Meeting Summary

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Quick recap

The meeting covered advanced pharmacological concepts related to allosteric modulators of GPCRs, including their mechanisms, analysis methods, and potential applications in drug discovery. Various aspects of signaling kinetics and their implications for drug activity were discussed. The team also emphasized the importance of understanding biology, collaborating across disciplines, and addressing challenges in translating preclinical findings to clinical trials.

Next steps

• Dr. Samuel Hoare will provide workshop participants with the user-defined equations and guidance for analyzing allosteric modulator data in Prism.

• Beth Fleck will lead the efforts to measure binding kinetics and residence times for unlabeled compounds to optimize drug candidates.

• The team will investigate signaling kinetics over time to understand mechanisms like desensitization and persistent signaling.

• Dr. Samuel Hoare will clarify the process for setting up one-on-one meetings with Terry Kane for project-specific discussions.

• Andreína will send out the certificates for the course on Monday.

Summary

Advanced GPCR Pharmacology Workshop

Andreína led the workshop on advanced topics in GPCR pharmacology, with Dr. Samuel Hoare presenting on allosteric modulators. Despite some technical issues, Dr. Samuel Hoare covered the diverse effects of allosteric modulators on GPCRs and highlighted recent discoveries, including M4 muscarinic receptor modulators showing efficacy as antipsychotics in clinical trials. He recommended further reading on the topic through review articles by Arthur Christopoulos and Terry, as well as a recent paper by Arthur on the history of allosteric modulators.

Allosteric Modifications and Drug Development

Dr. Samuel Hoare explained the mechanisms of action for allosteric modulators, which can either reduce or enhance the binding affinity of an orthosteric ligand. He presented data showing how these modulators can affect receptor activation by an orthosteric agonist and how their effects can be analyzed using cooperativity factors. Dr. Samuel Hoare also discussed an example of biased modulation, where an allosteric modulator can simultaneously act as a negative and positive allosteric modulator, thereby modifying the efficacy of the orthosteric agonist. He highlighted the potential for allosteric modulation in drug development, particularly in relation to GPCRs.

Analyzing Allosteric Pharmacology Data Process

Dr. Samuel Hoare explained the process of analyzing allosteric pharmacology data, including the measurement of cooperativity factors and modulator affinity using curve fitting. He detailed the steps for loading user-defined equations into Prism's equation library, removing non-specific binding, and assessing the variability of fitted parameter values. Dr. Samuel Hoare also presented the results of an analysis, discussed the interpretation of binding experiments with triple ligands, and introduced the concept of signaling activity. Lastly, he mentioned the creation of an Excel simulator for the team to experiment with.

Different Models for Allosteric Modification Analysis

Dr. Samuel Hoare discussed the complexities and trade-offs of using different models for allosteric modulation analysis. He emphasized that while complete models, like the cube models, are available, starting with the full model is more practical due to its reliability and ease of use. He demonstrated how to quantify allosteric behavior using an equation in Prism and cautioned that large standard error values can indicate unreliable fitted parameters when the data doesn't allow for good estimation. He also introduced a simplified equation for data with a full agonist, which allows for a combined cooperativity factor but doesn't permit independent estimation of Alpha and Beta. Finally, he highlighted the importance of binding kinetics in understanding receptor-ligand interaction and recommended a chapter in the Assay Guidance Manual for further reading.

Dissociation Rates and Residence Times in Pharmacology Assays

Dr. Samuel Hoare discussed the importance of dissociation rates and residence times in determining drug activity and artefacts in pharmacology assays. He highlighted that a longer residence time can be beneficial for in vivo activity but can complicate in vitro assays by making it difficult to quantify affinity. Dr. Samuel Hoare also emphasized that a long residence time can protect against surges in endogenous ligand concentration. However, he noted that this can lead to a prolonged equilibration time for ligands, which is particularly problematic for high-affinity therapeutic candidates in the later stages of drug discovery.

Limitations of Short Incubation Assays Discussed

Dr. Samuel Hoare discussed the limitations of short incubation assays for ligand optimization, using the example of their work with Neurocrane Biosciences and GSK on developing antagonists for the corticotropin-releasing factor receptor. He highlighted how the assay ceiling, caused by insufficient incubation time, can prevent the detection of more potent compounds. Dr. Samuel Hoare and his team then developed a kinetic binding assay to measure the true affinity values of their lead molecules, which revealed that their newly developed compounds were less active in vivo due to weaker binding. This insight allowed them to identify more active molecules and advance a compound, Exaphon, into clinical trials, demonstrating the importance of advanced pharmacology in drug discovery.

Signaling Kinetics in Drug Discovery

Dr. Samuel Hoare led a discussion on the significance of signaling kinetics in drug discovery and pharmacology, focusing on the work done with Montana Molecular. He highlighted the importance of measuring the persistence of signaling, especially for chronic administration, and the development of a suite of equations for analyzing time course data. He demonstrated the application of these equations using real data, showing the differences in signal decline for various receptors and agonists. Dr. Samuel Hoare emphasized the increasing utilization of kinetic analysis in the literature and the potential benefits for patients through advanced pharmacology.

Cell Signaling Models and Data Normalization

Dr. Samuel Hoare led a workshop on cell signaling models and data normalization, answering questions from Jay, Angela, Anastasia, and Rosanna. Dr. Samuel Hoare clarified that the affinity of the orthosteric agonist doesn't always need to be known for modeling and suggested using both the Alpha Beta model and the full signaling model to find the best fit. Dr. Samuel Hoare also promised to verify a topic and get back to Jay later. Angela's question about user-defined allosteric equations in GradPat led Dr. Samuel Hoare to reconsider his initial decision, while other questions from Anastasia and Rosanna were not specified in the transcript.

Discussing Allosteric Compounds and Binding Assays

Anastasia and Dr. Samuel Hoare discussed the use of labeled and unlabeled ligands in binding assays, with Dr. Samuel Hoare providing a clinical example using muscarinic receptors and their endogenous ligand, acetylcholine. The discussion also covered the concept of allosteric compounds and their ability to function as partial agonists, with references to relevant literature. Furthermore, Dr. Samuel Hoare explained a paper by Georgian that demonstrated a reduction in Emax under certain conditions, indicating the presence of an allosteric modulator. Questions about terminology and specifics were addressed, and the need for further investigation was acknowledged.

Kinetics, Association Rates, and Agonists

Dr. Samuel Hoare provided an overview of kinetics and association rates, emphasizing the importance of understanding these concepts for advanced pharmacology research. He explained the challenges in intuiting kinetics and the usefulness of mathematical equations to understand the same. Andreína and Marc posed questions related to the use of labeled and unlabeled agonists in experiments and the potential complications that could arise. Dr. Samuel Hoare clarified that labeled agonists could indeed pose challenges due to potential binding at different sites on the receptor. Tarsis then raised a practical question about setting up an efficient process for screening and filtering molecules across multiple pathways and kinetics. Dr. Samuel Hoare acknowledged the importance of this question but did not provide a direct answer.

Advanced Pharmacology Drug Discovery Strategies

Dr. Samuel Hoare emphasized the importance of discipline and clear communication in advanced pharmacology drug discovery. He argued that pharmacologists should focus on developing persistent signaling agonists and quantifying the decline rate of their effects, rather than relying on a large number of assays to differentiate between compounds. Dr. Samuel Hoare also cautioned that chemists should remain engaged in the process to ensure they understand the implications of the data. Angela, who has been primarily a lab person, asked for advice on determining what they were looking for and what to recommend. Dr. Samuel Hoare advised her to trust her own judgment and not to get too caught up in kinetics or other complexities.

Drug Discovery, Target Profiles, and Certificates Update

Luis highlighted the importance of understanding biology for effective drug discovery and collaborating with experts in new research areas. Marc emphasized the need for a target product profile and a team effort across disciplines. The team discussed challenges in translating preclinical research to clinical trials and the role of pharmacodynamics in understanding target engagement and efficacy. Andreína announced delayed availability of certificates, additional upcoming courses by Terry Kenakin, and a feedback session to improve future offerings from Dr. GPCR University. The team also mentioned the success of GLP1 antagonists and the potential of DP4 inhibitors.