Molecular Modeling, Structure–Activity Relationships and Functional Antagonism Studies of 4-Hydroxy-1-methyl-4-(4-methylphenyl)-3-piperidyl 4-Methylphenyl Ketones as a Novel Class of Dopamine Transporter Inhibitors (original) (raw)
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Journal of Pharmacology and Experimental Therapeutics, 2013
ABSTRACT An N-butyl analog of benztropine, JHW007, binds to dopamine transporters (DAT), but has reduced cocaine-like behavioral effects and antagonizes various effects of cocaine. The present studies further examined mechanisms underlying these effects. Cocaine dose-dependently increased locomotion, whereas JHW007 was minimally effective, but increased activity 24-hr after injection. JHW007 (3-10 mg/kg) dose-dependently and fully antagonized the locomotor-stimulant effects of cocaine (5-60 mg/kg), whereas N-methyl and N-allyl analogs and the dopamine (DA) uptake inhibitor, GBR12909, stimulated activity and failed to antagonize effects of cocaine. JHW007 also blocked the locomotor-stimulant effects of the DAT inhibitor, GBR12909, but not stimulation produced by the δ-opioid agonist, SNC80, which increases activity through non-dopaminergic mechanisms. JHW007 blocked locomotor-stimulant effects of cocaine in both DA D2 and CB1 receptor knock-out and wild-type mice, indicating a lack of involvement of these targets. Further, JHW007 also blocked effects of cocaine on stereotyped rearing but enhanced stereotyped sniffing; suggesting that interference with locomotion by enhanced stereotypies is not responsible for the cocaine-antagonist effects of JHW007. Time-course data indicate that administration of JHW007 antagonized the locomotor-stimulant effects of cocaine within 10-min of injection, whereas occupancy at the DAT determined in vivo did not reach a maximum until 4.5 hr after injection. The sigma1-receptor antagonist, BD1008, blocked the locomotor-stimulant effects of cocaine. Overall, these findings suggest that the JHW007 has cocaine-antagonist effects that are deviate from its DAT occupancy and that some other mechanism, possibly sigma-receptor antagonist activity, may contribute to the cocaine-antagonist effect of JHW007 and like drugs.
Journal of Medicinal Chemistry, 2000
A novel, fairly potent dopamine transporter (DAT) inhibitor, 4-hydroxy-1-methyl-4-(4-methylphenyl)-3-piperidyl 4-methylphenyl ketone (3, K i values of 492 and 360 nM in binding affinity and inhibition of dopamine reuptake, respectively), with significant functional antagonism against cocaine and a different in vitro pharmacological profile from cocaine at the three transporter sites (dopamine, serotonin, and norepinephrine) was discovered through 3Ddatabase pharmacophore searching. Through structure-activity relationships and molecular modeling studies, we found that hydrophobicity and conformational preference are two additional important parameters that determine affinity at the DAT site. Chemical modifications of the lead compound (3) led to a high affinity analogue (6, K i values of 11 and 55 nM in binding affinity and inhibition of dopamine reuptake, respectively). In behavioral pharmacological testing, 6 mimics partially the effect of cocaine in increasing locomotor activity in mice but lacks cocaine-like discriminative stimulus effect in rats. Taken together, these data suggest that 6 represents a promising lead for further evaluations as potential therapy for the treatment of cocaine abuse. * To whom correspondence and request of reprints should be sent.
Journal of Pharmacology and Experimental Therapeutics, 2002
Drugs that block dopamine uptake often function as positive reinforcers but can differ along the dimension of strength or effectiveness as a positive reinforcer. The present study was designed to examine pharmacological mechanisms that might contribute to differences in reinforcing strength between the piperidine-based cocaine analog (ϩ)-methyl 4-(4-chlorophenyl)-1-methylpiperidine-3-␣-carboxylate [(ϩ)-CPCA] and cocaine. Drugs were made available to rhesus monkeys (n ϭ 5) for i.v. self-administration under a progressive ratio schedule. Both compounds maintained responding with sigmoidal or biphasic dose-response functions (0.1-1.0 mg/kg/injection). (ϩ)-CPCA was one-fourth as potent as cocaine and maintained fewer injections per session, at maximum. For in vitro binding in monkey brain tissue, (ϩ)-CPCA was about one-half as potent as cocaine at the dopamine transporter (DAT), and the two compounds had similar affinities at the norepinephrine transporter. (ϩ)-CPCA was less than 1/10 as potent as cocaine at the serotonin transporter. In ex vivo binding in rat striatum, occupancy of the DAT increased directly with dose to a maximum of approximately 80% for both compounds, and (ϩ)-CPCA was about one-fourth as potent as cocaine. Ex vivo DAT occupancy was significantly higher for cocaine than (ϩ)-CPCA at 2 min after injection but similar at other times. Thus, the primary differences between these compounds were in serotonin transporter affinity and the kinetics of DAT binding. These results suggest that (ϩ)-CPCA is a weaker positive reinforcer than cocaine because it has a slower onset of action over the first few minutes after i.v. injection.
Identification of a Dopamine Transporter Ligand That Blocks the Stimulant Effects of Cocaine
Journal of Neuroscience, 2005
There is a large unmet medical need for cocaine addiction treatments. Studies have indicated that the dopamine transporter (DAT) is the primary biological target of cocaine, and most drugs that have DAT affinity have behavioral effects like those of cocaine. However, analogs of benztropine have high DAT affinity and behavioral effects that show varying degrees of similarity to cocaine. We now report the discovery that a benztropine analog, JHW007, with high affinity for the DAT does not have cocaine-like behavioral effects and antagonizes the effects of cocaine. JHW007 occupied the DAT in vivo more slowly than did cocaine and had not reached an apparent plateau up to 270 min after injection. The in vivo binding of cocaine to the DAT suggested rate of DAT occupancy as an important contributor to its behavioral effects, and the slow association with the DAT may provide an explanation for JHW007 being relatively devoid of cocaine-like behavioral effects. The antagonism of cocaine suggests that DAT ligands with reduced cocaine-like activity can function as cocaine antagonists and suggests JHW007 as a lead for discovery of cocaine-abuse pharmacotherapeutics.
Journal of Medicinal Chemistry, 2003
A series of threo-1-aza-3 or 4-substituted-5-phenyl[4.4.0]decanes (quinolizidines), which were envisioned as restricted rotational analogues (RRAs) of methylphenidate (MP), was synthesized and tested for inhibitory potency against [ 3 H]WIN35,428, [ 3 H]citalopram, and [ 3 H]nisoxetine binding to the dopamine, serotonin, and norepinephrine transporters, respectively. Two different synthetic schemes were used; a Wittig reaction or acylation (followed by an intramolecular condensation) was a key feature of each scheme. The unsubstituted RRA, threo(trans)-1-aza-5-phenyl[4.4.0]decane (12a), was equipotent to unconstrained threo-MP against [ 3 H]WIN35,428 binding. The extra ring in these RRAs (which reduces the conformational freedom) and the orientation and polarity of substituents at the 4-position on this extra ring are of critical importance to the biological activity. Generally, the RRAs paralleled the corresponding unconstrained MP derivatives in binding affinity to the three transporters. The results suggest that the conformation of MP in which the carbonyl group of the methyl ester is H-bonded to the piperidinyl N-H may be the bioactive form of the molecule.
Probes for the cocaine receptor. Potentially irreversible ligands for the dopamine transporter
Journal of Medicinal Chemistry, 1992
Several potentially irreversible ligands (Le., wash-resistant binding inhibitors) for the cocaine receptor site on the dopamine transporter, derived from (-)-cocaine or 3B-phenyltropan-28-carboxylic acid methyl ester (WIN 35,065-2), were prepared and shown to produce wash-resistant inhibition of [3H]-3&(p-fluorophenyl)tropan-2~-carboxylic acid methyl ester ([3H]WIN 35,428) binding. All the compounds prepared had the game absolute configuration as cocaine; they include analogues possessing chemically reactive groups such as the isothiocyanato and bromoacetamido as well as photoactive azido groups. The potentially irreversible ligands, as well as all the intermediates prepared in this study, were evaluated for their ability to inhibit the binding of SH]WIN 35,428 in coincubation experiments. Of the potentially irreversible ligands, 3 & ( p c h l o r o p h e n y l ) t r~~~~l i c acid 2-[p(bromoacetamido)phenyl]ethyl ester (6c) had the higheat apparent potency. The potentially irreversible ligands were also preincubated, and inhibition of [3H]WIN 35,428 binding was determined both before and after washing the ligand-exposed tissues. The most effective ligands in this regard were 3~-(3-iodo-4-azidophenyl)tropan-2/3-carboxylic acid methyl ester (5) and 38-@-chlorophenyl)hpan-ropan-2gcarboxylic acid 2-(3-iodo4azidophenyl)ethyl ester (Sa). The structureadivity relationships of these data are discussed. Ritz, M. C.; Lamb, R. J.; Goldberg, S. R.; Kuhar, M. J. Cocaine Receptors on Dopamine Transporters Are Related to Self-administration of Cocaine. Science 1987,237, 1219-1223. Bergman, J.; Madras, B. K.; Johnson, S. E.; Spealman, R. D. Effecta of Cocaine and Related Drug in Nonhuman Primates. 111. Self-administration by Squirrel Monkeys. J. Pharrnacol. Exp. Ther. 1989,251, 150-155. Carroll, F. I.; Lewin, A. H.; Boja, J. W.; Kuhar, M. J. Cocaine Receptor: Biochemical Characterization and Structure-Activity Relationships for the Dopamine Transporter. J. Med. Chern., in press. Boja, J. W.; Rahman, M. R.; Philip, A.; Lewin, A. H.; Carroll, F. I.; Kuhar, M. J. Isothiocyanate Derivatives of Cocaine: Irreversible Inhibition of Ligand Binding at the Dopamine Transporter. Mol. Phormacol. 1991,39,339-345. Lew, R.; Boja, J. W.; Simantov, R.; Carroll, F. I.; Lewin, A.; Kuhar, M. J. New Photoaffinity Probes for the Cocaine Receptor. SOC. Neurosci. Abstr. 1990, 16, 746. Lewin, A. H.; Gao, Y.; Abraham, P.; Boja, J. W.; Kuhar, M. J.; Carroll, F. I. P&Substituted Analogs of Cocaine. Syntheais and Inhibition of Binding to the Cocaine Receptor.
Journal of Medicinal Chemistry, 1999
A series of 2-substituted-6-amino-5-phenylbicyclo[2.2.2]octanes was synthesized and tested for inhibitor potency in [ 3 H]WIN 35,428 (WIN) binding at the dopamine (DA) transporter and [ 3 H]DA uptake assays. To demonstrate transporter selectivity for the compounds, inhibitor potency was also tested using [ 3 H]nisoxetine and [ 3 H]paroxetine binding assays for the norepinephrine (NE) and serotonin (5-HT) transporters, respectively. Synthesis was accomplished by bisannulation of the enamine derived from phenylacetaldehyde and dimethylamine with 2-cyclohexenone to give a mixture of endo-and exo-trans-6-amino-5-phenylbicyclo[2.2.2]octan-2-ones. The separated ketones were reduced to the four diastereomeric alcohols which were converted to acetyl and benzoyl esters. The ketones, alcohols, and acetyl esters generally have low affinity for the three transporters and do not effectively inhibit the uptake of [ 3 H]DA. In all cases, the benzoates show significantly greater inhibition of WIN binding compared to the corresponding ketones, alcohols, or acetate esters. One compound, (1R/S,4R/S)-6R/S-(N,Ndimethylamino)-5R/S-phenylbicyclo[2.2.2]oct-2S/R-yl benzoate, is almost as potent as cocaine in binding to the DA transporter (IC 50) 270 nM versus 159 nM for cocaine). The C-2 epimer, (1R/S,4R/S)-6R/S-(N,N-dimethylamino)-5R/S-phenylbicyclo[2.2.2]oct-2R/S-yl benzoate, was selective and potent in binding to the 5-HT transporter (IC 50) 53 nM versus 1050 nM for cocaine) as compared to the DA transporter (IC 50) 358 nM). A preliminary molecular modeling study of the benzoyl esters indicates that their relative potencies in the WIN binding assay are not correlated to the nitrogen to benzoate phenyl (centroid) distance or to the deviation of the nitrogen from the plane defined by the benzoate ring.
Previous structure-activity relationship studies indicate that a series of cocaine analogs, 3b-aryltropanes with 2b-diarylmethoxy substituents, selectively bind to the dopamine transporter (DAT) with nanomolar affinities that are 10-fold greater than the affinities of their corresponding 2a-enantiomers. The present study compared these compounds to cocaine with respect to locomotor effects in mice, and assessed their ability to substitute for cocaine (10 mg/kg, i.p.) in rats trained to discriminate cocaine from saline. Despite nanomolar DAT affinity, only the 2b-Ph 2 COCH 2-3b-4-Cl-Ph analog fully substituted for cocaine-like discriminative effects. Whereas all of the 2b compounds increased locomotion, only the 2b-(4-ClPh)PhCOCH 2-3b-4-Cl-Ph analog had cocaine-like efficacy. None of the 2a-substituted compounds produced either of these cocaine-like effects. To explore the molecular mechanisms of these drugs, their effects on DAT conformation were probed using a cysteine-accessibility assay. Previous reports indicate that cocaine binds with substantially higher affinity to the DAT in its outward (extracellular)-compared with inward-facing confor-mation, whereas atypical DAT inhibitors, such as benztropine, have greater similarity in affinity to these conformations, and this is postulated to explain their divergent behavioral effects. All of the 2b-and 2a-substituted compounds tested altered cysteine accessibility of DAT in a manner similar to cocaine. Furthermore, molecular dynamics of in silico inhibitor-DAT complexes suggested that the 2-substituted compounds reach equilibrium in the binding pocket in a cocaine-like fashion. These behavioral, biochemical, and computational results show that aryltropane analogs can bind to the DAT and stabilize outward-facing DAT conformations like cocaine, yet produce effects that differ from those of cocaine.
J Med Chem, 2003
Both dopamine uptake inhibitors and σ 1 receptor antagonists have been implicated as potential pharmacotherapeutics for the treatment of cocaine abuse. While the dopamine uptake inhibitors may share with cocaine neurochemical mechanisms underlying reinforcing properties, σ 1 antagonists have been shown to attenuate some behavioral actions and toxic side effects associated with cocaine overdose. Rimcazole, a σ 1 receptor antagonist that binds to the DAT (K i) 224 nM), is not behaviorally cocaine-like and attenuates some of the behavioral actions of cocaine. To determine the roles of both DAT and σ 1 receptors in the behavioral actions of rimcazole, a series of analogues was synthesized. Initial studies identified two analogues (1 and 4) that showed high to moderate affinities for both DAT and σ 1 receptors and failed to show cocaine-like discriminative stimulus (DS) effects. A second series of bis(4′-fluorophenyl)amine analogues have now been prepared in which the most potent DAT compound, 19 (K i) 8.5 nM), was selective over serotonin transporter (SERT/DAT) 94), norepinephrine transporter (NET/DAT) 63), and σ 1 receptor binding (σ 1 /DAT) 44). In addition, two other analogues 10 and 17 showed superior selectivity for DAT over SERT (170-and 140-fold, respectively) and DAT over NET (219-and 190-fold, respectively) but were essentially equipotent at DAT and σ 1 receptors (10; K i) 77 and 124 nM, respectively, 17; K i) 28 and 13 nM, respectively). CoMFA studies at both DAT and σ 1 receptors were performed to examine structural requirements for optimal binding at these two targets as well as to assess differences between them. Behavioral evaluation of analogues with varying affinities for both DAT and σ 1 receptors may provide a novel approach toward designing medications for cocaine abuse.
Psychopharmacology, 2001
Rationale: Previous SAR studies demonstrated that small halogen substitutions on the diphenylether system of benztropine (BZT), such as a para-Cl group, retained high affinity at the cocaine binding site on the dopamine transporter. Despite this high affinity, the compounds generally had behavioral effects different from those of cocaine. However, compounds with meta-Cl substitutions had effects more similar to those of cocaine. Objectives: A series of phenyl-ring analogs of benztropine (BZT) substituted with 3′-, 4′-, 3′,4′′- and 4′,4′′-position Cl-groups were synthesized and their pharmacology was evaluated in order to assess more fully the contributions to pharmacological activity of substituents in these positions. Methods: Compounds were synthesized and their pharmacological activity was assessed by examining radioligand binding and behavioral techniques. Results: All of the compounds displaced [3H]WIN 35,428 binding with affinities ranging from 20 to 32.5 nM. Affinities at norepinephrine ([3H]nisoxetine) and serotonin ([3H]citalopram) transporters, respectively, ranged from 259 to 5120 and 451 to 2980 nM. Each of the compounds also inhibited [3H]pirenzepine binding to muscarinic M1 receptors, with affinities ranging from 0.98 to 47.9 nM. Cocaine and the BZT analogs produced dose-related increases in locomotor activity in mice. However, maximal effects of the BZT analogs were uniformly less than those produced by cocaine, and were obtained 2–3 h after injection compared to the relatively rapid onset (within 30 min) of cocaine effects. In rats trained to discriminate IP saline from 29 µmol/kg cocaine (10 mg/kg), cocaine produced a dose-related increase in responding on the cocaine lever, reaching 100% at the training dose; however, none of the BZT analogs fully substituted for cocaine, with maximum cocaine responding from 20 to 69%. Despite their reduced efficacy compared to cocaine in cocaine discrimination, none of the analogs antagonized the effects of cocaine. As has been reported previously for 4′-Cl-BZT, the cocaine discriminative-stimulus effects were shifted leftward by co-administration of the present BZT analogs. Conclusions: The present results indicate that although the BZT analogs bind with relatively high affinity and selectivity at the dopamine transporter, their behavioral profile is distinct from that of cocaine. The present results suggest that analogs of BZT may be useful as treatments for cocaine abuse in situations in which an agonist treatment is indicated. These compounds possess features such as reduced efficacy compared to cocaine and a long duration of action that may render them particularly useful leads for the development of therapeutics for cocaine abusers.