Novel prodrugs of tegafur that display improved anticancer activity and antiangiogenic properties.

New and more potent prodrugs of the 5-fluorouracyl family derived by hydroxymethylation or acyloxymethylation of 5-fluoro-1-(tetrahydro-2-furanyl)-2,4(1H,3H)-pyrimidinedione (tegafur, 1) are described. The anticancer activity of the butyroyloxymethyl-tegafur derivative 3 and not that of tegafur was attenuated by the antioxidant N-acetylcysteine, suggesting that the increased activity of the prodrug is in part mediated by an increase of reactive oxygen species. Compound 3 in an in vitro matrigel assay was found to be a more potent antiangiogenic agent than tegafur. In vivo 3 was significantly more potent than tegafur in inhibiting 4T1 breast carcinoma lung metastases and growth of HT-29 human colon carcinoma tumors in a mouse xenograft. In summary, the multifunctional prodrugs of tegafur display selectivity toward cancer cells, antiangiogenic activity, and anticancer activities in vitro and in vivo, superior to those of tegafur. 5-fluoro-1-(tetrahydro-2-furanyl)-2,4(1 H,3 H)-pyrimidinedione (tegafur, 1), the oral prodrug of 5-FU, has been widely used for treatment of gastrointestinal malignancies with modest efficacy. The aim of this study was to develop and characterize new and more potent prodrugs of the 5-FU family derived by hydroxymethylation or acyloxymethylation of tegafur. Comparison between the effect of tegafur and the new prodrugs on the viability of a variety of cancer cell lines showed that the IC50 and IC90 values of the novel prodrugs were 5-10-fold lower than those of tegafur. While significant differences between the IC50 values of tegafur were observed between the sensitive HT-29 and the resistant LS-1034 colon cancer cell lines, the prodrugs affected them to a similar degree, suggesting that they overcame drug resistance. The increased potency of the prodrugs could be attributed to the antiproliferative contribution imparted by formaldehyde and butyric acid, released upon metabolic degradation. The anticancer activity of the butyroyloxymethyl-tegafur derivative 3 and not that of tegafur was attenuated by the antioxidant N-acetylcysteine, suggesting that the increased activity of the prodrug is in part mediated by an increase of reactive oxygen species. Compound 3 in an in vitro matrigel assay was found to be a more potent antiangiogenic agent than tegafur. In vivo 3 was significantly more potent than tegafur in inhibiting 4T1 breast carcinoma lung metastases and growth of HT-29 human colon carcinoma tumors in a mouse xenograft. In summary, the multifunctional prodrugs of tegafur display selectivity toward cancer cells, antiangiogenic activity and anticancer activities in vitro and in vivo, superior to those of tegafur.

Synthesis and cytotoxicity of novel fatty acid-nucleoside conjugates.

N(3)-Hydroxyethyltegafur (3) was synthesized in 91.0% yield under a new condition. A series of novel fatty acid esters of 3 were synthesized. These fatty acid-nucleoside conjugates have shown cytotoxicities against Ec9706 cells and A549 cells, and the structure activity relationship was discussed.

[Synthesis and antitumor activity of selenophosphocholine analogues containing tegafur].

AIM: To synthesize the selenophosphocholine analogues containing tegafur and test their antitumor activities. METHODS: The cyclic glyceroselenophospholopid conjugate of tegafur was synthesized by the reaction of hexaethylphosphorous triamide with N1-(2-furanidyl)-N3-(hydroxyalkyl)-5-fluyorouracil and 1-O-hexadecyl glycerol as well as selenium in one-pot. Cyclic glyceroselenophospholopid conjugate of tegafur reacted with triethylamine to give title compounds. RESULTS: Six new compounds have been synthesized. Their structures were confirmed by 1H NMR, 13P NMR and elemental analysis. Antitumor activity of the title compounds against PGA1 was tested. CONCLUSION: The reaction of triethylamine with cyclic glyceroselenophospholopid conjugate of tegafur very readily occurred, which was finished within 2 h at room temperature. The opening-ring products of trans isomers showed antimutor activity against human uriaryl bladder cancer cell more effective than that of the tegafur.

Prevention of peritoneal metastasis of human gastric cancer cells in nude mice by S-1, a novel oral derivative of 5-Fluorouracil.

OBJECTIVE: Recent clinical trials have suggested that oral administration of a new anti-cancer agent, S-1, seems a promising therapy for advanced gastric cancer. In this study, we assessed the efficacy of S-1 against peritoneal dissemination of gastric cancer in a newly developed animal model and investigated the efficacy of S-1 from a pharmacokinetic angle. METHODS: Human gastric cancer cells (MKN-45) were injected into the peritoneal cavity of nude mice. The cancer cells were transduced using an enhanced green fluorescent protein (EGFP)-expressing plasmid vector, enabling micrometastatic foci to be accurately assessed with a high level of detection sensitivity. To investigate pharmacokinetics, the concentration of 5-FU was determined in tumor, peritoneum and plasma. RESULTS: Fourteen and 21 days after intraperitoneal injection, a significant difference in the number of fluorescent foci was observed between the control group and the S-1 group (p = 0.02 and p = 0.0024, respectively. The therapeutic effect of S-1 was significantly greater than that of 5-FU. Furthermore, S-1 treatment greatly improved the survival time and cachexia. The area under the curve of 5-FU in tumor was higher than in the peritoneum and plasma. CONCLUSION: Oral S-1 is a promising chemotherapy for peritoneal dissemination of gastric cancer.

Synthesis, structure, and conformation of anti-tumor agents in the solid and solution states: hydroxyl derivatives of Ftorafur.

The pyrimidine antimetabolite Ftorafur [FT; 5-fluoro-1-(tetrahydro-2-furyl)uracil] has shown significant antitumor activity in several adenocarcinomas with a spectrum of activity similar to, but less toxic than, 5-fluorouracil (5-FU). It is considered as a prodrug that acts as a depot form of 5-FU, and hence the two drugs exhibit a similar spectrum of chemotherapeutic activity. Ftorafur is metabolized in animals and humans when hydroxyl groups are introduced into the tetrahydrofuran moiety. These metabolites are also thought to be as active as ftorafur but less toxic than 5-FU. Hydroxyl derivatives: 2'-hydroxyftorafur (III), 3'-hydroxyftorafur (IV) and 2',3'-dihydroxyftorafur (II) were synthesized and X-ray and NMR studies of these hydroxyl derivatives were undertaken in our laboratories to study the structural and conformational features of Ftorafur and its metabolites in the solid and solution states. X-ray crystallographic investigations were carried out with data collected on a CAD-4 diffractometer. The structures were solved and refined using the SDP crystallographic package of Enraf-Nonius on PDP 11/34 and Microvax computers. All of the compounds studied had the base in the anti conformation. The glycosidic torsion angles varied from -20 to 60 degrees. There is an inverse correlation between the glycosyl bond distances and the chi angle. Molecules with a lower chi angle have a larger bond distance and vice versa. The sugar rings show a wide variation of conformations ranging from C2'-endo through C3'-endo to C4'-exo. The crystal structures are stabilized by hydrogen bonds involving the base nitrogen atom N3 and the hydroxyl oxygen atoms of the sugar rings as donors and the keto oxygens O2 and O4 of the base and the hydroxyl oxygen atoms O2' and O3' as acceptors. The NMR studies were carried out on Brüker 400 and 600 MHz instruments. Simulated proton spectra were obtained through Laocoon, and pseudorotational parameters were solved by Pseurot. Presence of syn or anti forms was demonstrated with the use of NOE experiments. The glycosyl conformations in solution vary more widely than in the solid state. The conformations of the sugar molecules are in agreement with the values obtained in the solid state. The studies of the structure and conformation in the solid and solution states give a model for the Ftorafur molecule that could be used in structure, function and biological activity correlation studies.

Synthesis and biological activities of ftorafur metabolites. 3'- and 4'-hydroxyftorafur.

Four isomers of ftorafur were synthesized as authentic samples of possible ftorafur (FT) metabolites. 2,3-Dihydrofuran was treated with perbenzoic acid in MeOH to give 2-methoxy-3-hydroxytetrahydrofuran, which upon treatment with Ac2O/pyridine yielded the key intermediate 2-methoxy-3-acetoxytetrahydrofuran. The other intermediate, 2-ethoxy-4-acetoxytetrahydrofuran, was prepared by acid hydrolysis (HCl/50% EtOH) of 1,1-diethoxy-3,4-dihydroxybutane, followed by acetylation (Ac2O/pyridine). Treatment of 2,4-bis(trimethylsilyl)-5-fluorouracil with either 2-methoxy-3-acetoxytetrahydrofuran or 2-ethoxy-4-acetoxytetrahydrofuran in 1,2-dichloroethane at room temperature using SnCl4 as catalyst afforded cis- and trans-3'-OAc-FT or 4'-OAc-FT, respectively. However, trans-3'-OAc-FT and cis-4'-OAc-FT were the major condensation products. In each case, separation of these cis and trans isomers was achieved by silica gel column chromatography. Treatment of 3'- or 4'-OAc-FT with NH3/CH3OH at 5 degrees C overnight yielded the described hydroxylated FT. Both trans-3'-OH-FT and cis-4'-OH-FT showed no significant activity against L1210 up to 100 mg/kg. These two agents produced an inhibitory effect on HeLa cell growth equal to that of ftorafur, with ID50 = 200 MICROGRAMS/KG.

Studies on antitumor agents, 2. Syntheses and antitumor activities of 1-(tetrahydro-2-furanyl)-5-fluorouracil and 1,3-bis(tetrahydro-2-furanyl)-5-fluorouracil.

Convenient and efficient methods were developed for preparing 1-(tetrahydro-2-furanyl)-5-fluorouracil (Thf-FU, 3) [trade name, Futraful (Ftorafur) or FT-207], which is used clinically as an antitumor agent, and 1,3-bis(tetrahydro-2-furanyl)-5-fluorouracil (Thf2-FU, 4). For the syntheses, 2,4-bis(trimethylsily)-5-fluorouracil (Me3Si-FU, 1) and 2-acetoxytetrahydrofuran (Thf-OAc, 2) were condensed in the presence of Friedel-Crafts catalysts, such as SnCl4 and BF3-Et2O in dichloromethane, or in the presence of NaI in acetonitrile to give Thf-Fu or Thf2-FU depending on the reaction conditions and workup procedure. A trace of 3-(tetrahydro-2-furanyl)-5-fluorouracil (3-Thf-FU, 5) was formed in these reactions. Thf2-FU was easily hydrolyzed to Thf-FU. 2-Methoxytetrahydrofuran can be used instead of Thf-OAc for preparation of Thf-FU under similar conditions. The optimal ratios of Me3Si-FU, Thf-OAc, and SnCl4 or NaI for preparation of Thf-FU and Thf2-FU were determined. In all cases, 2-2.5 equiv of Thf-OAc with respect to Me3Si-FU gave the best results. The yields of Thf-FU and more especially of Thf2-FU were greatly dependent on the relative amount of SnCl4, and 0.01-0.1 equiv of the catalyst with respect to Me3Si-FU gave the best results. Thf2-FU was found to be effective against murine solid tumors and it was less toxic than Thf-FU when given orally. The antitumor activity of 3-Thf-FU is also reported.

Studies of antitumor agents. 1. Resolution of racemic 1-(tetrahydro-2-furanyl)-k-fluorouracil into the R and S isomers and examination of the biological activities of the isomers.

1-(Tetrahydro-2-furanyl)-5-fluorouracil (Thf-FU), which is named Ftorafur or FT-207 and is used clinically as an antitumor agent, was conveniently synthesized by condensation of the trimethylsilyl derivative of 5-fluorouracil with 2-acetoxytetrahydrofuran using NaI as a catalyst. This optically inactive Thf-FU was resolved into optically active (R)-(+)- and (S)-(-)-Thf-FU in high optical purity and excellent yield by formation of diastereoisomers with brucine. 13C NMR data were obtained on Thf-FU and related compounds and the antibacterial activities and in vivo antitumor activities of these isomers were tested. The degradations of these isomers to 5-fluorouracil by liver microsomes were also examined. No significant differences were found in any of these properties of these isomers.