Unanticipated Characteristics of a Selective, Potent Neuromedin-U Receptor 2 Agonist.

Neuromedin-U (NMU) mediates several physiological functions via its two cognate receptors, NMUR1 and NMUR2. Disentangling the individual roles of each receptor has largely been undertaken through the use of transgenic mice bearing a deletion in one of the two receptors or by testing native molecules (NMU or its truncated version NMU-8) in a tissue-specific manner, in effect, taking advantage of the distinct receptor expression profiles. These strategies have proved quite useful despite the inherent limitations of overlapping receptor roles and potential compensatory influences of germline gene deletion. With these considerations in mind, the availability of potent, selective NMU compounds with appropriate pharmacokinetic profiles would advance the capabilities of investigators undertaking such efforts. Here, we evaluate a recently reported NMUR2-selective peptide (compound 17) for its in vitro potency (mouse and human), binding affinity, murine pharmacokinetic properties, and in vivo effects. Despite being designed as an NMUR2 agonist, our results show compound 17 unexpectedly binds but does not have functional activity on NMUR1, thereby acting as an R1 antagonist while simultaneously being a potent NMUR2 agonist. Furthermore, evaluation of compound 17 across all known and orphan G-protein-coupled receptors demonstrates multiple receptor partners beyond NMUR2/R1 binding. These properties need to be appreciated for accurate interpretation of results generated using this molecule and may limit the broader ability of this particular entity in disentangling the physiological role of NMU receptor biology.

A Novel Method to Gently Mix and Uniformly Suspend Particulates for Automated Assays.

The SpinVessel system provides a methodology using pulsed radial flow to gently mix and uniformly suspend particulates (cells, magnetic beads, silica beads, and microcarrier beads) for automated assays. SpinVessels are well suited for aliquoting on robotic liquid handlers and with robotic reagent dispensers, as well as manually. The SpinVessel system combines two critical features: (1) special internal side fins and projections in the bottom of the vessels and (2) an instrument that quickly spins the vessels and repeatedly reverses the spin direction. This rapid reversing motion sends multiple pulses of fluid up the side walls of the SpinVessel, creating a circular radial flow pattern. We tested five different particulates and six different SpinVessels with volume capacities varying from 50 mL to 1200 mL. SpinVessels are compatible with either single-, 8-, 12-, 96-, or 384-channel pipettors or with siphon tubing on robotic reagent dispensers. Experiments have demonstrated high viability of cells and undamaged morphology of microcarrier beads even after hours of constant agitation. The uniformity of aliquots collected at various vertical depths and horizontally across the SpinVessels demonstrated that cells, magnetic beads, and silica beads were uniformly suspended throughout the height and breadth of the SpinVessels, and uniformity of samples was consistent from the beginning to the end of the aliquoting procedure. Only 5 min of mixing is required to resuspend settled particulates. This novel mixing methodology has many applications in laboratory automation where particulate aliquot uniformity and/or particulate integrity are important to automating assays.

Diet-induced mouse model of fatty liver disease and nonalcoholic steatohepatitis reflecting clinical disease progression and methods of assessment.

Shortcomings of previously reported preclinical models of nonalcoholic steatohepatitis (NASH) include inadequate methods used to induce disease and assess liver pathology. We have developed a dietary model of NASH displaying features observed clinically and methods for objectively assessing disease progression. Mice fed a diet containing 40% fat (of which ∼18% was trans fat), 22% fructose, and 2% cholesterol developed three stages of nonalcoholic fatty liver disease (steatosis, steatohepatitis with fibrosis, and cirrhosis) as assessed by histological and biochemical methods. Using digital pathology to reconstruct the left lateral and right medial lobes of the liver, we made comparisons between and within lobes to determine the uniformity of collagen deposition, which in turn informed experimental sampling methods for histological, biochemical, and gene expression analyses. Gene expression analyses conducted with animals stratified by disease severity led to the identification of several genes for which expression highly correlated with the histological assessment of fibrosis. Importantly, we have established a biopsy method allowing assessment of disease progression. Mice subjected to liver biopsy recovered well from the procedure compared with sham-operated controls with no apparent effect on liver function. Tissue obtained by biopsy was sufficient for gene and protein expression analyses, providing the opportunity to establish an objective method of assessing liver pathology before subjecting animals to treatment. The improved assessment techniques and the observation that mice fed the high-fat diet exhibit many clinically relevant characteristics of NASH establish a preclinical model for identifying pharmacological interventions with greater likelihood of translating to the clinic.

Biological activity of AC3174, a peptide analog of exendin-4.

Exenatide, the active ingredient of BYETTA (exenatide injection), is an incretin mimetic that has been developed for the treatment of patients with type 2 diabetes. Exenatide binds to and activates the known GLP-1 receptor with a potency comparable to that of the mammalian incretin GLP-1(7-36), thereby acting as a glucoregulatory agent. AC3174 is an analog of exenatide with leucine substituted for methionine at position 14, [Leu(14)]exendin-4. The purpose of these studies was to evaluate the glucoregulatory activity and pharmacokinetics of AC3174. In RINm5f cell membranes, the potency of AC3174 for the displacement of [(125)I]GLP-1 and activation of adenylate cyclase was similar to that of exenatide and GLP-1. In vivo, AC3174, administered as a single IP injection, significantly decreased plasma glucose concentration and glucose excursion following the administration of an oral glucose challenge in both non-diabetic (C57BL/6) and diabetic db/db mice (P<0.05 vs. vehicle-treated). The magnitude of glucose lowering of AC3174 was comparable to exenatide. The ED(50) values of AC3174 for glucose lowering (60 minute post-dose) were 1.2 microg/kg in db/db mice and 1.3 microg/kg in C57BL/6 mice. AC3174 has insulinotropic activity in vivo. Administration of AC3174 resulted in a 4-fold increase in insulin concentrations in normal mice following an IP glucose challenge. AC3174 was also shown to inhibit food intake and decrease gastric emptying in rodent models. AC3174 was stable in human plasma (>90% of parent peptide was present after 5 h of incubation). In rats, the in vivo half-life of AC3174 was 42-43 min following SC administration. In summary, AC3174 is an analog of exenatide that binds to the GLP-1 receptor in vitro and shares many of the biological and glucoregulatory activities of exenatide and GLP-1 in vivo.

Discovery and structure-activity relationship of 2-phenyl-oxazole-4-carboxamide derivatives as potent apoptosis inducers.

As a continuation of our efforts to discover novel apoptosis inducers as anticancer agents using a cell-based caspase HTS assay, 2-phenyl-oxazole-4-carboxamide derivatives were identified. The structure-activity relationships of this class of molecules were explored. Compound 1k, with EC(50) of 270 nM and GI(50) of 229 nM in human colorectal DLD-1 cells, was selected and demonstrated the ability to cleave PARP and displayed DNA laddering, the hallmarks of apoptosis. Compound 1k showed 63% tumor growth inhibition in human colorectal DLD-1 xenograft mouse model at 50 mpk, bid.

Discovery and mechanism of action of a novel series of apoptosis inducers with potential vascular targeting activity.

A novel series of 2-amino-4-(3-bromo-4,5-dimethoxy-phenyl)-3-cyano-4H-chromenes was identified as apoptosis-inducing agents through our cell-based apoptosis screening assay. Several analogues from this series, MX-58151, MX-58276, MX-76747, MX-116214, MX-126303, and MX-116407, were synthesized and further characterized. MX-116407, a lead compound from this series, induced apoptosis with an EC50 of 50 nmol/L and inhibited cell growth with a GI50 of 37 nmol/L in T47D breast cancer cells. Treatment of cells with these analogues led to G2-M arrest, cleavage of essential proapoptotic caspase substrates, and induction of nuclear fragmentation. We identified these compounds as tubulin destabilizers with binding site at or close to the colchicine binding site. Compounds in this series were also active in drug-resistant cancer cell lines with a GI50 value for one of the analogues (MX-58151) of 2.5 nmol/L in paclitaxel-resistant, multidrug-resistant MES-SA/DX5 tumor cells. This series of compounds displayed high selectivity against proliferating versus resting cells. Interestingly, these compounds were shown to disrupt preformed endothelial cell capillary tubules in vitro and affect functional vasculature to induce tumor necrosis in vivo and are thus likely to work as tumor vasculature targeting agents. Among these compounds, MX-116407 showed capillary tubule disruption activity in vitro at concentrations well below the cytotoxic dose. In a separate study, we further characterized the antitumor efficacy and pharmacokinetic profile of this series of compounds and identified MX-116407 as a potent apoptosis-inducing agent with apparent activity as tumor vasculature targeting agent.

Discovery of 4-aryl-4H-chromenes as a new series of apoptosis inducers using a cell- and caspase-based high-throughput screening assay. 1. Structure-activity relationships of the 4-aryl group.

By applying a novel cell- and caspase-based HTS assay, 2-amino-3-cyano-7-(dimethylamino)-4-(3-methoxy-4,5-methylenedioxyphenyl)-4H-chromene (1a) has been identified as a potent apoptosis inducer. Compound 1a was found to induce nuclear fragmentation and PARP cleavage, as well as to arrest cells at the G(2)/M stage and to induce apoptosis as determined by the flow cytometry analysis assay in multiple human cell lines (e.g. Jurkat, T47D). Through structure-activity relationship (SAR) studies of the 4-aryl group, a 4- and 7-fold increase in potency was obtained from the screening hit 1a to the lead compounds 2-amino-4-(3-bromo-4,5-dimethoxyphenyl)-3-cyano-7-(dimethylamino)-4H-chromene (1c) and 2-amino-3-cyano-7-(dimethylamino)-4-(5-methyl-3-pyridyl)-4H-chromene (4e), with an EC(50) of 19 and 11 nM in the caspase activation assay in T47D breast cancer cells, respectively. The 2-amino-4-aryl-3-cyano-7-(dimethylamino)-4H-chromenes also were found to be highly active in the growth inhibition MTT assay, with GI(50) values in the low nanomolar range for compound 1c. Significantly, compound 1c was found to have a GI(50) value of 2 nM in the paclitaxel resistant, p-glycoprotein overexpressed, MES-SA/DX5 tumor cells. Functionally, compound 1c was found to be a potent inhibitor of tubulin polymerization and to effectively inhibit the binding of colchicine to tubulin. These results confirm that the cell-based caspase activation assay is a powerful tool for the discovery of potent apoptosis inducers and suggest that the 4-aryl-4H-chromenes have the potential to be developed into future anticancer agents.

Discovery, characterization and SAR of gambogic acid as a potent apoptosis inducer by a HTS assay.

Gambogic acid (2), a natural product isolated from the resin of Garcinia hurburyi tree, was discovered to be a potent apoptosis inducer using our cell- and caspase-based high-throughput screening assays. Gambogic acid was found to have an EC(50) of 0.78 microM in the caspase activation assay in T47D breast cancer cells. The apoptosis-inducing activity of gambogic acid was further characterized by a nuclear fragmentation assay and flow cytometry analysis in human breast tumor cells T47D. Gambogic acid was found to induce apoptosis independent of cell cycle, which is different from paclitaxel that arrests cells in the G2/M phase. To understand the structure-activity relationship (SAR) of gambogic acid, derivatives of 2 with modifications to different function groups were prepared. SAR studies of gambogic acid, as measured by the caspase activation assay, showed that the 9,10 carbon-carbon double bond of the alpha,beta-unsaturated ketone is important for biological activity, while the 6-hydroxy and 30-carboxy group can tolerate a variety of modifications. The importance of the 9,10 carbon-carbon double bond was confirmed by the traditional growth inhibition assay. The high potency of 2 as an inducer of apoptosis, its novel mechanism of action, easy isolation and abundant supply, as well as the fact that it is amenable to chemical modification, makes gambogic acid an attractive molecule for the development of anticancer agents.

Discovery of substituted N-phenyl nicotinamides as potent inducers of apoptosis using a cell- and caspase-based high throughput screening assay.

By applying a novel cell- and caspase-based HTS assay, a series of N-phenyl nicotinamides has been identified as a new class of potent inducers of apoptosis. Through SAR studies, a 20-fold increase in potency was achieved from a screening hit N-(4-methoxy-2-nitrophenyl)pyridine-3-carboxamide (1) to lead compound 6-methyl-N-(4-ethoxy-2-nitrophenyl)pyridine-3-carboxamide (10), with an EC(50) of 0.082 microM in the caspase activation assay in T47D breast cancer cells. The N-phenyl nicotinamides also were found to be active in the growth inhibition assay where compound 10 had a GI(50) value of 0.21 microM in T47D cells. More importantly, compound 10 was found to be equipotent in MES-SA cells and paclitaxel-resistant, p-glycoprotein overexpressed MES-SA/DX5 cells. Compounds 1 and 6-chloro-N-(4-ethoxy-2-nitrophenyl)pyridine-3-carboxamide (8), a more potent analogue, were found to arrest T47D cells in G(2)/M phase of the cell cycle followed by induction of apoptosis as measured by flow cytometry. Compound 8, which was more potent than 1 in the caspase activation assay, also was found to be more potent in G(2)/M arrest and apoptosis assay. These data confirm that the cell-based caspase activation assay is useful for screening for inducers of apoptosis, as well as for SAR studies and lead optimization. Upon further characterization, N-phenyl nicotinamides were found to be inhibitors of microtubule polymerization in vitro. The identification of N-phenyl nicotinamides as a novel series of inducers of apoptosis demonstrates that our cell- and caspase-based HTS assay is useful for the discovery and optimization of potentially novel anticancer agents.