GLP-1 receptor agonists

What is a GLP-1 receptor agonist

What is a GLP-1 receptor agonist?A drug that mimics the action of the intestinal hormone GLP-1 and promotes insulin secretion in response to blood glucose levels via GLP-1 receptors (GLP-1R).In addition, by delaying gastric emptying and acting on the appetite-regulation mechanism in the brain, it enhances feelings of fullness and suppresses appetite. Originally developed as a treatment for type 2 diabetes, its therapeutic applications have now expanded to obesity, and research is underway to extend its use to metabolic diseases such as MASH (formerly NASH) and neurodegenerative diseases including Alzheimer's disease. In drug discovery, modalities are diversifying; alongside conventional peptide formulations, these include small molecules that enable oral administration and multi-agonists that combine the effects of GLP-1 with those of GIP, glucagon, and others.

Representative examples of GLP-1 receptor agonists

Liraglutide

Liraglutide is a fatty acid-acylated peptide based on native GLP-1. By adding a fatty acid chain, it enhances binding affinity to serum albumin, and the GLP-1Protects against degradation by DPP-4 and extends the blood half-lifefeatures molecular design that. It stimulates the GLP-1 receptor more persistently than native GLP-1, exerting effects such as promoting insulin secretion and suppressing appetite.

Semaglutide

Semaglutide isAmino acid substitutions to increase DPP-4 resistance and introduction of a C18 dibasic acid via a spaceris a long-acting GLP-1 receptor agonist with strong binding affinity to albumin, achieving once-weekly administration. An oral formulation containing the absorption enhancer SNAC has also been developed, enabling oral administration.

Orforglipron or Tirzepatide

At the forefront of drug discovery,the non-peptide GLP-1 receptor agonist orforglipron and the GIP/GLP-1 dual agonist tirzepatideis attracting attention. Advanced molecular design is progressing, such as biased agonism prioritizing G-protein signaling in orforglipron, and synergistic metabolic improvement through action on multiple receptors in tirzepatide.

Key challenges in GLP-1 receptor agonist development

Control of duration of action and tolerance through G protein bias and receptor internalization

Sustained stimulation of GLP-1R isinduces receptor desensitization and β-arrestin-dependent internalizationIt leads to signal reduction and diminished drug efficacy. Biased signaling, which preferentially activates G-protein signaling while suppressing the β-arrestin pathway, is gaining attention, but designing and evaluating it to balance receptor kinetics and long-term efficacy is not easy.

Translational predictability in NASH/MASH and obesity disease models, as well as Taneichi models

GLP-1R isSpecies differences in expression localization and central/peripheral metabolic responses between rodents and humansand complicates the extrapolation of non-clinical data. Since drug responsiveness differs between the simple obesity model of DIO mice and the complex pathophysiology of human severe obesity or NASH/MASH with fibrosis, improving the prediction accuracy of clinical efficacy remains a challenge.

Risks associated with gastrointestinal disorders and increased heart rate (on-target toxicity) and prolonged duration of action

With strong GLP-1R stimulation,gastrointestinal symptoms such as nausea and vomiting, and an increase in resting heart ratewhich causes a loss of clinical continuity and becomes a factor that impairs it. Especially for highly potent agonists and long-acting formulations, it is important to quantify the exposure- and time-dependencies of drug efficacy and on-target toxicity at the non-clinical stage, and to properly separate the two.

Nonclinical evaluation required for GLP-1 receptor agonists

High-precision in vitro signaling assay elucidating receptor dynamics

Binding affinity for GLP-1R alone cannot predict the duration of drug efficacy or tolerance. Therefore,Quantify G protein activation and $\beta$-arrestin recruitment via cAMP productionFurthermore, we evaluate receptor internalization and recycling dynamics using real-time analysis via BRET/FRET or HCS. We then correlate these with in vivo PK/PD to select leads with superior persistence.

Evaluation 2: Translational disease models and Multi-Omics analysis to enhance extrapolation to human pathologies

In a simple obesity model, other than weight losscytoprotective effects and the synergistic effects of multi-agonistscannot be fully evaluated. In addition to NASH/MASH models and non-human primate obesity/diabetes models, we analyze multifaceted effects on pathophysiology and biomarkers using transcriptomics and scRNA-seq. Furthermore, by combining clamp tests and MRI-based quantification of liver lipids, we enhance the extrapolation to FIH trials.

Rating 3: PK/PD and tissue distribution translational evaluation linking blood pharmacokinetics and target tissue disposition

Blood concentration alone cannot accurately capture the central and peripheral effects of GLP-1 receptor agonists. Therefore,combining tissue distribution analysis using MSI or QWBA with PK/PD and PBPK modelingWe evaluate the time course of blood half-life, receptor occupancy, tissue exposure, and drug efficacy. Furthermore, we simultaneously analyze brain penetration and the suppression of food intake to determine the optimal balance between central and peripheral actions.

Rating 4: Functional safety and on-target toxicity evaluation for early prediction of gastrointestinal motility and autonomic nervous system effects

Nausea and increased heart rate are clinical dropout factors, soQuantifying on-target functional toxicity from the non-clinical stageIt is important to measure heart rate, blood pressure, and electrocardiogram using telemetry, and to evaluate the safety margin using CTA and behavioral tests such as the Pica test. Furthermore, by integrating PK and pharmacodynamic responses and analyzing Cmax-dependency and AUC-dependency, it leads to appropriate dose titration and dosing design.

Key points when choosing a contract research organization (CRO) for non-clinical studies

In the development of GLP-1 receptor agonists, pharmacokinetic evaluation alone is not sufficient. It is important to comprehensively evaluate receptor signaling, efficacy, disease models, tolerance, and on-target toxicity to enhance clinical translatability. Utilizing a CRO capable of consistently handling everything from pharmacokinetics to efficacy, disease, and tolerance models is the key to development success.