Design of a novel oral fluoropyrimidine carbamate, capecitabine, which generates 5-fluorouracil selectively in tumours by enzymes concentrated in human liver and cancer tissue

Capecitabine (N4-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) is a novel oral fluoropyrimidine carbamate, which is converted to 5-fluorouracil (5-FU) selectively in tumours through a cascade of three enzymes. The present study investigated tissue localisation of the three enzymes in humans, which was helpful for us to design the compound. Carboxylesterase was almost exclusively located in the liver and hepatoma, but not in other tumours and normal tissue adjacent to the tumours. Cytidine (Cyd) deaminase was located in high concentrations in the liver and various types of solid tumours. Finally, thymidine phosphorylase (dThdPase) was also more concentrated in various types of tumour tissues than in normal tissues. These unique tissue localisation patterns enabled us to design capecitabine. Oral capecitabine would pass intact through the intestinal tract, but would be converted first by carboxylesterase to 5'-deoxy-5-fluorocytidine (5'-dFCyd) in the liver, then by Cyd deaminase to 5'-deoxy-5-fluorouridine (5'-dFUrd) in the liver and tumour tissues and finally by dThdPase to 5-FU in tumours. In cultures of human cancer cell lines, the highest level of cytotoxicity was shown by 5-FU itself, followed by 5'-dFUrd. Capecitabine and 5'-dFCyd had weak cytotoxic activity only at high concentrations. The cytotoxicity of the intermediate metabolites 5'-dFCyd and 5'-dFCyd was suppressed by inhibitors of Cyd deaminase and dThdPase, respectively, indicating that these metabolites become effective only after their conversion to 5-FU. Capecitabine, which is finally converted to 5-FU by dThdPase in tumours, should be much safer and more effective than 5-FU, and this was indeed the case in the HCT116 human colon cancer and the MX-1 breast cancer xenograft models.

Antipicornavirus flavone Ro 09-0179

Ro 09-0179 (4',5-dihydroxy-3,3',7-trimethoxyflavone), isolated from a Chinese medicinal herb, was found to have potent antiviral activity. It selectively inhibited the replication of human picornaviruses, such as rhinoviruses and coxsackieviruses in tissue culture, but not other DNA and RNA viruses. Ro 09-0298 (4',5-diacetyloxy-3,3',7-trimethoxyflavone), an orally active derivative of Ro 09-0179, prevented coxsackievirus (B1) infection in mice. The critical time for the inhibition of rhinovirus replication by Ro 09-0179 was 2 to 4 h after virus adsorption, i.e., in the early stages of virus replication. It markedly inhibited coxsackievirus and rhinovirus RNA synthesis in infected HeLa cells, but not in a cell-free system using the RNA polymerase complex isolated from the infected cells. In the infected cells, the RNA polymerase complex was not formed in the presence of Ro 09-0179. Therefore, it is suggested that Ro 09-0179 interferes with some process of viral replication which occurs between viral uncoating and the initiation of viral RNA synthesis.

The design and synthesis of a new tumor-selective fluoropyrimidine carbamate, capecitabine

To identify an orally available fluoropyrimidine having efficacy and safety profiles greatly improved over those of parenteral 5-fluorouracil (5-FU: 1), we designed a 5-FU prodrug that would pass intact through the intestinal mucisa and be sequentially converted to 5-FU by enzymes that are highly expressed in the human liver and then in tumors. Among various N4-substituted 5'-deoxy-5-fluorocytidine derivatives, a series of N4-alkoxycarbonyl derivatives were hydrolyzed to 5'-deoxy-5-fluorocytidine (5'-DFCR: 8) specifically by carboxylesterase, which exists preferentially in the liver in humans and monkeys. Particularly, derivatives having an N4-alkoxylcarbonyl moiety with a C4-C6 alkyl chain were the most susceptible to the human carboxylesterase. Those were then converted to 5'-deoxy-5-fluorouridine (5'-DFUR: 4) by cytidine deaminase highly expressed in the liver and solid tumors and finally to 5-FU by thymidine phosphorylase (dThdPase) preferentially located in tumors. When administered orally to monkeys, a derivative having the N4-alkoxylcarbonyl moiety with a C5 alkyl chain (capecitabine: 6) The highest AUC and Cmax for plasma 5'-DFUR. In tests with various human cancer xenograft models, capecitabine was more efficacious at wider dose ranges than either 5-FU or 5'-DFUR and was significantly less toxic to the intestinal tract than the others in monkeys.

Antivirus agent, Ro 09-0410, binds to rhinovirus specifically and stabilizes the virus conformation

The antiviral mechanisms of Ro 09-0410 (4'-ethoxy-2'-hydroxy-4,6'-dimethoxychalcone), which inactivates rhinovirus exclusively, have been investigated. It was suggested that Ro 09-0410 bound to human rhinovirus type 2 (HRV-2) and made it inactive, since the reduced infectivity was completely restored to original levels by extraction of the agent with chloroform [H. Ishitsuka, Y. Ninomiya, C. Ohsawa, M. Fujiu, and Y. Suhara (1982) Antimicrob. Agents Chemother. 22, 617-621]. This was confirmed using radioactively labeled Ro 09-0410 and HRV-2. HRV-2 was inactive while bound to the agent, whereas a subline of HRV-2 resistant to the agent had no binding site for the agent. Ro 09-0410 appeared to bind to some specific site(s) on the virion of susceptible virus strains. Treatment of rhinovirus at pH 5 or 56 degrees caused a change of the virion size and greatly reduced its infectivity. Ro 09-0410 could no longer bind to HRV-2 after such treatment. On the other hand, when the virion bound with Ro 09-0410 was treated at pH 5 or 56 degrees, the Ro 09-0410 remained bound and the conformational alteration of the virion did not take place. Furthermore, Ro 09-0410 protected HRV-2 from the reduction of infectivity caused by mild acid or heat treatment, as revealed by infectivity measurements after extraction of the agent with chloroform. These results suggest that Ro 09-0410 binds to the HRV-2 virion and prevents viral replication in the cell.

Synthesis and structure-activity relationships of novel fungal chitin synthase inhibitors

A novel Candida albicans chitin synthase 1 (CaChs1) inhibitor, RO-41-0986 (1) was discovered by random screening. Systematic modification led to the identification of a highly potent CaChs1 inhibitor, RO-09-3024 (2), having strong antifungal activity against Candida spp. in vitro.

Comparative antitumor activity and intestinal toxicity of 5'-deoxy-5-fluorouridine and its prodrug trimethoxybenzoyl-5'-deoxy-5-fluorocytidine

N4-Trimethoxybenzoyl-5'-deoxy-5-fluorocytidine (Ro 09-1390), a prodrug of the cytostatic 5'-deoxy-5-fluorouridine (5'-DFUR), was synthesized with the aim of reducing of the dose-limiting toxicity of 5'-DFUR, which is diarrhea. In mice bearing Lewis lung carcinoma, 5'-DFUR given po produced a substantial amount of 5-fluorouracil (5-FU) in the intestinal tract as well as tumors, where the enzyme pyrimidine nucleoside phosphorylase, essential for conversion of 5'-DFUR to 5-FU, is predominantly located. With the oral administration of Ro 09-1390 only a small amount of 5-FU was formed in the intestine; however, the administration of Ro 09-1390 and 5'-DFUR at the same dose produced similar amounts of 5-FU in tumor tissues. These differences in metabolism were reflected in their toxicity and antitumor efficacy. The administration of 5'-DFUR resulted in damage to the intestinal mucosal membrane and diarrhea in normal mice, whereas Ro 09-1390 was much less toxic to the intestinal tract. As regards antitumor activity, Ro 09-1390 and 5'-DFUR at equivalent doses inhibited the growth of Lewis lung carcinoma to similar extents. Since Ro 09-1390 was much less toxic to the intestinal tract than 5'-DFUR, mice bearing Lewis lung carcinoma could be given Ro 09-1390 daily over a longer period and at a higher dose, resulting in a longer survival time.

New alpha-amylase inhibitor, trestatins. II. Structure determination of trestatins A, B and C

The structures of trestatins A (C56H94N2O40), B (C37H63NO28) and C (C75H125N3O52), new basic oligosaccharides with potent inhibitory activity against various alpha-amylases, have been shown by spectroscopic and chemical methods to be 1, 2 and 3, respectively.

Determination of felodipine and its metabolites in plasma using capillary gas chromatography with electron-capture detection and their identification by gas chromatography-mass spectrometry

A novel method for the determination of felodipine and its metabolites in plasma by capillary gas chromatography (GC) with electron capture detection was developed. Felodipine and its oxidized metabolite were assayed by capillary GC after solid-phase extraction with the aid of a cool on-column injection technique. Acid metabolites, methyl monoacid and ethyl monoacid and diacid, were extracted with diethyl ether and propylated with 1-n-propyl-3-p-tolyltriazene before being submitted to capillary GC. These methods were very sensitive and useful for the pharmacokinetic study of felodipine. Felodipine and its metabolites were identified by GC-mass spectrometry. The mass spectral patterns of the peaks of extracts from human plasma samples after oral administration of felodipine were in good agreement with those of reference compounds.

Enzyme immunoassay discrimination of a new angiotensin-converting enzyme (ACE) inhibitor, cilazapril, and its active metabolite

Simple and sensitive enzyme immunoassays (EIAs), discriminating a new angiotensin-converting enzyme (ACE) inhibitor, cilazapril [9(s) - [1(s)-(ethoxycarbonyl)-3-phenylpropylamino]-octahydro-10-oxo-6H- pyridazo[1,2-a] [1,2]diazepine-1(s)carboxylic acid] and its active metabolite [9(s)-[1(s)-carboxy-3-phenylpropylamino]-octahydro-10-oxo-6H- pyridazo[1,2-a][1,2]diazepine-1(s)carboxylic acid] were developed for pharmacokinetic studies of this drug which is used as an antihypertensive agent. These assays can be performed directly on serum or plasma specimens without pretreatment. The EIA for cilazapril (prodrug) allowed the determination of as little as 30 pg/mL, while a 1000-times greater concentration of its active metabolite was required to achieve the same extent of inhibition. The EIA for the active metabolite exhibited a sensitivity and specificity similar to those of the prodrug. Plasma specimens from a human volunteer study and a marmoset subacute toxicity study were assayed by these two newly developed EIAs. The plasma levels of active metabolite determined by the EIA were compared with those assayed by radioenzymatic assay, and a good correlation was observed between them.

Role of cations in the flocculation of Saccharomyces cerevisiae and discrimination of the corresponding proteins

Asexual yeast flocculation was studied using strong flocculents of Saccharomyces cerevisiae. The inhibitory effect of cations on flocculation is considered to be caused by competition between those cations and Ca2+ at the binding site of the Ca(2+)-requiring protein that is involved in flocculation. Inhibition of flocculation by various cations occurred in the following order: La3+, Sr2+, Ba2+, Mn2+, Al3+, and Na+. Cations such as Mg2+, Co2+, and K+ promoted flocculation. This promoting effect may be based on the reduction of electrostatic repulsive force between cells caused by binding of these cations anionic groups present on the cell surface. In flocculation induced by these cations, trace amounts of Ca2+ excreted on the cell surface may activate the corresponding protein. The ratio of Sr2+/Ca2+ below which cells flocculated varied among strains: for strains having the FLO5 gene, it was 400 to 500; for strains having the FLO1 gene, about 150; and for two alcohol yeast strains, 40 to 50. This suggests that there are several different types of cell surface proteins involved in flocculation in different yeast strains.

Synthesis and structure-activity relationships of a novel antifungal agent, azoxybacilin

A new antifungal substance, azoxybacilin (an unusual amino acid with an azoxy moiety) and its derivatives have been synthesized from Boc-L-Asp-OtBu utilizing the Moss procedure for the preparation of the azoxy moiety. The ester derivative, Ro 09-1824, showed more potent antifungal activity and a broader antifungal spectrum than azoxybacilin did.

Comparative studies on the antitumor and immunosuppressive effects of the new fluorouracil derivative N4-trimethoxybenzoyl-5'-deoxy-5-fluorocytidine and its parent drug 5'-deoxy-5-fluorouridine

N4-Trimethoxybenzoyl-5'-deoxy-5-fluorocytidine (Ro 09-1390), a new prodrug of 5'-deoxy-5-fluorouridine (5'-dFUrd), was synthesized for the purpose of finding a drug with less intestinal toxicity than the parent compound. The present study compared the antitumor activity and immunotoxicity of Ro 09-1390 with those of 5'-dFUrd, 5-fluorouracil (5-FUra) and tegafur in various transplantable tumor models. The antitumor efficacy of Ro 09-1390 was comparable to 5'-dFUrd and these two agents were much more effective than the others. However, Ro 09-1390 was much less toxic to the intestinal tract and less immunosuppressive in both humoral and cellular immune reactions than 5'-dFUrd. Consequently, Ro 09-1390 showed higher therapeutic indices and higher efficacy than 5'-dFUrd at high dosages. The antitumor spectrum of Ro 09-1390 was somewhat different from that of 5'-dFUrd, though it shows the efficacy after it converts to 5'-dFUrd. The activity of Ro 09-1390 was partly associated with cytidine deaminase in the tumors treated. Ro 09-1390 appeared to be more effective against tumors with a high concentration of the enzyme by which the major metabolite 5'-deoxy-5-fluorocytidine (5'-dFCyd) is metabolized to 5'-dFUrd.

Evaluation of [125I]IPOS as a molecular imaging probe for hypoxia-inducible factor-1-active regions in a tumor: comparison among single-photon emission computed tomography/X-ray computed tomography imaging, autoradiography, and immunohistochemistry

To image hypoxia-inducible factor-1 (HIF-1)-active tumors, we previously developed a chimeric protein probe ([(123/125) I]IPOS) that is degraded in the same manner as HIF-1α under normoxic conditions. In the present study, we aim to show that the accumulation of radioiodinated POS reflects the expression of HIF-1. In vivo single-photon emission computed tomography (SPECT)/X-ray CT (CT) imaging, autoradiography, and double-fluorescent immunostaining for HIF-1α and pimonidazole (PIMO) were carried out 24 h after the injection of [(125) I]IPOS. Tumor metabolite analysis was also carried out. A tumor was clearly visualized by multi-pinhole, high-resolution SPECT/CT imaging with [(125) I]IPOS. The obtained images were in accordance with the corresponding autoradiograms and with the results of ex vivo biodistribution. A metabolite analysis revealed that 77% of the radioactivity was eluted in the macromolecular fraction, suggesting that the radioactivity mainly existed as [(125) I]IPOS in the tumors. Immunohistochemistry revealed that the HIF-1α-positive areas and PIMO-positive areas were not always identical, only some of the regions were positive for both markers. The areas showing [(125) I]IPOS accumulation were positively and significantly correlated with the HIF-1α-positive areas (R = 0.75, P < 0.0001). The correlation coefficient between [(125) I]IPOS-accumulated areas and HIF-1α-positive areas was significantly greater than that between the [(125) I]IPOS-accumulated areas and the PIMO-positive areas (P < 0.01). These findings indicate that [(125) I]IPOS accumulation reflects HIF-1 expression. Thus, [(123/125) I]IPOS can serve as a useful probe for the molecular imaging of HIF-1-active tumors.

Determination of miloxacin and metabolites in human serum and urine by high-pressure liquid chromatography

A sensitive and reliable high-pressure liquid chromatography (HPLC) assay for miloxacin and its two principal metabolites, 5,8-dihydro-8-oxo-2H-1,3-dioxolo[4,5-g]quinoline-7-carboxylic acid (M-1) and 1,4-dihydro-1,6-dimethoxy-7-hydroxy-4-oxoquinoline-3-carboxylic acid (M-2), in human serum and urine was developed. A strong anion-exchange Zipax SAX column using a mobile phase of 0.01 M citric acid solution containing 0.03 M sodium nitrate with pH 5.0 was used to achieve separation of the three compounds. The retention times of miloxacin, M-1, and M-2 were 3.8, 9.3, and 5.9 min, respectively. Serum and urine concentrations of these compounds as low as 10 ng/ml were measured. When results from the HPLC assay were compared with those from the microbiological assay of serum and urine samples from human subjects receiving miloxacin orally, the correlation coefficients were 0.94 for the serum and 0.99 for the urine. The HPLC assay method presents an alternative to the microbiological assay and permits future pharmacokinetic investigations of miloxacin.

18 kDa protein tyrosine phosphatase in the ocular lens

Protein tyrosyl phosphorylation and dephosphorylation play essential roles in regulating cellular events such as proliferation and differentiation, and their involvement in the lens development and transparency is also suggested. The level of tyrosine phosphorylation in a given protein is regulated by the opposing actions of protein-tyrosine kinases (Tyr kinases) and protein-tyrosine phosphatases (TyrPases). Recent studies have revealed that some Tyr kinases, such as platelet-derived growth factor receptor and fibroblast growth factor receptor, are present in the lens, however, little is known about TyrPases in the lens. In this study, we found a 18 kDa protein tyrosine phosphatase (18 kDa TyrPase) predominantly present in the ocular lens of various animals. We purified the phosphatase from the lens of chick embryo and characterized its activity.Phosphatase activity was determined in chick embryo, mouse, rabbit and bovine lenses using p -nitrophenyl phosphate (p NPP) as substrate. All lenses examined dephosphorylated p NPP under acidic conditions, and a large portion of the activity resided in a low molecular weight protein, ca. 18 kDa, following high-resolution gel permeation column chromatography. The brain and liver showed high dephosphorylation activities, but most of their activity was present in high molecular weight fractions, unlike that in the lens. The 18 kDa phosphatase was purified from the lens of 17 day old chick embryos to near-homogeneity with two-step rapid chromatography. This phosphatase showed strict substrate specificity for phosphotyrosine and phosphotyrosyl peptides, suggesting that it was a kind of protein tyrosine phosphatases (TyrPases). Several known inhibitors of TyrPases, such as SH blockers, vanadate and phenylarsine oxide, strongly inhibited the enzyme activity. The molecular weight, substrate specificity, and responses to various inhibitors and activators coincide well with those reported for the low molecular weight protein tyrosine phosphatase (LMW-TyrPase), belonging to the TyrPase superfamily. These results suggest that the 18 kDa phosphatase found in the lens is a LMW-TyrPase. The 18 kDa TyrPase is the predominant phosphatase in the ocular lens. It may be involved in regulation of lens cell proliferation, differentiation and/or lens transparency.