First-in-class, dual-action, 3,5-disubstituted indole derivatives having human nitric oxide synthase (nNOS) and norepinephrine reuptake inhibitory (NERI) activity for the treatment of neuropathic pain

A family of different 3,5-disubstituted indole derivatives having 6-membered rings were designed, synthesized, and demonstrated inhibition of human nitric oxide synthase (NOS) with norepinephrine reuptake inhibitory activity (NERI). The structure-activity relationship (SAR) within the cyclohexane ring showed the cis-isomers to be more potent for neuronal NOS and selective over endothelial NOS compared to their trans-counterparts. Compounds, such as cis-(+)-37, exhibited dual nNOS and NET inhibition (IC(50) of 0.56 and 1.0 μM, respectively) and excellent selectivity (88-fold and 12-fold) over eNOS and iNOS, respectively. The lead compound (cis-(+)-37) showed lack of any direct vasoconstriction or inhibition of ACh-mediated vasorelaxation in isolated human coronary arteries. Additionally, cis-(+)-37 was effective at reversing both allodynia and thermal hyperalgesia in a standard Chung (spinal nerve ligation) rat neuropathic pain model. Overall, the data suggest that cis-(+)-37 is a promising dual action development candidate having therapeutic potential for the treatment of neuropathic pain.     

Discovery of cis-N-(1-(4-(methylamino)cyclohexyl)indolin-6-yl)thiophene-2-carboximidamide: a 1,6-disubstituted indoline derivative as a highly selective inhibitor of human neuronal nitric oxide synthase (nNOS) without any cardiovascular liabilities

A series of 1,6-disubstituted indoline derivatives were synthesized and evaluated as inhibitors of human nitric oxide synthase (NOS) designed to mitigate the cardiovascular liabilities associated with previously reported tetrahydroquinoline-based selective neuronal NOS inhibitors due to higher lipophilicity ( J. Med. Chem. 2011 , 54 , 5562 - 5575 ). This new series produced similar potency and selectivity among the NOS isoforms and was devoid of any cardiovascular liabilities associated with QT prolongation due to hERG activity or endothelial NOS mediated vasoconstriction effect. The SAR studies led to the identification of cis-45, which was shown to reverse thermal hyperalgesia in vivo in the spinal nerve ligation model of neuropathic pain with excellent safety profile (off-target activities at 80 CNS related receptors/ion channels/transporters). The results presented in this report make cis-45 as an ideal tool for evaluating the potential role of selective nNOS inhibitors in CNS related disorders where excess NO produced by nNOS is thought to play a crucial role.     

Design, synthesis, and biological evaluation of 3,4-dihydroquinolin-2(1H)-one and 1,2,3,4-tetrahydroquinoline-based selective human neuronal nitric oxide synthase (nNOS) inhibitors

Neuronal nitric oxide synthase (nNOS) inhibitors are effective in preclinical models of many neurological disorders. In this study, two related series of compounds, 3,4-dihydroquinolin-2(1H)-one and 1,2,3,4-tetrahydroquinoline, containing a 6-substituted thiophene amidine group were synthesized and evaluated as inhibitors of human nitric oxide synthase (NOS). A structure-activity relationship (SAR) study led to the identification of a number of potent and selective nNOS inhibitors. Furthermore, a few representative compounds were shown to possess druglike properties, features that are often difficult to achieve when designing nNOS inhibitors. Compound (S)-35, with excellent potency and selectivity for nNOS, was shown to fully reverse thermal hyperalgesia when given to rats at a dose of 30 mg/kg intraperitonieally (ip) in the L5/L6 spinal nerve ligation model of neuropathic pain (Chung model). In addition, this compound reduced tactile hyperesthesia (allodynia) after oral administration (30 mg/kg) in a rat model of dural inflammation relevant to migraine pain.     

Dipeptides containing L-arginine analogs: new isozyme-selective inhibitors of nitric oxide synthase.

Several L-arginine analogs are known as potent inhibitors of nitric oxide synthase (NOS). We recently synthesized dipeptides containing such amino acids, and found that they are potent and isozyme-selective NOS inhibitors. For example, S-methyl-L-isothiocitrullinyl-L-phenylalanine showed 66-fold selectivity for iNOS over nNOS, while S-methyl-L-isothiocitrullinyl-L-leucine and N(G)-nitro-L-argininyl-L-phenylalanine showed 20- and 14-fold selectivity, respectively. Interestingly, S-methyl-L-isothiocitrullinyl-D-phenylalanine showed no selectivity, and S-methyl-L-isothiocitrullinyl-L-phenylalanine showed competitive inhibition. These results suggest that each NOS isozyme has a cavity of different size near the C-terminal of the L-arginine binding site, and that the selectivity of inhibitors is due to the differences in the size of the cavity.     

N(omega)-Nitroarginine-containing dipeptide amides. Potent and highly selective inhibitors of neuronal nitric oxide synthase.

Selective inhibition of the isoforms of nitric oxide synthase (NOS) could be therapeutically useful in the treatment of certain disease states arising from the overproduction of nitric oxide (NO). Recently, we reported the dipeptide methyl ester, D-Phe-D-Arg(NO)()2-OMe (19), as a modest inhibitor of nNOS (K(i) = 2 microM), but with selectivity over iNOS as high as 1800-fold (Silverman, R. B.; Huang, H.; Marletta, M. A.; Martasek, P. J. Med. Chem. 1997, 40, 2813-2817). Here a library of 152 dipeptide amides containing nitroarginine and amino acids other than Phe are synthesized and screened for activity. Excellent inhibitory potency and selectivity for nNOS over eNOS and iNOS is achieved with the dipeptide amides containing a basic amine side chain (20-24), which indicates a possible electrostatic (or hydrogen bonding) interaction at the enzyme active site. The most potent nNOS inhibitor among these compounds is L-Arg(NO)()2-L-Dbu-NH(2) (23) (K(i) = 130 nM), which also exhibits the highest selectivity over eNOS (>1500-fold) with a 192-fold selectivity over iNOS. These compounds do not exhibit time-dependent inhibition. The order and the chirality of the amino acids in the dipeptide amides have profound influences on the inhibitory potency as well as on the isoform selectivity. These dipeptide amide inhibitors open the door to the design of potent and highly selective inhibitors of nNOS.     

Heterocyclic analogues of N-(4-(4-(2,3-dichlorophenyl)piperazin-1-yl)butyl)arylcarboxamides with functionalized linking chains as novel dopamine D3 receptor ligands: potential substance abuse therapeutic agents

Dopamine D3 receptor antagonists and partial agonists have been shown to modulate drug-seeking effects induced by cocaine and other abused substances. Compound 6 [PG01037, (N-(4-(4-(2,3-dichlorophenyl)piperazin-1-yl)-trans-but-2-enyl)-4-pyridine-2-ylbenzamide)] and related analogues are currently being evaluated in animal models of drug addiction. In these studies, a discrepancy between in vitro binding affinity, in vivo occupancy, and behavioral potency has been observed. The purpose of this study was to examine (1) modifications of the 2-pyridylphenyl moiety of 6 and (2) hydroxyl, acetyl, and cyclopropyl substitutions on the butylamide linking chain systematically coupled with 2-fluorenylamide or 2-pyridylphenylamide and 2-methoxy- or 2,3-dichloro-substituted phenylpiperazines to measure the impact on binding affinity, D2/D3 selectivity, lipophilicity, and function. In general, these modifications were well tolerated at the human dopamine D3 (hD3) receptor (Ki = 1-5 nM) as measured in competition binding assays. Several analogues showed >100-fold selectivity for dopamine D3 over D2 and D4 receptors. In addition, while all the derivatives with an olefinic linker were antagonists, in quinpirole-stimulated mitogenesis at hD3 receptors, several of the hydroxybutyl-linked analogues (16, 17, 21) showed partial agonist activity. Finally, several structural modifications reduced lipophilicities while retaining the desired binding profile.     

Fluorination of 3-(3-(piperidin-1-yl)propyl)indoles and 3-(3-(piperazin-1-yl)propyl)indoles gives selective human 5-HT1D receptor ligands with improved pharmacokinetic profiles.

It has previously been reported that a 3-(3-(piperazin-1-yl)propyl)indole series of 5-HT1D receptor ligands have pharmacokinetic advantages over the corresponding 3-(3-(piperidin-1-yl)propyl)indole series and that the reduced pKa of the piperazines compared to the piperidines may be one possible explanation for these differences. To investigate this proposal we have developed versatile synthetic strategies for the incorporation of fluorine into these ligands, producing novel series of 4-fluoropiperidines, 3-fluoro-4-aminopiperidines, and both piperazine and piperidine derivatives with one or two fluorines in the propyl linker. Ligands were identified which maintained high affinity and selectivity for the 5-HT1D receptor and showed agonist efficacy in vitro. The incorporation of fluorine was found to significantly reduce the pKa of the compounds, and this reduction of basicity was shown to have a dramatic, beneficial influence on oral absorption, although the effect on oral bioavailability could not always be accurately predicted.     

Novel bis(1H-indol-2-yl)methanones as potent inhibitors of FLT3 and platelet-derived growth factor receptor tyrosine kinase

FLT3 receptor tyrosine kinase is aberrantly active in many cases of acute myeloid leukemia (AML). Recently, bis(1H-indol-2-yl)methanones were found to inhibit FLT3 and PDGFR kinases. To optimize FLT3 activity and selectivity, 35 novel derivatives were synthesized and tested for inhibition of FLT3 and PDGFR autophosphorylation. The most potent FLT3 inhibitors 98 and 102 show IC50 values of 0.06 and 0.04 microM, respectively, and 1 order of magnitude lower PDGFR inhibiting activity. The derivatives 76 and 82 are 20- to 40-fold PDGFR selective. Docking at the recent FLT3 structure suggests a bidentate binding mode with the backbone of Cys-694. Activity and selectivity can be related to interactions of one indole moiety with a hydrophobic pocket including Phe-691, the only different binding site residue (PDGFR Thr-681). Compound 102 inhibited the proliferation of 32D cells expressing wildtype FLT3 or FLT3-ITD similarly as FLT3 autophosphorylation, and induced apoptosis in primary AML patient blasts.     

A selective human H(4)-receptor agonist: (-)-2-cyano-1-methyl-3-[(2R,5R)-5- [1H-imidazol-4(5)-yl]tetrahydrofuran-2-y] methylguanidine

A series of 16 compounds related to chiral 4(5)-(5-aminomethyltetrahydrofuran-2-yl)imidazoles (1) have been designed, synthesized, and examined in vitro by radioligand displacement studies and functional assays for both the human H(3)- and H(4)-receptors expressed in SK-N-MC cells. Among them, the (2S,5S)-isomer 1d of amino compounds showed approximately 300-fold higher selectivity at the H(3)-receptor than the H(4)-receptor. On the other hand, (2R,5S)- and (2R,5R)-cyanoguanidines 3b and 3c, in which the amino group of the compounds 1b and 1c was substituted by the cyanoguanidino moiety, bound to the H(4)-receptor with a pEC(50) value of 6.65 and 7.11, respectively, and had >40-fold selectivities over the H(3)-receptor. As such, 3b and 3c are the first selective H(4) receptor agonists.     

Aromatic reduced amide bond peptidomimetics as selective inhibitors of neuronal nitric oxide synthase

Nitric oxide synthase inhibitors could act as important therapies for disorders arising from overstimulation or overexpression of individual nitric oxide synthase (NOS) isoforms. But preservation of physiologically important nitric oxide functions require the use of isoform-selective inhibitors. Recently we reported reduced amide bond pseudodipeptide analogues as potent and selective neuronal nitric oxide synthase (nNOS) inhibitors (Hah, J.-M.; Roman, L. J.; Martasek, P.; Silverman, R. B. J. Med. Chem. 2001, 44, 2667-2670). To increase the lipophilicity a series of aromatic, reduced amide bond analogues (6-25) were designed and synthesized as potential selective nNOS inhibitors. The hypothesized large increase in isoform selectivity of nNOS over inducible NOS was not obtained in this series. However, the high potency with nNOS as well as high selectivity of nNOS over endothelial NOS was retained in some of these compounds (15, 17, 21), as well as good selectivity over inducible NOS. The most potent nNOS inhibitor among these compounds is N-(4S)-[4-amino-5-[2-(2-aminoethyl)phenylamino]-pentyl]-N'-nitroguanidine (17) (K(i) = 50 nM), which also shows the highest selectivity over eNOS (greater than 2100-fold) and 70-fold selectivity over iNOS. Further modification of compound 17 should lead to even more potent and selective nNOS inhibitors.     

Synthesis and serotonergic activity of 3-[2-(pyrrolidin-1-yl)ethyl]indoles: potent agonists for the h5-HT1D receptor with high selectivity over the h5-HT1B receptor

The design, synthesis, and biological evaluation of a novel series of 3-[2-(pyrrolidin-1-yl)ethyl]indoles with excellent selectivity for h5-HT1D (formerly 5-HT1Dalpha) receptors over h5-HT1B (formerly 5-HT1Dbeta) receptors are described. Clinically effective antimigraine drugs such as Sumatriptan show little selectivity between h5-HT1D and h5-HT1B receptors. The differential expression of h5-HT1D and h5-HT1B receptors in neural and vascular tissue prompted an investigation of whether a compound selective for the h5-HT1D subtype would have the same clinical efficacy but with reduced side effects. The pyrrolidine 3b was initially identified as having 9-fold selectivity for h5-HT1D over h5-HT1B receptors. Substitution of the pyrrolidine ring of 3b with methylbenzylamine groups gave compounds with nanomolar affinity for the h5-HT1D receptor and 100-fold selectivity with respect to h5-HT1B receptors. Modification of the indole 5-substituent led to the oxazolidinones 24a,b with up to 163-fold selectivity for the h5-HT1D subtype and improved selectivity over other serotonin receptors. The compounds were shown to be full agonists by measurement of agonist-induced [35S]GTPgammaS binding in CHO cells expressed with h5-HT receptors. This study suggests that the h5-HT1D and h5-HT1B receptors can be differentiated by appropriate substitution of the ligand in the region which binds to the aspartate residue and reveals a large binding pocket in the h5-HT1D receptor domain which is absent for the h5-HT1B receptor. The compounds described herein will be important tools to delineate the role of h5-HT1D receptors in migraine.     

Discovery of ((S)-5-(methoxymethyl)-7-(1-methyl-1H-indol-2-yl)-2-(trifluoromethyl)-4,7-dihydropyrazolo[1,5-a]pyrimidin-6-yl)((S)-2-(3-methylisoxazol-5-yl)pyrrolidin-1-yl)methanone as a potent and selective I(Kur) inhibitor

Previously disclosed dihydropyrazolopyrimidines are potent and selective blockers of I(Kur) current. A potential liability with this chemotype is the formation of a reactive metabolite which demonstrated covalent binding to protein in vitro. When substituted at the 2 or 3 position, this template yielded potent I(Kur) inhibitors, with selectivity over hERG which did not form reactive metabolites. Subsequent optimization for potency and PK properties lead to the discovery of ((S)-5-(methoxymethyl)-7-(1-methyl-1H-indol-2-yl)-2-(trifluoromethyl)-4,7-dihydropyrazolo[1,5-a]pyrimidin-6-yl)((S)-2-(3-methylisoxazol-5-yl)pyrrolidin-1-yl)methanone (13j), with an acceptable PK profile in preclinical species and potent efficacy in the preclinical rabbit atrial effective refractory period (AERP) model.     

1-(3-Cyanobenzylpiperidin-4-yl)-5-methyl-4-phenyl-1, 3-dihydroimidazol-2-one: a selective high-affinity antagonist for the human dopamine D(4) receptor with excellent selectivity over ion channels.

After the requirement of pseudocycle formation in the ureas 3 and 7 for hD(4) binding and selectivity was confirmed, structural hybridization with the known hD(4) ligand 2 led to the design and identification of the lead 4-(2-oxo-1, 3-dihydroimidazol-2-yl)piperidine 8. Optimization studies were carried out on 8 with the aim of achieving 1000-fold selectivity for hD(4) over all other receptors while retaining the good pharmacokinetic properties of the lead. After initial preparation of 8 as a minor component in a low-yielding reaction, a novel and regioselective "four-step/one-pot" procedure was developed which proved to be applicable to rapid investigation of the SAR of the 1, 3-dihydroimidazol-2-one ring. Various changes to substituents attached to the 3-, 4-, or 5-position of the 1, 3-dihydroimidazol-2-one core of 8 did not significantly improve selectivity for hD(4) over hD(2) and hD(3). Greater selectivity (>1000-fold) was ultimately achieved by meta substitution of the benzyl group of 8 with various substituents. Compounds 28, 31, and 32 all possess the required selectivity for hD(4) over the other dopamine subtypes, but only 32 has >1000-fold selectivity over all the key counterscreens we tested against. Compound 32 is an antagonist at hD(4) and has a good pharmacokinetic profile in the rat, with excellent estimated in vivo receptor occupancy, thus making it a potentially useful pharmacological tool to investigate the role of the D(4) receptor.     

Discovery of 9-(6-aminopyridin-3-yl)-1-(3-(trifluoromethyl)phenyl)benzo[h][1,6]naphthyridin-2(1H)-one (Torin2) as a potent, selective, and orally available mammalian target of rapamycin (mTOR) inhibitor for treatment of cancer

The mTOR mediated PI3K/AKT/mTOR signal transduction pathway has been demonstrated to play a key role in a broad spectrum of cancers. Starting from the mTOR selective inhibitor 1 (Torin1), a focused medicinal chemistry effort led to the discovery of an improved mTOR inhibitor 3 (Torin2), which possesses an EC(50) of 0.25 nM for inhibiting cellular mTOR activity. Compound 3 exhibited 800-fold selectivity over PI3K (EC(50): 200 nM) and over 100-fold binding selectivity relative to 440 other protein kinases. Compound 3 has significantly improved bioavailability (54%), metabolic stability, and plasma exposure relative to compound 1.     

N-Arylsulfonylindole derivatives as serotonin 5-HT(6) receptor ligands.

A series of N(1)-arylsulfonyltryptamines were found to be potent ligands of the human serotonin 5-HT(6) receptor with the 5-methoxy-1-benzenesulfonyl analogue (19) having the highest affinity. Additionally, it was discovered that a group such as 3-(3-methoxybenzyl)-1,2,4-oxadiazol-5-yl in the 2-position of the indole ring (43) can replace the arylsulfonyl substituent in the 1-position with no loss of affinity. This suggested that the binding conformation of the aminoethyl side chain at this receptor was toward the 4-position of the indole ring and was supported by the fact that the 4-(aminoethyl)indoles (45) also displayed high affinity, as did the conformationally rigid 1,3,4,5-tetrahydrobenz[c,d]indole (49). Molecular modeling showed that 19, 43, and 45 all had low-energy conformers that overlaid well onto 49. Both 19 and 49 had good selectivity over other serotonin receptors tested, with 49 also showing excellent selectivity over all dopamine receptors. In a functional adenylate cyclase stimulation assay, 19 and 49 had no agonist activity, whereas 45 behaved as a partial agonist. Finally, it was shown that 19 had good activity in the 5-HT(2A) centrally mediated mescaline-induced head twitch assay, which implies that it is brain-penetrant.     

Synthesis and pharmacological evaluation of 5-(4-biphenyl)-3-methyl-4-phenyl-1,2,4-triazole derivatives as a novel class of selective antagonists for the human vasopressin V(1A) receptor

A series of 5-(4-biphenyl)-3-methyl-4-phenyl-1,2,4-triazole derivatives were prepared and evaluated as selective antagonists for the human vasopressin V(1A) receptor. The compounds were examined for their affinity to the cloned human V(1A) receptor (hV(1A)) and selectivity vs the cloned human V(2) receptor (hV(2)). By utilizing the structure-activity relationship on 4,4-difluoro-5-methylidene-2,3,4,5-tetrahydrobenzazepine derivatives as dual antagonists for the V(1A) and V(2) receptors in our previous study, we found that substituting the methoxy group at the 2-position of the 4-phenyl ring with (4-methylpiperazin-1-yl)alkoxy moieties brought about marked improvement of both affinity to hV(1A) and selectivity vs hV(2). Further introduction of a methyl group into the 6-position of the 4-phenyl ring resulted in additional improvement of selectivity. One particular compound, 5-(4-biphenyl)-3-methyl-4-[2-[6-(4-methyl-1-piperazinyl)hexyloxy]phenyl]-1,2,4-triazole (19) showed potent affinity to hV(1A) with a K(i) value of 1.04 nM and high selectivity with a 1700-fold selectivity vs hV(2). We also found marked differences in the affinity of compounds in this series between the human and the rat receptors. Compound 19 was further examined for its V(1A) receptor antagonist activity in rats. As a result, 19 demonstrated antagonist activities toward an arginine vasopressin-induced increase in diastolic blood pressure after intravenous or oral administration and long-lasting oral activity.     

Design and synthesis of novel alpha(1)(a) adrenoceptor-selective antagonists. 1. Structure-activity relationship in dihydropyrimidinones

Dihydropyrimidinones such as compound 12 exhibited high binding affinity and subtype selectivity for the cloned human alpha(1a) receptor. Systematic modifications of 12 led to identification of highly potent and subtype-selective compounds such as (+)-30 and (+)-103, with high binding affinity (K(i) = 0.2 nM) for alpha(1a) receptor and greater than 1500-fold selectivity over alpha(1b) and alpha(1d) adrenoceptors. The compounds were found to be functional antagonists in human, rat, and dog prostate tissues. Compound (+)-103 exhibited excellent selectively to inhibit intraurethral pressure (IUP) as compared to lowering diastolic blood pressure (DBP) in mongrel dogs (K(b)(DBP)/K(b)(IUP) = 40) suggesting uroselectivity for alpha(1a)-selective compounds.     

Muscarinic subtype affinity and functional activity profile of 1-methyl-2-(2-methyl-1,3-dioxolan-4-yl)pyrrolidine and 1-methyl-2-(2-methyl-1,3-oxathiolan-5-yl)pyrrolidine derivatives

Starting from two previously studied muscarinic full agonists, characterized by a 1,3-dioxolane ((+)-1) and a 1,3-oxathiolane ((+)-2) cycle, two new series of muscarinic ligands were designed, obtained by the steric complication of the parent compounds produced by freezing the aminoalkyl chain into a pyrrolidine ring. Both tertiary amines and the corresponding iodomethyl derivatives were synthesised and studied, and several compounds of the series which behaved as muscarinic agonists have been selected, on the basis of preliminary binding experiments on rat cortex homogenates, for the present work. Results are presented obtained from testing the affinity of the selected compounds against cloned human muscarinic receptors expressed in CHO cells, in order to evaluate subtype selectivity. Their functional activity on classical models of M1-M4 receptors, in guinea pig and rabbit tissues is also reported. With respect to parent compounds, the new molecules present some selectivity toward hm2 receptors; fair M2 selectivity is also evident in functional studies, where these compounds behave as partial agonists. Among the other compounds of the series (2S, 4'R, 2'S)-1,1-dimethyl-2-(2-methyl-1,3-dioxolan-4-yl)pyrrolidinium iodide (-)-3 and (2R, 5'S, 2'S)-1-methyl-2-(2-methyl-1,3-oxathiolan-5-yl)pyrrolidine (+)-5 present a promising pharmacological profile. Compound (-)-3 shows modest hm2 selectivity in binding experiments but a clearcut M2 selectivity in functional tests, where it behaves as a weak antagonist on M1 and M4 subtypes, as a weak full agonist on the M3 subtype and as a potent partial agonist on M2 subtype. Tertiary amine (+)-5 presents a quite similar profile but appears more interesting since, lacking a permanent charge on the nitrogen atom, it may represent an interesting tool to study CNS muscarinic receptors. Our results confirm that sterical complication of parent compounds (+)-1 and (+)-2 produces more selective muscarinic agonists.     

Reduced amide bond peptidomimetics. (4S)-N-(4-amino-5-[aminoakyl]aminopentyl)-N'-nitroguanidines, potent and highly selective inhibitors of neuronal nitric oxide synthase

Selective inhibition of the isoforms of nitric oxide synthase (NOS) could be therapeutically useful in the treatment of certain disease states arising from the overproduction of nitric oxide. Recently, we reported nitroarginine-containing dipeptide amides (Huang, H; Martasek, P.; Roman, L. J.; Masters, B. S. S.; Silverman, R. B. J. Med. Chem. 1999, 42, 3147.) and some peptidomimetic analogues (Huang, H; Martasek, P.; Roman, L. J.; Silverman, R.B. J. Med Chem. 2000, 43, 2938.) as potent and selective inhibitors of neuronal NOS (nNOS). Here, reduced amide bond pseudodipeptide analogues are synthesized and evaluated for their activity. The deletion of the carbonyl group from the amide bond either preserves or improves the potency for nNOS. Significantly, the selectivities for nNOS over eNOS (endothelial NOS), and iNOS (inducible NOS) are greatly increased in these series. The most potent nNOS inhibitor among these compounds is (4S)-N-(4-amino-5-[aminoethyl]aminopentyl)-N'-nitroguanidine (7) (K(i) = 120 nM), which also shows the highest selectivity over eNOS (greater than 2500-fold) and 320-fold selectivity over iNOS. The reduced amide bond is an excellent surrogate of the amide bond, and it will facilitate the design of new potent and selective inhibitors of nNOS.     

3-Oxoisoindoline-1-carboxamides: Potent, State-Dependent Blockers of Voltage-Gated Sodium Channel Na(V)1.7 with Efficacy in Rat Pain Models

The voltage-gated sodium channel Na(V)1.7 is believed to be a critical mediator of pain sensation based on clinical genetic studies and pharmacological results. Clinical utility of nonselective sodium channel blockers is limited due to serious adverse drug effects. Here, we present the optimization, structure-activity relationships, and in vitro and in vivo characterization of a novel series of Na(V)1.7 inhibitors based on the oxoisoindoline core. Extensive studies with focus on optimization of Na(V)1.7 potency, selectivity over Na(V)1.5, and metabolic stability properties produced several interesting oxoisoindoline carboxamides (16A, 26B, 28, 51, 60, and 62) that were further characterized. The oxoisoindoline carboxamides interacted with the local anesthetics binding site. In spite of this, several compounds showed functional selectivity versus Na(V)1.5 of more than 100-fold. This appeared to be a combination of subtype and state-dependent selectivity. Compound 28 showed concentration-dependent inhibition of nerve injury-induced ectopic in an ex vivo DRG preparation from SNL rats. Compounds 16A and 26B demonstrated concentration-dependent efficacy in preclinical behavioral pain models. The oxoisoindoline carboxamides series described here may be valuable for further investigations for pain therapeutics.