Diphenylsulfone muscarinic antagonists: piperidine derivatives with high M2 selectivity and improved potency

Piperidine analogues of our previously described piperazine muscarinic antagonists are described. Piperidine analogues show a distinct structure-activity relationship (SAR) that differs from comparable piperazines. Compounds with high selectivity and improved potency for the M2 receptor have been identified. The lead compound, 12b, increases acetylcholine release in vivo. Compounds of this class may be useful for the treatment of cognitive disorders such as Alzheimer's disease (AD).     

Quantitative structure-selectivity relationship for M2 selectivity between M1 and M2 of piperidinyl piperidine derivatives as muscarinic antagonists

Muscarinic M2 receptor antagonists with high subtype selectivity (M2/M1) will decrease the toxicity in central nervous system in treatment of AD. The exploration of quantitative structure-selectivity relationship (QSSR) to muscarinic M2 receptor antagonists will provide design information for drug with fewer side effects. In this paper, CoMFA models of pK(i)(M1), pK(i)(M2) and p[K(i)(M2)/K(i)(M1)] (pK(i)(M2)-pK(i)(M1)) were used to study the subtype selectivity (M2/M1) of piperidinyl piperidine derivatives as muscarinic M2 subtype receptor antagonists. The parameters of the three models are: 0.633, 0.636 and 0.726 for cross-validated r(2) (r(cv)(2)), 0.109, 0.204 and 0.09 for the Standard error of estimate (SD), respectively. The results show the model of p[K(i)(M2)/K(i)(M1)] is the best one for design of piperidinyl piperidine derivatives as muscarinic antagonists with high subtype selectivity (M2/M1).     

Benzylidene ketal derivatives as M2 muscarinic receptor antagonists

Benzylidene ketal derivatives were investigated as selective M₂ receptor antagonists for the treatment of Alzheimer's disease. Compound 10 was discovered to have subnanomolar M₂ receptor affinity and 100-fold selectivity against other muscarinic receptors. Also, 10 demonstrated in vivo efficacy in rodent models of muscarinic activity and cognition.     

The effect of absolute configuration on activity,subtype selectivity (M3/M2) of 3α-acyloxy-6β-acetoxyltropane derivatives as muscarinic M3 receptor antagonists

Both enantiomers of 3α-acyloxy-6β-acetoxyltropane derivatives 1–4 were prepared respectively and underwent functional studies and radioreceptor binding assays. 6S Enantiomers showed obvious muscarinic M3, M2 antagonistic activity, while the 6R ones elicited little muscarinic activity by functional studies. Besides, the affinity of 6S enantiomers to muscarinic M3 receptors of rat submandibulary gland, M2 receptors of rat left atria was much larger than that of corresponding 6R enantiomers. All these pharmalogical results indicated 6S configuration was favorable for 3α-acyloxy-6β-acetoxyltropane derivatives to bind with muscarinic M3 or M2 receptors and elicited antagonistic activity. Furthermore, the muscarinic M3 activity and subtype selectivity (M3/M2) of 6S enantiomers could be improved by increasing the electron density of carbonyl oxygen or introducing methylene group between the carbonyl and phenyl ring in C-3α position. Understanding the effect of absolute configuration on activity, subtype selectivity (M3/M2) of 3α-acyloxy-6β-acetoxyltropane derivatives will provide the clues for designing muscarinic M3 antagonists with high activity and low side effects or toxicity.     

Isopropyl amide derivatives of potent and selective muscarinic M2 receptor antagonists

Low molecular weight amide derivatives were synthesized and evaluated as M(2) receptor antagonists for the treatment of Alzheimer's disease. Isopropyl amides 19 and 31 are highly potent, selective and low molecular weight M(2) receptor antagonists with structural features different from our clinical candidate 1.     

Muscarinic receptor subtypes: M1 and M2 biochemical and functional characterization

The heterogeneity of muscarinic receptors was examined in sympathetic ganglia and atria by “in vitro” binding techniques and functional studies. As tools we have used the classical antagonist atropine, the selective antagonist pirenzepine and the unique muscarinic agonist McN-A-343. In binding studies atropine showed similar affinities to muscarinic sites in ganglionic and atrial membranes with dissociation constants of 1.1 and 3.2 nM, respectively. In contrast, pirenzepine displayed a distinctly different binding profile. In atria it bound to an homogenous population of low affinity sites (diss. const. 620 nM) while in ganglia it revealed the presence of two sites: a major population of high affinity sites (diss. const. 11 nM) and a minor one of lower affinity (diss. const. 280 nM). The functional correlate of the receptor properties in the two tissues was studied in the pithed rat by measuring A) the increase of arterial pressure evoked by McN-A-343 through selective activation of muscarinic receptors in ganglia and B) the bradycardia elicited by acetylcholine release in the heart through vagal stimulation. Mirroring the “in vitro” binding data atropine inhibited both muscarinic responses in the same narrow range of doses (2–30 μg/kg i.v.) whereas pirenzepine showed similar potency to atropine in inhibiting ganglionic stimulation (ED50 4.1 μg/kg i.v.) but was almost two orders of magnitude weaker in blocking vagal bradycardia (ED50 172 μg/kg i.v.). These data suggest that McN-A-343 and pirenzepine act selectively on a common muscarinic receptor subtype, a finding which agrees with the view that muscarinic receptors are heterogenous and that excitatory ganglionic receptors (Ml) are distinguishable from those (M2) present in effector organs like smooth muscle and heart.     

Analogs of caffeine: antagonists with selectivity for A2 adenosine receptors

Several analogs of caffeine have been investigated as antagonists at A2 adenosine receptors stimulatory to adenylate cyclase in membranes from rat pheochromocytoma PC12 cells and human platelets and at A1 adenosine receptors inhibitory to adenylate cyclase from rat fat cells. Among these analogs, 1-propargyl-3,7-dimethylxanthine was about 4- to 7-fold and 7-propyl-1,3-dimethylxanthine about 3- to 4-fold more potent than caffeine at A2 receptors of PC12 cells and platelets. At A1 receptors of fat cells, both compounds were about 2-fold less potent than caffeine. These caffeine analogs have an A1/A2 selectivity ratio of about 10-20 and are the first selective A2 receptor antagonists yet reported. The results may provide the basis for the further development of highly potent and highly selective A2 adenosine receptor antagonists.     

Muscarinic antagonists with multiple stereocenters: Synthesis, affinity profile and functional activity of isomeric 1-methyl-2-(2,2-alkylaryl-1,3-oxathiolan-5-yl)pyrrolidine sulfoxide derivatives

Completing a long-lasting research on 1,3-oxathiolane muscarinic ligands, we have synthesized a set of isomeric 1-methyl-2-(2,2-alkylaryl-1,3-oxathiolan-5-yl)pyrrolidine 3-sulfoxide derivatives, containing three or four stereogenic centers. In general the compounds are very potent antagonists even if, unlike the corresponding agonists, they show modest subtype selectivity.     

Anthranilic sulfonamide CCK1/CCK2 dual receptor antagonists II: Tuning of receptor selectivity and in vivo efficacy

In the previous article we demonstrated how certain CCK2R-selective anthranilic amides could be structurally modified to afford high-affinity, selective CCK1R activity. We now describe our efforts at modulating and optimizing the CCK1R and CCK2R affinities aimed at producing compounds with good pharmacokinetics properties and in vivo efficacy in rat models of gastric acid and pancreatic amylase secretion.     

In vivo activity of an azole series of CCR2 antagonists

Optimisation of a series of biaryl sulphonamides resulted in the identification of compound 7 which demonstrated dose-dependent and strain-specific inhibition of monocyte recruitment in a thioglycollate-induced peritonitis model of inflammation.     

Novel thiophene derivatives as PTP1B inhibitors with selectivity and cellular activity

A series of novel thiophene derivatives was designed, synthesized and their activities as competitive inhibitors of protein tyrosine phosphatase (PTPs) 1B (PTP1B) inhibitors were evaluated. All the compounds showed inhibitory potencies, and 10 of these exhibited moderate inhibitory activities with IC₅₀ values less than 10 μM. The activity of the most potent compound P28 (IC₅₀ = 2.1 μM) was 15 times higher than that of the hit compound P01. Further, four representative compounds (P19, P22, P28, and P31) demonstrated remarkably high selectivities against other PTPs (e.g., PTPα, LAR, CD45, and TCPTP); P19 exhibited greater than sixfold selectivity over highly homologous TCPTP. More importantly, these compounds are permeable to cell membranes. The treatment of CHO-K1 cells with P28 (10 μM) resulted in increased phosphorylation of AKT, which suggested extensive cellular activity of this compound. The novel chemical entities reported in this study could be used for overcoming the poor selectivity and low cellular activity of PTP1B inhibitors and might represent a starting point for development of therapeutic PTP inhibitors.     

Muscarinic acetylcholine receptor antagonists: SAR and optimization of tyrosine ureas

SAR exploration of multiple regions of a tyrosine urea template led to the identification of very potent muscarinic acetylcholine receptor antagonists such as 10b with good subtype selectivity for M(3) over M(1). The structure-activity relationships (SAR) and optimization of the tyrosine urea series are described.     

Isoquinoline-pyridine-based protein kinase B/Akt antagonists: SAR and in vivo antitumor activity

The structure-activity relationships of a series of isoquinoline-pyridine-based protein kinase B/Akt antagonists have been investigated in an effort to improve the major short-comings of the lead compound 3, including poor pharmacokinetic profiles in several species (e.g., mouse i.v. t(1/2) = 0.3 h, p.o. F = 0%). Chlorination at C-1 position of the isoquinoline improved its pharmacokinetic property in mice (i.v. t(1/2) = 5.0 h, p.o. F = 51%) but resulted in >500-fold drop in potency. In a mouse MiaPaCa-2 xenograft model, an amino analog 10y significantly slowed the tumor growth, however was accompanied by toxicity.     

Quinazolines as adenosine receptor antagonists: SAR and selectivity for A2B receptors

We have recently reported the discovery of numerous new compounds that are selective inhibitors of all of the subtypes of the adenosine receptor family via a pharmacophore database searching and screening strategy. During the course of this work we made the unexpected discovery of a potent A(2B) receptor antagonist, 4-methyl-7-methoxyquinazolyl-2-(2'-amino-4'-imidazolinone) (38, CMB 6446), which showed selectivity for this receptor and functioned as an antagonist, with a binding K(i) value of 112 nM. We explored the effects of both substituent- and ring-structural variations on the receptor affinity in this series of derivatives, which were found to be mostly non-selective adenosine receptor ligands with K(i) values in the micromolar range. Since no enhancement of A(2B) receptor affinity of 38 was achieved, the previously reported pharmacophore-based searching strategy yielded the most potent and selective structurally-related hit in the database originally searched.     

Discovery of benzothiazole-based adenosine A2B receptor antagonists with improved A2A selectivity

The highly potent but modestly selective N-(2-amino-4-methoxy-benzothiazol-7-yl)-N-ethyl-acetamide derivative 2 was selected as the starting point for the design of novel selective A_2B antagonists, due to its excellent potency, and good drug-like properties. A series of compounds containing nonaromatic amides or ureas of five- or six-membered rings, and also bearing an m-trifluoromethyl-phenyl group (shown to impart superior potency) was prepared and evaluated for their selectivity against the A_2A and A₁ receptors. This work resulted in the identification of compound 30, with excellent potency and high selectivity against both A_2A and A₁ receptors.     

Non-acidic 1,3,4-trisubstituted-pyrazole derivatives as lonazolac analogs with promising COX-2 selectivity,anti-inflammatory activity and gastric safety profile

Twelve new compounds of 1,3,4-trisubstituted-pyrazole derivatives possessing two cyclooxygenase-2 (COX-2) pharmacophoric moieties (SO₂Me or/and SO₂NH₂) 11a-c, 12a-c, 13a-c and 14a-c were designed and synthesized to be evaluated for their COX inhibition, anti-inflammatory activity, ulcerogenic liability. All compounds were more selective for COX-2 isozyme and showed good in vivo anti-inflammatory activity. The bisaminosulphonyl derivatives (14a-c) were the most COX-2 selective compounds (S.I. = 9.87, 9.50 and 9.22 respectively) and showed good anti-inflammatory potency (ED₅₀ = 15.06, 42.51 and 50.43 μmol/kg respectively) in comparison with celecoxib (COX-2 S.I. = 8.61, ED₅₀ = 82.2 μmol/kg). Also, compounds 14a-c were less ulcerogenic (ulcer indexes = 2.72–3.72) than ibuprofen (ulcer index = 20.25) and comparable to celecoxib (ulcer index = 2.93). In addition, to explain the preferential (COX-2) inhibitory and selectivity, the designed compounds were subjected to molecular docking studies. It was found that compound 14c with the highest COX-2 activity and selectivity exhibited a binding pattern and interactions similar to that of celecoxib with formation of more hydrogen-bond features.     

In vitro activity of novel dual action MDR anthranilamide modulators with inhibitory activity on CYP-450 (Part 2)

Synthesis and in vitro cytotoxicity assays of new anthranilamide MDR modulators have been performed to assess their inhibition potency on the P-glycoprotein (P-gp) transporter. Previous studies showed that the replacement of the aromatic spacer group between nitrogen atoms (N(1) and N(2)) in the P-gp inhibitor XR9576 with ethyl or propyl chain is optimal for P-gp inhibition potency. To confirm that observation, the ethyl or the propyl linker arm was replaced with a pyrrolidine or an alicyclic group such as cyclohexyl. In addition, an arylpiperazinyl group and two methoxyl groups onto the anthranilic part were introduced to assess their effect on the anti P-gp activity. Five molecules were prepared and evaluated on CEM/VLB500. All new anthranilamides were more potent than verapamil, most of them exhibited a lower cytotoxicity than XR9576. Compound 5 was the most potent and its inhibition activity was similar to XR9576. Interestingly, in vitro biotransformation studies of compounds 4 and 5 using human CYP-450 isoforms revealed, that conversely to XR9576, compounds 4 and 5 inhibited CYP3A4, an enzyme that colocalizes with P-gp in the intestine and contributes to tumor cell chemoresistance by enhancing the biodisposition of numerous drugs, notably paclitaxel. In that context, 5 might be suitable for further drug development.     

Respiratory syncytial virus fusion inhibitors. Part 3: Water-soluble benzimidazol-2-one derivatives with antiviral activity in vivo

The introduction of acidic and basic functionality into the side chains of respiratory syncytial virus (RSV) fusion inhibitors was examined in an effort to identify compounds suitable for evaluation in vivo in the cotton rat model of RSV infection following administration as a small particle aerosol. The acidic compounds 2r, 2u, 2v, 2w, 2z, and 2aj demonstrated potent antiviral activity in cell culture and exhibited efficacy in the cotton rat comparable to ribavirin. In a BALB/c mouse model, the oxadiazolone 2aj reduced virus titers following subcutaneous dosing, whilst the ester 2az and amide 2aab exhibited efficacy following oral administration. These results established the potential of this class of RSV fusion inhibitors to interfere with infection in vivo following topical or systemic administration.