The team at BioAscent has leading expertise in GPCR drug discovery. Our capabilities encompass assay development, optimisation, and screening using all major label-based and label-free GPCR assay technologies; medicinal chemistry; in-silico / computational chemistry approaches; and fully integrated GPCR drug discovery projects.
GPCRs are the largest family of membrane proteins encoded by the human genome. They are key regulators of a variety of physiological processes, such as neurotransmission, hormone regulation, immune response, metabolic homeostasis and sensory perception. Their well-defined binding sites and recent advances in structural biology and computational techniques make them an attractive target class for discovering and rationally designing potent and selective drugs, which is why GPCRs remain a very rich hunting ground for drug discovery. Due to their nature as a key driver of cell-to-cell communication, the development of small molecules targeting GPCRs’ functions remains the most common approach to targeting them, surpassing natural products, antibodies, or peptides [1].
With wide-ranging background from big pharma, biotech and academia, our team has a median drug discovery experience of 15 years. Currently, almost 50% of the target portfolio are GPCR projects, encompassing bespoke lead characterisation projects, through to fully integrated multi-FTE, hit-to-lead and lead optimisation programmes.
Below we present a summary of services and expertise offered at BioAscent in the various aspects of GPCR drug discovery.
The discovery of high-quality hits for GPCRs demands a good understanding of the molecular signalling mechanisms employed by the receptor. BioAscent offers considerable expertise in developing assays using cell types that endogenously express or over-express target GPCRs, and using them to identify and characterise novel agonists, antagonists, and inverse agonists. High throughput screening (HTS) assays for GPCRs rely primarily on monitoring changes in the intracellular concentration of secondary messengers downstream of receptor activation:
Utilisation of label-free phenotypic screening by measuring cellular impedance in the drug discovery projects allows us to broaden our understanding of the molecular complexity of the drug’s mode of action (MoA). The ability to pharmacologically dissect the coupling pathway in a manner that is unburdened by the use of light-dependent labels increases the productivity and success rate of the drug discovery ventures.
Our team at BioAscent has an unmatched experience in assay development and screening using the xCELLigence cell analysis system. The xCELLigence is a microelectronic biosensor system that measures cellular impedance, which can change in response to the activation of a diverse array of cellular pathways. It has been designed for label-free cell-based assays in various cell types. The system offers dynamic and real-time cellular analysis, across a wide range of research applications with a very limited propensity for compound interference, and a particular strength in analysing responses to GPCR pathway activation.
At BioAscent, our unparalleled expertise, state-of-the-art automation systems, and robust compound management capabilities position us as leaders in developing both target-based and phenotypic assays and using them to discover new chemical modulators of GPCRs using High Throughput Screening.
We excel in transferring established assays or devising new ones, ensuring they meet rigorous specifications for HTS. Our meticulous quality control measures extend to the miniaturisation of assays to 384- or 1536-well plates. During cell-based assay development for GPCR studies, we conduct comprehensive assessments of the robustness criteria. These include optimising cell seeding densities, carrying out signal tests, evaluating the potency and efficacy of known agonists and antagonists, assessing tolerance to DMSO, analysing media composition, and gauging assay sensitivity using BioAscent’s PAINS library - a curated collection of known assay-interfering compounds. Moreover, our hit finding campaigns are highly flexible. We conduct screens using a combination of client-focused libraries and BioAscent's internal collections, ensuring comprehensive coverage and tailored solutions for our clients' needs. We are also highly collaborative and keep the client fully informed and involved in important project progression decision making. Our screening campaigns progress through several stages:
"Our project, against a novel GPCR target, has been a career highlight. We’ve worked closely with BioAscent from the initial assay development and screen, through hit confirmation, hit-to-lead and lead-optimisation, to the point where we have two preclinical candidates. We asked BioAscent to make some really challenging compounds to support our SAR hypotheses, and without the expertise, initiative and tenacity of the BioAscent chemistry team, this project would not have succeeded. In summary, BioAscent has been the best chemistry CRO I’ve worked with.”
Director, Medicinal Chemistry, Biotech
Understanding the mechanism of action for newly discovered GPCR agonists and antagonists is pivotal in the pre-clinical drug discovery process. Leveraging our extensive expertise in GPCR biology, we design and execute studies that accurately reveal whether an antagonist directly competes with an agonist at the orthosteric site or binds allosterically to modulate receptor activity through indirect mechanisms.
Our deep knowledge of allosteric modulation - where compounds interact with sites distinct from the orthosteric site to enhance or inhibit receptor function - allows us to model receptor behaviour with greater precision and provide critical insights that inform the drug design process. This comprehensive and methodical approach ensures our clients gain a profound understanding of how their compounds engage with GPCRs, driving the development of more effective and targeted therapies.
BioAscent offers tailored generation of stable cell lines designed to meet the specific needs of your project. Utilising a monoclonal culture system, we ensure the development of consistent and reliable cell lines. The process begins with selecting appropriate markers, optimising culture conditions, and implementing precise transfection procedures. To establish the selective conditions, a kill curve is determined, ensuring the survival of only the desired cells. Stable clones are then carefully analysed to confirm their characteristics. Additionally, BioAscent provides the option to generate mutants of the target of interest, enabling in-depth selectivity studies and enhancing the relevance and accuracy of your research. Newly established cell lines are characterised for receptor expression levels and assessment of localisation to the plasma membrane.
The field of targeting GPCRs remains dominated by small molecules, including organic and inorganic compounds, as well as natural products [1]. BioAscent’s medicinal chemists have extensive experience in designing and synthesising compounds targeting GPCRs, and successfully prosecuting GPCR drug discovery campaigns from hit confirmation to candidate selection and beyond. We offer experience in various modalities, including covalent and photoactive ligands, which are gaining popularity in GPCR research. BioAscent chemists have experience in hit-to-lead and lead optimisation of GPCR programmes [7,8]. When designing compounds, we take a holistic approach, considering all relevant properties such as biological activity, selectivity, ADME, and safety profiles to ensure we are creating the right molecules for your programme.
In addition to our broad experience in medicinal chemistry, BioAscent chemists are highly skilled in synthetic chemistry, including multi-step synthesis of complex molecules, route design, and the parallel synthesis of ligand arrays, facilitating rapid access to the desired target compounds.
At BioAscent, integrated projects encompass a comprehensive range of drug discovery services designed to streamline the development process. These projects begin with de novo assay development, assay optimisation, or assay transfer, ensuring robust and reliable methods for screening. Discovery of new molecules can be knowledge based, via ligand and structure-based virtual screening, or involve High Throughput Screening using either BioAscent's in-house libraries or externally sourced compounds. Orthogonal assays are employed to validate hits. Further series development, including structure-activity relationship (SAR) studies, is managed by BioAscent's chemistry team, with subsequent testing carried out by the biology department. Throughout the project, compound management services ensure efficient handling of chemical libraries, and additional support is provided by the in silico team and regular ADME testing, enhancing the overall success of the drug discovery process.
“The BioAscent biosciences team worked as independent contributors, suggesting and successfully developing assays for a novel GPCR target, and deploying these to support rapid design-make-test cycles. As well supplying assays and data of extremely high quality, the initiative the BioAscent team showed when designing and interpreting experiments was a critical factor in the success of this project. Ours was very much a team of intellectual equals, and this intellectual collaboration was very much a driving force behind the success of this programme.”
Head of GPCR Pharmacology, Biotech
In addition to virtual screening, our in silico discovery team offers robust capabilities to drive drug discovery efforts targeting GPCRs. We harness a variety of structural modelling techniques, including homology modelling, to construct precise structural models of GPCRs. Additionally, we utilise AlphaFold-generated structures, meticulously evaluating their binding site competency for desired actions, such as activation or inhibition, before incorporating them into our computational studies.
Recognising the dynamic nature of proteins, we employ molecular dynamics (MD) simulations to explore receptor flexibility, ligand stability, and the relevance of potential water networks. Subsequently, our virtual screening prowess, powered by docking simulations and pharmacophore searches, facilitates the swift identification of promising hit compounds.
Moreover, our capabilities extend to investigating biased signalling pathways within GPCRs. MD simulations elucidate how the GPCR's conformational landscape shifts upon binding different ligands - agonists, biased agonists, or antagonists - revealing distinct states associated with various signalling pathways. Techniques like dynamic residue network (DRN) analysis allow us to scrutinise how ligand binding at the orthosteric site alters communication networks and energy flow within the GPCR, highlighting critical residues and pathways for biased signalling.
Furthermore, our computational mutagenesis analysis predicts key amino acids crucial for specific signalling pathways, which can then be experimentally validated. We emphasise the synergy between computational predictions and experimental validation through mutagenesis, biophysical assays, and functional signalling studies.
