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Factors affecting binding of trans-N-[2-(methylamino)cyclohexyl]benzamides at the primary morphine receptor.

In this paper, we describe the synthesis of a series of trans-N-[2-(methylamino)cyclohexyl]benzamides possessing morphine-like pharmacological properties. The affinity of the compounds for the agonist and antagonist states of the mu opioid receptor has been established by means of an in vitro binding assay. We have investigated the geometry and electronic structure of the molecules using molecular mechanics and an ab initio SCF-MO procedure with FSGO basis sets. Comparison to naloxone reveals properties of possible importance in receptor association. We have considered both the S,S and R,R isomers in the binding model. Statistical analyses imply that three factors play a significant role in binding: (1) membrane-water partitioning, (2) the capacity of the aromatic ring and amine N-substituent to act as electron acceptors, (3) the conformational energy required to attain the binding configuration.

Animals↗

Synthesis and anticonvulsant activity of analogues of 4-amino-N-(1-phenylethyl)benzamide.

A group of amides and amines related to 4-amino-N-(1-phenylethyl)benzamide, 1, were prepared in a study on the relationship of structure to anticonvulsant activity in this compound. Acylation and alkylation of the amino group of 1 resulted in almost total loss of anticonvulsant activity. Insertion of a methylene between the 4-amino group and the aromatic ring of 1 produced a slight increase in anticonvulsant potency and a significant increase in toxicity. Hydride reduction of the amide carbonyl in 1 also yielded compounds having a slightly lower ED50 against convulsions induced by electroshock and a much lower TD50 in the rotorod assay. Modification of the 1-phenylethyl group of 1 also decreased anticonvulsant potency.

Animals↗

Dopamine D-2 receptor imaging radiopharmaceuticals: synthesis, radiolabeling, and in vitro binding of (R)-(+)- and (S)-(-)-3-iodo-2-hydroxy-6-methoxy-N- [(1-ethyl-2-pyrrolidinyl)methyl]benzamide.

In developing central nervous system (CNS) dopamine D-2 receptor imaging agents, enantiomers, R-(+) and S-(-) isomers, of 3-[125I]iodo-2-hydroxy-6-methoxy-N-[(1-ethyl-2- pyrrolidinyl)methyl]benzamide, [125I]IBZM, were synthesized, and their in vitro binding characteristics were evaluated in rat striatum tissue preparation. The (S)-(-)-[125I]IBZM showed high specific dopamine D-2 receptor binding (Kd = 0.43 nM, Bmax = 0.48 pmol/mg of protein). Competition data of various ligands for IBZM binding displayed the following rank order of potency: spiperone greater than (S)-(-)-IBZM greater than (+)-butaclamol much greater than (R)-(+)-IBZM greater than (S)-(-)-BZM greater than dopamine greater than ketanserin greater than SCH23390 much greater than propanolol. The results indicate that [125I]IBZM binds specifically to the dopamine D-2-receptor with stereospecificity. The [123I]IBZM is potentially useful as an imaging agent for the investigation of dopamine D-2 receptors in humans.

Animals↗

Substituted benzamides. 1. Potential nondopaminergic antagonists of chemotherapy-induced nausea and emesis.

A series of new substituted benzamides has been synthesized and evaluated for dopamine antagonist activity and for antagonism of cisplatin-induced emesis in the dog and in the ferret. It was found that modification of the 2-methoxy substituent of metoclopramide was detrimental to dopaminergic D2 antagonism but not necessarily to antagonism of cisplatin-induced emesis. A number of analogues having a beta-keto, beta-hydroxy, beta-methoxy, beta-imino, or beta-unsaturated alkyloxy substituent instead of methoxy have shown equal or superior protection from emesis to that of metoclopramide. At the same time these compounds were found to be free of dopaminergic D2 antagonism in both in vitro ([3H]spiperone binding) and in vivo tests (rat catalepsy, antagonism of apomorphine-induced stereotypy in the rat, and apomorphine-induced emesis in the dog).

Animals↗

Stereoselective preparation of N-[(R,R)-(E)-1-(3,4-dichlorobenzyl)-3- (2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide, a potent and orally active dual neurokinin NK(1)/NK(2) receptor antagonist.

In a program aimed at the development of neurokinin antagonists, N-[(R,R)-(E)-1-(3,4-dichlorobenzyl)-3-(2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide (1, DNK333) has been discovered as a potent and balanced neurokinin (tachykinin) NK(1)/NK(2) receptor antagonist. Enantiomerically pure (>99.5% ee) 1 can be prepared in 6 + 1 synthetic steps starting from commercially available optically active BOC-d-3,4-dichlorophenylalanine in an overall yield of ca. 25-30%. 1 showed potent affinities to cloned human NK(1) (pK(i) = 8.38) and NK(2) (pK(i) = 8.02) receptors. When 1 was compared to the other possible three diastereoisomers, it could be demonstrated that only the R,R-isomer (1) exhibits potent and balanced affinity for the cloned human NK(1) and NK(2) receptors. 1 exhibited favorable pharmacokinetic properties in guinea pigs following oral administration and demonstrated in vivo activity in pharmacological models of substance P- and neurokinin A (NKA)-induced bronchoconstriction in guinea pigs after intravenous and in squirrel monkeys after oral application.

Administration, Oral↗

Discovery of positive allosteric modulators for the metabotropic glutamate receptor subtype 5 from a series of N-(1,3-diphenyl-1H- pyrazol-5-yl)benzamides that potentiate receptor function in vivo.

This report describes the discovery of the first centrally active allosteric modulators of the metabotropic glutamate receptor subtype 5 (mGluR5). Appropriately substituted N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamides (e.g., 8) have been identified as a novel class of potent positive allosteric modulators of mGluR5 that potentiate the response to glutamate. An iterative analogue library synthesis approach provided potentiators with excellent potency and selectivity for mGluR5 (vs mGluRs 1-4, 7, 8). Compound 8q demonstrated in vivo proof of concept in an animal behavior model where known antipsychotics are active, supporting the development of new antipsychotics based on the NMDA hypofunction model for schizophrenia.

Allosteric Regulation↗

Novel inhibitor of p38 MAP kinase as an anti-TNF-alpha drug: discovery of N-[4-[2-ethyl-4-(3-methylphenyl)-1,3-thiazol-5-yl]-2-pyridyl]benzamide (TAK-715) as a potent and orally active anti-rheumatoid arthritis agent.

The p38 mitogen-activated protein (MAP) kinase has been implicated in the proinflammatory cytokine signal pathway, and its inhibitors are potentially useful for the treatment of chronic inflammatory diseases such as rheumatoid arthritis (RA) and inflammatory bowel disease. To develop a new drug for RA, we synthesized a novel series of 4-phenyl-5-pyridyl-1,3-thiazoles and evaluated their inhibition of p38 MAP kinase, lipopolysaccharide (LPS)-stimulated release of tumor necrosis factor-alpha (TNF-alpha) from human monocytic THP-1 cells in vitro, and LPS-induced TNF-alpha production in vivo in mice. During the course of the study, we found that these compounds risk the inhibition of cytochrome P450 (CYP) isoforms by coordination of the 4-pyridyl nitrogen with heme iron. We therefore investigated the effects of substitution at the 2-position of the pyridyl ring on the inhibitory activity of p38 MAP kinase and CYPs in more detail. As a result, N-[4-[2-ethyl-4-(3-methylphenyl)-1,3-thiazol-5-yl]-2-pyridyl]benzamide (8h, TAK-715) exhibited potent inhibitory activity in these assays (inhibition of p38alpha, IC50 = 7.1 nM; LPS-stimulated release of TNF-alpha from THP-1, IC50 = 48 nM; LPS-induced TNF-alpha production in mice, 87.6% inhibition at 10 mg/kg, po) and no inhibitory activity for major CYPs, including CYP3A4. This compound also showed good bioavailability in mice and rats and significant efficacy in a rat adjuvant-induced arthritis model. Compound 8h was selected as a clinical candidate and is now under clinical investigation for the treatment of RA.

Administration, Oral↗

Design and synthesis of tri-ring P3 benzamide-containing aminonitriles as potent, selective, orally effective inhibitors of cathepsin K.

We have prepared a series of achiral aminoacetonitriles, bearing tri-ring benzamide moieties and an aminocyclohexanecarboxylate residue at P2. This combination of binding elements resulted in sub-250 pM, reversible, selective, and orally bioavailable cathepsin K inhibitors. Lead compounds displayed single digit nanomolar inhibition in vitro (of rabbit osteoclast-mediated degradation of bovine bone). The best compound in this series, 39n (CRA-013783/L-006235), was orally bioavailable in rats, with a terminal half-life of over 3 h. 39n was dosed orally in ovariectomized rhesus monkeys once per day for 7 days. Collagen breakdown products were reduced by up to 76% dose-dependently. Plasma concentrations of 39n above the bone resorption IC50 after 24 h indicated a correlation between functional cellular and in vivo assays. Inhibition of collagen breakdown by cathepsin K inhibitors suggests this mechanism of action may be useful in osteoporosis and other indications involving bone resorption.

Administration, Oral↗

Discovery of 3-methyl-N-(1-oxy-3',4',5',6'-tetrahydro-2'H-[2,4'-bipyridine]-1'-ylmethyl)benzamide (ABT-670), an orally bioavailable dopamine D4 agonist for the treatment of erectile dysfunction.

The goal of this study was to identify a structurally distinct D(4)-selective agonist with superior oral bioavailability to our first-generation clinical candidate 1a (ABT-724) for the potential treatment of erectile dysfunction. Arylpiperazines such as (heteroarylmethyl)piperazine 1a, benzamide 2, and acetamides such as 3a,b exhibit poor oral bioavailability. Structure-activity relationship (SAR) studies with the arylpiperidine template provided potent partial agonists such as 4d and 5k that demonstrated no improvement in oral bioavailability. Further optimization with the (N-oxy-2-pyridinyl)piperidine template led to the discovery of compound 6b (ABT-670), which exhibited excellent oral bioavailability in rat, dog, and monkey (68%, 85%, and 91%, respectively) with comparable efficacy, safety, and tolerability to 1a. The N-oxy-2-pyridinyl moiety not only provided the structural motif required for agonist function but also reduced metabolism rates. The SAR study leading to the discovery of 6b is described herein.

Action Potentials↗

Synthesis and central dopaminergic effects of N-(4,6-dimethyl-2-pyridinyl)benzamides.

N-(4,6-Dimethyl-2-pyridinyl)benzamides 1-24 and the corresponding tertiary derivatives 29-33 were synthesized and studied for possible dopamine-inhibitory properties by testing their effect on motility of naive and reserpinized mice. Unlike the orthopramides, they failed to show any antidopaminergic properties, but some of the secondary derivatives showed instead effects of postsynaptic dopaminergic agonism. The latter compounds were subsequently studied for their effects on apomorphine reversal of reserpine-induced akinesia and on cerebral HVA levels in rats. Contraversive circling induced by compound 11 in 6-hydroxydopamine-lesioned mice suggests that a direct mechanism was involved.

Animals↗

A potential melanoma tracer: synthesis, radiolabeling, and biodistribution in mice of a new nitridotechnetium bis(aminothiol) derivative pharmacomodulated by a N-(diethylaminoethyl)benzamide.

Radioiodobenzamides are the best-known agents under study for the diagnosis of cutaneous melanoma and its metastases. We report the synthesis of a new BAT derivative radiopharmaceutical in which radioiodine is replaced by 99m-technetium. The cyclic intermediary methyl 4-[3-(4,4,7,7-tetramethyl-5,6-dithia-2, 9-diazacyclodecyl)-2-oxapropyl]benzoate (5) occurred in two different conformations identified by spectroscopic analysis. The final BAT ligand was radiolabeled using the nitridotechnetium core by a ligand-exchange reaction. Two different complexes were purified. After macroscopic 99-technetium synthesis, syn and anti isomers were identified. The global radiochemical yield was over 80%. The biodistribution of these two complexes was evaluated in mice bearing murine B16 melanoma. Extensive liver and kidney uptake was observed, but the benzamide tropism for the tumor was partially preserved.

Animals↗

Molecular moment similarity between clozapine and substituted [(4-phenylpiperazinyl)-methyl] benzamides: selective dopamine D4 agonists.

Moment descriptors of the molecular charge and mass distributions are investigated within the context of molecular similarity. Euclidean distances in the moment descriptor space are shown to yield molecular proximities in accord with chemical intuition for a substituted [(4-phenylpiperazinyl)-methyl] benzamide series of dopamine D4 agonists. The proximity of the dopamine D4 antagonist clozapine to the molecules of this series is also examined in the moment space.

Benzamides↗

Mechanism of action for N-substituted benzamide-induced apoptosis.

We have analysed the mechanism of action for induction of apoptosis by N-substituted benzamides using declopramide as a lead compound. We show here that declopramide at doses above 250 microM in the mouse 70Z/3 pre-B cell line or in the human promyeolocytic cancer cell line HL60 induced cytochrome c release into the cytosol and caspase-9 activation. The broad spectrum caspase inhibitor zVADfmk and caspase-9 inhibitor zLEDHfmk inhibited apoptosis and improved cell viability when administrated to cells 1 h before exposure to declopramide, whereas the caspase-8 inhibitor zIEDHfmk had less effect. Also, the over expression of Bcl-2 by transfection in 70Z/3 cells inhibited declopramide-induced apoptosis. Prior to the induction of apoptosis, a G(2)/M cell cycle block was induced by declopramide. The cell cycle block was also observed in the presence of broad spectrum caspase inhibitor zVADfmk and in a transfectant expressing high levels of Bcl-2. Furthermore, while p53 was induced in 70Z/3 cells by declopramide, neither the apoptotic mechanism nor the G(2)/M cell cycle block were dependent on p53 activation since both effects were also seen in p53 deficient HL60 cells after addition of declopramide.

Apoptosis↗

Maintenance of ATP favours apoptosis over necrosis triggered by benzamide riboside.

A new synthetic drug, benzamide riboside (BR) exhibited strong oncolytic activity against leukemic cells in the 5-10 microM range. Higher BR-concentrations (20 microM) predominantly induced necrosis which correlated with DNA strand breaks and subsequent depletion of ATP- and dATP levels. Replenishment of the ATP pool by addition of adenosine prevented necrosis and favoured apoptosis. This effect was not a pecularity of BR-treatment, but was reproduced with high concentrations of all trans-retinoic acid (120 microM) and cyanide (20 mM). Glucose was also capable to suppress necrosis and to favour apoptosis of HL-60 cells, which had been treated with necrotic doses of BR and cyanide. Apoptosis eliminates unwanted cells without affecting the microenvironment, whereas necrosis causes severe inflammation of surrounding tissues due to spillage of cell fluids into the peri-cellular space. Thus, the monitoring and maintenance of cellular energy pools during therapeutic drug treatment may help to minimize nonspecific side effects and to improve attempted drug effects.

Adenosine↗

Structural studies on D2 dopamine receptors: mutation of a histidine residue specifically affects the binding of a subgroup of substituted benzamide drugs.

A histidine residue (His394) that is likely to be located in the ligand-binding region of the D2 dopamine receptor has been mutated to a leucine (Leu394), and the properties of the mutant receptor have been determined. For a range of antagonists the mutation has only a minor effect on the affinity of the receptor for the antagonist. The mutation does, however, elicit a structurally specific effect on the affinity with which certain members of the substituted benzamide class of antagonist bind to the receptor. Some of these drugs, e.g., sulpiride, sultopride, and tiapride, bind with reduced affinity to the mutated receptor, whereas others, e.g., clebopride and metoclopramide, bind with increased affinity. However, the Na+/H+ sensitivity of the binding of sulpiride to the receptor is not reduced by the mutation. These findings have been interpreted in terms of the productive or unfavourable interaction of the His394 residue with these compounds.

Amino Acid Sequence↗

Multiple mechanisms of action of the benzamides and nicotinamides as sensitizers of radiotherapy: opportunities for drug design.

The benzamides and nicotinamides are a well-known class of drugs that contain many analogs having radio- and chemosensitizing properties. This study reports on a structural analysis in order to explain the chemical features important to their mechanisms of action. In general, N-substituted analogs are distinguished from the non-N-substituted analogs because they (i) are susceptible to radiolysis, (ii) induce cytotoxicity by apoptosis but not necrosis, (iii) inhibit cell proliferation, (iv) activate poly adenosine diphosphate ribosyl transferase (poly ADPRT), and (v) have a much-reduced effect on microregional tumor blood perfusion. It was concluded that the mechanism of action of N-substituted analogs is shifted from primary effects on tumor vascularization as is seen with the non-N-substituted analogs to one where radiosensitization can be explained by selective induction of apoptosis via radiolysis and accumulation of DNA damage. This knowledge may be useful in the design of drugs possessing multiple mechanisms of radiosensitizing action.

Animals↗

Substituted benzamides as ligands for visualization of dopamine receptor binding in the human brain by positron emission tomography.

Two substituted benzamides, FLB 524 and raclopride, were labeled with 11C and examined for their possible use as ligands for positron emission tomography (PET)-scan studies on dopamine-2 (D-2) receptors in the brains of monkeys and healthy human subjects. Both ligands allowed the in vivo visualization of D-2 receptor binding in the corpus striatum caudate nucleus/putamen complex in PET-scan images. [11C]Raclopride showed a high ratio of specific striatal to nonspecific cerebellar binding, and the kinetics of binding of this ligand made it optimal for PET studies. The in vivo binding of [11C]raclopride in the striatum of cynomolgus monkeys was markedly reduced by displacement with haloperidol. This and previous in vitro data indicate that [11C]raclopride binds selectively to striatal D-2 dopamine receptors. In healthy human subjects, [11C]raclopride binding in the caudate nucleus/putamen was 4- to 5-fold greater than nonspecific binding in the cerebellum. In comparison with previously available ligands for PET-scan studies on central dopamine receptors in man, [11C]raclopride appears to be advantageous with regard to (i) specificity of binding to D-2 receptors, (ii) the high ratio between binding in dopamine-rich (caudate, putamen) and dopamine-poor (cerebellum) human brain regions, and (iii) rapid association and reversibility of specific binding. [11C]Raclopride should be a valuable tool for characterizing D-2 receptors in the brains of patients with neuropsychiatric disorders.

Animals↗