Effect of consecutive lower-dose cisplatin in enhancement of 5-fluorouracil cytotoxicity in experimental tumor cells in vivo

The 1,10-Phenanthroline Ligand Enhances the Antiproliferative Activity of DNA-Intercalating Thiourea-Pd(II) and -Pt(II) Complexes Against Cisplatin-Sensitive and -Resistant Human Ovarian Cancer Cell Lines

Ovarian cancer is the most lethal gynecological malignancy, often because of the frequent insurgence of chemoresistance to the drugs currently used. Thus, new therapeutical agents are needed. We tested the toxicity of 16 new DNA-intercalating agents to cisplatin (cDDP)-sensitive human ovarian carcinoma cell lines and their resistant counterparts. The compounds were the complexes of Pt(II) or Pd(II) with bipyridyl (bipy) and phenanthrolyl (phen) and with four different thiourea ancillary ligands. Within each of the four series of complexes characterized by the same thiourea ligand, the Pd(phen) drugs invariably showed the highest anti-proliferative efficacy. This paralleled both a higher intracellular drug accumulation and a more efficient DNA intercalation than all the other metal-bidentate ligand combinations. The consequent inhibition of topoisomerase II activity led to the greatest inhibition of DNA metabolism, evidenced by the inhibition of the expression of the folate cycle enzymes and a marked perturbation of cell-cycle distribution in both cell lines. These findings indicate that the particular interaction of Pd(II) with phenanthroline confers the best pharmacokinetic and pharmacodynamic properties that make this class of DNA intercalators remarkable inhibitors, even of the resistant cell growth.

Phase II trial of capecitabine plus modified cisplatin (mXP) as first-line therapy in Japanese patients with metastatic gastric cancer (KSCC1104)

Purpose

Capecitabine plus cisplatin (XP) is a standard therapy for metastatic gastric cancer (mGC). However, while results from previous phase III trials suggested that the cisplatin dosage should be reduced in Japanese patients, no clinical data exist to support this. Here, we conducted a multicenter study to evaluate the efficacy and safety of modified XP (mXP) in Japanese patients with mGC.

Methods

Patients with previously untreated mGC received mXP (cisplatin 60 mg/m² on day 1 plus capecitabine 1000 mg/m² twice daily on days 1–14) every 3 weeks. The primary endpoint was the Response Evaluation Criteria in Solid Tumors-confirmed overall response rate (ORR). A sample size of 40 was planned for a threshold ORR of 30% and an expected value of 50%, with a one-sided α of 0.05 and a beta of approximately 0.2.

Results

Forty-two patients were enrolled. One patient did not fulfill the eligibility criteria; therefore, a total of 41 patients were assessed. The results were as follows: complete response in 2 patients, partial response in 16, stable disease in 14, progressive disease in 8, and no evaluation in 1. The confirmed ORR was 43.9% (95% confidence interval 28.7–59.1%). The median progression-free survival and median overall survival were 4.6 and 11.3 months, respectively. The most common grade 3 or 4 adverse events were neutropenia (37.5%), anemia (24.4%), anorexia (24.4%), and nausea (12.2%).

Conclusions

First-line chemotherapy with mXP in Japanese patients with mGC did not reach its primary objective. However, it did show a promising response rate and an acceptable tolerability profile.

5-Fluorouracil derivatives: a patent review

INTRODUCTION

The fluorinated analog of uracil 5-FU is an antimetabolite, active against a wide range of solid tumors. The main mechanism of action consists in interfering with DNA synthesis and mRNA translation. However, patients treated with 5-FU display several side effects, a result of its nonspecific cytotoxicity for tumor cells. Numerous modifications of the 5-FU structure have been performed in order to overcome these disadvantages.

AREAS COVERED

In this review, the metabolic pathways, pharmacokinetics and clinical pharmacology of 5-FU are briefly introduced. Moreover, several derivatives developed and patented, including oral 5-FU prodrugs and combinations with other active compounds, are presented. Finally, new innovative methods for administration and vehiculization of 5-FU and its derivatives are described.

EXPERT OPINION

The search for less toxic 5-FU derivatives, which diminish or circumvent some of its disadvantages, has allowed the development of selective antitumor prodrugs and novel methods for tissue-specific drug delivery. Although some of these oral prodrugs are being used clinically, either alone or in combination therapy with other anticancer agents, it seems that the potential of personalized medicine, including pharmacogenomics and targeted therapy with novel 5-FU derivatives, will improve the management and clinical responses of patients treated with 5-FU-based therapy.

A comprehensive review of S-1 in the treatment of advanced gastric adenocarcinoma

Gastric cancer is the fourth most common malignancy worldwide with Japan, Korea, Taiwan, China, Mongolia and many countries in South America and eastern Europe, as well as parts of the Middle East, contributing to the majority of cases. In the USA, it was estimated that approximately 10,620 deaths would be caused by gastric cancer in 2010. Gastric cancer is often diagnosed in its advanced stages. Current first-line treatment for advanced gastric cancer (AGC) using triplet combination chemotherapy containing a platinum-based compound, a fluoropyrimidine with an anthracycline (frequently added in Europe) or a taxane (more often used in the USA and elsewhere) has resulted in higher response rates and modest improvement in overall survival compared with doublet combinations. However, triplet combinations can be associated with increased toxicity compared with the doublets and patient selection becomes important. A desirable research strategy is to improve outcomes of patients with AGC by identifying treatments that are effective, convenient and safe. The interest in oral agents compared with intravenous agents is mounting. One oral fluoropyrimidine, S-1, is novel as it combines tegafur, 5-chloro-2,4-dihydroxypyridine and potassium oxonate. S-1 is approved in Japan, China, Taiwan, Korea and Singapore for the treatment of patients with gastric cancer, and more recently has been approved in 27 European countries to treat AGC. Initial clinical trials in the USA and Europe observed diarrhea as the dose-limiting toxicity; however, initial Japanese studies reported myelosuppression as the dose-limiting toxicity. The differing dose tolerance in these two populations is likely due to polymorphisms in the CYP2A6 gene. Based on our review of Phase II and III studies, we conclude that S-1 is a convenient oral fluoropyrimidine that provides safety advantage over intravenous fluorouracil without compromising efficacy against AGC.

Distamycin A and derivatives as synergic drugs in cisplatin-sensitive and -resistant ovarian cancer cells

Acquired resistance to cisplatin (cDDP) is a multifactorial process that represents one of the main problems in ovarian cancer therapy. Distamycin A is a minor groove DNA binder whose toxicity has limited its use and prompted the synthesis of derivatives such as NAX001 and NAX002, which have a carbamoyl moiety and different numbers of pyrrolamidine groups. Their interaction with a B-DNA model and with an extended-TATA box model, [Polyd(AT)], was investigated using isothermal titration calorimetry (ITC) to better understand their mechanism of interaction with DNA and therefore better explain their cellular effects. Distamycin A interactions with Dickerson and Poly[d(AT)(6)] oligonucleotides show a different thermodynamic with respect to NAX002. The bulkier distamycin A analogue shows a non optimal binding to DNA due to its additional pyrrolamidine group. Cellular assays performed on cDDP-sensitive and -resistant cells showed that these compounds, distamycin A in particular, affect the expression of folate cycle enzymes even at cellular level. The optimal interaction of distamycin A with DNA may account for the down-regulation of both dihydrofolate reductase (DHFR) and thymidylate synthase (TS) and the up-regulation of spermidine/spermine N1-acetyltransferase (SSAT) caused by this compound. These effects seem differently modulated by the cDDP-resistance phenotype. NAX002 which presents a lower affinity to DNA and slightly affected these enzymes, showed a synergic inhibition profile in combination with cDDP. In addition, their combination with cDDP or polyamine analogues increased cell sensitivity to the drugs suggesting that these interactions may have potential for development in the treatment of ovarian carcinoma.

MEDROXYPROGESTERONE ACETATE INDUCES C6 GLIOMA CHEMOSENSITIZATION VIA ANTIDEPRESSANT-LIKE LYSOSOMAL PHOSPHOLIPIDOSIS/MYELINOSISIN VITRO

The authors have previously shown that medroxyprogesterone acetate (MPA) inhibits growth and increases drug sensitivity in C6 glioma with myeloid bodies. Myeloid bodies can occur in cells either due to robust toxicity with mitochondrial membrane disruption or due to milder events such as seen in lysosomal-phospholipidosis. Exact patterns of myelinosis accompanying to MPA chemo-sensitization is important, because uncoupling of nuclear versus mitochondrial toxicity of anti-neoplastics by MPA would lead to safer employment of glioma chemotherapy with reduced neurotoxicity. By monitoring and comparing cell kinetics with fine structural features of cell death, the authors estimated subcellular effects accompanying growth-inhibitory drug actions in C6 glioma. The analysis revealed that MPA induced mainly lysosomal phospholipidosis, while inhibiting clonogenicity alone and augmenting procarbazine efficacy. It induced apoptosis in combination with cisplatin. It reduced mitochondrial-damage-based early cytotoxicity of methotrexate, yet it did not hinder its anti-clonogenic efficacy. Progesterone analogues - similar to antidepressants - inhibit cholesterol esterification, and this efficacy relates with their P-glycoprotein inhibition. Reducing esterification and plasma-membrane localization of cholesterol may lead MPA induction of lysosomal phospholipidosis, growth indolency, and drug sensitization in glioma.

Phase I/II and pharmacokinetic study of S-1 and oxaliplatin in previously untreated advanced gastric cancer

BACKGROUND

We aimed to determine the maximum-tolerated dose (MTD) of S-1 when given with oxaliplatin, to evaluate S-1 pharmacokinetics, and to determine the efficacy and safety of this regimen as a first-line treatment for advanced gastric cancer (AGC).

METHODS

Oxaliplatin was fixed at a dose of 130 mg/m2 on day 1 (D1). S-1 was administered from D1 to D14 of a 3-week cycle, and escalated by 10 mg/m2 per day from 70 mg/m2 per day up to 100 mg/m2 per day. Pharmacokinetic analyses were performed following a single dose of S-1 on D-5 and D1 of the first cycle.

RESULTS

In phase I (n=18), MTD was not defined. In phase II (n=47) with the planned maximum dose, partial response was achieved in 26 patients (55.3%) and stable disease in 14 patients (29.8%). The median time to progression was 6.6 months (95% CI 4.0-9.2 months) and the median overall survival was 12.5 months (95% CI 9.2-15.9 months). Frequent grade 3/4 toxicities included thrombocytopenia (39%), neutropenia (28%), anemia (17%), and leukopenia (13%). There was one grade 5 febrile neutropenia during the first cycle.

CONCLUSIONS

The pharmacokinetics of S-1 was not influenced by oxaliplatin. S-1/Oxaliplatin combination therapy is highly active against AGC and has a favorable toxicity profile.

S-1: a promising new oral fluoropyrimidine derivative

S-1 is an oral fluoropyrimidine that is designed to improve the antitumor activity of 5-fluorouracil (5-FU) concomitantly with an intent to reduce its toxicity. S-1 consists of tegafur, a prodrug of 5-FU combined with two 5-FU biochemical modulators:5-chloro-2,4-dihydroxypyridine (gimeracil or CDHP), a competitive inhibitor of dihydropyrimidine dehydrogenase and oteracil potassium which inhibits phosphorylation of 5-FU in the gastrointestinal tract decreasing serious gastrointestinal toxicities,including nausea, vomiting, stomatitis and diarrhea. Being an oral agent, S-1 offers convenience of administration and prevents complications of central venous access such as infection, thrombosis and bleeding. S-1 has shown efficacy in both gastrointestinal as well non-gastrointestinal malignancies. The authors review the current literature and provide their expert opinion on the incorporation of S-1 in the treatment of solid malignancies [corrected].

Development history and concept of an oral anticancer agent S-1 (TS-1): its clinical usefulness and future vistas

Dushinsky et al. left a great gift to human beings with the discovery of 5-fluorouracil (5-FU). Approximately 50 years have elapsed from that discovery to the development of S-1 (TS-1^®). The concept of developing an anticancer agent that simultaneously possesses both efficacy-enhancing and adverse reaction-reducing effects could be achieved only with a three-component combination drug. S-1 is an oral anticancer agent containing two biochemical modulators for 5-FU and tegafur (FT), a metabolically activated prodrug of 5-FU. The first modulator, 5-chloro-2,4-dihydroxypyridine (CDHP), enhances the pharmacological actions of 5-FU by potently inhibiting its degradation. The second modulator, potassium oxonate (Oxo), localizing in mucosal cells of the gastrointestinal (GI) tract after oral administration, reduces the incidence of GI toxicities by suppressing the activation of 5-FU in the GI tract. Thus, S-1 combines FT, CDHP and Oxo at a molar ratio of 1:0.4:1. In 1999–2007, S-1 was approved for the treatment of the following seven cancers: gastric, head and neck, colorectal, non-small cell lung, breast, pancreatic and biliary tract cancers. ‘S-1 and low-dose cisplatin therapy’ without provoking Grade 3 non-hematologic toxicities was proposed to enhance its clinical usefulness. Furthermore, ‘alternate-day S-1 regimen’ may improve the dosing schedule for 5-FU by utilizing its strongly time-dependent mode of action; the former is characterized by the low incidences of myelotoxicity and non-hematologic toxicities (e.g. ≤Grade 1 anorexia, fatigue, stomatitis, nausea, vomiting and taste alteration). These two approaches are considered to allow long-lasting therapy with S-1.

Capecitabine in the treatment of advanced gastric cancer

Although the role of systemic chemotherapy has been established for the treatment of advanced gastric cancer, the prognosis of these patients remains poor, with a median overall survival of less than 1 year. Based on the results of several randomized Phase III trials, 5-fluorouracil continuous infusion plus cisplatin, with or without epirubicin, has become the global reference regimen for this patient population. However, treatment with fluorouracil infusion requires either frequent hospitalizations or the use of a central venous access device, harboring potential complications. Capecitabine, a tumor-activating oral prodrug of fluorouracil, may be more advantageous in terms of patient convenience, safety and efficacy. Two recent randomized Phase III trials have shown that capecitabine could replace infusional fluorouracil in cisplatin-based regimens. Furthermore, Phase II trials have shown that many other capecitabine-based doublet or triplet chemotherapy regimens incorporating newer cytotoxic agents are active and well tolerated. Many promising biological agents are now being tested in Phase III trials, incorporating capecitabine combinations as control arms, in patients with advanced gastric cancer.

Phase I/II study of 3-week combination of S-1 and cisplatin chemotherapy for metastatic or recurrent gastric cancer

PURPOSE

To define the maximum-tolerated dose (MTD) of S-1, given daily for 2 weeks followed by a 1-week rest, with a fixed dose of cisplatin on the initial day, and to determine the activity and safety of this regimen at the recommended dose (RD) when used as first line treatment of advanced gastric cancer (AGC).

PATIENTS AND METHODS

Cisplatin was fixed at a dose of 60 mg/m2 on day 1 (D1) and the starting dose of S-1 was 60 mg/m2/day (30 mg/m2 bid) (level I) on D1 to D14, every 3 weeks. The dose of S-1 was increased by 5 mg/m2 bid up to 100 mg/m2/day (level V) unless the MTD was achieved.

RESULTS

Sixty-two eligible patients were enrolled. MTD was set at level V with two of three patients developing grade 3 diarrhea or febrile neutropenia. The RD was determined at level IV (90 mg/m2/day). After the first 20 patients were enrolled in phase II, the protocol was amended; the S-1 dose was reduced to 80 mg/m2/day (N=23) because of poor bone marrow recovery. The objective response was observed in 20 of 42 evaluable patients (48%). SD was achieved in 15 (36%). The median PFS was 5.3 months (95% CI, 4.6-6.0 months) with a median OS of 10.0 months (95% CI, 5.1-14.8 months). Grade 3-4 toxicities included neutropenia (33%), anemia (31%), and anorexia (24%).

CONCLUSIONS

The 3-week combination of cisplatin plus S-1 is active against AGC with favorable toxicitiy profiles. The phase II schedule or doses may need further refinements.

Anti-tumor activity of heptaplatin in combination with 5-fluorouracil or paclitaxel against human head and neck cancer cells in vitro

Heptaplatin (HTP), a newly developed platinum analog, has been approved for the treatment of gastric cancers in South Korea. In this study we explored the potential of HTP for the treatment of head and neck squamous cell cancers (HNSCC). The anti-proliferative activity of HTP was evaluated in FaDu, a human HNSCC cell line. Combinations of HTP with 5-fluorouracil (5-FU) or paclitaxel (PTX) were determined using combination indexes, and were compared with combinations of cisplatin and 5-FU or PTX. In order to evaluate the transport of HTP into tumor tissue, its penetration through multicell layers (MCLs) of cancer cells was measured. Cisplatin+5-FU and HTP+5-FU showed additive to antagonistic interactions. In terms of the HTP+paclitaxel combination, HTP showed antagonism and additivity at the 50 and 80% growth inhibition levels, respectively. An additive interaction was obtained and apoptosis was increased by 2-fold at both inhibition levels when the combinatorial PTX dose was reduced to 1/10. HTP, but not cisplatin or oxaliplatin (L-OHP), maintained its anti-proliferative activity after MCL penetration at clinically relevant concentrations, which can be attributed to lower protein binding of HTP. In conclusion, the present study suggests that low-dose PTX may sensitize tumor cells to HTP. HTP also showed greater penetration through multilayers of tumor cells compared to cisplatin and L-OHP, which may be an important characteristic for solid tumor treatment. Overall, the present study supports the clinical development of HTP in combination with low-dose PTX against HNSCC.

Effect of combination of TS-1 and low-dose cisplatin on sarcoma-180 mouse sarcoma

TS-1 contains tegaful (FT), 5-chloro-2,4-dihydroxypyridine (CDHP; an inhibitor of 5-fluorouracil (5-FU) degradation) and potassium oxonate (Oxo; an inhibitor of 5-FU assimilation mainly in the digestive tract) in a molar ratio of 1:0.4:1. We evaluated the combination of TS-1 and low-dose cisplatin on mouse sarcoma. Male ddy strain mice at 6 weeks of age were s.c. transplanted with 5 x 106 sarcoma-180 (S-1800) cells and divided into groups of seven animals each: Group A, no treatment; Group B, 5-FU alone by continuous i.p. infusion of 10 mg/kg with a minipump (Alzet); Group C, TS-1 10 mg/kg p.o. alone; Group D, cisplatin 0.2 mg/kg i.p. alone; Group E, B+D; Group F, C+D. Treatment was given for 5 days. Antitumor activity was evaluated on the basis of the tumor weight on day 8, and white blood cell count, red blood cell count, platelet count, BUN, GOT and GPT were determined to detect adverse effects. Tumor weights (g, mean+/-SD) were 0.54+/-0.15 in Group A, 0.52+/-0.17 in Group B, 0.34+/-0.05 in Group C, 0.46+/-0.12 in Group D, 0.34+/-0.07 in Group E and 0.16+/-0.03 in Group F. There were no noticeable adverse effects. The combined TS-1+cisplatin regimen showed considerably enhanced antitumor activities since sarcomas were significantly (p<0.05) decreased as compared with tissue. Mean AUC(0-12) (ng/ml.h) estimated in the groups receiving 5-FU+cisplatin or TS-1 alone was measured to calculate AUC(0-12) by the trapezoidal rule. 5-FU concentrations in blood and tumor from blood concentration data were 435 in Group B, 2651 in Group C, 343 in Group E and 1538 in Group F, while mean AUC(0-12) (ng/g.h) estimated from tumor tissue concentration data were 345 in Group B, 3548 in Group C, 324 in Group E and 2020 in Group F. Cisplatin acted as a modulator of 5-FU, suggesting clinical benefits of the combination of TS-1 and low-dose daily cisplatin.

Relation between intracellular accumulation and cytotoxic activity of cis-[((1R, 2R)-1, 2-cyclohexanediamine-N, N')bis(myristato)]platinum(II) suspended in Lipiodol

SM-11355, cis-[((1R, 2R)-1, 2-cyclohexanediamine-N, N')bis(myristato)]platinum(II), suspended in Lipiodol (SM-11355/Lipiodol) showed cytotoxic activity in hepatic tumor models in vivo and tumor cell lines in vitro. SM-11355/Lipiodol demonstrated selective retention in tumor tissue in vivo and high accumulation in tumor cells in vitro. This study was aimed to clarify the relation between the cytotoxicity of SM-11355/Lipiodol and intracellular platinum content. The cytotoxic activities were estimated by using WST-1 reagent. Intracellular platinum content and platinum-DNA adduct were estimated following exposure with SM-11355/Lipiodol when methionine was added. Methionine clearly inhibited the cytotoxic activities of SM-11355/Lipiodol. Moreover, intracellular platinum content and platinum-DNA adduct following exposure of SM-11355/Lipiodol decreased with increases in methionine concentration. The characteristic release of SM-11355/Lipiodol was not affected by addition of methionine. The present results suggested that one of platinum compounds exposed to cells following SM-11355/Lipiodol treatment is very similar in cytotoxic mechanism to cisplatin.

Intermittent FLDP: 24-h infusion of 5-FU on days 1, 3 and 5 combined with low-dose cisplatin on days 1-5 for gastric cancer, and its pharmacologic and kinetic rationale

PURPOSE

To improve the therapeutic efficacy and minimize the toxicity of 5-fluorouracil (5-FU), intermittent therapy consisting of alternate 24-h intravenous infusion and based on differences in generation time (T(G)) between normal cells and tumor cells was investigated.

METHODS

Two human gastric cancer cell lines MKN-7 and MKN-74 with T(G) of 35 h and 17 h, respectively, were used in an in vitro cytotoxic assay. The drug exposure schedule consisted of a continuous 144-h exposure and alternate 24-h exposures. In a clinical trial, a total of 23 patients with advanced or recurrent gastric cancer were treated with intermittent therapy consisting of 24-h intravenous infusion with 5-FU 700 mg/m(2) per day on days 1, 3 and 5 in combination with low-dose cisplatin (CDDP) at 3.3 mg/m(2) per day on days 1 to 5. One cycle of the combined chemotherapy lasted for four consecutive weeks, followed by withdrawal over 1-2 weeks. Plasma 5-FU concentrations were measured by high-performance liquid chromatography in 15 patients and dihydropyrimidine dehydrogenase (DPD) activity in peripheral blood mononuclear cells (PBMC) was measured in 13 patients.

RESULTS

The in vitro study revealed no statistically significant difference in cytotoxicity of 5-FU between the two drug exposure schedules in MKN-7 cells. In MKN-74 cells, however, a statistically significant decrease in cytotoxicity was found with the alternate 24-h exposure. In a clinical trial, plasma 5-FU concentrations showed a trapezoidal pattern. There was a significant correlation between DPD activity in PBMC and total body clearance of 5-FU. There were eight partial responders (8/22, 36%). Toxicities were very mild in severity, with no grade 3 or 4 toxicity. In particular, diarrhea and stomatitis were infrequent (one patient), and none of the patients developed thrombocytopenia.

CONCLUSIONS

Toxicities which may be observed in rapidly growing cells such as bone marrow cells and gastrointestinal epithelial cells following continuous intravenous infusion of 5-FU seemed to be reduced by intermittent therapy of 5-FU consisting of alternate 24-h intravenous infusions.

Clinical studies of three oral prodrugs of 5-fluorouracil (capecitabine, UFT, S-1): a review

Although 5-fluorouracil (5-FU) was first introduced in 1957, it remains an essential part of the treatment of a wide range of solid tumors. 5-FU has antitumor activity against epithelial malignancies arising in the gastrointestinal tract and breast as well as the head and neck, with single-agent response rates of only 10%-30%. Although 5-FU is still the most widely prescribed agent for the treatment of colorectal cancer, less than one-third of patients achieve objective responses. Recent research has focused on the biomodulation of 5-FU to improve the cytotoxicity and therapeutic effectiveness of this drug in the treatment of advanced disease. As all the anticancer agents, 5-FU leads to several toxicities. The toxicity profile of 5-FU is schedule dependent. Myelotoxicity is the major toxic effect in patients receiving bolus doses. Hand-foot syndrome (palmar-plantar erythrodysesthesia), stomatitis, and neuro- and cardiotoxicities are associated with continuous infusions. Other adverse effects associated with both bolus-dose and continuous-infusion regimens include nausea and vomiting, diarrhea, alopecia, and dermatitis. All these reasons explain the need for more effective and less toxic fluoropyrimidines. In the first part of this review, we briefly present the metabolic pathways of 5-FU responsible for the efficacy and toxicity of this drug. This knowledge is also necessary to understand the target(s) of biomodulation. The second part is devoted to a review of the literature on three recent prodrugs of 5-FU, i.e., capecitabine, UFT (ftorafur [FTO] plus uracil), and S-1 (FTO plus 5-chloro-2,4-dihydroxypyridine plus potassium oxonate). The pharmacological principles that have influenced the development of these new drugs and our current knowledge of the clinical pharmacology of these new agents, focusing on antitumor activity and toxicity, are presented. The literature was analyzed until March 2002. This review is intended to be as exhaustive as possible since it was conceived as a work tool for readers wanting to go further.