2-Arylimino-5,6-dihydro-4H-1,3-thiazines as a new class of cannabinoid receptor agonists. Part 2: orally bioavailable compounds

Structure-activity relationships and efforts to optimize the pharmacokinetic profile of a class of 2-arylimino-5,6-dihydro-4H-1,3-thiazines as cannabinoid receptor agonists are described. Among the compounds examined, compound 14 showed potent affinity and high selectivity for CB2, and compound 23 showed potent affinities against CB1 and CB2. These compounds displayed oral bioavailability.     

2-Arylimino-5,6-dihydro-4H-1,3-thiazines as a new class of cannabinoid receptor agonists. Part 3: Synthesis and activity of isosteric analogs

Structure-activity relationships and efforts to optimize the pharmacokinetic profile of isosteric analogs of 2-arylimino-5,6-dihydro-4H-1,3-thiazines as cannabinoid receptor agonists are described. Among those examined, compound 25 showed potent affinity for cannabinoid receptor 1 (CB1) and receptor 2 (CB2). This compound displayed oral bioavailability and analgesic activity.     

Sulfonamide derivatives as new potent and selective CB2 cannabinoid receptor agonists

A novel series of sulfonamide derivatives 3, the CB(2) receptor agonists, was synthesized and evaluated for activity against the human CB(2) receptor. We first identified sulfonamide 3a, which was obtained by random screening of our in-house chemical library as a moderately active (CB(2) IC(50)=340nM) CB(2) receptor agonist. We then attempted to test its analogues to identify compounds with a high affinity for the CB(2) receptor. One of these, compound 3f, exhibited high affinity for the human CB(2) receptor (IC(50)=16nM) and high selectivity for CB(2) over CB(1) (CB(1) IC(50)/CB(2)IC(50)=106), and behaved as a full CB(2) receptor agonist in the [(35)S]GTPgammaS binding assay (CB(2) EC(50)=7.2nM, E(max)=100%).     

Novel pyridine derivatives as potent and selective CB2 cannabinoid receptor agonists

Replacement of the phenyl ring in our previous (morpholinomethyl)aniline carboxamide cannabinoid receptor ligands with a pyridine ring led to the discovery of a novel chemical series of CB₂ ligands. Compound 3, that is, 2,2-dimethyl-N-(5-methyl-4-(morpholinomethyl)pyridin-2-yl)butanamide was identified as a potent and selective CB₂ agonist exhibiting in vivo efficacy after oral administration in a rat model of neuropathic pain.     

Imine derivatives as new potent and selective CB2 cannabinoid receptor agonists with an analgesic action

In this study, a novel series of CB(2) receptor agonist imine derivatives, 1-6, was synthesized and evaluated for activity against the CB(2) receptor. In a previous paper we reported the synthesis and SARs of thiazole derivative 1, a potent CB(2) receptor agonist, but we had not assessed chemical modifications of the 5-membered heteroring of 1. In the present study, we therefore tried chemically modifying the 5-membered heteroring of 1 in an attempt to further improve binding affinity for the CB(2) receptor. In the course of making the structural modifications, we discovered that a novel pyrazole derivative 6b (CBS0550) had high affinity for the CB(2) receptor (IC(50)=2.9 nM, EC(50)=1.8 nM, E(max)=85%), high selectivity for CB(2) (CB(1) IC(50)/CB(2) IC(50)=1400), and good physicochemical properties (solubility in water: 5.9 mg/100mL at 25 degrees C). Oral administration of 6b to rats at a dose of 10mg/kg resulted in significant plasma concentrations, and orally administered compound 6b significantly reversed mechanical hyperalgesia in the Randall-Selitto model of inflammatory pain in rats.     

N-Alkylidenearylcarboxamides as new potent and selective CB(2) cannabinoid receptor agonists with good oral bioavailability

A novel series of N-alkylidenearylcarboxamides 4, a CB(2) receptor agonist, were synthesized and evaluated for activity against the human CB(2) receptor. In a previous paper, we reported that sulfonamide derivative 1 acted as a potent CB(2) receptor agonist (IC(50)=65 nM, EC(50)=19 nM, E(max)=90%). However, compound 1 also exhibited poor metabolic stability in human liver microsomes. During the structural modification of 1, we found that a novel series of N-alkylidenearylcarboxamide, 4-1, had a moderate affinity for the CB(2) receptor (IC(50)=260 nM, EC(50)=86 nM, E(max)=100%) and good metabolic stability in human liver microsomes. We explored its analogues to discover compounds with a high affinity for the CB(2) receptor and with good oral bioavailability. Among them, compounds 4-9 and 4-27 had high affinities for the human CB(2) receptor (CB(2) IC(50)=13 nM and 1.2 nM) and a high selectivity for CB(2) (CB(1) IC(50)/CB(2) IC(50)=270 and 1600); furthermore, significant plasma levels were observed following oral administration in rats (C(max)=233 ng/mL and 148 ng/mL, respectively, after a dose of 10 mg/kg). Furthermore, compound 4-9 had good oral bioavailability (F=52%, 3mg/kg).     

Lactams as prostanoid receptor ligands. Part 4: 2-Piperidones as selective EP4 receptor agonists

2-Piperidones were prepared bearing heptanoic acid or a thioether heptanoic acid at the 1-position as well as appropriately substituted at the 6-position to mimic the structure of prostaglandins. The stereochemical purity at the 6-position was determined to be 95% ee for an advanced synthetic intermediate. The 2-piperidones were identified as potent agonists at the EP4 prostanoid receptor. They displayed a high affinity (Ki 5-130 nM) at EP4 and subtype selectivity.     

Lead optimization of 5,6-diarylpyridines as CB1 receptor inverse agonists

Optimization of the biological activity for 5,6-diarylpyridines as CB1 receptor inverse agonists is described. Food intake and pharmacokinetic evaluation of 3f and 15c indicate that these compounds are effective orally active modulators of CB1.     

The discovery of novel indole-2-carboxamides as cannabinoid CB(1) receptor antagonists

The discovery and structure-activity relationship of a novel series of indole-2-carboxamide antagonists of the cannabinoid CB(1) receptor is disclosed. Compound 26i was found to be a high potency, selective cannabinoid CB(1) antagonist.     

Two distinct classes of novel pyrazolinecarboxamides as potent cannabinoid CB1 receptor agonists

The synthesis and SAR of 3-alkyl-4-aryl-4,5-dihydropyrazole-1-carboxamides 1–23 and 1-alkyl-5-aryl-4,5-dihydropyrazole-3-carboxamides 24–27 as two novel cannabinoid CB₁ receptor agonist classes were described. The target compounds elicited high affinities to the CB₁ as well as the CB₂ receptor and were found to act as CB₁ receptor agonists. The key compound 19 elicited potent CB₁ agonistic and CB₂ inverse agonistic properties in vitro and showed in vivo activity in a rodent model for multiple sclerosis after oral administration.     

Arylsulfonamides as a new class of cannabinoid CB1 receptor ligands: identification of a lead and initial SAR studies

High-throughput screening of the UCB sample collection identified the piperidinyl-sulfonyl benzoic ester 1 as a novel agonist for CB(1) receptor with nanomolar affinity. We report here the pharmacological profile of compound 1 as well as preliminary biological activities in pain model. Diverse close analogs of 1 were purchased and the structure-affinity relationships among this novel class are discussed.     

Lactams as EP4 prostanoid receptor subtype selective agonists. Part 1: 2-Pyrrolidinones-stereochemical and lower side-chain optimization

A series of 7-[(5R)-substituted 2-oxo-1-pyrrolidinyl]-heptanoic acids were prepared, their isomeric purity determined, and pharmacologically evaluated. Lactams with affinity for the EP(4) receptor displayed agonist behavior. The lower side-chain of the lactam template could be substituted to afford ligands (e.g., 17, 24, 30, 31, and 33) of high potency and greater than 1000-fold affinity for EP(4) versus the other EP prostanoid receptors.     

Triaryl bis-sulfones as a new class of cannabinoid CB2 receptor inhibitors: identification of a lead and initial SAR studies

A novel class of cannabinoid CB2 receptor ligands is described. These triaryl bis-sulfones are nanomolar inhibitors of the CB2 receptor and show high selectivity over the cannabinoid CB1 receptor. One example of this new class decreases ligand-induced GTPgammaS binding to recombinant CB2 cell membranes, identifying the compound as a CB2-selective inverse agonist.     

Discovery of a novel class of selective human CB1 inverse agonists

Ligand-based virtual screening led to the discovery of a new class of potent inverse agonists of the human cannabinoid receptor 1, hCB(1), which are selective versus hCB(2). These CB(1) ligands present intriguing departures from a classical CB(1) antagonist pharmacophore. Elements of SAR are discussed in this context.     

1,4-Diazepane compounds as potent and selective CB2 agonists: optimization of metabolic stability

A high-throughput screening campaign has identified 1,4-diazepane compounds which are potent Cannabinoid receptor 2 agonists with excellent selectivity against the Cannabinoid receptor 1. This class of compounds suffered from low metabolic stability. Following various strategies, compounds with a good stability in liver microsomes and rat PK profile have been identified.     

7-Azaindolequinuclidinones (7-AIQD): A novel class of cannabinoid 1 (CB1) and cannabinoid 2 (CB2) receptor ligands

A series of N-benzyl-7-azaindolequinuclidinone (7-AIQD) analogs have been synthesized and evaluated for affinity toward CB1 and CB2 cannabinoid receptors and identified as a novel class of cannabinoid receptor ligands. Structure–activity relationship (SAR) studies indicate that 7-AIQD analogs are dual CB1/CB2 receptor ligands exhibiting high potency with somewhat greater selectivity towards CB2 receptors compared to the previously reported indolequinuclidinone (IQD) analogs. Initial binding assays showed that 7-AIQD analogs 8b, 8d, 8f, 8g and 9b (1 μM) produced more that 50% displacement of the CB1/CB2 non-selective agonist CP-55,940 (0.1 nM). Furthermore, Ki values determined from full competition binding curves showed that analogs 8a, 8b and 8g exhibit high affinity (110, 115 and 23.7 nM, respectively) and moderate selectivity (26.3, 6.1 and 9.2-fold, respectively) for CB2 relative to CB1 receptors. Functional studies examining modulation of G-protein activity demonstrated that 8a acts as a neutral antagonist at CB1 and CB2 receptors, while 8b exhibits inverse agonist activity at these receptors. Analogs 8f and 8g exhibit different intrinsic activities, depending on the receptor examined. Molecular docking and binding free energy calculations for the most active compounds (8a, 8b, 8f, and 8g) were performed to better understand the CB2 receptor-selective mechanism at the atomic level. Compound 8g exhibited the highest predicted binding affinity at both CB1 and CB2 receptors, and all four compounds were shown to have higher predicted binding affinities with the CB2 receptor compared to their corresponding binding affinities with the CB1 receptor. Further structural optimization of 7-AIQD analogs may lead to the identification of potential clinical agents.     

Synthesis of quinolinyl and isoquinolinyl phenyl ketones as novel agonists for the cannabinoid CB2 receptor

A series of quinolinyl and isoquinolinyl phenyl ketones was synthesized and their CB₂ receptor-dependent G-protein activities were determined using the [³⁵S]GTPγS binding assay. Both quinoline and isoquinoline derivatives exhibited similar CB₂ receptor agonist activity, the most potent ligands being the 2-(Me₂N)-phenyl substituted derivatives, which were also full agonists at the CB₂-receptor.     

5,6-Diarylanthranilo-1,3-dinitriles as a new class of antihyperglycemic agents

Various functionalized mono- and diarylanthranilo-1,3-dinitriles were synthesized and evaluated for their in vitro antihyperglycemic activity against the PTP-1B, glucose-6-phosphatase, glycogen phosphorylase and α-glucosidase enzymes. Among various screened compounds, 5,6-diaryl substituted anthranilo-1,3-dinitriles 3a, 3b, and 3d showed good inhibitory activity against PTP-1B with IC₅₀ values of 58–72 μM. Three of the test compounds showed significant (25–37%) lowering of plasma glucose level at 24 h in sucrose-challenged streptozotocin-induced diabetic Sprague–Dawley rat model.     

Characterization of a new class of selective nonsteroidal progesterone receptor agonists

The identification of a new series of selective nonsteroidal progesterone receptor (PR) agonists is reported. Using a high-throughput screening assay based on the measurement of transactivation of a mouse mammary tumor virus promoter-driven luciferase reporter (MMTV-Luc) in human breast cancer T47D cells, a benzimidazole-2-thione analog was identified. Compound 1 showed an apparent EC50 of 53 nM and efficacy of 93% with respect to progesterone. It binds to PR with high affinity (Ki nM), but had no or very low affinity for other steroid hormone receptors. Structure-activity relationship studies of a series of benzimidazole-2-thione analogs revealed critical positions for high PR binding affinity and transactivation potency as well as receptor selectivity, as exemplified by 25. Compound 25 binds to human PR with high affinity (Ki nM) and had at least > 1000-fold selectivity for PR versus other steroid receptors. Molecular modeling studies suggested that these agonists overlap favorably with progesterone in the ligand-binding domain of PR. In T47D cells, compound 25 acted as a full agonist in the MMTV-Luc reporter assay, as well as in the induction of endogenous alkaline phosphatase activity with apparent EC50 values of 4 and 9 nM, respectively. In the immature rat model, compound 25 provided a significant suppression of estrogen-induced endometrium hypertrophy as measured by luminal epithelial height. In contrast, compound 25 was inactive in the luteinizing hormone release assay in young ovariectomized rats. These benzimidazole-2-thione analogs constitute a new series of nonsteroidal PR agonists with an excellent steroid receptor selectivity profile. The differential activities observed in the in vivo progestogenic assays in rat models suggest that these analogs can act as selective PR modulators.     

Desulfohaplosamate, a new phosphate-containing steroid from Dasychalina sp., is a selective cannabinoid CB2 receptor ligand

From the polar organic extract of the Indonesian sponge Dasychalina sp. we have isolated haplosamate A (1), a unique C(28) sterol containing a sulfate group at C-3 and a methyl phosphate at C-15, along with its new desulfo analogue 2, whose structure has been secured by detailed NMR investigation. Compounds 1 and 2, as well as their semi-synthetic analogues 3-5, have been evaluated for interaction with CB(1) and CB(2) receptors through a binding test. Desulfohaplosamate (2) showed a selective affinity for CB(2) receptors in the low μM range, while a semi-synthetic derivative with cleaved ring B showed a complete loss of affinity for both receptors, highlighting the importance of an intact steroid nucleus. To our knowledge, haplosamate derivatives represent the first CB receptor ligands belonging to the class of steroids.