Jayashree Pyati

Cell Lines for Drug Discovery: Elevating Target-Protein Levels Using Engineered Transcription Factors:

Drug discovery requires high-quality, high-throughput bioassays for lead identification and optimization. These assays are usually based on immortalized cell lines, which express the selected drug target either naturally or as a consequence of transfection with the cDNA encoding the target. Natural untransfected cell lines often fail to achieve the levels of expression required to provide assays of sufficient quality with a high enough signal-to-noise ratio. Unfortunately, the use of cDNA is increasingly restricted, as the sequences for more and more genes become subject to patent restrictions. To overcome these limitations, the authors demonstrate that engineered transcription factors with Cys2-His2 zinc finger DNA-binding domains can be used to effectively activate an endogenous gene of interest without the use of isolated cDNA of the target gene. Using this approach, the authors have generated a cell line that provides a high-quality and pharmacologically validated G-protein-coupled receptor bioassay. In principle, this technology is applicable to any gene of pharmaceutical importance in any cell type. (Journal of Biomolecular Screening 2004:44-51)

3-[5-(3,4-Dichloro-phenyl)-1-(4-methoxy-phenyl)-1H-pyrazol-3-yl]-2-m-tolyl-propionate (JNJ-17156516), a Novel, Potent, and Selective Cholecystokinin 1 Receptor Antagonist: In Vitro and in Vivo Pharmacological Comparison with Dexloxiglumide

3-[5-(3,4-Dichloro-phenyl)-1-(4-methoxy-phenyl)-1H-pyrazol-3-yl]-2-m-tolyl-propionate (JNJ-17156516) is a novel, potent, and selective cholecystokinin (CCK)1-receptor antagonist. In this study, the pharmacology of JNJ-17156516 was investigated both in vitro and in vivo, and the pharmacokinetic profile was evaluated in rats. JNJ-17156516 expressed high-affinity at the cloned human (pKI = 7.96 ± 0.11), rat (pKI = 8.02 ± 0.11), and canine (pKI = 7.98 ± 0.04) CCK1 receptors, and it was also highly selective for the CCK1 receptor compared with the CCK2 receptor across the same species (∼160-, ∼230-, and ∼75-fold, respectively). The high affinity of JNJ-17156516 at CCK1 receptors in vitro was confirmed in radioligand binding studies on fresh human gallbladder tissue (pKI = 8.22 ± 0.05). In a functional in vitro assay of guinea pig gallbladder contraction, JNJ-17156516 behaved as a competitive antagonist, with apKB value of 8.00 ± 0.07. In vivo, JNJ-17156516 produced a parallel, rightward shift in the CCK-8S-evoked contraction of the guinea pig gallbladder. The dose required to shift the CCK-8S dose-response curve was 240 nmol kg–1 i.v. In the anesthetized rat, JNJ-17156516 produced a dose-related decrease in the number of duodenal contractions evoked by infusion of CCK-8S, with an ED50 = 484 nmol kg–1. Pharmacokinetic analysis of JNJ-17156516 in rats, revealed that JNJ-17156516 had a half-life of 3.0 ± 0.5 h and a very high bioavailability (108 ± 10%) in this species. Overall, we have demonstrated that JNJ-17156516 is a high-affinity selective human CCK1 receptor antagonist with good pharmacokinetic properties in rats.

Functional Characterization of the Canine Heme-Regulated eIF2α Kinase: Regulation of Protein Synthesis

The heme-regulated inhibitor (HRI) negatively regulates protein synthesis by phosphorylating eukaryotic initiation factor-2α (eIF2α) thereby inhibiting protein translation. The importance of HRI in regulating hemoglobin synthesis in erythroid cells makes it an attractive molecular target in need of further characterization. In this work, we have cloned and expressed the canine form of the HRI kinase. The canine nucleotide sequence has 86%, 82%, and 81% identity to the human, mouse, and rat HRI, respectively. It was noted that an isoleucine residue in the ATP binding site of human, rat, and mouse HRI is replaced by a valine in the canine kinase. The expression of canine HRI protein by in vitro translation using wheat germ lysate or in Sf9 cells using a baculovirus expression system was increased by the addition of hemin. Following purification, the canine protein was found to be 72 kD and showed kinase activity determined by its ability to phosphorylate a synthetic peptide substrate. Quercetin, a kinase inhibitor known to inhibit mouse and human HRI, inhibits canine HRI in a concentration-dependent manner. Additionally, quercetin is able to increase de novo protein synthesis in canine reticulocytes. We conclude that the canine is a suitable model species for studying the role of HRI in erythropoiesis.

JNJ-26070109 [( R )4-Bromo- N -[1-(2,4-difluoro-phenyl)-ethyl]-2-(quinoxaline-5-sulfonylamino)-benzamide]: A Novel, Potent, and Selective Cholecystokinin 2 Receptor Antagonist with Good Oral Bioavailability

JNJ-26070109 [(R)4-bromo-N-[1-(2,4-difluoro-phenyl)-ethyl]-2-(quinoxaline-5-sulfonylamino)-benzamide] is a representative of a new chemical class of competitive antagonists of cholecystokinin 2 (CCK2) receptors. In this study, the primary in vitro pharmacology of JNJ-26070109 was evaluated along with the pharmacokinetic and pharmacodynamic properties of this compound in rat and canine models of gastric acid secretion. JNJ-26070109 expressed high affinity for human (pKI = 8.49 ± 0.13), rat (pKI = 7.99 ± 0.08), and dog (pKI = 7.70 ± 0.14) CCK2 receptors. The selectivity of JNJ-26070109 at the CCK2 receptor versus the CCK1 receptor was species-dependent, with the greatest degree of selectivity (>1200-fold) measured at the human isoforms of the CCK1 receptor (selectivity at CCK2 versus CCK1 receptors: human, ∼1222-fold; rat, ∼324-fold; dog ∼336-fold). JNJ-26070109 behaved as a surmountable, competitive, antagonist of human CCK2 receptors in a calcium mobilization assay (pKB = 8.53 ± 0.05) and in pentagastrin-stimulated gastric acid secretion in the isolated, lumen-perfused, mouse stomach assay (pKB = 8.19 ± 0.13). The pharmacokinetic profile of this compound was determined in vivo in rats and dogs. JNJ-26070109 was shown to have high oral bioavailability (%F rat = 73 ± 16; %F dog = 92 ± 12) with half lives of 1.8 ± 0.3 and 1.2 ± 0.1 h in rat and dog, respectively. The pharmacodynamic properties of this compound were investigated using two in vivo models. In conscious rat and dog chronic gastric fistula models of pentagastrin-stimulated acid secretion, JNJ-26070109 had oral EC50 values of 1.5 and 0.26 μM, respectively. Overall, we have demonstrated that JNJ-26070109 is a high-affinity, selective CCK2 receptor antagonist with good pharmacokinetic properties.