(1/1750) Persistent induction of apoptosis and suppression of mitosis as the basis for curative therapy with S-1, an oral 5-fluorouracil prodrug in a colorectal tumor model.
In an effort to improve the therapeutic selectivity of 5-fluorouracil (FUra) against colorectal cancer, S-1, a combination agent including a prodrug of FUra with two modulators, was recently developed by Taiho Pharmaceuticals Co. S-1 is a combination of tegafur (FT), 5-chloro-2,4-hydroxypyridine, and potassium oxonate in the molar ratio of 1.0:0.4:1.0, with the latter two components as inhibitors of dihydropyrimidine dehydrogenase and phosphoribosylpyrophosphate transferase, respectively. In this study, the therapeutic selectivity and efficacy of S-1 (oral) was compared with FT (oral) and FUra (i.v. infusion) in rats bearing advanced colorectal cancer by using clinically relevant schedules. The maximum tolerated doses (MTDs) of S-1, FT, and FUra were 31.5, 200, and 25 mg/kg/d for 7 days and 22.5, 150, and 12.5 mg/kg/d for 28 days, respectively. The therapeutic index of S-1 was 4- to 5-fold higher than that of either FT or FUra. S-1 achieved 100% complete tumor regression (CR) at its MTD in both 7-day and 28-day schedules. Furthermore, the high incidences of stomatitis, alopecia, and diarrhea observed with FUra and FT, were not observed with S-1. In an attempt to understand the basis for the observed superior therapeutic selectivity with S-1, we studied pharmacokinetic analysis of FUra, drug-induced apoptosis, suppression of mitosis, and inhibition of thymidylate synthase (TS) after S-1, FUra, or FT administration. The peak plasma FUra concentrations derived from FUra or S-1 (FT) at comparable MTDs were similar, but the plasma level of FUra was higher with S-1 than with FUra. Induction of high and sustained apoptosis was achieved with S-1. Although the initial level of apoptosis induced by FUra was comparable to S-1, it was not sustained. The sustained level of apoptosis appears to correlate with tumor growth inhibition. Mitotic figures were more greatly suppressed with S-1 treatment than with FUra. Studies on TS inhibition indicated that, although both S-1 and FUra caused a 4- to 6-fold induction of total TS protein, single oral administration of S-1 was superior to 24-h infusion of FUra in suppressing free TS. The data are consistent with the observation that the therapeutic efficacy of S-1 (100% cure) over FUra is associated with high and sustained levels of drug-induced apoptosis, greater suppression of mitosis, and inhibition of free TS in tumor tissues. (+info)
(2/1750) In vivo activities of peptidic prodrugs of novel aminomethyl tetrahydrofuranyl-1 beta-methylcarbapenems.
A series of novel aminomethyl tetrahydrofuranyl (THF)-1 beta-methylcarbapenems which have excellent broad-spectrum antibacterial activities exhibit modest efficacies against acute lethal infections (3.8 mg/kg of body weight against Escherichia coli and 0.9 mg/kg against Staphylococcus aureus) in mice when they are administered orally. In an effort to improve the efficacies of orally administered drugs through enhanced absorption by making use of a peptide-mediated transport system, several different amino acids were added at the aminomethyl THF side chains of the carbapenem molecules. The resulting peptidic prodrugs with L-amino acids demonstrated improved efficacy after oral administration, while the D forms were less active than the parent molecules. After oral administration increased (3 to 10 times) efficacy was exhibited with the alanine-, valine-, isoleucine-, and phenylalanine-substituted prodrugs against acute lethal infections in mice. Median effective doses (ED50s) of < 1 mg/kg against infections caused by S. aureus, E. coli, Enterobacter cloacae, or penicillin-susceptible Streptococcus pneumoniae were obtained after the administration of single oral doses. Several of the peptidic prodrugs were efficacious against Morganella morganii, Serratia marcescens, penicillin-resistant S. pneumoniae, extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, and E. coli infections, with ED50s of 1 to 14 mg/kg by oral administration compared with ED50s of 14 to > 32 mg/kg for the parent molecules. In general, the parent molecules demonstrated greater efficacy than the prodrugs against these same infections when the drugs were administered by the subcutaneous route. The parent molecule was detectable in the sera of mice after oral administration of the peptidic prodrugs. (+info)
(3/1750) In vivo demonstration of H3-histaminergic inhibition of cardiac sympathetic stimulation by R-alpha-methyl-histamine and its prodrug BP 2.94 in the dog.
1. The aim of this study was to investigate whether histamine H3-receptor agonists could inhibit the effects of cardiac sympathetic nerve stimulation in the dog. 2. Catecholamine release by the heart and the associated variation of haemodynamic parameters were measured after electrical stimulation of the right cardiac sympathetic nerves (1-4 Hz, 10 V, 10 ms) in the anaesthetized dog treated with R-alpha-methyl-histamine (R-HA) and its prodrug BP 2.94 (BP). 3. Cardiac sympathetic stimulation induced a noradrenaline release into the coronary sinus along with a tachycardia and an increase in left ventricular pressure and contractility without changes in mean arterial pressure. Intravenous administration of H3-receptor agonists significantly decreased noradrenaline release by the heart (R-HA at 2 micromol kg(-1) h(-1): +77 +/- 25 vs +405 +/- 82; BP 2.94 at 1 mg kg(-1): +12 +/- 11 vs +330 +/- 100 pg ml(-1) in control conditions, P < or = 0.05), and increases in heart rate (R-HA at 2 micromol kg(-1) h(-1): +26 +/- 8 vs +65 +/- 10 and BP 2.94 at 1 mg kg(-1): +30 +/- 8 vs 75 +/- 6 beats min(-1), in control conditions P < or = 0.05), left ventricular pressure, and contractility. Treatment with SC 359 (1 mg kg(-1)) a selective H3-antagonist, reversed the effects of H3-receptor agonists. Treatment with R-HA at 2 micromol kg(-1) h(-1) and BP 2.94 at 1 mg kg(-1) tended to decrease, while that with SC 359 significantly increased basal heart rate (from 111 +/- 3 to 130 +/- 5 beats min(-1), P < or = 0.001). 4. Functional H3-receptors are present on sympathetic nerve endings in the dog heart. Their stimulation by R-alpha-methyl-histamine or BP 2.94 can inhibit noradrenaline release by the heart and its associated haemodynamic effects. (+info)
(4/1750) Metabolism of the new liposomal anticancer drug N4-octadecyl-1-beta-D-arabinofuranosylcytosine in mice.
Metabolism and excretion of the new antitumor drug N4-octadecyl-1-beta-D-arabinofuranosylcytosine (NOAC) was investigated in mice. Mice were injected i.v. with tritium-labeled liposomal NOAC (4 micromol/mouse). Analysis of HPLC-purified extracts of liver homogenates by liquid chromatography coupled with mass spectrometry revealed only the presence of unmetabolized drug. To study the excretion of the administered drug, mice were injected with tritium-labeled liposomal NOAC or as comparison with 1-beta-D-arabinofuranosylcytosine (ara-C; 4 micromol/mouse) and housed up to 48 h in metabolic cages. Urine and feces were collected at different time points and the kinetics of excreted radioactivity were determined. After 48 h, 39% of the injected [5-3H]NOAC radioactivity was excreted in urine and 16% in feces, whereas ara-C radioactivity was only found in urine with 48% of the injected dose. Feces extracts and urine were purified by HPLC and radioactive fractions were further analyzed by liquid chromatography coupled with mass spectrometry. The radioactivity of feces extracts of NOAC-treated mice was composed of unmetabolized NOAC, hydroxylated NOAC (NOAC + OH), its sulfated derivative (NOAC + OSO3H), and unidentified metabolites, whereas in urine, the hydrophilic molecules ara-C and ara-U were found. During the period of 48 h only 2% of the injected NOAC was eliminated in its unmetabolized form, whereas 25% was identified as main metabolite ara-C. Urine collected during 48 h in ara-C-treated mice contained 33% of the injected dose as unmetabolized drug and 13% as the main metabolite ara-U. Thus, NOAC is metabolized by two major pathways, one leading to the hydrophilic metabolites ara-C and ara-U and the other to hydroxylated and sulfated NOAC. (+info)
(5/1750) Oxidative bioactivation of the lactol prodrug of a lactone cyclooxygenase-2 inhibitor.
The lactol derivative of a lactone cyclooxygenase-2 inhibitor (DFU) was evaluated in vivo and in vitro for its potential suitability as a prodrug. DFU-lactol was found to be 10 to 20 times more soluble than DFU in a variety of aqueous vehicles. After administration of DFU-lactol at 20 mg kg-1 p.o. in rats, a Cmax of 7.5 microM DFU was reached in the plasma. After oral administration, the ED50s of DFU-lactol in the carrageenan-induced paw edema and lipopolysaccharide-induced pyresis assays in rats are comparable with the ED50s observed when dosing with DFU. Incubations of DFU-lactol with rat and human hepatocytes demonstrated that the oxidation of DFU-lactol can be mediated by liver enzymes and that a competing pathway is direct glucuronidation of the DFU-lactol hydroxyl group. Assays with subcellular fractions from rat liver indicated that most of the oxidation of DFU-lactol occurs in the cytosolic fraction and requires NAD(P)+. Human liver cytosol can also support the oxidation of DFU-lactol to DFU when NAD(P)+ is added to the incubations. Fractionation of human liver cytosolic proteins showed that at least three enzymes are capable of efficiently effecting the oxidation of DFU-lactol to DFU. Incubations with commercially available dehydrogenases suggest that alcohol and hydroxysteroid dehydrogenases are involved in this oxidative process. These data together suggest that lactols may represent useful prodrugs for lactone-containing drugs. (+info)
(6/1750) GR-891: a novel 5-fluorouracil acyclonucleoside prodrug for differentiation therapy in rhabdomyosarcoma cells.
Differentiation therapy provides an alternative treatment of cancer that overcomes the undesirable effects of classical chemotherapy, i.e. cytotoxicity and resistance to drugs. This new approach to cancer therapy focuses on the development of specific agents designed to selectively engage the process of terminal differentiation, leading to the elimination of tumorigenic cells and recovery of normal cell homeostasis. A series of new anti-cancer pyrimidine acyclonucleoside-like compounds were designed and synthesized by structural modifications of 5-fluorouracil, a drug which causes considerable cell toxicity and morbidity, and we evaluated their applicability for differentiation therapy in human rhabdomyosarcoma cells. We tested the pyrimidine derivative GR-891, (RS)-1-[[3-(2-hydroxyethoxy)-1-isopropoxy]propyl]-5-fluorouracil, an active drug which shows low toxicity in vivo and releases acrolein which is an aldehyde with anti-tumour activity. Both GR-891 and 5-fluorouracil caused time- and dose-dependent growth inhibition in vitro; however, GR-891 showed no cytotoxicity at low doses (22.5 micromol l(-1) and 45 micromol l(-1)) and induced terminal myogenic differentiation in RD cells (a rhabdomyosarcoma cell line) treated for 6 days. Changes in morphological features and in protein organization indicated re-entry in the pathway of muscular maturation. Moreover, GR-891 increased adhesion capability mediated by the expression of fibronectin, and did not induce overexpression of P-glycoprotein, the mdr1 gene product, implicated in multidrug resistance. New acyclonucleoside-like compounds such as GR-891 have important potential advantages over 5-fluorouracil because of their lower toxicity and their ability to induce myogenic differentiation in rhabdomyosarcoma cells. Our results suggest that this drug may be useful for differentiation therapy in this type of tumour. (+info)
(7/1750) Anti-inflammatory and ulcerogenic effects of 3-(N,N-diethylamino) propylindometacin HCl.
AIM: To study anti-inflammatory effects of a novel indometacin ester, 3-(N,N-diethylamino) propyl-indometacin HCl (prodrug) and its ulcerogenicity in fats. METHODS: Carrageenin (Car)-induced paw edema and ulcer index were examined. RESULTS: Car-induced paw edema was inhibited by 36.6% (P < 0.01) at 3 h and 34.6% (P < 0.01) at 5 h after a single i.p. injection of the prodrug 7.09 mg.kg-1. On the same molar basis, indometacin (Ind) 5 mg.kg-1 i.p. inhibited edema by 45.6% at 3 h and 39.2% at 5 h, however, there was no statistical significant difference (P > 0.05) between the edema-inhibitory effect of the prodrug and that of Ind. The dose 10 micrograms/paw exhibited 64% inhibition of the swelling, the prodrug > 10 micrograms/paw showed no additional inhibition of swelling; the acute gastric lesion properties of the prodrug were much lower than those of Ind 6 h after p.o. CONCLUSION: The prodrug is a potent anti-inflammatory agent with lower ulcerogenicity in the stomach. (+info)
(8/1750) Stable incorporation of a lipophilic daunorubicin prodrug into apolipoprotein E-exposing liposomes induces uptake of prodrug via low-density lipoprotein receptor in vivo.
Many tumors express elevated levels of low-density lipoprotein (LDL) receptors. Therefore, native LDL and synthetic LDL-like particles have been proposed as carriers for antineoplastic drugs. We demonstrated earlier that small apolipoprotein E (apoE)-exposing liposomes were specifically recognized by the LDL receptor. In this study, we incorporated a lipophilic derivative of daunorubicin (LAD) into the apoE liposomes. Up to 11 molecules of LAD could be incorporated per particle without significantly changing the size, lipid composition, and ability to bind apoE of the liposomes. The biological fate of the prodrug was largely determined by its carrier (70% of the initially incorporated LAD was still associated to the liposomes after 4 h of circulation in mice). Compared with free daunorubicin, the circulation half-life of the liposome-associated prodrug was substantially prolonged and undesired tissue disposition was reduced. The role of the LDL receptor in the metabolism of LAD-loaded apoE liposomes was demonstrated in rats with up-regulated hepatic LDL receptors. In these rats, the liver uptake of the prodrug and carrier was increased 5-fold. The addition of apoE was essential for LDL receptor-mediated uptake of the drug-carrier complex. In LDL receptor-deficient mice, the circulation time of both the prodrug and the carrier increased approximately 2-fold compared with wild-type mice. We conclude that LAD-loaded apoE liposomes constitute a stable drug-carrier complex that is well suited for LDL receptor-mediated selective drug delivery to tumors. (+info)