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Wednesday, April 30th

8:00 am Breakout Group Discussions: Meet the Experts
Brainstorming discussion groups moderated by experts in the area. Attendees are invited to choose the topic according to their main interest; however, they may switch between groups. We emphasize that this discussion is for an interactive informal exchange among scientists and is not meant to be, in any way, a corporate or product discussion.

Table 1: Outlook for Structure-Based Drug Design for GPCR Targets
Moderator: Sid Topiol, Ph.D., Associate Director, Computational Chemistry, Lundbeck Research, USA

• Homology Model Considerations (How broadly applicable are today's X-ray structures as templates?)
• X-ray Structure Considerations (How important are: class/subclass, state, extracellular loops?)
• What Level of Calculation and/or Model Details are Needed for What Questions? 

GPCR SCREENING

9:00 Chairperson’s Remarks

9:05 Use of Transiently Transfected Cells for Orphan Receptor Lead Discovery
Alice (Yu) Chen, Ph.D., Group Leader, Drug Discovery, Genomics Institute of Novartis Research Foundation (GNF)
Finding natural or surrogate ligands for orphan receptors is critical to understanding their function. A large profiling experiment was carried out using transiently transfected HEK293 and CHO cells in aequorin and beta-arrestin formats. Thirty-seven GPCRs, most of them orphans, were screened against a focused 100,000-compound collection in 1536-well format using GNF’s Automated Compound Profiling (ACP) system. Confirmed hits were identified for both orphan and non-orphan receptors, validating this approach for fast tool compound discovery for GPCRs.

9:35 Development and Application to Screening of Antibodies that Identify the Active State of G Proteins
Graeme Milligan, Ph.D., Professor of Molecular Pharmacology, University of Glasgow
Production of antisera able to recognize individual hetero-trimeric G protein α subunits resulted in the rapid expansion of information on their distribution and function. However, no antibodies have been available that specifically recognize the active state. Four-way primary screening of 763 hybridomas generated from mice immunized with GTPγS-loaded Gα_i1 and isolated using an automated robotic colony picker identified three antibodies that interacted with the constitutively active, Q²⁰⁴L, mutant but neither the constitutively inactive, G²⁰³A, mutant nor wild-type Gα_i1. This profile extended to other closely related G_i-family G proteins but not to the less closely related Gα_s and Gα_q/Gα₁₁ families. Each antibody was, however, also able to identify wild-type, GDP-bound G_i-family G proteins in the presence of AlF₄-, which mimics the presence of the terminal phosphate of GTP and hence generates an active/transition-state conformation. Stimulation of cells co-expressing a wild-type Gα_i subunit and the dopamine D2 receptor with the agonist ligand nor-apomorphine also allowed these conformationally selective antibodies to bind the G protein. Such reagents allow the specific identification of activated G proteins in a native environment and may allow the development of label-free screening assays for G protein-coupled receptor-mediated activation of G_i-family G proteins.

10:05  High-Throughput Screening to Identify Modulators of GPCR Function
Stephen Rees, Director, Screening and Compound Profiling, GlaxoSmithKline
High-throughput screening (HTS) has become a major source for the identification of novel modulators of GPCR function for subsequent lead optimization. In this talk, I will describe the assay biology, automation, informatics, library design, and compound-handling inputs required to enable a robust HTS, and outline the bioassay strategies adopted to support an ongoing lead-to-candidate chemistry program.   

10:35 Networking Coffee Break, Poster and Exhibit Viewing

11:15 Evaluation of Cellular Impedance Assays for Assessing Complex GPCR Pharmacology in Drug Discovery
Matthew F. Peters, Ph.D., Principal Scientist, Lead Generation Dept., AstraZeneca R&D Wilmington
Cellular dielectric spectroscopy (CDS) is an emerging technology that can distinguish Gs, Gi/o, and Gq signal transduction in a whole-cell label-free format, enabling one to monitor activation pathways by different ligands within the same assay condition. We show that GPCR agonists, antagonists, inverse agonists, and allosteric modulators can be quantified by CDS with precision suitable for drug discovery SAR studies. Furthermore, agonist ligands for one GPCR reveal Gs-dominant coupling in HEK cells versus Gi-dominant coupling in CHO cells. Other ligands showed inverse agonism against Gi coupling only, consistent with either ligand-specific trafficking or pathway-specific constitutive activity. These findings support broad use of CDS for SAR studies including ligand-induced functional selectivity.

11:45 Selection of Functional Human Antibodies for GPCRs from Phage Display Libraries
Eldar Kim, Ph.D., Senior Director of Research, MSM Protein Technologies, Inc.
The integral membrane proteins (GPCRs, ion channels, transporters)—the largest pool of therapeutic targets—remain notoriously difficult for targeting with human functional antibodies due to the lack of reliable technologies for their presentation.  Highly heterogeneous cells or cell membrane preparations are very inefficient for antibody discovery. Small and constrained extracellular portions characteristic to multispanners preclude the use of peptides or denatured proteins. MSM has developed proprietary platforms allowing efficient selection of antibodies for integral membrane proteins from phage display libraries. The data on selections of functional antibodies for GPCRs will be provided.

12:15 pm Luncheon Technology Workshop
 (Sponsorship Available) or Lunch on Your Own

1:15 Break

CASE STUDIES:
GPCR AGONISTS/ANTAGONISTS

1:40 Chairperson’s Remarks

1:45 Macrocyclic Peptidomimetics: From a New Class of Conformationally Restrained Molecules to the Discovery of Potent Modulators of Gastrointestinal Motility
Eric Marsault, Ph.D., Director, Medicinal Chemistry, Tranzyme Pharma Inc.
A new class of macrocyclic peptidomimetics, featuring a tripeptide backbone cyclized with a non-peptidic tether, forms the basis for a successful and versatile drug discovery technology termed MaTCh^TM (Macrocyclic Template Chemistry). This technology led to the discovery and rapid optimization of potent agonists and antagonists to human G protein-coupled receptors involved in the regulation of gastrointestinal motility. The more advanced candidates are currently in clinical development for the treatment of gastrointestinal motility disorders such as post-operative ileus and gastroparesis.

2:15 Histamine 3 Receptor Inverse Agonists for the Control of Food Intake and Beyond
Rosa María Rodríguez Sarmiento, Ph.D., Team Leader/Senior Scientist, Medicinal Chemistry, F. Hoffmann-La Roche Ltd.
Generation of several novel H₃R inverse agonists with high affinity, metabolic stability, good safety profile, and brain penetration will be presented. Moreover, investigations securing H₃R as a valid target for the control of food intake will be detailed.

2:45 Technology Watch (Sponsorship Available)

3:00  Networking Refreshment Break, Poster and Exhibit Viewing

3:30 Discovery of Agonists of the Niacin Receptor (GPR109a)
Graeme Semple, Ph.D., Vice President, Discovery Chemistry, Arena Pharmaceuticals, Inc.
Niacin (nicotinic acid) is a water-soluble vitamin that, at high doses in humans, favorably modulates essentially all serum lipid and lipoprotein parameters. As a result, niacin has been used for the prevention and treatment of cardiovascular disease for many years. The recent resurgence of interest in this area since the discovery of a molecular target for niacin (GPR109a) has focused on niacin’s ability to increase high-density lipoprotein cholesterol (HDL-C) to a greater extent than other currently available drugs. The use of niacin as a therapeutic, however, is limited by a number of associated side effects, most notably a highly uncomfortable cutaneous flushing response which can limit patient compliance. The development of novel agonists of the niacin receptor that have the beneficial lipid effects but with fewer side effects would clearly be of value.

In this presentation, the identification of agonist ligands for GPR109a via a classical SAR approach will be described, leading to the discovery of MK-0354. In vivo, MK-0354 inhibited lipolysis with comparable efficacy to niacin in acute models and showed a markedly improved therapeutic window between plasma FFA reduction and cutaneous flushing across multiple species. In Phase I studies in healthy volunteers, MK-0354 was well tolerated, induced a robust reduction of plasma FFA comparable to an extended-release niacin formulation, and showed only a modest flushing effect at high doses.

4:00 Structure-Activity Relationships of Alpha-Melanocyte-Stimulating Hormone (Alpha-MSH) Analogues Targeting the Human Melanocortin Receptors
Minying Cai, Research Assistant Professor, Department of Chemistry, University of Arizona 
GPCRs regulate virtually all known physiological processes in mammals including the senses of smell, taste, vision, and many human behaviors. Also, they are targets for hormone, neurotransmitter, cytokine etc. More than 50%–60% of marketed drugs target GPCRs either directly or indirectly. In this talk we will discuss the ligand conformation-based drug design and the receptor conformation when it is binding to its selective ligand, which will be critically important for future drug design.

The rationale of the Discovery program leading to the identification of aclidinium bromide, and the subsequent characterization of the mode of action of the compound, will be described.

5:00  Close of Conference