Structure-activity relationships of sparsomycin and its analogues. Inhibition of peptide bond formation in cell-free systems and of L1210 and bacterial cell growth

The biological activity of 14 analogues of sparsomycin (1) was studied in cell-free systems of Escherichia coli, Saccharomyces cerevisiae, and Sulfolobus solfataricus by measuring the inhibition of protein synthesis. The inhibition of L1210 colony formation in soft agar and bacterial cell growth in solid as well as in liquid medium was also examined. Each analogue possesses not more than two structural modifications of the sparsomycin molecule. This enabled us to determine unambiguously several structural and stereochemical features that are required for an optimal biological activity in these assays. Sparsomycin, having the SCRS chirality, is the most potent of the four possible stereoisomers. The results obtained with compounds 5-7 indicate that the presence of an oxygen atom on the S (alpha) atom is essential. Substitution of the bivalent sulfur atom by a CH2 group (10) or of the SCH3 moiety by a Cl atom (12) affects the activity of the molecule partially. Compound 12 is surprisingly active against intact cells. Substitution of the C(6)-CH3 group by a H(14) reduces the activity of the molecule. Isomerization of the trans double bond into the cis double bond yields cis-sparsomycin (15), which is inactive. The hydrophobic derivatives 8, 9, and 11 are considerably more active than sparsomycin; thus the ribosomal binding site for sparsomycin may have a hydrophobic character.     

Structure-activity relationships of sparsomycin and its analogues. Octylsparsomycin: the first analogue more active than sparsomycin

Nine analogues of sparsomycin were synthesized, and their cytostatic activity was studied in an in vitro clonogenic L1210 assay by measuring the inhibition of colony formation. The activity of an analogue, expressed as an ID50 value, was compared to that of sparsomycin. Each possesses not more than two structural modifications of the sparsomycin molecule 1. Comparison of the activity of with that of the stereomers, having RCSS, SCSS, and RCRS chirality, respectively, shows that the S configuration of the chiral carbon atom is essential for an optimal activity, whereas the R chirality of the sulfoxide sulfur atom of sparsomycin is of importance. Study of the ID50 values of the S-deoxo analogues, as well as the compounds having the beta-sulfoxide function, indicate that the presence of an oxygen atom on the alpha-sulfur atom is essential. Isomerization of the trans double bond into the cis double bond yields isosparsomycin, (Scheme II), which has a low activity. The cytostatic activity of sparsomycin seems to be related to its lipophilicity: octylsparsomycin was shown to be three times as effective as sparsomycin.     

Inhibition of ribonucleotide reductase and growth of human colon carcinoma HT-29 cells and mouse leukemia L1210 cells by N-hydroxy-N'-aminoguanidine derivatives

A series of N-hydroxy-N'-aminoguanidine (HAG) derivatives were studied and compared for their effects on ribonucleotide reductase activity in cell-free extracts; on nucleic acid synthesis and the growth of human colon carcinoma HT-29 cells; and on mouse leukemia L1210 cells in culture. The HAG derivatives [RCH=NNHC(=NH)NHOH-tosylate] studied could be grouped as: (1) hydroxybenzylidines; (2) methoxybenzylidines; and (3) nitrobenzylidines substituted at the R position. 2'-Hydroxybenzylidine-HAG, the lead compound, was relatively active in both HT-29 cells and L1210 cells (20 +/- 5 and 13 +/- 4 microM for 50% inhibition of HT-29 and L1210 cell growth respectively). The monohydroxybenzylidene compounds were generally more active than the dihydroxy- and trihydroxybenzylidene-HAG derivatives. The methoxybenzylidene-HAGs were as active as the monohydroxybenzylidene-HAGs. 2'-Hydroxy-4'-methoxybenzylidene-HAG was much more active than 2',4'-dihydroxybenzylidene-HAG. The mononitrobenzylidene-HAGs were more active than the dinitrobenzylidene-HAG compound. In general, L1210 cells were more sensitive to the effects of the HAG compounds than were HT-29 cells. There was good agreement between the concentration of drug required to inhibit the growth of HT-29 cells and that required to inhibit the growth of L1210 cells. There was also good correlation between the ability of HAG derivatives to inhibit ribonucleotide reductase activity and to inhibit tumor cell growth. Some derivatives, such as 2',3',4'- and 3',4',5'-trihydroxybenzylidene-HAG inhibited L1210 cell growth by 50% at lower concentrations (7.8 and 11.9 microM respectively) than the concentrations needed for 50% inhibition of HT-29 cell growth (196 and 234 microM respectively) and ribonucleotide reductase activity (122 and 188 microM respectively). The studies of nucleic acid synthesis in L1210 cells using [3H]cytidine as a precursor showed that 2',3',4'-trihydroxybenzylidine-HAG inhibited DNA synthesis at a lower concentration (29 microM for 50% inhibition) than was needed for the inhibition of RNA synthesis and formation of [3H]deoxycytidine nucleotides in the acid-soluble fraction (320 and 820 microM for 50% inhibition respectively). These results indicate that 2',3',4'-trihydroxybenzylidine-HAG inhibits DNA synthesis in L1210 cells through other mechanisms rather than exclusively through the inhibition of ribonucleotide reductase activity.     

In vitro percutaneous absorption of prednisolone derivatives based on solubility parameter

A series of ester derivatives of prednisolone (I–VII) with various lipophilicities was synthesized to investigate their in vitro percutaneous absorption and their distribution and accumulation in the skin. Experimental findings were supported with theoretical calculations, using the solubility parameter as an indicator of the lipophilicity of the derivatives. The solubility parameters of the derivatives were well correlated with their partition coefficients in an octanol-water system and increase in lipophilicity was well correlated with the theoretical and experimental values of drug distribution into the skin. Drug distribution into the skin was increased, but the drug diffusion rate was decreased with increasing derivative lipophilicity. These findings indicated that accumulation of the derivatives in the skin increased with increasing derivative lipophilicity. This suggests that retention of prednisolone derivatives in the skin is a function of their solubility parameters and that derivatives are partitioned in the skin relative to their lipophilicities.     

Methotrexate analogues. 30. Dihydrofolate reductase inhibition and in vitro tumor cell growth inhibition by N epsilon-(haloacetyl)-L-lysine and N delta-(haloacetyl)-L-ornithine analogues and an acivicin analogue of methotrexate

Analogues of methotrexate (MTX) with strong alkylating activity were prepared by replacing the L-glutamate side chain with N omega-haloacetyl derivatives of L-lysine and L-ornithine. Haloacetylation was accomplished in 30-40% yield by reaction of the preformed L-lysine and L-ornithine analogues of MTX with p-nitrophenyl bromoacetate or chloroacetate in aqueous sodium bicarbonate at room temperature. All four haloacetamides were potent inhibitors in spectrophotometric assays measuring noncovalent binding to purified dihydrofolate reductase (DHFR) from L1210 cells. In experiments designed to measure time-dependent inactivation of DHFR from L1210 cells and Candida albicans, the N epsilon-(bromoacetyl)-L-lysine and N delta-(bromoacetyl)-L-ornithine analogues gave results consistent with covalent binding, whereas N epsilon- and N delta-chloroacetyl analogues did not. The N delta-(bromoacetyl)-L-ornithine analogue appeared to be the more reactive one toward both enzymes. Amino acid analysis of acid hydrolysates of the L1210 enzyme following incubation with the bromoacetamides failed to demonstrate the presence of a carboxymethylated residue, suggesting that alkylation had perhaps formed an acid-labile bond. In growth inhibition assays with L1210 cultured murine leukemia cells, the four haloacetamides were all more potent than their nonacylated precursors but less potent than MTX. The greater than 40,000-fold MTX-resistant mutant cell line L1210/R81 was only partly cross-resistant to the haloacetamides. An analogue of MTX with acivicin replacing glutamate was a potent inhibitor of DHFR from chicken liver and L1210 cells but was 200 times less potent than MTX against L1210 cells in culture.     

Effect of the dialdehyde derivative of 5'-deoxyinosine on pyrimidine deoxyribonucleoside metabolism in L1210 cells

The effects of the dialdehyde derivatives of inosine (Inox) and 5'-deoxyinosine (5'-dInox) on L1210 cells were compared. The growth of L1210 cells was inhibited to a greater extent by 5'-dInox than by Inox. The increased inhibition of L1210 cell growth by 5'-dInox was also reflected by the increased inhibition of the incorporation of precursors into RNA, DNA and proteins. Even though 5'-dInox was a more potent inhibitor, Inox accumulated in the L1210 cells to levels 4- to 5-fold greater than 5'-dInox. The metabolism of [5-3H]deoxycytidine and [5-3H]deoxyuridine by L1210 cells in culture, in the presence of Inox or 5'-dInox, indicated that dCMP deaminase was an intracellular site of action for 5'-dInox. The dCMP deaminase activity in cell-free extracts prepared from 5'-dInox-treated cells was reduced markedly. This decrease in activity was not reversed by increased substrate concentrations nor was the activity subject to allosteric activation by dCTP. Deoxyuridine and deoxycytidine were able to reverse the effects of 5'-dInox on the inhibition of L1210 cell growth.     

Triapine (3-aminopyridine-2-carboxaldehyde- thiosemicarbazone): A potent inhibitor of ribonucleotide reductase activity with broad spectrum antitumor activity

Previous studies from our laboratories have shown that (a) Triapine() is a potent inhibitor of ribonucleotide reductase activity and (b) hydroxyurea-resistant L1210 leukemia cells are fully sensitive to Triapine. In an analogous manner, Triapine was similarly active against the wild-type and a hydroxyurea-resistant subline of the human KB nasopharyngeal carcinoma. Triapine was active in vivo against the L1210 leukemia over a broad range of dosages and was curative for some mice. This agent also caused pronounced inhibition of the growth of the murine M109 lung carcinoma and human A2780 ovarian carcinoma xenografts in mice. Optimum anticancer activity required twice daily dosing due to the duration of inhibition of DNA synthesis which lasted about 10 hr in L1210 cells treated with Triapine in vivo. DNA synthesis in normal mouse tissues (i.e. duodenum and bone marrow) uniformly recovered faster than that in L1210 leukemia cells, demonstrating a pharmacological basis for the therapeutic index of this agent. Triapine was more potent than hydroxyurea in inhibiting DNA synthesis in L1210 cells in vivo, and the effects of Triapine were more pronounced. In addition, the duration of the inhibition of DNA synthesis in leukemia cells from mice treated with Triapine was considerably longer than in those from animals treated with hydroxyurea. Combination of Triapine with various classes of agents that damage DNA (e.g. etoposide, cisplatin, doxorubicin, and 1-acetyl-1,2-bis(methylsulfonyl)-2-(2-chloroethyl)hydrazine) resulted in synergistic inhibition of the L1210 leukemia, producing long-term survivors of tumor-bearing mice treated with several dosage levels of the combinations, whereas no enhancement of survival was found when Triapine was combined with gemcitabine or cytosine arabinoside. The findings demonstrate the superiority of Triapine over hydroxyurea as an anticancer agent and further suggest that prevention by Triapine of repair of DNA lesions created by agents that damage DNA may result in efficacious drug combinations for the treatment of cancer.     

Naphthazarin derivatives (VIII): Synthesis, inhibitory effect on DNA topoisomerase-I, and antiproliferative activity of 6-(1-acyloxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones.

6-(1-Acyloxyalkyl)-5,8-dimethoxy-1,4-naphthoquinone (DMNQ; 5,8-dimethoxy-1,4-naphthoquinone) derivatives were synthesized and examined for their inhibitory effect on DNA topoisomerase-I (Topo I) and their antiproliferative activity against L1210 cells. The Topo-I inhibitory effect of 6-(1-hydroxyalkyl)-DMNQ derivatives was found to be dependent on the size of the alkyl chains, suggesting that lipophilicity might be one important factor influencing the inhibitory effect. It was found that acylation of 6-(1-hydroxyalkyl)-DMNQ derivatives possessing alkyl chains of C2-C5 enhanced both bioactivities, suggesting that an increase of electrophilicity in the quinoid moiety makes the electrophilic arylation of bionucleophiles more favorable. It is noteworthy that 6-(1-heptanoyloxyethyl)-DMNQ exhibited both the most potent Topo I inhibitory activity (IC50, 11.5 microM) and the greatest antiproliferative activity (ED50, 0.05 microM) upon L1210 cells.     

Optimization of the Schiff bases of N-hydroxy-N'-aminoguanidine as anticancer and antiviral agents

Hydroxyurea, hydroxyguanidine, and some thiosemicarbazones have been shown to have anticancer and antiviral activities. One of their possible sites of action is the enzyme ribonucleotide reductase (RR). Combination of the structural features of these compounds led to the design and synthesis of the Schiff bases of N-hydroxy-N'-aminoguanidine. Synthesis and structure-activity studies of some of these compounds point to increased size and lipophilicity as important factors for activity. To optimize the activities of this series of compounds, 13 derivatives of high lipophilicity and molecular size have been synthesized and their biological activities studied. The most active anticancer compounds against L1210 in vitro (compounds 9 and 12) are about 7 times more active than hydroxyguanidine and hydroxyurea. The most active antiviral compounds against Rous sarcoma virus transformation of chick fibroblasts in vitro (7, 9) are about 40 times more active than hydroxyguanidine. One of the compounds (4) shows promising activity in vivo (% T/C = 140 against P388 leukemia in mice) and is undergoing further studies by the National Cancer Institute (NCI). Studies of the inhibition of transformation of chick embryo cells by Rous sarcoma virus show that all these compounds inhibit transformation while some compounds inhibit viral replication as well.     

2- or 6-(1-azidoalkyl)-5,8-dimethoxy-1,4-naphthoquinone: Synthesis, evaluation of cytotoxic activity; Antitumor activity and inhibitory effect on DNA topoisomerase-I

6-(1-azidoalkyl)-DMNQ derivatives compared to 2-(1-azidoalkyl)-DMNQ isomers, exhibited higher cytotoxic activity against L1210 mouse leukemia cells and stronger inhibition of DNA topoisomerase-I (TOPO-I), suggesting involvement of steric hindrance. However, similar antitumor activity against mice bearing S-180 cell was shown by 2- and 6-(1-azidoalkyl)-DMNQ derivatives.     

Antitubulin effects of derivatives of 3-demethylthiocolchicine, methylthio ethers of natural colchicinoids, and thioketones derived from thiocolchicine. Comparison with colchicinoids

Esterification of the phenolic group in 3-demethylthiocolchicine and exchange of the N-acetyl group with other N-acyl groups or a N-carbalkoxy group afforded many compounds which showed superior activity over the parent drug as inhibitors of tubulin polymerization and of the growth of L1210 murine leukemia cells in culture. A comparison of naturally occurring Colchicum alkaloids with thio isosters, obtained by replacing the OMe group at C(10) with a SCH3 group, showed the thio ethers to be invariably more potent in these assays. The comparison included 3-demethylthiodemecolcine prepared from 3-demethylthiocolchicine by partial synthesis. Thiation of thiocolchicine with Lawesson's reagent afforded novel thiotropolones which exhibited high antitubulin activity. Their structures are fully secured by spectral data. Colchicine and several of its analogues show good antitumor effect in mice infected with P388 lymphocytic leukemia, and all of them show high affinity for tubulin and inhibit tubulin polymerization at low concentration. Consequently, antitubulin assays with this class of compounds can serve as valuable prescreens for the initial evaluation of potential antitumor drugs.     

Synthesis and antiproliferative activity of unsaturated quinoline derivatives

In our previous work Knoevenagel condensation of quinoline 2-, 3- and 4-carbaldehyde with malononitrile derivatives was used to produce a series of heteroarylidene malononitrile derivatives. Some of these heteroaromatic tyrphostins were potent inhibitors of the epidermal growth factor (EGF) receptor kinase. This work has now been extended by using 6-, 7-, and 8-quinolinecarbaldehyde to prepare 23 new quinoline-tyrphostins 1-23. Most of these compounds were moderately active against the MCF7 breast cancer cell line. The order of potency was 7- > 6 > 8-substituted quinoline, which indicates that increased activity of the 7-substituted quinolines is associated with electron deficiency at the 7-position in the quinoline ring. The most active compound, 12, formed from 7-quinolinecarbaldehyde and ethyl cyanoacetate, had an IC50 value of 2.3 microM. Compounds 1-23 showed similar IC50 values against the MCF7 and MCF7/ADR cell lines (the latter shows fourfold increased protein tyrosine kinase activity) except for the compounds 1 and 15 formed from 6-quinolinecarbaldehyde and malononitrile and 7-quinolinecarbaldehyde and cyanoacetamide, which showed a significant (11- and 42-fold, respectively) increase in potency against the MCF7/ADR cell line. Furthermore, no association was found between growth inhibition and inhibition of the EGFR protein tyrosine kinase (PTK), using a cell-free assay. In addition, new compounds were prepared from 2- and 4-quinolinecarbaldehyde with extended conjugation in the side chains (24-27) or with methoxypolyethoxyethyl esters in the side chain to increase water solubility (28 and 29). These compounds showed substantial cytotoxicity, with IC50 values in the range 1-25 microM, but similar values were observed against both cell lines. No association was found between inhibition of PTK and growth inhibition, again indicating that their mode of action may not be specific for the EGF receptor.     

Regiospecific gamma-conjugation of methotrexate to poly(L-lysine). Chemical and biological studies

Regiospecific syntheses of gamma- and alpha-conjugates of methotrexate and poly(L-lysine) are described. The alpha- and gamma-t-butyl esters, respectively, of methotrexate were coupled to poly(L-lysine) with diphenylphosphoryl azide in N,N-dimethylformamide, the ester-protecting group was cleaved with 15% hydrogen bromide in acetic acid, and small molecules were removed by dialysis. Poly(L-lysine) of Mr = 1,500-8,000 and 8,000-30,000 was used to prepare six different conjugates, which were characterized by ultraviolet absorbance measurement and quantitative amino acid analysis. The degree of substitution varied from one methotrexate per 4.7 lysines to one methotrexate per 10.2 lysines. Dihydrofolate reductase inhibition in a cell-free assay was observed with alpha- and gamma-conjugates, but the latter had the greater affinity (only 3-fold less than that of methotrexate itself). The binding of the conjugates exhibited a slight pH dependence, with affinity being greater at pH 7.2 than at pH 8.5 for both alpha- and gamma-conjugates. Toxicity to cultured rat hepatoma cells (H35) was also greater for the gamma-conjugates, and showed some dependence on the chain-length and degree of substitution of the poly(L-lysine) carrier. Cells resistant to methotrexate by virtue of a transport defect (H35R0.3 line) retained their sensitivity to the gamma-conjugate, but less so to the alpha-conjugate. There was also some retention of sensitivity in a more highly resistant cell line (H35R10) with impaired methotrexate transport and a concomitant increase in dihydrofolate reductase activity. gamma-Conjugation was likewise more favorable in cytotoxicity assays against L1210 murine leukemia cells, and there was partial retention of activity against highly methotrexate-resistant lines (L1210/R71 and L1210/R81) with a transport defect and/or an elevation of dihydrofolate reductase content. In antitumor assays against intraperitoneal L1210 leukemia in mice, a gamma-conjugate with Mr = 8,000-30,000 and one methotrexate per 5.5 lysines produced a 35-75% increase in lifespan when administered intraperitoneally at single doses equivalent to 10-20 mg/kg of methotrexate. A similar increase in lifespan with methotrexate alone on the single-dose regimen required 50-150 mg/kg. An alpha-conjugate of similar Mr and degree of substitution was inactive at nontoxic doses, as were other gamma-conjugates of lower Mr and/or degree of substitution.(ABSTRACT TRUNCATED AT 400 WORDS)     

The cytotoxicity of helenalin, its mono and difunctional esters, and related sesquiterpene lactones in murine and human tumor cells.

Naturally occurring sesquiterpene lactones and their semisynthetic derivatives, such as the O = C-C = CH-bearing helenalin and its esters, have been shown to demonstrate potent cytotoxicity against the growth of murine L1210 lymphoid leukemia and human Tmolt3 leukemia, colon adenocarcinoma, HeLaS3, lung bronchogenic, KB, osteosarcoma, and glioma cells. The modes of action of helenalin in L1210 cells are the inhibition of DNA, RNA, and protein syntheses. This study confirms that thiol bearing enzymes of nucleic acid metabolism were significantly inhibited, e.g. DNA polymerase alpha, IMP hydrogenase, and ribonucleoside reductase. The addition of GSH to the reaction medium demonstrated total recovery of L1210 ribonucleoside reductase activity. Helenalin reduced cellular GSH levels in L1210 cells. Helenalin also reduced all four pool levels of d(NTP)s which would account for part of the observed inhibition of DNA synthesis. Reductions in the ribonucleotide pool levels were also generally evident after drug treatment. Thus, the sesquiterpene lactones appear to have more than one mode of action in L1210 cells. All of the modes of actions of helenalin are feasible mechanisms to lower nucleic acid synthesis and cause cell death of the L1210 leukemia cells.     

Inhibition of ribonucleotide reductase and L1210 cell growth by N-hydroxy-N'-aminoguanidine derivatives

A series of N-hydroxy-N'-aminoguanidine derivatives was studied for their effects on L1210 cell growth and ribonucleotide reductase activity. With the twelve compounds studied, there was a good correlation between the inhibition of L1210 cell growth and the inhibition of ribonucleotide reductase activity. The most potent compound required concentrations of only 1.4 and 2 microM for 50% inhibition of L1210 cell growth and ribonucleotide reductase activity respectively. These guanidine analogs specifically inhibited the conversion of [14C]cytidine and deoxycytidine nucleotides in the nucleotide pool and the incorporation of [14C]cytidine into DNA without altering the incorporation of [14C]cytidine into RNA. Ribonucleotide reductase activity in drug-treated cells was reduced markedly. Iron-chelating agents did not either increase or decrease the inhibition caused by the N-hydroxy-N'-aminoguanidine derivatives. No evidence was obtained that these derivatives selectively inactivated one of the subunits of ribonucleotide reductase. These compounds appear to inhibit ribonucleotide reductase by a mechanism different from hydroxyurea or the thiosemicarbazone derivatives.     

Long term instability and molecular mechanism of 5-azacytidine-induced DNA hypomethylation in normal and neoplastic tissues in vivo

We have previously shown that treatment of normal and neoplastic cells with the antileukemic drug, 5-azacytidine, led to the rapid synthesis of a low molecular weight RNA containing 5-azacytosine. This fraudulent RNA inhibited tRNA (cytosine-5)-methyltransferase early after drug administration. The absence of tRNA (cytosine-5)-methyltransferase activity resulted in the synthesis of tRNA specifically deficient in 5-methylcytosine. Here, we show that treatment of L1210 cells, grown intraperitoneally in mice, with 5-azacytidine led to a rapid and prolonged inactivation of DNA (cytosine-5)-methyltransferase activity and to the synthesis of undermethylated DNA. DNA isolated from the treated tissue was found to inactivate the DNA methylase (decreased Vmax) in in vitro DNA (cytosine-5)-methyltransferase assays. Kinetic analysis showed noncompetitive inhibition of the substrate by the inhibitor. The persistence of DNA undermethylation after treatment with 5-azadeoxycytidine or 5-azacytidine in animals has not been measured directly; therefore, we have investigated this phenomenon in the intact animal. Prolonged treatment with 5-azacytidine was required to maintain a a fraction of undermethylated sites in DNA of L1210 cells in vivo for up to 4 months or longer after drug withdrawal. Such treatment led to instability of DNA methylation levels in L1210 cells in vivo. At least a partial restoration of DNA 5-methylcytosine levels was observed after acute and chronic 5-azacytidine treatment, respectively. 5-Azacytidine was also found to induce DNA hypomethylation in regenerating, but not in normal adult mouse liver cells. Our results show that: 1) it was extremely difficult to decrease the DNA methylation level to less than 50% of control; and 2) it was also difficult to maintain stable DNA methylation levels in vivo after exposure to the drug.     

Design, synthesis and biological activity of a series of torasemide derivatives, potent blockers of the Na+ 2Cl- K+ co-transporter: in-vitro study.

Pharmacomodulation of the torasemide molecule, a loop diuretic inhibiting Na+ 2Cl- K+ co-transport in the thick ascending limb of the loop of Henlé has been performed in order to obtain new long-acting diuretics. The aim of this study was to decrease the metabolism of the drug and to slow down its rate of excretion by increasing its hydrophobicity. The present study describes the synthesis and the inhibitory potency of new torasemide derivatives in the bioassay system of the cortical thick ascending limb of rabbit. A correlation between the lipophilicity (log P') of these substances and their activity as inhibitors of the Na+ Cl- K+ co-transporter was observed. The present design led to compounds more active than torasemide. Structure-activity relationships permit us to propose an interaction model between torasemide derivatives and the Na+ 2Cl- K+ co-transport system of the cortical thick ascending limb.     

Reactive 5'-substituted 2',5'-dideoxyuridine derivatives as potential inhibitors of nucleotide biosynthesis

5'-(Bromoacetamido)-2',5'-dideoxyuridine (3) and derivatives (8, 10, 12, and 14) substituted at the 5-position with bromo, iodo, fluoro, and ethyl groups have been synthesized as potential inhibitors of enzymes that metabolize pyrimidine nucleosides. Also prepared were 2',5'-dideoxyuridine derivatives (4-6) substituted at the 5'-position with 2-bromopropionamido, iodoacetamido, and 4-(fluorosulfonyl)benzamido groups. Compounds 3, 5, 8, 12, and 14 were examined for effect on macromolecular synthesis in L1210 leukemia cells in culture and compared with 5'-(bromoacetamido)-5'-deoxythymidine (1, BAT), a compound with demonstrated cytotoxicity and activity in vivo against P388 murine leukemia. Compounds 3, 8, 12, and 14 inhibited DNA synthesis without significant inhibition of RNA synthesis, and protein synthesis was affected less than DNA synthesis. Compounds 3, 5, 6, 8, 10, 12, and 14 were cytotoxic to H.Ep.-2 and L1210 cells in culture, and 3, 5, 8, and 12 showed activity in the P388 mouse leukemia screen.     

Thiourea derivatives as specific inhibitors of picorna viruses.

30 compounds with antipicorna virus activity were selected from 173 N,N'-disubstituted thiourea derivatives. The spectrum of antiviral activity was determined in vitro using entero, FMD, rhino and EMC viruses. Structure-activity relationships were studied. Several compounds produced marked activity against coxsackie viruses A and B infection of mice and FMD infection in mice and guinea pigs. N-Phenyl-N'-3-hydroxyphenyl-thiourea (PTU-23) inhibited poliovirus production by more than 99% without influencing the FL host cell. EMC virus was readily inhibited by PTU-23 in Kreb-II cells. Virus RNA synthesis was significantly reduced. Under the effect of PTU-23 the amount of 37S ssRNA extracted from EMC virus infected cells was considerably more reduced than that of the 20S ds RNA. PTU-23 did not influence the activity of virus-induced RNA polymerase in a cell-free system.     

Synthesis of hydroxy- and amino-substituted benzohydroxamic acids: inhibition of ribonucleotide reductase and antitumor activity.

Benzohydroxamic acids inhibit mammalian ribonucleotide reductase and exhibit antineoplastic activity in L1210 leukemic mice. Five new hydroxy- and amino-substituted benzohydroxamic acids (3,4- and 3,5-OH, 3,4-NH2, 2,3,4- and, 3,4,5-OH) were prepared and tested along with 12 previously reported benzohydroxamic acids (BHA) for enzyme inhibition and antitumor activity. The most potent enzyme inhibitor in this series was 2,3,4-OH-BHA (ID50 = 3.5 microM), which is 140 times more potent than hydroxyurea, but its toxicity limited the antitumor activity to a 30% increase in life span of L1210 bearing mice at 125 (mg/kg)/day ip for 8 days. The most effective antitumor agent in this series was 3,4-OH-BHA which prolonged the life span of L1210 bearing mice 103% at 600 (mg/kg)/day ip for 8 days.