Discovery of pyrrolo[2,1-f][1,2,4]triazine-based inhibitors of adaptor protein 2-associated kinase 1 for the treatment of pain.

Adaptor protein 2-associated kinase 1 (AAK1) is a member of the Ark1/Prk1 family of serine/threonine kinases and plays a role in modulating receptor endocytosis. AAK1 was identified as a potential therapeutic target for the treatment of neuropathic pain when it was shown that AAK1 knock out (KO) mice had a normal response to the acute pain phase of the mouse formalin model, but a reduced response to the persistent pain phase. Herein we report our early work investigating a series of pyrrolo[2,1-f][1,2,4]triazines as part of our efforts to recapitulate this KO phenotype with a potent, small molecule inhibitor of AAK1. The synthesis, structure-activity relationships (SAR), and in vivo evaluation of these AAK1 inhibitors is described.

Bicyclic Heterocyclic Replacement of an Aryl Amide Leading to Potent and Kinase-Selective Adaptor Protein 2-Associated Kinase 1 Inhibitors.

Adaptor protein 2-associated kinase 1 (AAK1) is a serine/threonine kinase that was identified as a therapeutic target for the potential treatment of neuropathic pain. Inhibition of AAK1 in the central nervous system, particularly within the spinal cord, was found to be the relevant site for achieving an antinociceptive effect. We previously reported that compound 7 is a brain-penetrant, AAK1 inhibitor that showed efficacy in animal models for neuropathic pain. One approach we took to improve upon the potency of 7 involved tying the amide back into the neighboring phenyl ring to form a bicyclic heterocycle. Investigation of the structure-activity relationships (SARs) of substituents on the resultant quinazoline and quinoline ring systems led to the identification of (S)-31, a brain-penetrant, AAK1-selective inhibitor with improved enzyme and cellular potency compared to 7. The synthesis, SAR, and in vivo evaluation of a series of quinazoline and quinoline-based AAK1 inhibitors are described herein.

Design, synthesis, and evaluation of phenylglycinols and phenyl amines as agonists of GPR88.

Small molecule modulators of GPR88 activity (agonists, antagonists, or modulators) are of interest as potential agents for the treatment of a variety of psychiatric disorders including schizophrenia. A series of phenylglycinol and phenylamine analogs have been prepared and evaluated for their GPR88 agonist activity and pharmacokinetic (PK) properties.

Serendipitous oxidation product of BIBN4096BS: a potent CGRP receptor antagonist.

An oxidation product (5) formed during the synthesis of BIBN-4096BS (1) was found to be a potent CGRP antagonist (IC50=0.11nM). While 5 was found to be ten-fold less potent than 1, another analog 8 with lower molecular weight containing the oxidized fragment demonstrated twenty-fold higher activity than its parent 7. Alternative conditions which preclude the formation of the oxidation product are described. The activities of 1, 5, 7 and 8 in functional cAMP assay are also discussed.

Synthesis and structure-activity relationships of pyrido[3,2-b]pyrazin-3(4H)-ones and pteridin-7(8H)-ones as corticotropin-releasing factor-1 receptor antagonists.

Pyrido[3,2-b]pyrazin-3(4H)-ones and pteridin-7(8H)-ones were evaluated as corticotropin-releasing factor-1 receptor antagonists. The synthesis, SAR studies and pharmacokinetic evaluation of these analogs are described herein.

Discovery of 6-chloro-2-trifluoromethyl-7-aryl-7H-imidazo[1,2-a]imidazol-3-ylmethylamines, a novel class of corticotropin-releasing factor receptor type 1 (CRF1R) antagonists.

A novel series of [6-chloro-2-trifluoromethyl-7-aryl-7H-imidazo[1,2-a]imidazol-3-ylmethyl]-dialkylamines was discovered as potent CRF(1)R antagonists. The optimization of binding affinity in the series by the parallel reaction approach is discussed herein.

Design, synthesis and evaluation of constrained tetrahydroimidazopyrimidine derivatives as antagonists of corticotropin-releasing factor type 1 receptor (CRF1R).

Several tetrahydroimidazopyrimidines were prepared using silver assisted cyclization as the key step. The binding affinities of compounds thus prepared were evaluated in vitro toward hCRF(1)R. Initial lead compound 16 (K(i)=32 nM) demonstrated modest putative anxiolytic effects in the mouse canopy test. Further optimization using parallel synthesis provided compounds with K(i)'s <50 nM.

Separation of maxi-K channel opening 3-substituted-4-arylquinolinone atropisomers by enantioselective supercritical fluid chromatography.

Many 3-substituted-4-arylquinolinones containing an ortho substituent on the aryl ring were known as a class of compounds with maxi-K opening activity. These quinolinones, which contained a stereogenic axis in their structures due to their bulky ortho substituents on the two aryl rings, exhibited atropisomerism. The rotationally hindered atropisomers could have differential biological and pharmacological activity, and it was highly desirable to separate them and test the individual atropisomers in biological assays. To explore the potential of supercritical fluid chromatography (SFC) to separate the atropisomers of this class of compounds, six 3-substituted-4-arylquinolinones with various hydrophilic and hydrophobic substituents in various positions were screened using three alcoholic modifiers (methanol, ethanol and 2-propanol) with four polysaccharide-based chiral stationary phases (Chiralpak AD-H and AS-H, Chiralcel OD-H and OJ-H). Our results showed that all six compounds studied were successfully resolved under multiple SFC conditions regardless of their structural differences and polarity. The majority of the separations were completed within 10 min. The Chiralpak AD-H column appeared to be superior to the other three chiral columns, and methanol and ethanol showed higher successful rate than 2-propanol in separating atropisomers of this class of compounds. These SFC methods were efficient and easily scalable for preparative separation. Thus, SFC was found to be the methodology of choice for resolving the atropisomers of this class of compounds.

Atropisomeric 3-(beta-hydroxyethyl)-4-arylquinolin-2-ones as Maxi-K potassium channel openers.

The synthesis of a series of 3-beta-hydroxyethyl-4-arylquinolin-2-ones is described. These compounds contain hydrophilic and hydrophobic substituents ortho to the phenolic OH in the C ring of the quinolinone. Electrophysiological evaluation of the panel of compounds revealed that 11 and 16 with an unbranched ortho substituent retain activity as maxi-K ion channel openers. Members of this series of compounds can exist as stable atropisomers. Calculated estimates of the energy barrier for rotation around the aryl-aryl single bond in 3 is 31 kcal/mol. The atropisomers of (+/-)-3, (+/-)-4, and (+/-)-11 were separated by chiral HPLC and tested for their effect on maxi-K mediated outward current in hSlo injected X. laevis oocytes. The (-) isomer in each case was found to be more active than the corresponding (+) isomer, suggesting that the ion channel exhibits stereoselective activation. X-ray crystallographic structures of (+)-3 and (+)-11 were determined. Evaluation of the stability of (-)-3 at 80 degrees C in n-butanol indicated a 19.6% conversion to (+)-3 over 72 h. In human serum at 37 degrees C (-)-3 did not racemize over the course of the 30 h study.

Analogs of a potent maxi-K potassium channel opener with an improved inhibitory profile toward cytochrome P450 isozymes.

Quinolinone 1 is a potent maxi-K potassium channel opener. In an effort to design analogs of 1 with a better inhibitory profile toward the CYP2C9 isozyme, the two acidic sites were chemically modified independently to generate a number of analogs. These analogs were evaluated as maxi-K channel openers in vitro using Xenopus laevis oocytes expressing cloned hSlo maxi-K channels. Compounds 15, 17, and 19 showed potent activity as maxi-K channel openers and were further evaluated for inhibition of the activity of the CYP2C9 isozyme. Compounds 17 and 19 showed diminished inhibitory potency against 2C9 and also against a panel of other more common CYP isozymes.