Development of biotinylated and magnetic bead-immobilized enzymes for efficient glyco-engineering and isolation of antibodies

The chemoenzymatic remodeled monoclonal antidodies with well-defined glycan structure at the Fc domain display improved biological activities, such as ADCC and ADCP, and are more likely to yield a better safety profile by eliminating the non-human glycans derived from CHO cell culture. We covalently immobilize wild type endoglycosidase S (EndoS), fucosidase, and EndoS2 mutant on magnetic beads through a linker to efficiently generate homogeneous antibody glycoforms without additional purification step to remove endoglycosidase and fucosidase. We also used the biotinylated wild type EndoS2 and EndoS2 mutant in combination with covalently immobilized fucosidase on magnetic beads to allow the sequential removal of endoglycosidases and fucosidase for efficient glyco-engineering and isolation of antibodies without purifying deglycosylated antibody intermediate. Notably, the relatively expensive fucosidase can be recovered to reduce the cost, and the strong affinity of streptavidin to biotin would complete the isolation of biotinylated enzymes. We used Trastuzumab as a model to demonstrate both approaches were reliable for the large-scale production and isolation of antibodies without the residual contamination of endoglycosidase to avoid deglycosylation over storage time.

Development of glycosynthases with broad glycan specificity for the efficient glyco-remodeling of antibodies

The first systematic investigation of the effect of high mannose, hybrid, and bi- and tri-antennary complex type glycans on the effector functions of antibodies was achieved by the discovery of novel Endo-S2 mutants generated by site-directed mutagenesis as glycosynthases with broad substrate specificity.

Correction: Development of glycosynthases with broad glycan specificity for the efficient glyco-remodeling of antibodies

Correction for ‘Development of glycosynthases with broad glycan specificity for the efficient glyco-remodeling of antibodies’ by Sachin S. Shivatare et al., Chem. Commun., 2018, 54, 6161–6164.

An Effective Bacterial Fucosidase for Glycoprotein Remodeling

Fucose is an important component of many oligo- and polysaccharide structures as well as glycoproteins and glycolipids, which are often associated with a variety of physiological processes ranging from fertilization, embryogenesis, signal transduction, and disease progression, such as rheumatoid arthritis, inflammation, and cancer. The enzyme α-l-fucosidase is involved in the cleavage of the fucosidic bond in glycans and glycoconjugates, particularly the Fuc-α-1,2-Gal, Fuc-α-1,3/4-GlcNAc, and Fuc-α-1,6-GlcNAc linkages. Here, we report a highly efficient fucosidase, designated as BfFucH identified from a library of bacterial glycosidases expressed in E. coli from the CAZy database, which is capable of hydrolyzing the aforementioned fucosidic linkages, especially the α-1,6-linkage from the N-linked Fuc-α-1,6-GlcNAc residue on glycoproteins. Using BfFucH coupled with endoglycosidases and the emerging glycosynthases allows glycoengineering of IgG antibodies to provide homogeneous glycoforms with well-defined glycan structures and optimal effector functions.

Phenyl Glycolipids with Different Glycosyl Groups Exhibit Marked Differences in Murine and Human iNKT Cell Activation

Glycosphingolipids (GSLs) bearing the α-galactosyl headgroup and the acyl chain terminated with a phenyl derivative were found to be more potent than α-galactosyl ceramide (αGalCer) to stimulate both murine and human invariant natural killer T (iNKT) cells and to induce an antibody isotope switch to IgG. In this study, we replaced the galactosyl group with glucose (αGlc) and its fluoro-analogs and found that phenyl GSLs with αGlc (C34-Glc) and its fluoro-analog 6F-C34-Glc were stronger than those with αGal in stimulating human iNKT cells but weaker in mice. Their activities have a strong correlation with the binding avidities of the ternary interaction between the iNKT-cell receptor (iNKTCR) and CD1d-GSL complex. It was the iNKTCR rather than CD1d that dictated the species-specific responses. C34-Glc was further used as an adjuvant for a SSEA4-crm-197 vaccine, and after immunization in mice, the vaccine was highly effective against Lewis lung carcinoma.

Discovery of 3H-benzo[4,5]thieno[3,2-d]pyrimidin-4-ones as potent, highly selective, and orally bioavailable inhibitors of the human protooncogene proviral insertion site in moloney murine leukemia virus (PIM) kinases

Pim-1, Pim-2, and Pim-3 are a family of serine/threonine kinases which have been found to be overexpressed in a variety of hematopoietic malignancies and solid tumors. Benzothienopyrimidinones were discovered as a novel class of Pim inhibitors that potently inhibit all three Pim kinases with subnanomolar to low single-digit nanomolar K(i) values and exhibit excellent selectivity against a panel of diverse kinases. Protein crystal structures of the bound Pim-1 complexes of benzothienopyrimidinones 3b (PDB code 3JYA), 6e (PDB code 3JYO), and 12b (PDB code 3JXW) were determined and used to guide SAR studies. Multiple compounds exhibited potent antiproliferative activity in K562 and MV4-11 cells with submicromolar EC(50) values. For example, compound 14j inhibited the growth of K562 cells with an EC(50) value of 1.7 muM and showed K(i) values of 2, 3, and 0.5 nM against Pim-1, Pim-2, and Pim-3, respectively. These novel Pim kinase inhibitors efficiently interrupted the phosphorylation of Bad in both K562 and LnCaP-Bad cell lines, indicating that their potent biological activities are mechanism-based. The pharmacokinetics of 14j was studied in CD-1 mice and shown to exhibit bioavailability of 76% after oral dosing. ADME profiling of 14j suggested a long half-life in both human and mouse liver microsomes, good permeability, modest protein binding, and no CYP inhibition below 20 muM concentration.

Cyclin B1 is an efficacy-predicting biomarker for Chk1 inhibitors

Chk1 is the major mediator of cell-cycle checkpoints in response to various forms of genotoxic stress. Although it was previously speculated that checkpoint abrogation due to Chk1 inhibition may potentiate the efficacy of DNA-damaging agents through induction of mitotic catastrophe, there has not been direct evidence proving this process. Here, through both molecular marker and morphological analysis, we directly demonstrate that specific downregulation of Chk1 expression by Chk1 siRNA potentiates the cytotoxicities of topoisomerase inhibitors through the induction of premature chromosomal condensation and mitotic catastrophe. More importantly, we discovered that the cellular cyclin B1 level is the major determinant of the potentiation. We show that downregulation of cyclin B1 leads to impairment of the induction of mitotic catastrophe and correspondingly a reduction of the potentiation ability of either Chk1 siRNA or a small molecule Chk1 inhibitor. More significantly, we have extended the study by examining a panel of 10 cancer cell-lines with different tissue origins for their endogenous levels of cyclin B1 and the ability of a Chk1 inhibitor to sensitize the cells to DNA-damaging agents. The cellular levels of cyclin B1 positively correlate with the degrees of potentiation achieved. Of additional interest, we observed that the various colon cancer cell lines in general appear to express higher levels of cyclin B1 and also display higher sensitivity to Chk1 inhibitors, implying that Chk1 inhibitor may be more efficacious in treating colon cancers. In summary, we propose that cyclin B1 is a biomarker predictive of the efficacy of Chk1 inhibitors across different types of cancers. Unlike previously established efficacy-predictive biomarkers that are usually the direct targets of the therapeutic agents, cyclin B1 represents a non-drug-target biomarker that is based on the mechanism of action of the target inhibitor. This finding may be potentially very useful for the stratification of patients for Chk1 inhibitor clinical trials and hence, maximize its chance of success.

Investigation of novel 7,8-disubstituted-5,10-dihydro-dibenzo[b,e][1,4]diazepin-11-ones as potent Chk1 inhibitors

The synthesis and structure-activity relationships (SAR) of Chk1 inhibitors based on a 5,10-dihydro-dibenzo[b,e][1,4]diazepin-11-one core are described. Specifically, an exploration of the 7 and 8 positions on this previously disclosed core afforded compounds with improved enzymatic and cellular potency.

Discovery of 4′-(1,4-dihydro-indeno[1,2-c]pyrazol-3-yl)-benzonitriles and 4′-(1,4-dihydro-indeno[1,2-c]pyrazol-3-yl)-pyridine-2′-carbonitriles as potent checkpoint kinase 1 (Chk1) inhibitors

An extensive structure-activity relationship study of the 3-position of a series of tricyclic pyrazole-based Chk1 inhibitors is described. As a result, 4'-(1,4-dihydro-indeno[1,2-c]pyrazol-3-yl)-benzonitriles (4) and 4'-(1,4-dihydro-indeno[1,2-c]pyrazol-3-yl)-pyridine-2'-carbonitriles (29) emerged as new lead series. Compared with the original lead compound 2, these new leads fully retain the biological activity in both enzymatic inhibition and cell-based assays. More importantly, the new leads 4 and 29 exhibit favorable physicochemical properties such as lower molecular weight, lower Clog P, and the absence of a hydroxyl group. Furthermore, structure-activity relationship studies were performed at the 6- and 7-positions of 4, which led to the identification of ideal Chk1 inhibitors 49, 50, 51, and 55. These compounds not only potently inhibit Chk1 in an enzymatic assay but also significantly potentiate the cytotoxicity of DNA-damaging agents in cell-based assays while they show little single agent activity. A cell cycle analysis by FACS confirmed that these Chk1 inhibitors efficiently abrogate the G2/M and S checkpoints induced by DNA-damaging agent. The current work paved the way to the identification of several potent Chk1 inhibitors with good pharmacokinetics that are suitable for in vivo study with oral dosing.

Cyanopyridyl containing 1,4-dihydroindeno[1,2-c]pyrazoles as potent checkpoint kinase 1 inhibitors: Improving oral biovailability

A series of 1,4-dihydroindeno[1,2-c]pyrazole compounds with a cyanopyridine moiety at the 3-position of the tricyclic pyrazole core was explored as potent CHK-1 inhibitors. The impact of substitutions at the 6 and/or 7-position of the core on pharmacokinetic properties was studied in detail. Compounds carrying a side chain with an ether linker at the 7-position and a terminal morpholino group, such as 29 and 30, exhibited much-improved oral biovailability in mice as compared to earlier generation inhibitors. These compounds also possessed desirable cellular activity in potentiating doxorubicin and will serve as valuable tool compounds for in vivo evaluation of CHK-1 inhibitors to sensitize DNA-damaging agents.

Design, Synthesis, and Biological Activity of 5,10-Dihydro-dibenzo[b,e][1,4]diazepin-11-one-Based Potent and Selective Chk-1 Inhibitors

A novel series of 5,10-dihydro-dibenzo[b,e][1,4]diazepin-11-ones have been synthesized as potent and selective checkpoint kinase 1 (Chk1) inhibitors via structure-based design. Aided by protein X-ray crystallography, medicinal chemistry efforts led to the identification of compound 46d, with potent enzymatic activity against Chk1 kinase. While maintaining a low cytotoxicity of its own, compound 46d exhibited a strong ability to abrogate G2 arrest and increased the cytotoxicity of camptothecin by 19-fold against SW620 cells. Pharmacokinetic studies revealed that it had a moderate bioavailabilty of 20% in mice. Two important binding interactions between compound 46b and Chk1 kinase, revealed by X-ray cocrystal structure, were hydrogen bonds between the hinge region and the amide bond of the core structure and a hydrogen bond between the methoxy group and Lys38 of the protein.

Synthesis and biological evaluation of 4'-(6,7-disubstituted-2,4-dihydro-indeno[1,2-c]pyrazol-3-yl)-biphenyl-4-ol as potent Chk1 inhibitors

A new series of potent tricyclic pyrazole-based Chk1 inhibitors are described. Analogues disubstituted on the 6- and 7-positions show improved Chk1 inhibition potency compared with analogues with a single substituent on either the 6- or 7-position. Based on the lead compound 4'-(6,7-dimethoxy-2,4-dihydro-indeno[1,2-c]pyrazol-3-yl)-biphenyl-4-ol (2), detailed SAR studies on the 6- and 7-positions were performed. 3'-morpholin-4'-yl-propoxy, pyridin-4'-ylmethoxy, pyridin-3'-ylmethoxy, 2'-(5''-ethyl-pyridin-2''-yl)-ethoxy, pyridin-2'-ylethoxy, (6'-methyl-pyridin-2'-yl)-propoxyethoxy, 2',3'-dihydroxyl-1'-yl-propoxy, and tetrahydro-furan-3'-yloxy have been identified as the best groups on the 6-position when the 7-position is substituted with methoxyl group. Pyridin-2'-ylmethoxy and pyridin-3'-ylmethoxy have been identified as the best substituents at the 7-position while the 6-position bearing methoxyl group. These compounds significantly potentiate the cytotoxicity of DNA-damaging antitumor agents in a cell-based assay and efficiently abrogate the doxorubicin-induced G2/M and the camptothecin-induced S checkpoints, suggesting that their potent biological activities are mechanism-based through Chk1 inhibition.

Structure-based design, synthesis, and biological evaluation of potent and selective macrocyclic checkpoint kinase 1 inhibitors

Based on the crystallographic analysis of a urea-checkpoint kinase 1 (Chk1) complex and molecular modeling, a class of macrocyclic Chk1 inhibitors were designed and their biological activities were evaluated. An efficient synthetic methodology for macrocyclic ureas was developed with Grubbs metathesis macrocyclization as the key step. The structure-activity relationship studies demonstrated that the macrocyclization retains full Chk1 inhibition activity and that the 4-position of the phenyl ring can tolerate a wide variety of substituents. These novel Chk1 inhibitors exhibit excellent selectivity over a panel of more than 70 kinases. Compounds 5b, 5c, 5f, 15, 16d, 17g, 17h, 17k, 18d, and 22 were identified as ideal Chk1 inhibitors, which showed little or no single-agent activity but significantly potentiate the cytotoxicities of the DNA-damaging antitumor agents doxorubicin and camptothecin. These novel Chk1 inhibitors abrogate the doxorubicin-induced G2 and camptothecin-induced S checkpoint arrests, confirming that their potent biological activities are mechanism-based through Chk1 inhibition.

Discovery of 1,4-dihydroindeno[1,2-c]pyrazoles as a novel class of potent and selective checkpoint kinase 1 inhibitors

A new class of checkpoint kinase 1 (CHK-1) inhibitors bearing a 1,4-dihydroindeno[1,2-c]pyrazole core was developed after initial hits from high throughput screening. The efficient hit-to-lead process was facilitated by X-ray crystallography and led to potent inhibitors (<10nM) against CHK-1. X-ray co-crystal structures of bound inhibitors demonstrated that two sub-series of this class of compounds, exemplified by 21 and 41, exhibit distinctive hydrogen bonding patterns in the specificity pocket of the active site. Two compounds, 41 and 43, were capable of potentiating doxorubicin and camptothecin, both DNA-damaging agents, in cell proliferation assays (MTS and soft agar assays) and abrogating G2/M checkpoint in a mechanism-based FACS assay.

Selective Chk1 inhibitors differentially sensitize p53-deficient cancer cells to cancer therapeutics

The majority of cancer therapeutics induces DNA damage to kill cells. Normal proliferating cells undergo cell cycle arrest in response to DNA damage, thus allowing DNA repair to protect the genome. DNA damage induced cell cycle arrest depends on an evolutionarily conserved signal transduction network in which the Chk1 kinase plays a critical role. In mammalian cells, the p53 and RB pathways further augment the cell cycle arrest response to prevent catastrophic cell death. Given the fact that most tumor cells suffer defects in the p53 and RB pathways, it is likely that tumor cells would depend more on the Chk1 kinase to maintain cell cycle arrest than would normal cells. Therefore Chk1 inhibition could be used to specifically sensitize tumor cells to DNA-damaging agents. We have previously shown that siRNA-mediated Chk1 knockdown abrogates DNA damage-induced checkpoints and potentiates the cytotoxicity of several DNA-damaging agents in p53-deficient cell lines. In this study, we have developed 2 potent and selective Chk1 inhibitors, A-690002 and A-641397, and shown that these compounds abrogate cell cycle checkpoints and potentiate the cytotoxicity of topoisomerase inhibitors and gamma-radiation in p53-deficient but not in p53-proficient cells of different tissue origins. These results indicate that it is feasible to achieve a therapeutic window with 1 or more Chk1 inhibitors in potentiation of cancer therapy based on the status of the p53 pathway in a wide spectrum of tumor types.

Chk1 Inhibitors for Novel Cancer Treatment

Chemo- and radiotherapies that target DNA are the mainstay of cancer treatment. In response to DNA damage, cells are arrested in multiple checkpoints in the cell cycle to allow the damaged DNA to be repaired before progressing into mitosis. Normal cells are arrested in the G1 phase mediated by the p53 tumor suppressor, and p53-deficient cancer cells are arrested in the S or G2 phase. Checkpoint kinase 1 (Chk 1) is a serine / threonine protein kinase and a key mediator in the DNA damage-induced checkpoint network. When the G2 or S checkpoint is abrogated by the inhibition of Chk1, p53-deficient cancer cells undergo mitotic catastrophe and eventually apoptosis, whereas normal cells are still arrested in the G1 phase. Thus, Chk1 inhibitors can preferentially potentiate the efficacy of DNA damaging agents in cancer cells, and Chk1 is an attractive therapeutic target for cancer treatment, especially since approximately 50% of all human cancers are p53-deficient. This review discusses the rationale of Chk1 as an anticancer target, the structural basis for designing Chk1 inhibitors, and recently disclosed Chk1 inhibitors.

Synthesis and biological evaluation of 1-(2,4,5-trisubstituted phenyl)-3-(5-cyanopyrazin-2-yl)ureas as potent Chk1 kinase inhibitors

Based on the X-ray crystallography of our lead compound 1-(5-chloro-2,4-dimethoxyphenyl)-3-(5-cyanopyrazin-2-yl)urea in the checkpoint kinase 1 (Chk1) enzyme, we modified R4, and to a lesser extent, R2, and R5 of the phenyl ring, and made a variety of N-aryl-N'-pyrazinylurea Chk1 inhibitors. Enzymatic activity less than 20 nM was observed in 15 of 41 compounds. Compound 8i provided the best overall results in the cellular assays as it abrogated doxorubicin-induced cell cycle arrest (IC50=1.7 microM) and enhanced doxorubicin cytotoxicity (IC50=0.44 microM) while displaying no single agent activity.

A highly potent and selective farnesyltransferase inhibitor ABT-100 in preclinical studies

Ras mutation has been detected in approximately 20-30% of all human carcinomas, primarily in pancreatic, colorectal, lung and bladder carcinomas. The indirect inhibition of Ras activity by inhibiting farnesyltransferase (FTase) function is one therapeutic intervention to control tumor growth. Here we report the preclinical anti-tumor activity of our most advanced FTase inhibitor (FTI), ABT-100, and a direct comparison with the current clinical candidates. ABT-100 is a highly selective, potent and orally bioavailable FTI. It broadly inhibits the growth of solid tumors in preclinical animal models. Thus, ABT-100 is an attractive candidate for further clinical evaluation. In addition, our results provide plausible insights to explain the impressive potency and selectivity of ABT-100. Finally, we have demonstrated that ABT-100 significantly suppresses the expression of vascular endothelial growth factor (VEGF) mRNA and secretion of VEGF protein, as well as inhibiting angiogenesis in the animal model.

Synthesis and biological evaluation of 3-ethylidene-1,3-dihydro-indol-2-ones as novel checkpoint 1 inhibitors

Chk1 inhibitors have emerged as a novel class of neoplastic agents for abrogating the G2 DNA damage checkpoint arrest. Analogs of the Chk1 inhibitor, 3-ethylidene-1,3-dihydro-indol-2-one, were synthesized and tested in vitro for their inhibitory activities. The most promising compound identified from this series is analog 28, which possesses potent enzymatic and cellular activities.

Antitumor activity of orally bioavailable farnesyltransferase inhibitor, ABT-100, is mediated by antiproliferative, proapoptotic, and antiangiogenic effects in xenograft models

PURPOSE

To evaluate the preclinical pharmacokinetics, antitumor efficacy, and mechanism of action of a novel orally active farnesyltransferase inhibitor, ABT-100.

EXPERIMENTAL DESIGN

In vitro sensitivity of a panel of human cell lines was determined using proliferation and clonogenic assays. In vivo efficacy of ABT-100 was evaluated in xenograft models (flank or orthotopic) by assessing angiogenesis, proliferation, and apoptosis in correlation with pharmacokinetics. Efficacy of the racemate of ABT-100 (A-367074) was also compared with R115777 (tipifarnib).

RESULTS

ABT-100 inhibited proliferation of cells in vitro carrying oncogenic H-Ras (EJ-1 bladder; IC(50) 2.2 nmol/L), Ki-Ras (DLD-1 colon, MDA-MB-231 breast, HCT-116 colon, and MiaPaCa-2 pancreatic; IC(50) range, 3.8-9.2 nmol/L), and wild-type Ras (PC-3 and DU-145; IC(50), 70 and 818 nmol/L, respectively) as well as clonogenic potential. ABT-100 shows 70% to 80% oral bioavailability in mice. ABT-100 regressed EJ-1 tumors (2-12.5 mg/kg/d s.c., every day for 21 days) and showed significant efficacy in DLD-1, LX-1, MiaPaCa-2, or PC-3 tumor-bearing mice (6.25-50 mg/kg/d s.c. once daily or twice daily orally). A-367074 showed equivalent efficacy to R115777 given at approximately one-fourth the total dose of R115777 for a shorter duration (EJ-1 and LX-1). Antitumor activity was associated with decreased cell proliferation (Ki-67), increased apoptosis (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling), and decreased angiogenesis. A reduction in tumor angiogenic cytokine levels (vascular endothelial growth factor, basic fibroblast growth factor, and interleukin-8) correlated with a reduction in tumor vascularity (CD31).

CONCLUSIONS

Overall, ABT-100 has an acceptable pharmacokinetic profile, is well tolerated, and possesses broad-spectrum antitumor activity against a series of xenograft models similar to farnesyltransferase inhibitors in clinical development; therefore, it is an attractive candidate for clinical evaluation.

1-(5-Chloro-2-alkoxyphenyl)-3-(5-cyanopyrazin-2-yl)ureas [correction of cyanopyrazi] as potent and selective inhibitors of Chk1 kinase: synthesis, preliminary SAR, and biological activities

The discovery of 1-(5-chloro-2-alkoxyphenyl)-3-(5-cyanopyrazin-2-yl)ureas as a new class of potent (IC(50) values of 3-10 nM) and selective inhibitors of Chk1 kinase was described. One of these compounds (2e) potentiates HeLa cells by over 22-fold against doxorubicin in an antiproliferation assay, and SW620 cells against camptothecin by 20-fold in an antiproliferation assay and 14-fold in a soft agar assay. Flow cytometry (FACS) analysis confirmed that 2e abrogated G2 checkpoint arrest of H1299 cells caused by doxorubicin and S checkpoint arrest caused by camptothecin.

Synthesis and biological evaluation of 1-benzyl-5-(3-biphenyl-2-yl-propyl)-1H-imidazole as novel farnesyltransferase inhibitor

Farnesyltransferase inhibitors (FTIs) have emerged as a novel class of anti-cancer agents. Analogs of the potent FTI, 1-benzyl-5-(3-biphenyl-2-yl-propyl)-1H-imidazole, were synthesized and tested in vitro for their inhibitory activities. The most promising compound identified from this series is analog 29 that possesses potent enzymatic and cellular activities.

ABT-089: pharmacological properties of a neuronal nicotinic acetylcholine receptor agonist for the potential treatment of cognitive disorders

ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine dihydrochloride salt] is a selective neuronal nicotinic receptor (NNR) modulator with cognitive enhancing properties in animal models of cognitive functioning. Amongst NNR subtypes, ABT-089 shows selectivity for the cytisine binding site on the alpha4beta2 receptor subtype as compared to the alpha-bungarotoxin (alpha-BgT) binding sites on the alpha7 and alpha1beta1deltagamma receptor subtypes. In functional in vitro electrophysiological and cation flux assays, ABT-089 displays differential activity including agonism, partial agonism and antagonism depending upon the NNR subtype and assay. ABT-089 is as potent and efficacious as (-)-nicotine at evoking acetylcholine (ACh) release from hippocampal synaptosomes. Furthermore, ABT-089 is neuroprotective against excitotoxic glutamate insults, with even greater potency seen after chronic treatment. Similarly, ABT-089 is effective in models of cognitive functioning, including enhancement of baseline functioning as well as improvement of impaired cognitive functioning seen following septal lesioning and natural aging. In neuroprotective assays the compound is most potent by chronic administration. In stark contrast to the positive effects in the cognitive models, ABT-089 shows little propensity to induce adverse effects such as ataxia, hypothermia, seizures, cardiovascular or gastrointestinal side effects. Together these data suggest that ABT-089 is a NNR modulator with the potential for treating cognitive disorders with markedly limited adverse cardiovascular and gastrointestinal side effects.

Synthesis of 1H-pyridin-2-one derivatives as potent and selective farnesyltransferase inhibitors

Two novel series of potent and selective FTase inhibitors have been synthesized using structure-based design. Medicinal chemistry efforts led to the discovery of compound 4e with potent cellular activity and good oral bioavailability in dog. A synthetic route toward novel heterocycles 1,5-dimethyl-6-oxo-4-aryl-1,6-dihydro-pyridine-2-carbonitrile was established. The structure of compound 5c was confirmed by X-ray crystallography.

Design, Synthesis, and Biological Activity of 4-[(4-Cyano-2-arylbenzyloxy)-(3-methyl-3H-imidazol-4-yl)methyl]benzonitriles as Potent and Selective Farnesyltransferase Inhibitors

A novel series of 4-[(4-cyano-2-arylbenzyloxy)-(3-methyl-3H-imidazol-4-yl)methyl]benzonitriles have been synthesized as selective farnesyltransferase inhibitors using structure-based design. X-ray cocrystal structures of compound 20-FTase-HFP and A313326-FTase-HFP confirmed our initial design. The decreased interaction between the aryl groups and Ser 48 in GGTase-I binding site could be one possible reason to explain the improved selectivity for this new series of FTase inhibitors. Medicinal chemistry efforts led to the discovery of compound 64 with potent cellular activity (EC(50) = 3.5 nM) and outstanding pharmacokinetic profiles in dog (96% bioavailable, 18.4 h oral t(1/2), and 0.19 L/(h x kg) plasma clearance).

Pyridone-containing farnesyltransferase inhibitors: synthesis and biological evaluation

Farnesyltransferase inhibitors (FTIs) have been developed as potential anti-cancer agents due to their efficacy in blocking malignant growth in a variety of murine models of human tumors. To that end, we have developed a series of pyridone farnesyltransferase inhibitors with potent in vitro and cellular activity. The synthesis, SAR and biological properties of these compounds will be discussed.

Synthesis and biological evaluation of 4-[(3-methyl-3H-imidazol-4-yl)-(2-phenylethynyl-benzyloxy)-methyl]-benzonitrile as novel farnesyltransferase inhibitor

Farnesyltransferase inhibitors (FTIs) have emerged as a novel class of anticancer agents. Analogues of the potent FTI, 4-[3-biphenyl-1-hydroxy-1-(3-methyl-3H-imidazol-4-yl)-prop-2-ynyl]-1-yl-benzonitrile, were synthesized and tested in vitro for their inhibitory activities. The most promising compound identified from this series is analogue 11 that possesses potent enzymatic and cellular activities.

Pyridone-Containing farnesyltransferase inhibitors: synthesis and biological evaluation

Farnesyltransferase inhibitors (FTIs) have been developed as potential anti-cancer agents due to their efficacy in blocking malignant growth in a variety of murine models of human tumors. To that end, we have developed a series of pyridone farnesyltransferase inhibitors with potent in vitro and cellular activity. The synthesis, SAR and biological properties of these compounds will be discussed.

Discovery of potent imidazole and cyanophenyl containing farnesyltransferase inhibitors with improved oral bioavailability

A pyridyl moiety was introduced into a previously developed series of farnesyltransferase inhibitors containing imidazole and cyanophenyl (such as 4), resulting in potent inhibitors with improved pharmacokinetics.

Synthesis and biological evaluation of 4-[3-biphenyl-2-yl-1-hydroxy-1-(3-methyl-3H-imidazol-4-yl)-prop-2-ynyl]-1-yl-benzonitrile as novel farnesyltransferase inhibitor

Farnesyltransferase inhibitors (FTIs) have emerged as a novel class of anti-cancer agents. Analogues of the potent FTI, 4-[3-biphenyl-1-hydroxy-1-(3-methyl-3H-imidazol-4-yl)-prop-2-ynyl]-1-yl-benzonitrile, were synthesized and tested in vitro for their inhibitory activities. The synthesis and detailed biological data of this series of analogues are presented.

Synthesis and biological evaluation of pyridine-modified analogues of 3-(2-aminoethoxy)pyridine as novel nicotinic receptor ligands

Analogues of the potent nicotinic receptor agonist 3-(2-aminoethoxy)pyridine substituted at the 5' and 6'-positions of the pyridine ring were synthesized and tested in vitro for nicotinic receptor binding activity (displacement of [(3)H](-)cytisine from whole rat brain synaptic membranes). The substituted analogues exhibited K(i) values ranging from 0.076 to 319 nM compared to a K(i) value of 26 nM for compound 1. Among the compounds tested, 5'-vinyl-6'-chloro substituted 1 was the most potent.

Synthesis and structure-activity relationships of 5-substituted pyridine analogues of 3

In an effort to probe the steric influence of C5 substitution of the pyridine ring on CNS binding affinity, analogues of 1 substituted with a bulky moiety--such as phenyl, substituted phenyl, or heteroaryl-were synthesized and tested in vitro for neuronal nicotinic acetylcholine receptor binding affinity. The substituted analogues exhibited Ki values ranging from 0.055 to 0.69 nM compared to a Ki value of 0.15 nM for compound 1. Assessment of functional activity at subtypes of neuronal nicotinic acetylcholine receptors led to identify several agonists and antagonists.

Structure-activity studies on a novel series of cholinergic channel activators based on a heteroaryl ether framework

Analogs of compound 1 with a variety of azacycles and heteroaryl groups were synthesized. These analogs exhibited Ki values ranging from 0.15 to > 10,000 nM when tested in vitro for cholinergic channel receptor binding activity (displacement of [3H](-) cytisine from whole rat brain synaptic membranes).

Local circulation and aerosol water-soluble ions--a case study in Taiwan during Mei-yu season

The Mei-yu (plum rain) season is a short but important period when the weather changes from spring to summer in Taiwan. In this study, size-segregated aerosols were collected alternately at 5 sampling sites in northwestern Taiwan from June 16 to 24, 1994. For the first time in Taiwan, this study revealed the aerosol mass spectra and water-soluble ions in the Mei-yu season. For all samples, a bi-modal aerosol mass spectra was found with modal diameters at 3.2 and 0.32 microm, respectively. The aerosol samples were able to be divided into different groups to show their mass and ion spectra according to the calculated 5-hr backward air trajectory. The utilization of enrichment factors showed that aerosol Cl-, Na+, and Mg2+ for all sizes, and super-micron SO4(2-) were related to the sea. Both the scheme of "chlorine loss" (Ohta and Okita, 1990) and a multivariate analysis (Thurston and Spengler, 1985) for categorizing water-soluble ions showed that sea-salts were major contributors in the prevalence of a sea breeze. In contrast, the secondary salts were significant for land breeze and a mix of land-sea breeze. In conclusion, the influence of local circulation on the distribution of aerosol mass and ionic species was found to be prominent.

Structure-activity studies related to ABT-594, a potent nonopioid analgesic agent: effect of pyridine and azetidine ring substitutions on nicotinic acetylcholine receptor binding affinity and analgesic activity in mice

Analogs of A-98593 (1) and its enantiomer ABT-594 (2) with diverse substituents on the pyridine ring were prepared and tested for affinity to nicotinic acetylcholine receptor binding sites in rat brain and for analgesic activity in the mouse hot plate assay. Numerous types of modifications were consistent with high affinity for [3H]cytisine binding sites. By contrast, only selected modifications resulted in retention of analgesic potency in the same range as 1 and 2. Analogs of 2 with one or two methyl substituents at the 3-position of the azetidine ring also were prepared and found to be substantially less active in both assays.

ABT-594 [(R)-5-(2-azetidinylmethoxy)-2-chloropyridine]: a novel, orally effective antinociceptive agent acting via neuronal nicotinic acetylcholine receptors: II. In vivo characterization

The antinociceptive effects of ABT-594, a novel nicotinic acetylcholine receptor (nAChR) ligand, were examined in rats in models of acute thermal (hot box) and persistent chemical (formalin test) pain. Also, the effects of ABT-594 treatment on motor function and electroencephalogram (EEG) were determined. In the hot box and formalin test (i.e., phase 1 and 2), acute treatment with ABT-594 (0.03, 0.1 and 0.3 mumol/kg i.p.) produced significant dose-dependent antinociceptive effects. In the hot box, the efficacy of ABT-594 was maintained after a repeated dosing paradigm (5 days b.i.d.i.p.). ABT-594 was fully efficacious in the formalin test when administered before formalin, and also retained significant efficacy (0.3 mumol/kg i.p.) when administered after formalin injection. The antinociceptive effects of ABT-594 in the hot box and formalin tests were attenuated by pretreatment with the nAChR antagonist, mecamylamine, and in animals treated with the nAChR antagonist chlorisondamine, given centrally (10 micrograms/rat i.c.v. 5 days before), but not in animals pretreated with the opioid receptor antagonist, naltrexone. Acute treatment with ABT-594 produced an initial decrease in open-field locomotor activity, which was absent in animals dosed repeatedly (5 days b.i.d.) with ABT-594. Also, acute treatment with ABT-594 decreased body temperature and decreased the amount of time the animals could maintain balance in an edge-balance test. These effects were no longer present in animals dosed repeatedly with ABT-594. At antinociceptive doses, ABT-594 produced activation of free running EEG in contrast to the sedative-like effects of morphine. Full antinociceptive efficacy was maintained in both the hot box and formalin tests after oral administration, whereas the effects on motoric performance were attenuated. In conclusion, these data demonstrate that ABT-594 is a potent antinociceptive agent with full efficacy in models of acute and persistent pain and that these effects are mediated predominately by an action at central neuronal nAChRs. In addition, antinociceptive effects were maintained after repeated dosing, whereas effects of ABT-594 on motor and temperature measures were attenuated in animals treated repeatedly with ABT-594. Thus, compounds acting at nAChRs may represent a novel approach for the treatment of a variety of pain states.

Antinociceptive effects of the novel neuronal nicotinic acetylcholine receptor agonist, ABT-594, in mice

ABT-594 [5-((2R)-azetidinylmethoxy)-2-chloropyridine], a novel neuronal nicotinic acetylcholine receptor agonist, produced significant antinociceptive effects in mice against both acute noxious thermal stimulation--the hot-plate and cold-plate tests--and persistent visceral irritation--the abdominal constriction (writhing) assay (maximally-effective dose in each test 0.62 micromol/kg, i.p.). This effect was not stereoselective since the S-enantiomer, A-98593 [5-((2S)-azetidinylmethoxy)-2-chloropyridine], produced similar antinociceptive effects in this dose range. The effect in the hot-plate test peaked at 30 min after i.p. administration and was still present 60 min, but not 120 min, after injection. ABT-594 was orally active, but 10-fold less potent by this route than after i.p. administration. The antinociceptive effect of ABT-594 was prevented, but not reversed, by the noncompetitive neuronal nicotinic acetylcholine receptor antagonist mecamylamine (5 micromol/kg, i.p.). In contrast, the antinociceptive effect of ABT-594 was not prevented by hexamethonium (10 micromol/kg, i.p.), a neuronal nicotinic acetylcholine receptor antagonist that does not readily enter the central nervous system, nor by naltrexone (0.8 micromol/kg), an opioid receptor antagonist. Thus, initiation of antinociception by ABT-594 involves activation of central nicotinic acetylcholine receptors, but does not require activation of naltrexone-sensitive opioid receptors. The antinociceptive effects of morphine and ABT-594 in the mouse hot-plate test appeared to be additive, but ABT-594 did not potentiate the respiratory depression produced by morphine when the two compounds were coadministered. ABT-594 reduced body temperature and spontaneous exploration in the antinociceptive dose range, but did not reliably impair motor coordination in the rotarod test. Thus, it is unlikely that the antinociceptive effects result simply from impaired motor function. The compound also produced an anxiolytic-like effect in the elevated plus maze (at 0.019 and 0.062 micromol/kg, i.p.). Preliminary safety testing revealed an ED50 for overt seizure production of 1.9 micromol/kg, i.p. and an LD50 of 19.1 micromol/kg i.p. in mice, values 10 and 100 times the minimum effective antinociceptive dose of the compound. ABT-594 increased the duration of ethanol-induced hypnotic effects, tended to increase pentobarbital-induced hypnotic effects (P = 0.0502), and had no effect on pentobarbital-induced lethality. These data indicate that ABT-594 is a centrally acting neuronal nicotinic acetylcholine receptor agonist with potent antinociceptive and anxiolytic-like effects in mice.

Identification and initial structure-activity relationships of (R)-5-(2-azetidinylmethoxy)-2-chloropyridine (ABT-594), a potent, orally active, non-opiate analgesic agent acting via neuronal nicotinic acetylcholine receptors

New members of a previously reported series of 3-pyridyl ether compounds are disclosed as novel, potent analgesic agents acting through neuronal nicotinic acetylcholine receptors. Both (R)-2-chloro-5-(2-azetidinylmethoxy)pyridine (ABT-594, 5) and its S-enantiomer (4) show potent analgesic activity in the mouse hot-plate assay following either intraperitoneal (i.p.) or oral (p.o.) administration, as well as activity in the mouse abdominal constriction (writhing) assay, a model of persistent pain. Compared to the S-enantiomer and to the prototypical potent nicotinic analgesic agent (+/-)-epibatidine, 5 shows diminished activity in models of peripheral side effects. Structure-activity studies of analogues related to 4 and 5 suggest that the N-unsubstituted azetidine moiety and the 2-chloro substituent on the pyridine ring are important contributors to potent analgesic activity.

Synthesis and structure-activity relationships of pyridine-modified analogs of 3-[2-((S)-pyrrolidinyl)methoxy]pyridine, A-84543, a potent nicotinic acetylcholine receptor agonist

Analogs of 3-[2-((S)-pyrrolidinyl)methoxy]pyridine, (A-84543, 1) with 2-, 4-, 5-, and 6-substituents on the pyridine ring were synthesized. These analogs exhibited Ki values ranging from 0.15 to > 9,000 nM when tested in vitro for neuronal nicotinic acetylcholine receptor binding activity. Assessment of functional activity at subtypes of neuronal nicotinic acetylcholine receptors indicates that pyridine substitution can have a profound effect on efficacy at these subtypes, and several subtype-selective agonists and antagonists have been identified.

Intermittent intussusception caused by colonic lipoma

Colonic lipomas are rare, usually small, and occur most often in the right colon, particularly in the cecum. They are most common in elderly women. Intermittent episodes of intussusception are not uncommon in patients with colonic lipoma, but they are usually caused by larger pedunculated lipomas. We report a 43-year-old woman with a large colonic submucosal lipoma that induced intermittent colocolic intussusception. The patient presented with symptoms of peptic ulcer, including intractable upper abdominal pain, which did not resolve with treatment. Abdominal sonography showed typical findings of intussusception caused by a lipoma, but the manifestations on barium enema and computed tomography mimicked a malignant colonic tumor. The patient's abdominal pain disappeared after right hemicolectomy and the tumor was demonstrated to be a lipoma. The postoperative course was uneventful; there was no evidence of recurrence at follow-up 6 months later. Physicians should be aware that surrounding organs should also be evaluated in cases of chronic peptic ulcer with intractable upper abdominal pain.

ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine]: I. A potent and selective cholinergic channel modulator with neuroprotective properties

Accumulating preclinical and clinical evidence data suggests that compounds that selectively activate neuronal nicotinic acetylcholine receptor (nAChR) subtypes may have therapeutic utility for the treatment of several neurological disorders. In the present study, the in vitro pharmacological properties of the novel cholinergic channel modulator ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine], are described. In radioligand binding studies, ABT-089 was shown to display selectivity toward the high-affinity (-)-cytisine binding site present on the alpha4beta2 nAChR subtype (Ki = 16 nM) relative to the [125I]alpha-bungarotoxin binding site present on the alpha7 (Ki > or = 10,000 nM) and alpha1beta1deltagamma (Ki > 1000 nM) nAChR subtypes. In cation flux and channel current studies, ABT-089 displayed a more complex profile than (-)-nicotine having agonist, partial agonist and inhibitory activities depending on the nAChR subtype with which it interacts. ABT-089 differentially stimulated neurotransmitter release. The compound displayed a similar potency and efficacy to (-)-nicotine to facilitate ACh release (ABT-089, EC50 = 3 microM; (-)-nicotine, EC50 = 1 microM), but was markedly less potent and less efficacious than (-)-nicotine to stimulate dopamine release (ABT-089, EC50 = 1.1 microM; (-)-nicotine, EC50 = 0.04 microM). Additionally, ABT-089 was neuroprotective against the excitotoxic insults elicited by exposure to glutamate in both rat cortical cell cultures (EC50 = 10 +/- 3 microM) and differentiated human IMR32 cells (EC50 = 3 +/- 2 microM). The differential full agonist/partial agonist profile of ABT-089, as compared with (-)-nicotine and ABT-418, illustrates the complexity of nAChR activation and the potential to target responses at subclasses of the neuronal and peripheral receptors.

ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine dihydrochloride]: II. A novel cholinergic channel modulator with effects on cognitive performance in rats and monkeys

ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine dihydrochloride], a novel ligand at neuronal nicotinic acetylcholine receptors with reduced adverse effects and improved oral bioavailability relative to (-)-nicotine, was tested in a variety of cognitive tests in rats and monkeys. Administered acutely, ABT-089 only marginally improved the spatial discrimination water maze performance of septal-lesioned rats. However, more robust improvement (45% error reduction on the last training day) was observed when ABT-089 was administered continuously via subcutaneous osmotic pumps (minimum effective dose: 1.3 micromol/kg/day). Continuous infusion of (-)-nicotine produced comparable improvement in the spatial discrimination water maze performance of septal-lesioned rats, but a 40-fold higher dose of (-)-nicotine was required (62 micromol/kg/day). Continuous infusion of ABT-089 to aged rats enhanced spatial learning in a standard Morris water maze, as indexed by spatial bias exhibited during a probe trial conducted after 4 days of training, but not when they were subsequently trained in a two-platform spatial discrimination water maze. The compound induced a small impairment in young rats on the standard water maze, but not on the two-platform task. A probe trial conducted after additional training in the standard water maze revealed no age or drug effects. ABT-089 did not affect performance of either the aged or young rats during inhibitory (passive) avoidance training. Also, continuous infusion of ABT-089 did not affect responses to acoustic startle or prepulse inhibition of acoustic startle in young, aged or septal-lesioned rats and did not affect locomotor activity in either sham-lesioned or septal-lesioned rats. In monkeys, acute administration of ABT-089 modestly improved the delayed matching-to-sample performance of mature, adult monkeys and more robustly improved performance in aged monkeys. Improved performance in the aged monkeys was restricted to the longest delay intervals and was not accompanied by changes in response latencies.