Inhibitors of NF-kappaB and AP-1 gene expression: SAR studies on the pyrimidine portion of 2-chloro-4-trifluoromethylpyrimidine-5-[N-(3', 5'-bis(trifluoromethyl)phenyl)carboxamide]

We investigated the structure-activity relationship studies of N-[3, 5-bis(trifluoromethyl)phenyl][2-chloro-4-(trifluoromethyl)pyrimidin-5 -yl]carboxamide (1), an inhibitor of transcription mediated by both NF-kappaB and AP-1 transcription factors, with the goal of improving its potential oral bioavailability. Compounds were examined for cell-based activity, were fit to Lipinski's rule of 5, and were examined for potential gastrointestinal permeability using the intestinal epithelial cell line, Caco-2. Selected groups were substituted at the 2-, 4-, and 5-positions of the pyrimidine ring using solution-phase combinatorial methodology. The introduction of a fluorine in the place of 2-chlorine of 1 resulted in a compound with comparable activity. However, other substitutions at the 2-position resulted in a loss of activity. The trifluoromethyl group at the 4-position could be replaced with a methyl, ethyl, chlorine, or phenyl without a substantial loss of activity. The carboxamide group at the 5-position is critical for activity. If it was moved to the 6-position, the activity was lost. The 2-methyl analogue of 1 (81) showed comparable in vitro activity and improved Caco-2 permeability compared to 1.

Developments in solution-phase combinatorial chemistry

The use of solution-phase parallel synthesis as a means of producing libraries of compounds for lead discovery and optimization has increased steadily. More emphasis has been placed on the development of techniques that are applicable across a range of structures and chemistries. In addition, the techniques have been developed with a medicinal chemistry focus and therefore, can be used by a wide range of chemists in standard laboratory settings. This review highlights some of the developments over the last 12 to 18 months, including the use of multi-component reactions and high-throughput purification. New chemistry that may be applicable to parallel synthesis, useful scavenging techniques, and the combination of several polymer-bound reagents or applications.

2-Chloro-4-(trifluoromethyl)pyrimidine-5-N-(3',5'- bis(trifluoromethyl)phenyl)-carboxamide: a potent inhibitor of NF-kappa B- and AP-1-mediated gene expression identified using solution-phase combinatorial chemistry

Described is the identification of a novel series of compounds that blocks the activation of two key transcription factors, AP-1 and NF-kappa B. These transcription factors regulate the expression of several critical proinflammatory proteins and cytokines and represent attractive targets for drug discovery. Through the use of high throughput screening and solution-phase parallel synthesis, inhibitors of both NF-kappa B and AP-1 were identified. In subsequent testing, these compounds were also shown to block both IL-2 and IL-8 levels in the same cells. One of the most potent compounds in this series, 28, was active in several animal models of inflammation and immunosuppression, thus validating the importance of AP-1 and NF-kappa B as potential therapeutic targets. The synthesis and preliminary structure-activity relationships of these compounds is addressed.

Synthesis and antibacterial activity of new quinolones containing a 7-[3-(1-amino-1-methylethyl)-1-pyrrolidinyl] moiety. Gram-positive agents with excellent oral activity and low side-effect potential

A series of the R and S isomers of 7-[3-(1-amino-1-methylethyl)-1-pyrrolidinyl]-1,4-dihydro-4-oxoquinoline- and 1,8-naphthyridine-3-carboxylic acids was prepared to determine the effect on potency of the two methyl groups adjacent to the distal nitrogen in the pyrrolidinyl moiety. The antibacterial efficacy of these dimethylated derivatives was compared to the relevant 7-[3-(aminomethyl)-1-pyrrolidinyl] parent compounds and, to a lesser extent, the 7-[3-(1-aminoethyl)-1-pyrrolidinyl] analogues. The activity of the title and reference compounds was assayed in vitro using an array of Gram-negative and Gram-positive organisms and in vivo using a mouse infection model. Selected derivatives were then screened for potential side effects in a phototoxicity mouse model and an in vitro mammalian cell cytotoxicity protocol. The results showed that the R isomer displayed a 2-20-fold advantage in activity in vitro and a 2-15-fold advantage in vivo over the S isomer. Although equipotent to the 7-[3-(aminomethyl)-1-pyrrolidinyl] parent compounds in vitro, the R isomers of the 7-[3-(1-amino-1-methylethyl)-1-pyrrolidinyl] analogues showed a dramatic increase in in vivo potency, especially via the oral route of administration. These same R isomers also appeared to possess a reduced risk of phototoxicity and cytotoxicity. This combination of superior in vivo performance with a low degree of phototoxicity and mammalian cell cytotoxicity recommends these agents for further study. Of these agents, naphthyridine 16-R represents the optimal blend of potency and safety.

Quinolone antibacterials containing the new 7-[3-(1-aminoethyl)-1- pyrrolidinyl] side chain: the effects of the 1-aminoethyl moiety and its stereochemical configurations on potency and in vivo efficacy

A series of stereochemically pure 7-[3-(1-aminoethyl)-1-pyrrolidinyl]-1, 4-dihydro-4-oxoquinoline and 1,8-naphthyridine-3-carboxylic acids, with varied substituents at the 1-, 5-, and 8-positions, were synthesized to study the effects of the 7-[3-(1-aminoethyl)-1- pyrrolidinyl] moiety on potency and in vivo efficacy relative to the known 7-[3-(aminomethyl)-1- pyrrolidinyl] derivatives. The antibacterial efficacies of the target compounds and their relevant reference agents were determined in vitro using an assortment of Gram-negative and Gram-positive organisms and in vivo using Escherichia coli and Streptococcus pyogenes mouse infection models. The effects of the 7-[3-(1-aminoethyl)-1-pyrrolidinyl] moiety were also examined at the level of the target enzyme by employing a DNA-gyrase supercoiling inhibition assay. Selected compounds were further evaluated for potential phototoxic and clastogenic liabilities using a phototoxicity mouse model and an in vitro mammalian cell cytotoxicity assay. It was found that the differences in in vitro antibacterial activity between the stereoisomers were significantly greater than previously reported for other optically pure 3-substituted pyrrolidinyl side chains. Relative to their 7-[3-(aminomethyl)-1-pyrrolidinyl] analogs, the (3R,1S)-3-(1-aminoethyl)pyrrolidines generally conferred a 2-4-fold increase in Gram-positive in vitro activity and an average of 10-fold improvement in oral efficacy. The level of phototoxicity and cytotoxicity of the product quinolones was ultimately determined by the combined influence of the 7-[3-(1-aminoethyl)-1-pyrrolidinyl] side chains and the other quinolone substituents. From this study, several compounds were identified with outstanding antibacterial activity and low degrees of phototoxicity and mammalian cell cytotoxicity. One such agent, 34F-R,S (PD 140248), showed the best overall blend of safety and efficacy.

High capacity in vitro micronucleus assay for assessment of chromosome damage: results with quinolone/naphthyridone antibacterials

A high capacity in vitro micronucleus assay was developed to evaluate the ability of selected 6-fluorinated quinolone and naphthyridone antibacterial compounds to induce micronuclei (MN) in vitro in V79 Chinese hamster lung cells. Log-phase cells in six-well cluster dishes were exposed for 3 h in the absence of S9 to 34 compounds. After treatment, cells were refed with media containing cytochalasin B, incubated for 16 h, and harvested for cell-cycle kinetics (CCK) and MN analyses. The quinolones tested were grouped according to the substituent at the 8-position. All 4 compounds having a halogen substitution at position 8, five of the six 8-trifluoromethyl quinolones, and all eight 8-methoxy-substituted compounds induced a significant increase in MN. Only 5 of the 10 naphthyridone compounds tested, having a variety of substituents at the 7-position, were inducers of MN and the overall magnitude of the response was less than with the quinolones. The minimum clastogenic concentration for the quinolones ranged from 4 to 400 micrograms/ml and for the naphthyridones this range was from 22.5 to 100 micrograms/ml. In the groups examined, napthyridone compounds were less likely than quinolones to induce in vitro MN, particularly when the substituent at the 7-position in the naphthyridone contains some bulk (methyl groups) around the amine side-chain. Most of the quinolones tested induced MN, irrespective of the substituents at positions 7 or 8.

Fluoroquinolones: relationships between structural variations, mammalian cell cytotoxicity, and antimicrobial activity

Fluoroquinolones are potent inhibitors of bacterial topoisomerase II (DNA gyrase). They can also inhibit eukaryotic topoisomerases, which could possibly lead to clastogenicity and/or cellular toxicity. Recent studies have demonstrated a correlation between mammalian cell cytotoxicity of the fluoroquinolones and the potential of these compounds to induce micronuclei, a genetic toxicity endpoint. In an effort to identify potent nontoxic quinolone antibacterials, we have examined the structural features of the fluoroquinolones associated with mammalian cell cytotoxicity. An investigation of a wide variety of substituents at the 1, 5, 7, and 8 positions of a quinolone nucleus was conducted. The results indicate that no one position has a controlling effect on the observed cytotoxicity. Instead, a combination of the various substituents contributes to the effects seen. Certain trends were apparent, such as the fact that compounds with pyrrolidines at the R-7 position were more cytotoxic than those with piperazines, and halogens at R-8 (X-position) were associated with more cytotoxicity relative to hydrogen. A general trend also existed between the cytotoxicity of the compounds and their Gram-positive antibacterial activity. A detailed comparison between the various groups and positional variations as they controlled the cytotoxicity and antibacterial activity is presented.

The biochemistry and pharmacology of PD 116124 (8-amino-2'-nordeoxyguanosine), an inhibitor of purine nucleoside phosphorylase (PNP)

PD 116124 (8-amino-2'-nordeoxyguanosine; 2,8-diamino-1,9-dihydro-9- ([2-hydroxy-1-(hydroxymethyl)ethoxy]methyl)-6H-purin-6-one) is a competitive, reversible inhibitor of human purine nucleoside phosphorylase with an apparent inhibition constant of 0.41 microM. In a cell line system using human MOLT-4 and CEM T lymphoblasts and human MGL-8 and NC-37 B lymphoblasts, PD 116124 failed to inhibit [3H]thymidine uptake at concentrations up to 500 microM. However, in the presence of 10 microM 2'-deoxyguanosine (dGuo), a noninhibitory dGuo concentration by itself, PD 116124 produced potent inhibition of growth of both T cell lines but not of either B cell line. Significant elevation of intracellular 2'-deoxyguanosine triphosphate was observed in both inhibited T cell lines but not in either B cell line. Greater and more sustained accumulation of 2'-deoxyguanosine triphosphate was observed in T lymphoblasts cultured with PD 116124 plus dGuo than with dGuo only. PD 116124 was only weakly inhibitory in human mixed lymphocyte cultures (IC50 approximately equal to 1420 microM), but in the presence of 10 microM dGuo, the IC50 for PD 116124 was reduced to 108.7 microM. Administration of PD 116124 p.o. to normal male Wistar rats caused dose-dependent elevation of plasma inosine up through 500 mg/kg. Maximal inosine elevation occurred at 30 min after dosing, and elevation was significant even 24 hr after dosing. Guanosine was also elevated, although not in a dose-dependent manner. Administration of PD 116124 i.v. produced marked and statistically significant elevation of both inosine and guanosine.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacologic/pharmacokinetic evaluation of emesis induced by analogs of RSU 1069 and its control by antiemetic agents

RB 6145, the ring-opened analog of RSU 1069, and PD 130908, the desoxy ring-opened analog of RSU 1069, were compared to RSU 1069 for their emetic potential in dogs. When RB 6145 and PD 130908 were administered intravenously at doses ranging from 20% to 50% of the mouse equivalent maximum tolerated dose (MTD), both analogs were less emetic than RSU 1069 on a molar basis. Furthermore, the 5HT3 antagonist ondansetron prevented emesis at doses as high as 75% of the MTD. The reactivity, and hence the emetic liability of these compounds, is thought to be mediated by formation of the corresponding aziridine intermediate. In mouse plasma, both analogs rapidly converted to two products, the reactive aziridine and a stable oxiazolidinone species formed upon reaction with bicarbonate in the blood. A positive correlation exists between the amounts of aziridine formed by these analogs and their emetic potential.

Synthesis and evaluation of a series of 3,5-disubstituted benzisoxazole-4,7-diones. Potent radiosensitizers in vitro

A series of 3,5-disubstituted-2,1-benzisoxazole-4,7-diones was synthesized and evaluated as radiosensitizers both in vitro and in vivo. These compounds were designed as non-nitro electron-affinic agents in an effort to alleviate some of the toxicities seen with the 2-nitroimidazole radiosensitizers evaluated in the clinic. Several compounds in this series were potent radiosensitizers in vitro, with sensitizer enhancement ratios of 2.0-2.3 at concentrations less than 0.5 mM. Compounds with potent in vitro activity were also evaluated in vivo. However, none of these compounds showed radiosensitizing activity in vivo. The reduction potentials of these compounds were determined by cyclic voltammetry and compared to other electron-affinic radiosensitizers. In general, the reduction potentials of this series of compounds was slightly more positive than the 2-nitroimidazoles, but they fell within the range postulated as acceptable to yield in vivo activity. The results suggest that factors other than reduction potential may be responsible for the lack of in vivo radiosensitizing activity observed for this class of radiosensitizers.

A new class of analogues of the bifunctional radiosensitizer alpha-(1-aziridinylmethyl)-2-nitro-1H-imidazole-1-ethanol (RSU 1069): the cycloalkylaziridines

A series of compounds related to alpha-(1-aziridinylmethyl)-2-nitro-1H-imidazole-1-ethanol (RSU 1069, 1) were synthesized and evaluated as selective hypoxic cell cytotoxic agents and as radiosensitizers. The aziridine moiety was replaced with a number of other potential alkylating groups including cycloalkylaziridines and azetidines. The data indicated that modification of the aziridine of 1 resulted in a substantial decrease in the ability of the compounds to selectively kill hypoxic cells. However, these modifications did not affect the compounds' in vitro radiosensitizing activity since many of the derivatives were as potent as 1. All of the compounds that were evaluated in vivo were less toxic than 1, and several members of this series had significant activity. The best compound was trans-alpha-[[(4-bromotetrahydro-2H-pyran-3-yl) amino]methyl]-2-nitro-1H-imidazole-1-ethanol (18), which, due to its activity and log P value, is a candidate for additional in vivo studies.

Effect of PD 128763, a new potent inhibitor of poly(ADP-ribose) polymerase, on X-ray-induced cellular recovery processes in Chinese hamster V79 cells

The modifying effects of PD 128763 (3,4-dihydro-5-methyl-1(2H)-isoquinolinone), a potent inhibitor of poly(adenosine-diphosphate (ADP)-ribose) polymerase, on radiation-induced cell killing were examined in Chinese hamster V79 cells. This compound has an IC50 value against the purified enzyme approximately 50X lower than 3-aminobenzamide (3-AB), a widely used specific inhibitor of the enzyme. Exposure of exponentially growing cells to a noncytotoxic concentration (0.5 mM) of PD 128763 for 2 h immediately following X irradiation increased their radiation sensitivity, modifying both the shoulder and the slope of the survival curve. When recovery from sublethal damage and potentially lethal damage was examined in exponential and plateau-phase cells, respectively, postirradiation incubation with 0.5 mM PD 128763 was found not only to inhibit both these processes fully, but also to enhance further the level of radiation-induced cell killing. This is in contrast to the slight effect seen with the less potent inhibitor, 3-AB. The results presented suggest that the mechanism of radiosensitization by PD 128763 is related to the potent inhibition of poly(ADP-ribose) polymerase by this compound.

Dihydroisoquinolinones: the design and synthesis of a new series of potent inhibitors of poly(ADP-ribose) polymerase

A series of dihydroisoquinolinones, formally rigid analogs of 3-substituted benzamides, and a series of 2,3-disubstituted benzamides were synthesized and evaluated as inhibitors of poly(ADP-ribose) polymerase. The results indicated that the orientation of the amide with respect to the substituent on the aromatic ring was critical for optimum inhibitory activity. Selected compounds were also evaluated for their ability to modify the radiation response of mammalian cells to ionizing radiation. A number of the 5-substituted dihydroisoquinolinones, which were very potent inhibitors of the enzyme, were able to enhance the lethal effects of ionizing radiation in mammalian cells, as measured by changes in the survival curve parameters Do and/or Dq.

Dual-function radiosensitizers. Alpha-[[(2-bromoethyl)amino]methyl]-2-nitro-1H-imidazole-1-ethanol and related compounds: preparation via an aziridine equivalent

An improved synthesis of the dual-function radiosensitizer alpha-[[(2-bromoethyl)amino]methyl]-2-nitro-1H-imidazole-1-ethanol (2, RB 6145) has been developed. Previously, the synthetic difficulties associated with this compound limited its attractiveness as a clinical candidate, although its radiosensitizing activity in preclinical models warranted its further development. The synthesis described uses a 2-oxazolidinone as an aziridine equivalent and provides 2 in 47% yield.

Synthesis and evaluation of alpha-[[(2-haloethyl)amino]methyl]-2- nitro-1H-imidazole-1-ethanols as prodrugs of alpha-[(1-aziridinyl)methyl]-2- nitro-1H-imidazole-1-ethanol (RSU-1069) and its analogues which are radiosensitizers and bioreductively activated cytotoxins

alpha-[(1-Aziridinyl)methyl]-2-nitro-1H-imidazole-1-ethanols, of general formula ImCH2CH(OH)CH2NCR1R2CR3R4, where Im = 2-nitroimidazole and R1, R2, R3, R4 = H, Me, are radiosensitizers and selective bioreductively activated cytotoxins toward hypoxic tumor cells in vitro and in vivo. Treatment of the aziridines with hydrogen halide in acetone or aqueous acetone gave the corresponding 2-haloethylamines of general formula ImCH2CH(OH)CH2(+)-NH2CR1R2CR3R4X X-, where R1, R2, R3, R4 = H, Me, and X = F, Cl, Br, I. These 2-haloethylamines were evaluated as prodrugs of the parent aziridines. The rates of ring closure in aqueous solution at pH approximately 6 were found to increase with increasing methyl substitution and to depend on the nature of the leaving group (I approximately Br greater than Cl much greater than F). A competing reaction of ImCH2CH(OH)CH2+NH2CH2CH2X X- (X = Cl, Br) with aqueous HCO3- ions gives 3-[2-hyroxy-3-(2-nitro-1H-imidazol-1-yl)propyl]-2-oxazolidinone. The activities of these prodrugs as radiosensitizers or as bioreductively activated cytotoxins were consistent with the proportion converted to the parent aziridine during the course of the experiment. alpha-[[(2-Bromoethyl)amino]methyl]-2-nitro-1H-imidazole-1- ethanol (RB 6145, 10), the prodrug of alpha-[(1-aziridinyl)methyl]-2-nitro-1H-imidazole-1-ethanol (RSU-1069, 3), is identified as the most useful compound in terms of biological activity and rate of ring closure under physiological conditions.

1,4-Dihydropyridine antagonist activities at the calcium channel: a quantitative structure-activity relationship approach

The effect of 46 1,4-dihydropyridine-type calcium channel antagonists on the tonic contractile response of longitudinal muscle strips of guinea pig ileum was determined. 2,6-Dimethyl-3,5-dicarbomethoxy-4-phenyl-1,4-dihydropyridine (13) and 13 ortho-, 15 meta-, and seven para-monosubstituted and 10 polysubstituted aromatic derivatives of 13 were studied. The pharmacological activities of the monosubstituted derivatives were best correlated by eq 10, log 1/C = 0.68 pi + 2.50 sigma m -0.47Lmeta -3.40B1para + 11.31, which had a correlation coefficient of 0.89. The full data set was best correlated by eq 11, log 1/C = 0.62 pi + 1.96 sigma m -0.44Lmeta -3.26B1para -1.51Lmeta' + 14.23, which had a correlation coefficient of 0.90. Equations of similar form but involving an ortho steric term were found to correlate the radioligand binding data for this class of compounds.

8-Amino-9-substituted guanines: potent purine nucleoside phosphorylase (PNP) inhibitors

A series of 8-amino-9-substituted guanines was synthesized and their activity evaluated against human purine nucleoside phosphorylase (PNP). All compounds were found to be potent inhibitors of human PNP (IC50s: 0.17-126 microM). They were also selectively cytotoxic to MOLT-4 lymphoblasts in the presence of a nontoxic amount (10 microM) of the PNP substrate, 2'-deoxyguanosine (GdR). The most potent of these analogs, 2,8-diamino-1,9-dihydro-9-(2-thienylmethyl)-6H-purin-6-one (8-amino-9-(2-thienylmethyl)guanine; PD 119,229) has an IC50 of 0.17 microM (Ki = 0.067 microM), significantly more potent than the known standard, 8-aminoguanosine (IC50 = 1.40 microM). Thus it represents the most potent PNP inhibitor known to date when tested without limiting the concentration of inorganic phosphate.

Inhibitors of human purine nucleoside phosphorylase. Synthesis, purine nucleoside phosphorylase inhibition, and T-cell cytotoxicity of 2,5-diaminothiazolo[5,4-d]pyrimidin-7(6H)-one and 2,5-diaminothiazolo[4,5-d]pyrimidin-7(6H)-one. Two thio isosteres of 8-aminoguanine

8-Aminoguanine is a potent inhibitor of purine nucleoside phosphorylase (PNP) and also a substrate of PNP. Two thio isosteres of 8-aminoguanine, 2,5-diaminothiazolo[5,4-d]pyrimidin-7(6H)-one (2) and 2,4-diaminothiazolo[4,5-d]pyrimidin-7(6H)-one (3), which cannot be substrates of PNP, were synthesized and evaluated for their inhibitory activity against PNP. They were found to be weak inhibitors of PNP and to be noncytotoxic for MOLT-4 T-cells in culture.

Relative affinity of 17 alpha- and/or 21-esters and 17 alpha, 21-diesters of cortisol for a glucocorticoid receptor from rat thymocytes

The affinity, relative to cortisol (1), of 17 alpha- and 21-esters and 17 alpha,21-diesters of cortisol for the glucocorticoid receptor of rat thymus cytosol was determined by a competitive binding assay which used [3H]dexamethasone. Esterification of the 21-hydroxy group of cortisol caused a loss of relative affinity to 0.046 for acetate and 0.32 for valerate. Esterification of the 17 alpha-hydroxy group resulted in an increase in relative affinity to 1.14 for acetate, 12.4 for butyrate, and 11.5 for valerate. Diesters had relative affinities which reflected both trends. Thus, the 21-acetate, 21-propionate, 21-butyrate, and 21-valerate of cortisol 17-acetate had relative affinities of 0.036, 0.093, 0.152, and 0.272. The 21-acetate, 21-propionate, and 21-butyrate of cortisol 17-valerate had relative affinities of 0.76, 1.17, and 1.33.