte colony-stimulating factor. The maximum tolerated dose was the highest dose level with six or more patients in which less than one-third of the patients experienced severe neutropenia or DLT. Blood was collected during cycle 1 for pharmacokinetic analyses. Adverse events, tumor response, and survival were assessed.

RESULTS

Patients (N = 41) received a median of six cycles of treatment (range, 2-13). The maximum tolerated dose was trabectedin 1.1 mg/m(2) and doxorubicin 60 mg/m(2). Common grade 3/4 treatment-emergent adverse events were neutropenia (71%), alanine aminotransferase increase (46%), and thrombocytopenia (37%). Overall, 5 (12%) patients achieved a partial response and 34 (83%) maintained stable disease. Median progression-free survival was 9.2 months. Doxorubicin and trabectedin pharmacokinetics were not altered substantially with concomitant administration.

CONCLUSION

The combination of doxorubicin 60 mg/m(2) followed by trabectedin 1.1 mg/m(2) every 21 days is safe and active in patients with soft-tissue sarcoma.

A phase I study of the safety and pharmacokinetics of trabectedin in combination with pegylated liposomal doxorubicin in patients with advanced malignancies

BACKGROUND

To determine the maximum tolerated dose (MTD), safety, potential pharmacokinetic (PK) interactions, and effect on liver histology of trabectedin in combination with pegylated liposomal doxorubicin (PLD) for advanced malignancies.

PATIENTS AND METHODS

Entry criteria for the 36 patients included normal liver function, prior doxorubicin exposure <250 mg/m(2), and normal cardiac function. A 1-h PLD (30 mg/m(2)) infusion was followed immediately by one of six trabectedin doses (0.4, 0.6, 0.75, 0.9, 1.1, and 1.3 mg/m(2)) infused over 3 h, repeated every 21 days until evidence of complete response (CR), disease progression, or unacceptable toxicity. Plasma samples were obtained to assess PK profiles.

RESULTS

The MTD of trabectedin was 1.1 mg/m(2). Drug-related grade 3 and 4 toxic effects were neutropenia (31%) and elevated transaminases (31%). Six patients responded (one CR, five partial responses), with an overall response rate of 16.7%, and 14 had stable disease (less than a 50% reduction and less than a 25% increase in the sum of the products of two perpendicular diameters of all measured lesions and the appearance of no new lesions) >4 months (39%). Neither drug had its PK affected significantly by concomitant administration compared with trabectedin and PLD each given as a single agent.

CONCLUSION

Trabectedin combined with PLD is generally well tolerated at therapeutic doses of both drugs in pretreated patients with diverse tumor types and appears to provide clinical benefit. These results support the need for additional studies of this combination in appropriate cancer types.

Synthesis and cytotoxic evaluation of some cribrostatin-ecteinascidin analogues

Analogues of cribrostatin IV ( 1) and the potent antineoplastic agent ecteinascidin 743 ( 2) have been synthesized. The cytotoxic activity of these compounds ( 5, 14, 20) has been determined, and the cyanoamine-cribrostatin analogue ( 14) exhibits a 20-fold improvement with regard to the natural product 1.

Dynamics of cell cycle phase perturbations by trabectedin (ET-743) in nucleotide excision repair (NER)-deficient and NER-proficient cells, unravelled by a novel mathematical simulation approach

OBJECTIVES

Trabectedin (ET-743, Yondelis) is a natural marine product, with antitumour activity, currently in phase II/III clinical trials. Previous studies have shown that cells hypersensitive to ultraviolet (UV)-rays because of nucleotide excision repair (NER) deficiency, were resistant to trabectedin. The purpose of this study was to investigate whether this resistance was associated with different drug-induced cell cycle perturbations.

MATERIALS AND METHODS

An isogenic NER-proficient cellular system (CHO-AA8) and a NER-deficient one (CHO-UV-96), lacking functional ERCC-1, were studied. Flow cytometric assays showed progressive accumulation of cells in G2 + M phase in NER-proficient but not in NER-deficient cells. Applying a computer simulation method, we realized that the dynamics of the cell cycle perturbations in all phases were complex.

RESULTS

Cells exposed to trabectedin during G1 and G2 + M first experienced a G1 block, while those exposed in S phase were delayed in S and G2 + M phases but eventually divided. In the presence of functional NER, exit from the G1 block was faster; then, cells progressed slowly through S phase and were subsequently blocked in G2 + M phase. This G2 + M processing of trabectedin-induced damage in NER-proficient cells was unable to restore cell cycling, suggesting a difficulty in repairing the damage.

CONCLUSIONS

This might be due either to important damage left unrepaired by previous G1 repair, or that NER activity itself caused DNA damage, or both. We speculate that in UV-96 cells repair mechanisms other than NER are activated both in G1 and G2 + M phases.

A Phase II study of trabectedin single agent in patients with recurrent ovarian cancer previously treated with platinum-based regimens

The objective of this study was to determine the objective response rate in patients with platinum-sensitive and platinum-resistant recurrent ovarian cancer to treatment with trabectedin (Yondelis®) administered as a 3-h infusion weekly for 3 weeks of a 4-week cycle. We carried out a multicentre Phase II trial of trabectedin in patients with advanced recurrent ovarian cancer. Trabectedin (0.58 mg m⁻²) was administered via a central line, after premedication with dexamethasone, to 147 patients as a 3-h infusion weekly for 3 weeks followed by 1-week rest. Major eligibility criteria included measurable relapsed advanced ovarian cancer and not more than two prior platinum-containing regimens. Patients were stratified according to the treatment-free interval (TFI) between having either platinum-sensitive (⩾6 months TFI) or platinum-resistant disease (<6 months TFI)/platinum-refractory disease (progression during first line therapy). In the platinum-sensitive cohort, 62 evaluable patients with measurable disease had an overall response rate (ORR) of 29.0% (95% CI: 18.2–41.9%) and median progression-free survival (PFS) was 5.1 months (95% CI: 2.8–6.2). Four patients with measurable disease per Response Evaluation Criteria in Solid Tumours (RECIST) criteria had no follow-up scans at the end of treatment. In the platinum-resistant/refractory cohort, 79 patients were evaluable with an ORR of 6.3% (95% CI: 2.1–14.2%). Median PFS was 2.0 months (95% CI: 1.7–3.5 months). Two patients with measurable disease per RECIST criteria had no follow-up scans at the end of treatment. The most frequent (⩾2% of patients) drug-related treatment-emergent grade 3/4 adverse events were reversible liver alanine transferase elevation (10%), neutropaenia (8%), nausea, vomiting, and fatigue (5% each). Trabectedin is an active treatment, with documented responses in patients with platinum sensitive advanced relapsed ovarian cancer, and has a manageable toxicity profile.