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Introduction G protein-coupled receptors (GPCRs) remain one of the most important classes of drug targets, contributing to a significant proportion of marketed therapeutics across multiple disease areas. Among the many signaling pathways activated by GPCRs, calcium mobilization is one of the most widely used functional readouts because it provides a rapid and sensitive measure of receptor activation. For Gαq/11-coupled receptors, ligand binding stimulates phospholipase C, leading to IP3 production and the release of calcium from intracellular stores into the cytoplasm. This transient calcium response provides a valuable window into receptor activity and has become a cornerstone of GPCR screening and pharmacological characterization. However, selecting the most appropriate calcium assay requires understanding the strengths and limitations of the available detection technologies as well as the biological questions being addressed. In this article, you'll learn: How GPCR calcium signaling assays work The advantages and limitations of different calcium readout technologies How to select the most appropriate assay format for drug discovery and screening applications Understanding GPCR Calcium Assays A GPCR calcium assay measures changes in intracellular calcium concentrations following receptor activation. Upon activation of a Gαq-coupled receptor, phospholipase C generates IP3, which subsequently triggers calcium release from the endoplasmic reticulum. Because calcium acts as a second messenger, even modest receptor activation can produce detectable intracellular signals, making calcium mobilization a highly sensitive functional readout for studying GPCR pharmacology. Methods for measuring calcium activity Most calcium assays rely on fluorescent dyes that enter cells in an esterified form and are subsequently trapped intracellularly after cleavage by cellular esterases. As intracellular calcium concentrations rise, these dyes generate measurable fluorescent signals that can be monitored in real time. Dye-based calcium assay workflow illustrating GPCR activation, intracellular calcium release, and fluorescent signal generation. Figure 1. Calcium Assay Principle. In addition, several technologies are available for measuring intracellular calcium, each offering distinct advantages depending on assay requirements. Fluorescent Dye-Based Calcium Assays Fluorescent calcium dyes remain the most widely adopted approach for measuring calcium flux. Ratiometric dyes such as Fura-2 generate fluorescence in both calcium-bound and calcium-free states, enabling intracellular calcium levels to be quantified using signal ratios from two excitation wavelengths. This approach minimizes variability associated with dye loading and can improve quantitative consistency across experiments. However, the requirement for dual-wavelength measurements often reduces throughput and assay sensitivity. Non-ratiometric dyes such as Fluo-4 and Fluo-8 generate fluorescence primarily when bound to calcium. These dyes typically produce stronger signals and are well suited for high-throughput applications, although assay performance becomes more dependent on consistent cell numbers and dye loading across wells. Alternative Calcium Detection Approaches In addition to fluorescent dyes, calcium signaling can be measured using aequorin, a calcium-responsive photoprotein originally derived from jellyfish. Unlike fluorescent methods, aequorin produces luminescent signals with very low background noise and does not suffer from photobleaching. The primary limitation is that aequorin must be introduced into cells through genetic engineering or microinjection rather than simple dye loading. Researchers may also utilize genetically encoded calcium indicators (GECIs), which employ engineered fluorescent proteins that change conformation upon calcium binding. These systems can support live-cell imaging and single-cell measurements but typically require additional cell engineering and may exhibit sensitivity to intracellular pH changes. GPCR Calcium Assay Cell Models from Eurofins DiscoverX® Selecting the right cell model can be just as important as selecting the calcium detection technology itself. ChemiSCREEN™ Cell Lines ChemiSCREEN cell lines are engineered to enable calcium-based functional analysis of GPCRs regardless of their native G-protein coupling preferences. These cells express high levels of Gα15, a promiscuous G-protein capable of coupling diverse GPCRs to the calcium signaling pathway. In some models, additional G-protein chimeras further enhance coupling efficiency, creating a robust platform for fluorescence-based calcium assays. Figure 2. Calcium dose response curves and FLIPR trace data from ChemiSCREEN cell Top. Calcium dose response curve in fluorescence mode for the ChemiSCREEN D2 Dopamine Receptor Cell Line (cat. no. HTS039C). The assay depicts an increase in intracellular calcium indicating agonist activity. The EC50 for Quinpirole is 29 nM. Bottom. FLIPR trace data from a representative ChemiSCREEN cell line calcium assay with agonist addition at 10 second intervals. Note responses ensue within 10-20 seconds of agonist addition and peak before 80 seconds post-addition. ChemiBRITE® Cell Lines ChemiBRITE cell lines utilize a similar force-coupling strategy but additionally express a modified calcium-activated photoprotein derived from clytin. This allows researchers to perform either fluorescent or luminescent calcium measurements depending on instrumentation preferences and assay design. Figure 3. Calcium dose response curve in luminescence mode for the ChemiBRITE GLP-1 Receptor Ready-to-Assay Frozen Cells (cat. no. HTS163LRTA). The EC50 for GLP-1 is 2.67 µM. Native Gq-Coupled Calcium Assays For receptors that naturally signal through Gq proteins, Eurofins DiscoverX offers cell lines that preserve endogenous calcium signaling pathways without force-coupling modifications. These assays provide a more physiologically relevant representation of receptor biology while maintaining compatibility with established fluorescent detection approaches. They are assayed with traditional calcium-sensitive fluorescent dyes and have been tested and optimized with the Calcium No WashPLUS Detection Kit (cat. no. 90-0091), which is an easy-to-use, dye-based, complete assay detection system. PathHunter® Assays and Calcium Signaling Although PathHunter assays are primarily designed to measure β-arrestin recruitment, native Gq-coupled receptors can also generate endogenous calcium responses within these systems, enabling researchers to investigate multiple aspects of GPCR pharmacology using complementary readouts. Figure 4. Calcium dose response curve for the HTR2B (5-HT2B) Gq Stable Cell Line Calcium Signaling Assay (HEK 293) (cat. no. 795-1024C1). The EC50 for 5-HT is 11.55 µM. Why GPCR Calcium Assays Remain Valuable A GPCR calcium assay offers several advantages that have made calcium mobilization one of the most commonly used functional readouts in drug discovery. Because calcium signaling operates through second-messenger amplification, a single receptor activation event can trigger the release of many calcium ions, generating signals that are often easier to detect than more proximal signaling events. This amplification improves sensitivity and makes calcium assays particularly effective for identifying weak agonists and compounds with modest pharmacological activity. Calcium assays are also nondestructive and can be performed in living cells, allowing researchers to monitor signaling kinetics in real time while preserving the opportunity for subsequent downstream analyses. Their reproducibility and compatibility with automated workflows have further established calcium mobilization as a preferred format for high-throughput screening campaigns. Importantly, calcium assays often maintain a useful assay window during antagonist studies, supporting reliable characterization of inhibitory compounds during lead optimization. Figure 5. Calcium dose response curves with and without the HOE140 antagonist using the BDKRB1 Gq Stable Cell Line Calcium Signaling Assay (CHO-K1) (cat. no. 795-1011C2). Note the antagonist data retains the vast majority of the assay window seen in the agonist curve. Important Considerations When Selecting a GPCR Calcium Assay Despite their versatility, GPCR calcium assays present several experimental challenges that should be considered during assay selection. Calcium responses are typically extremely rapid and transient, frequently reaching peak levels within seconds of agonist addition and returning to baseline within minutes. Capturing these responses accurately often requires specialized instrumentation capable of automated reagent addition and rapid kinetic measurements across entire assay plates. Standard plate readers that measure wells sequentially may fail to capture these dynamics effectively. Researchers must also account for the fact that calcium serves as a ubiquitous intracellular messenger. Numerous endogenous pathways can contribute to changes in intracellular calcium levels, increasing the potential for biological crosstalk and off-target responses. Appropriate controls are therefore essential to confirm that observed signals originate from the receptor of interest. In addition, assay performance can be highly sensitive to variations in cell density and dye loading, particularly when non-ratiometric dyes are used. The signal amplification that makes calcium assays highly sensitive can occasionally complicate pharmacological interpretation. Partial agonists may generate responses resembling those of full agonists, making it difficult to distinguish between the two solely on the basis of calcium flux. For this reason, calcium assays are frequently paired with orthogonal readouts such as β-arrestin recruitment or cAMP measurements during later stages of compound characterization. Additionally, calcium mobilization is generally not suitable for studying inverse agonism because constitutive receptor activity does not reliably produce measurable changes in intracellular calcium concentrations. Conclusion GPCR calcium assays continue to serve as one of the most powerful and widely adopted approaches for measuring receptor activation, providing rapid, sensitive, and information-rich insights into GPCR function. As researchers balance assay sensitivity, biological relevance, and screening requirements, selecting the appropriate calcium assay format can significantly improve pharmacological decision-making and lead identification efforts. Moving forward, the integration of advanced calcium detection technologies with complementary functional readouts is expected to further enhance our ability to characterize GPCR biology and accelerate drug discovery programs. For more information on Eurofins DiscoverX calcium cell lines, cell lines assays, thaw-and-use frozen cells, or detection kit, visit GPCR Calcium Product Solutions.

The drugs reshaping obesity and type 2 diabetes have made one principle clear: engaging a metabolic GPCR is not the same as engaging it well. The clinical success of GLP-1 and GIP receptor agonists has pushed the field toward additional pathways that might extend or deepen those benefits, and amylin signaling has become one of the most actively pursued. It is also one of the most structurally demanding targets a discovery team can take on, because the amylin receptor is not a single, fixed protein at all. Why there is no standalone amylin receptor Amylin, also known as islet amyloid polypeptide, is co-secreted with insulin from pancreatic beta cells. It slows gastric emptying, suppresses glucagon secretion, and promotes satiety, and through those actions it helps govern glucose homeostasis and energy balance. That physiology is what makes it such a compelling lever for metabolic disease. The pharmacology is unusual. No gene encodes a dedicated amylin receptor. The functional receptor assembles only when the calcitonin receptor (CALCR), a class B GPCR, associates with one of three receptor activity-modifying proteins, or RAMPs. CALCR partnered with RAMP1, RAMP2, or RAMP3 produces three distinct amylin receptors: AMY1, AMY2, and AMY3. One core receptor, three identities, each with distinct pharmacological properties that must be measured independently. Three subtypes, three pharmacologies This heteromeric architecture is the reason amylin-directed drug design is hard. The three subtypes do not behave interchangeably. A compound's activity at AMY1 does not reliably predict its activity at AMY2 or AMY3, and a molecule's selectivity across the set can shape both its therapeutic effect and its side-effect profile. Characterizing a candidate therefore means resolving its behavior at each subtype rather than treating the amylin receptor as one entity. For a discovery team, that turns subtype identity into a first-order design question. Which receptor is being engaged, how selectively, and what does engagement actually trigger downstream? Answering those questions cleanly, and early, is what separates a rationally designed amylin therapeutic from a promising binder. Biased signaling: reading cAMP against β-arrestin Potency is only part of the picture. Two compounds matched on potency can still differ in signaling bias, the degree to which each drives one downstream pathway relative to another. Figure 1: cAMP accumulation assay. Receptor activation drives adenylate cyclase and changes intracellular cAMP, detected through an enzyme fragment complementation readout that produces a luminescent signal proportional to cAMP. At AMY and CALCR complexes, the two readouts these assays capture are cAMP accumulation (Figure 1) and β-arrestin recruitment (Figure 2). Figure 2: β-arrestin recruitment assay. Agonist binding drives β-arrestin recruitment to the activated receptor, bringing two enzyme fragments together to produce a luminescent signal proportional to recruitment. A ligand that favors cAMP over β-arrestin, or the reverse, can produce a meaningfully different functional outcome even at matched receptor occupancy. For metabolic targets, where the line between efficacy and tolerability is narrow, those signaling fingerprints are increasingly where differentiated drugs are defined. Capturing these differences requires measuring both pathways in parallel, at each receptor subtype, with enough reproducibility to compare compounds against one another with confidence. The drug classes driving the questions The urgency behind all of this comes from the pipeline. Several next-generation strategies are competing in obesity and diabetes development at once: amylin agonists, dual amylin and calcitonin receptor agonists (DACRAs), and GLP-1/amylin co-agonists. Each makes different demands on the receptor, and each benefits from a clear picture of subtype selectivity and signaling bias. That picture also has to extend beyond amylin alone. Because so many programs now pursue combination, dual, and triple-agonist approaches, profiling amylin pharmacology alongside GLP1R and GIPR signaling lets teams understand how a co-agonist behaves across all of its intended targets rather than one at a time. What amylin receptor signaling looks like when you can measure it Resolving this used to mean assembling partial readouts from mismatched sources. A suite of pathway-reflective, cell-based assays now enables direct profiling of CALCR and amylin receptor subtypes (AMY1, AMY2, AMY3). These systems provide quantitative readouts of ligand activity across both cAMP signaling and β-arrestin recruitment, allowing researchers to compare signaling profiles, detect biased agonism, and resolve subtype-specific pharmacology with high reproducibility. Covering the full arc of discovery, from screening to mechanistic profiling, they enable confident rank-ordering of compounds across all relevant receptor configurations. These assays are available from Eurofins DiscoverX, Dr. GPCR's Strategic Partner, across cell line assays, ready-to-use eXpress kits, membrane preparations, and detection reagents, with complementary GLP1R and GIPR assays for combination work. The throughline The lesson running through this generation of metabolic medicines is that signaling quality and selectivity, alongside potency, are what separate a candidate from a therapy. For amylin, that means seeing clearly across three closely related receptors and two signaling pathways. And getting there took solving a specific, stubborn assay problem first. Prefer to hear it straight from the bench? Gaurav Agrawal of Eurofins DiscoverX walks through the problem one scientist to another. He studied how GPCRs activate during his PhD and uncovered a new intracellular trafficking pathway as a postdoc, and he now works alongside the scientists running amylin programs, which keeps him close to the assay problems they hit. He walks through why a standard cell line reports calcitonin instead of amylin, and how the team built a line that finally reads real amylin pharmacology. In this conversation ► 00:00 The amylin receptor challenge, and why it matters now ► 00:40 The Novo dual-agonist data that drew the field in ► 01:40 What an amylin receptor really is: calcitonin plus a RAMP ► 02:30 Three amylin receptors, and which drive weight loss ► 03:00 The stoichiometry problem behind the assay ► 04:00 Why a naive readout reports calcitonin, not amylin ► 06:00 The low-expression promoter approach ► 07:00 Reading the real MOAs: cyclic AMP and β-arrestin ► 07:40 Ortholog assays: mouse, rat, and bridging in vivo data ► 08:40 A characterized amylin portfolio, from profiling to potency Once an amylin receptor line reports real amylin pharmacology instead of calcitonin, the rest follows: clean cAMP and β-arrestin readouts, the subtypes that matter for weight loss, and ortholog assays that tie bench data back to in vivo work. ► Explore the AMY/CALCR portfolio

Introduction G protein-coupled receptors (GPCRs) don't simply switch on or off. Most are pleiotropically coupled to multiple intracellular pathways, and different ligands at the same receptor can produce fundamentally different cellular outcomes, a phenomenon known as GPCR signaling bias, or functional selectivity. Two molecules with identical binding affinity can diverge sharply in their downstream effects: one emphasizing G protein activation, another driving receptor internalization and β-arrestin recruitment, each producing a distinct pharmacological fingerprint. Measuring GPCR signaling bias in drug discovery is critical, as it forms a selection criterion for agonism. Measuring and quantifying signaling bias reveals which candidates emphasize therapeutically beneficial pathways, and which may be falsely characterized as equivalent by single-pathway assays. Drug discovery programs that do not consider investigating for signaling bias often fail to fully understand the distinction and risk candidate molecules from advancing along the pipeline. In this article, you'll learn: Four reasons why bias measurements improve candidate selection at every stage of the discovery pipeline How biased ligands can emphasize beneficial signaling pathways, and actively suppress harmful ones How bias can expand pursuit of targets previously considered too toxic or undruggable Why measuring signaling bias across multiple pathways gives a more accurate picture of true molecular selectivity Obtaining a GPCR Pathway Pharmacological Fingerprint To obtain a pharmacological fingerprint (or profile) for GPCR therapeutics, it is best to show how signaling bias and receptor selectivity can be quantified using cell-based assays. These assays offer a simple approach to the comparison of agonist profiles across different pathways and biased signaling. For example, Figure 1 shows cell-based assay results from the cAMP G protein activation pathway and the β-arrestin recruitment pathway for several incretins (metabolic hormones and therapeutics) acting on GLP-1 and GIP receptors. Both assays provide unique profiles and a preferred receptor signaling bias for the therapeutics tested. Figure 1. Dose-response curves for incretin agonists on GLP-1 and GIP receptors. Comparison of the curves reveals the relative selectivity of retratutide for GLP-1 receptor over GIP receptor compared to tirzepatide and yields sufficient data to calculate the signaling bias of the agonists for β-arrestin over cAMP responses. This data is calculated from the estimated max and EC50. How GPCR Signaling Bias Strengthens Drug Discovery Programs There are four distinct reasons why bias measurements improve drug discovery outcomes. Bias can make better drugs by emphasizing beneficial signaling pathways and de-emphasizing harmful ones. Opioid receptors offer clear illustration of this: G protein-biased agonists at the μ-opioid receptor have been explored as a strategy to preserve analgesia, while reducing β-arrestin-dependent adverse effects such as respiratory depression and constipation (Raehal et al., 2005; DeWire et al., 2013). Another example is at the angiotensin AT1 receptor, biased ligands like TRV120027 block deleterious vasoconstriction, while engaging β-arrestin signals that provide beneficial effects in heart failure (Violin et al., 2010). Bias measurements can identify structurally differentiated hits from high-throughput screens. Two hits from a primary screen may appear equivalent in a single-pathway assay but diverge significantly when tested in orthogonal functional assays. Counter-screening in biased assays distinguishes molecules that are genuinely different on a molecular level, and therefore more likely to produce distinct phenotypes in complex therapeutic models. Bias reduces complex efficacy profiles to measurable, optimizable scales for medicinal chemistry. Efficacy (comprising of both quality and quantity attributes for different agonists) reveals how an expected overall cellular response can be achieved from cellular signals. The quality attribute can be captured by bias measurements allowing for the reduction of complex phenotypes to graded activation of signaling pathways. Once a favorable efficacy fingerprint is identified in therapeutic cells (through cell-based assays), medicinal chemists can work backward to amplify or tune the relevant bias. Bias measurements are essential for accurate selectivity profiling. Quantifying bias offers a way to determine selectivity based on all known signaling for a given molecule. For instance, a compound that appears highly selective at a target receptor based on cAMP readouts alone may show far less selectivity when β-arrestin signaling is included. The β2-adrenoceptor bronchodilator clenbuterol, for example, exhibits 500-fold selectivity for β2 over β1 receptors in cyclic AMP assays, but exhibits a reduced selectivity (approximately 5.7-fold) when β-arrestin-mediated effects are measured (Casella et al., 2011). Without multi-pathway assays, selectivity assessments can be misleading. Emphasizing Beneficial and De-emphasizing Harmful Signaling Pathways One of the most powerful applications of GPCR biased signaling is the ability to separate therapeutic effects from adverse ones at the receptor level, not achieved with binary pharmacology. As different ligands stabilize different receptor conformations, it is possible to design molecules that selectively engage the beneficial pathways over harmful ones. The opioid system offers a highly studied example. Morphine provides effective analgesia but carries debilitating side effects including respiratory depression. Studies in β-arrestin knockout mice demonstrated that morphine produces significantly less respiratory depression in the absence of β-arrestin 2 signaling — pointing directly to a G protein-biased opioid agonist as a potentially superior analgesic, one that preserves pain relief while reducing a life-threatening adverse effect (Raehal et al., 2005; DeWire et al., 2013). The angiotensin system illustrates a more nuanced application: not just de-emphasizing a harmful pathway but blocking it while simultaneously preserving a beneficial one. In congestive heart failure, elevated angiotensin signaling raises arterial pressure resulting in the failure of the myocardium. Standard angiotensin receptor blockers like losartan address this, but at the cost of eliminating beneficial β-arrestin-mediated signals. Biased ligands such as TRV120027 block the deleterious G protein-driven effects, while retaining the beneficial β-arrestin signals offering a meaningfully improved therapeutic profile (Violin et al., 2010). Expanding the Druggable Target Space Through Bias Beyond refining the pharmacology of established targets, biased signaling can rehabilitate entire target classes previously considered too toxic to pursue. The κ-opioid receptor illustrates this directly. κ-Opioid agonists carry genuine therapeutic potential in mood, cognition, and addiction but also produce serious dysphoria, which has historically precluded clinical development. Biased κ-opioid agonists that reduce dysphoric signaling, while preserving beneficial effects, offer a route into a target class that unbiased pharmacology cannot safely access (White et al., 2014). Rather than abandoning a target because of a harmful pathway, bias offers a different answer: design around the liability. Conclusion Bias measurements reveal that efficacy has quality as well as quantity attributes, and that quality can be engineered. A biased ligand can be designed to favor pathways. For example, a pathway that build bones, relieve pain, or stabilize a failing heart, while avoiding pathways that cause respiratory depression, dysphoria, or dangerous arterial pressure. In the case of κ-opioid agonists, bias may be the only route by which an otherwise excluded target class becomes clinically viable at all. Bias quantification increases the value of known lead compounds, sharpens selectivity assessments, and provides medicinal chemists with graded, optimizable scales to work from. Programs that characterize signaling bias early — across G protein, β-arrestin, and second messenger pathways through cell-based assay assessments — carry forward candidates whose vivo behavior can be fully understood providing a meaningful selection criteria and competitive advantage at every stage of drug discovery. Eurofins DiscoverX provides the largest portfolio of GPCR assays and a unique service that utilizes state-of-the-art tools developed by Professor Terry Kenakin at the University of North Carolina School of Medicine for characterization of ligand bias. With the appropriate β-arrestin, internalization, and second messenger assays to quantify selective response and statistical tools to scale these effects, harnessing bias to produce selective ligands is now made simple. For further reading on GPCR biased signaling and assay methodologies, explore the ‘Insights into GPCR Drug Discovery and Development’ eBook and ‘GPCR Functional Cell-based Assays – Assessing Biased Signaling of Agonists’ White Paper by Kenakin, T. et al. (2025). Visit Eurofins DiscoverX GPCR Products and Solutions to explore the full portfolio of GPCR assays from Eurofins DiscoverX. References Raehal, K.M., Walker, J.K., & Bohn, L.M. (2005). Morphine side effects in beta-arrestin 2 knockout mice. Journal of Pharmacology and Experimental Therapeutics, 314(3), 1195–1201. https://doi.org/10.1124/jpet.105.087254 DeWire, S.M., Yamashita, D.S., Rominger, D.H., Liu, G., Cowan, C.L., Graczyk, T.M., … Violin, J.D. (2013). A G protein-biased ligand at the μ-opioid receptor is potently analgesic with reduced gastrointestinal and respiratory dysfunction compared with morphine. Journal of Pharmacology and Experimental Therapeutics, 344 (3), 708–717. https://doi.org/10.1124/jpet.112.201616 Violin, J.D., DeWire, S.M., Yamashita, D., Rominger, D.H., Nguyen, L., Schiller, K., … Lark, M.W. (2010). Selectively engaging β-arrestins at the angiotensin II type 1 receptor reduces blood pressure and increases cardiac performance. Journal of Pharmacology and Experimental Therapeutics, 335 (3), 572–579. https://doi.org/10.1124/jpet.110.173005 Casella, I., Ambrosio, C., Grò, M.C., Molinari, P., & Costa, T. (2011). Divergent agonist selectivity in activating β1- and β2-adrenoceptors for G protein and arrestin coupling. Biochemical Journal, 438 (1), 191–202. https://doi.org/10.1042/BJ20110374 Kenakin, T., Watson, C., Muniz-Medina, V., Christopoulos, A., & Novick, S. (2012). A simple method for quantifying functional selectivity and agonist bias. ACS Chemical Neuroscience, 3 (3), 193–203. https://doi.org/10.1021/cn200111m Kenakin, T. (2019). Biased receptor agonism. Annual Review of Pharmacology and Toxicology, 59, 245–267. https://doi.org/10.1146/annurev-pharmtox-010818-021139

Explore the world of GPCRs with Dr. GPCR Podcast! Join industry leaders as they share insights, stories, and groundbreaking discoveries, enriching our understanding of GPCRs. Delve into the science behind these vital components shaping our collective knowledge. Welcome to the Dr. GPCR Podcast - The Voice of the Community Conversations with the world’s leading GPCR scientists. Exploring discoveries, careers, and ideas shaping human health. In each episode, we sit down with leading experts to explore their career journeys, groundbreaking discoveries, and the impact of their research on our shared understanding of GPCR biology. Launched at the height of the pandemic, the Dr. GPCR Podcast was created with three goals: Share discoveries – Highlight the latest advances in the GPCR field. Amplify voices – Provide scientists a platform to showcase their work. Inspire the future – Motivate the next generation to pursue GPCR research. At its core, Dr. GPCR’s mission is simple yet ambitious: to bring the GPCR community together - across borders and disciplines - to connect, exchange, and collaborate in order to improve human health through a deeper understanding of GPCR biology. Latest Podcast Episodes More podcast episodes Dr. GPCR Podcast Audience Survey We are currently planning our next season and need your help. This short survey will help us understand your needs to bring you exciting and informative content. We also know that you are busy, which is why we designed this short survey that should take you 5 minutes. Fill out this form Be our Guest In each episode, we chat with an expert about their career trajectory, discoveries, and how their research contributed to the shared pool of knowledge about GPCR biology. We’d love to have you on our podcast. To be a guest, fill out the form below, and we’ll be in touch in 48 hours. Fill out this form What others are saying about this podcast "You made it a very comfortable and engaging experience, and it felt like we were chatting over coffee — Yamina thoughtfully guided our chat throughout." Anita Nivedha I think it's really well done. I'm genuinely interested to see how it evolves and grows over time, as I feel it has the potential to develop into something even more impactful. Anonymous This came at just the most perfect time. I hadn't heard a scientific talk outside my lab since February and was starved to hear someone else talk passionately about GPCRs. I've listened to the episodes multiple times and it's just like being at a conference getting new ideas. I just couldn't be happier y'all created this podcast. Anonymous Great initiative, thanks. Carrier paths, choosing research topics, switching fields, late start, failures and successes. Anonymous I enjoy the breadth of questioning that goes beyond just the science, and reveals a bit about the scientists as individuals/mentors/people. Anonymous Really enjoyable science podcast! Dr. Yamina Berchiche interviews leading GPCR scientists on this vibrant, entertaining podcast. I really appreciate the way the podcast educates and mentors, particularly towards junior scientists but also to the community as a wholen Yamina is a great interviewer, getting insight and personal history from her guests. Am very grateful for Dr GPCR livening up the week in these difficult times! Sam @Pharmamechanic Listen and subscribe where you get your podcasts

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Learn about Celtarys Research through the Dr. GPCR Ecosystem. Explore their innovative GPCR projects, collaborations, and contributions to cutting-edge drug discovery. Partnership Dr. GPCR x Celtarys Reseach Empowering medicinal biochemists Celtarys empowers medicinal biochemists by providing innovative fluorescent probes that de-risk the pre-clinical drug discovery phase. Our proprietary conjugation technology and unparalleled scientific expertise ensure researchers can confidently advance their projects with greater precision and reliability. Visit Website About Celtarys Research Celtarys Research develops and commercializes new chemical tools to spread the use of fluorescence-based methods in the pre-clinical phase of drug discovery. Our proprietary chemical conjugation technology allows us to grow, in a competitive manner and in a short time (<3 months), customized fluorescent ligands with optimal pharmacological and photophysical properties for any druggable target. We have a catalogue of over 30 fluorescent ligands for different families of GPCRs, including adenosine, dopamine, serotonin, cannabinoid and muscarinic receptors. We also offer our expertise in the form of custom development services, where we tackle challenging targets and synthesize probes with the most suitable properties for your needs. Meet the Celtarys Team Wilson Gomes CEO Wilson Gomes holds a Mechanical Engineering degree, an MBA from the University of North Carolina, and completed the General Management Program at Harvard Business School. He has over 20 years of experience in the medtech and diagnostics industries, having held senior roles at Johnson & Johnson and Danaher across the EMEA region in sales, marketing, and general management. He joined Celtarys as CEO in 2024, where he is responsible for driving strategy and growth. His focus is on expanding commercial reach and accelerating the adoption of the company’s GPCR assay technologies. Maria Majellaro Co-Funder and CSO Dr. Maria Majellaro earned her degree in Pharmaceutical Chemistry and Technology from the University of Bari and completed her PhD in Biomolecular Sciences in Pharmacology and Medicine as “Doctor Europeus” in 2018. She then joined the University of Santiago de Compostela as a postdoctoral researcher in Prof. Eddy Sotelo’s group, contributing to the IGNICIA tech transfer project and the validation of Celtarys’ core technology. In 2021, she co-founded Celtarys and now leads the company’s scientific direction. Her work focuses on organic synthesis, medicinal chemistry, and the development of GPCR-targeted tools for pharma, biotech, and academic partners. Webinar Fluorescent Probes for GLP-1R and GIPR Imaging: From Cell Assays to In Vivo Systems Fluorescent tools for imaging endogenous incretin receptors across biological systems See Webinar Page Podcast Episodes See Podcast Page See Podcast Page See Podcast Page See Podcast Page Celtarys News & Updates A2A Fluorescent Competitive Binding: Advancing NanoBRET® Target Engagement for GPCR Drug Discovery The A₂A adenosine receptor NanoBRET® competitive binding assay enables real-time quantification of ligand–receptor interactions in living cells. By combining NanoLuc-tagged receptors with fluorescent tracers, this approach allows direct measurement of binding displacement, delivering robust pIC₅₀ and pKᵢ values that align with established pharmacology. In this article, we examine the assay principle, validation strategy, and performance across reference antagonists and agonis Lucía from Celtarys Research Mar 10 5 min read Illuminating C5aR Biology: The Role of Fluorescent Ligands in GPCR Research GPCRs are one of the most important families of therapeutic targets in the pharmaceutical industry. They are involved in several pathologies, ranging from neurological, oncological, degenerative, metabolic, immunological… around a third of the drugs in clinical use are GPCR ligands Lucía from Celtarys Research Feb 20 6 min read 1 2 3 4 5 Our Partnership Dr. GPCR and Celtarys Research Join Forces to Expand Access to Innovative GPCR Tools Boston, MA and Santiago de Compostela, Spain — June 3rd, 2025 — Dr. GPCR, the global knowledge hub for G protein-coupled receptor (GPCR) research and education, is proud to welcome Celtarys Research to its partner ecosystem. This collaboration aims to amplify the visibility and adoption of Celtarys’ cutting-edge fluorescent ligand technology and accelerate the development of GPCR-targeted therapeutics. Celtarys Research develops high-quality, fluorescently labeled ligands and innovative chemical biology tools to support real-time, non-radioactive GPCR assays. These tools enable high-resolution binding studies, kinetic analysis, and live-cell imaging, empowering both academic and industrial scientists to uncover GPCR biology with greater precision and speed. “We’re thrilled to partner with Celtarys and introduce their high-performance fluorescent ligands to our global GPCR community,” said Dr. Yamina Berchiche, Founder and CEO of Dr. GPCR. “These tools can dramatically improve how scientists measure ligand-receptor interactions, visualize binding in live cells, and design better experiments, core to advancing GPCR-targeted discovery.” “Dr. GPCR provides a unique platform to reach scientists at every stage of GPCR research,” said Wilson Gomes, CEO of Celtarys Research. “This partnership will help accelerate the adoption of our chemical tools and foster collaborations that turn receptor biology into therapeutic breakthroughs.” “We’re excited to support the GPCR community with tools that deliver clarity, sensitivity, and speed,” added Dr. Maria Majellaro, CSO of Celtarys. “Working with Dr. GPCR allows us to engage with researchers worldwide who are shaping the future of receptor-targeted therapies.” To explore Celtarys Research’s catalog and learn more about their GPCR tools, visit https://www.ecosystem.drgpcr.com/celtarys-research Services & Expertise NEW! High Content Screening Service Live‑cell HCS imaging in HEK‑293T–hCB2R with fluorescent ligand CELT-331; confocal capture on Operetta CLS. GPCR Expertise Specialized knowledge in adenosine, dopamine, serotonin, cannabinoid and muscarinic receptors for advanced research. Fluorescent Probes Innovative fluorescent probes that de-risk the pre-clinical drug discovery phase with optimal pharmacological properties. Custom Development Customized fluorescent ligands developed in less than 3 months with optimal properties for any druggable target. Product Catalog GPCR Ligands Our GPCR fluorescent ligands are the ideal solution for your High Throughput Screening (HTS) needs. GPCR Functional Assay Fluorescent GTPγS enables sensitive, non-radioactive GPCR activity assays for drug discovery. Custom Development Tailored fluorescent probes designed for unique research requirements. Contact Celtarys Research First name* Last name Email* Write a message Submit Get in Touch Address Avda. 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