In vitro
This study presents a novel chemical strategy for delivering protein-degrading molecules (PROTACs) selectively to pancreatic β-cells by exploiting the glucagon-like peptide-1 receptor (GLP-1R). The researchers engineered a modified GLP-1 peptide using a tryptophan-mediated multicomponent Petasis reaction (TMPR), a modular "stapling" technique that locks the peptide into a stable α-helical conformation. This stapled analogue was reported to show enhanced structural stability and improved GLP-1R potency compared with the wild-type peptide. The stapling strategy also incorporated a chemical handle allowing conjugation to a PROTAC — a bifunctional molecule designed to degrade bromodomain-containing protein 4 (BRD4), a transcriptional regulator implicated in various diseases. The resulting GLP-1–PROTAC conjugate reportedly retained GLP-1R agonist activity and selectively induced BRD4 degradation in GLP-1R-expressing cells, consistent with receptor-mediated uptake and intracellular degrader activation. The study was conducted entirely in cellular (in vitro) systems; no animal or human data were reported. Key limitations include the absence of in vivo validation, and the translational relevance to human β-cell biology remains to be established.
Angewandte Chemie (International ed. in English) · Jun 2026DOI ↗ In vitro
This study describes the development of a scalable, chemically defined protocol for differentiating human pluripotent stem cells (hPSCs) into hypothalamic neurons enriched for pro-opiomelanocortin (POMC)-expressing cells, which are key regulators of appetite, energy, and glucose balance. The researchers validated neuronal identity using multiple high-resolution techniques — including MERFISH single-cell transcriptomics, RNA-Seq, and ATAC-Seq — and benchmarked results against human hypothalamic tissue. The protocol was tested across multiple hPSC lines and demonstrated consistent induction of ventral diencephalon and hypothalamic markers, and was designed to be compatible with robotic, high-throughput cell culture platforms. Functional assays showed that derived neurons responded to insulin and the GLP-1 receptor agonist Exendin-4, and displayed transcriptional changes under altered glucose conditions. ATAC-Seq analysis identified candidate regulatory genomic regions associated with hypothalamic development and metabolic traits, and BMI-associated gene enrichment was observed in the derived neurons. Limitations include that this is an in vitro cell model and may not fully recapitulate the complexity of the intact human hypothalamus. No human clinical outcomes were assessed. The platform is positioned as a tool for studying the mechanisms underlying metabolic disease and for therapeutic screening.
Stem cell reports · Jun 2026DOI ↗ In vitro
This study describes the computational design and preliminary laboratory characterization of SR18, a rationally engineered 18-amino acid peptide candidate intended to act as a GLP-1 receptor (GLP-1R) agonist for potential use in Type 2 diabetes (T2DM). The researchers used in silico methods—including molecular docking and 1-microsecond molecular dynamics (MD) simulations—to design SR18 to be resistant to DPP-4 cleavage and to retain key amino acids that interact with GLP-1R, similar to endogenous GLP-1 and approved drugs like Semaglutide and Liraglutide. In laboratory experiments, circular dichroism confirmed that synthesized SR18 adopts a stable α-helical conformation across various solvent conditions. Dynamic light scattering, cytotoxicity, and hemolytic assays suggested acceptable basic pharmaceutical and safety properties for a lead peptide candidate. Computational analyses indicated that SR18 may bind GLP-1R with comparable or favorable affinity relative to GLP-1 and Semaglutide. Limitations include the absence of any cell-based receptor activation assays, animal studies, or human data; the evidence remains entirely in silico and in vitro. No conclusions about clinical efficacy can be drawn at this stage.
Frontiers in pharmacology · May 2026DOI ↗ In vitro
This in vitro study examined the effects of three incretin-based therapies — semaglutide (GLP-1 receptor agonist), tirzepatide (dual GLP-1/GIP agonist), and cagrilintide (amylin analogue) — on mitochondrial function in C2C12 skeletal muscle myotubes under both normal and lipotoxic conditions. Lipotoxicity was induced using palmitic acid (PA), which significantly reduced basal oxygen consumption rate and ATP production in treated cells. The study used Seahorse XFp metabolic flux analysis, mitochondrial DNA copy number quantification (qPCR), and oxidative phosphorylation complex protein expression (western blotting), with key findings replicated in primary human skeletal muscle cells. The researchers found that semaglutide and cagrilintide transiently reduced basal respiration in healthy myotubes, while tirzepatide demonstrated more sustained improvements in mitochondrial respiration under both healthy and lipotoxic conditions. The study's primary limitations include its reliance on cell culture models, meaning findings may not directly translate to whole-organism physiology, and the use of a single lipotoxic stimulus. The partial replication in human primary cells adds some translational relevance, but in vivo validation remains absent.
Journal of cachexia, sarcopenia and muscle · Apr 2026DOI ↗ In vitro
This study addressed the growing global burden of obesity and type 2 diabetes by designing novel peptide-based triagonists that simultaneously activate three receptors: GLP-1R (glucagon-like peptide-1 receptor), GCGR (glucagon receptor), and GIPR (glucose-dependent insulinotropic polypeptide receptor). The researchers used computer-aided drug design, bioinformatics analyses, and molecular dynamics simulations to rationally identify key sequence determinants, optimal modification sites, and to understand how peptide "stapling" (a structural stabilization technique) affects alpha-helical stability and conformational rigidity. Based on these computational insights, 22 novel triagonist peptide structures were designed and synthesized. Their activity was evaluated in vitro using fluorescence membrane potential assays, with pharmacological balance assessed via a "balanced triagonism score" measuring consistency of activity across all three receptors. Most compounds showed highly balanced activity profiles. The lead compound, P2-L4, demonstrated low-nanomolar potency across all three receptor targets, with efficacy reported as comparable to existing incretin-based reference therapeutics. The study is limited to in vitro findings only, with no animal or human data reported. Further preclinical and clinical validation is required before any therapeutic conclusions can be drawn.
RSC medicinal chemistry · Mar 2026DOI ↗ In vitro
This study developed and validated a stability-indicating High-Performance Liquid Chromatography (HPLC) method for the simultaneous quantification of two GLP-1 receptor agonists — Semaglutide (SEM) and Tirzepatide (TIR) — used in the treatment of type 2 diabetes and obesity. The method employed a C18 column with an isocratic mobile phase of 0.1% formic acid and acetonitrile (30:70), achieving rapid separation with retention times of 1.42 min for SEM and 1.68 min for TIR. The method was validated per ICH guidelines, demonstrating strong linearity (1–500 µg/mL, r > 0.9999), sensitivity (LOD: 10 ng/mL for TIR; 16 ng/mL for SEM), accuracy, and precision. The method successfully resolved both compounds from degradation products generated under acidic, basic, oxidative, and photolytic stress conditions. It was also applied to bulk drug, pharmaceutical dosage forms, and spiked rat plasma. A comprehensive six-pronged sustainability assessment was performed using nine analytical greenness, whiteness, blueness, and violet innovation tools. A key limitation is that the plasma work used spiked rat samples rather than real patient samples, meaning no clinical or pharmacokinetic conclusions about humans can be drawn.
BMC chemistry · Jan 2026DOI ↗ In vitro
This study describes the development of a high-yield Chinese hamster ovary (CHO) cell manufacturing platform for a biosimilar of dulaglutide, a GLP-1/IgG4-Fc fusion protein approved for type 2 diabetes. Researchers used apoptosis-resistant CHO 4BGD cells and sequentially transfected two expression plasmids encoding dulaglutide, employing a two-step transgene amplification strategy using methotrexate (MTX) followed by methionine sulfoximine (MSX) selection. The dual-selection approach resulted in approximately 30% higher titers in polyclonal populations compared to MTX amplification alone. Through a clonal cell line selection pipeline, the top clone (4BGD/Dul #73) achieved a product titer of 1.05 g/L in a 3-week fed-batch process, with a specific productivity of up to 22 pg·cell⁻¹·day⁻¹ and stable expression over 69 days without selective pressure. Purity assessed by size-exclusion HPLC showed ≥95% monomer content. Biological activity testing in a GLP-1 receptor/CRE-luciferase reporter assay yielded an EC₅₀ of 52 pM for the biosimilar candidate versus 76 pM for the reference drug. Limitations include the absence of in vivo or clinical data, with all findings limited to cell culture and in vitro bioassay systems.
Pharmaceuticals (Basel, Switzerland) · Dec 2025DOI ↗ In vitro
This study investigated PapB, a radical S-adenosyl-l-methionine (rSAM) enzyme involved in the biosynthesis of ribosomally synthesized and post-translationally modified peptides (RiPPs). Classically, RiPP maturase enzymes require an N-terminal leader sequence on the precursor peptide to guide substrate recognition and modification. The researchers discovered that PapB can function in a "leader-independent" manner — meaning it can process peptide substrates that entirely lack canonical leader sequences. To demonstrate the practical utility of this finding, the team applied PapB to three analogues of glucagon-like peptide (GLP-1) pathway agonists — a therapeutically relevant class of peptides — and showed that the enzyme achieved complete conversion of each linear peptide into a thioether-macrocyclized (C-terminally cyclized) product. The study is primarily a biochemical and enzymological characterization conducted in vitro, with no human or animal subjects involved. Limitations include that all work was performed outside of a biological system, and the therapeutic relevance of the resulting macrocyclic GLP-1 analogues in vivo remains to be established. The findings position PapB as a potentially versatile biocatalytic tool for generating conformationally constrained peptide drug candidates.
ACS bio & med chem Au · Oct 2025DOI ↗ In vitro
This study developed a dual-mode semi-preparative anion-exchange chromatography (AEX) method to fractionate and characterize charge variants of dulaglutide, a GLP-1 receptor agonist used in type 2 diabetes management. Because dulaglutide is an acidic Fc-fusion protein with complex charge heterogeneity, standard characterization methods are technically challenging. The researchers isolated acidic, main, and basic charge variant fractions and subjected them to comprehensive downstream analyses, including assessments of sialic acid content, post-translational modifications (phosphorylation, sialylation, deamidation, oxidation), size heterogeneity, aggregation, truncation, and biological activity. A key finding was that aggregates in basic variants are primarily held together by non-covalent interactions, while acidic variants contain covalently linked aggregates—a structurally meaningful distinction. Charge variants showed only slight differences in biological activity, potentially linked to aggregate presence. A comparative analysis between the innovator product Trulicity® and a biosimilar candidate revealed minor differences in acidic variants, likely attributable to variations in phosphorylation and sialylation profiles. Limitations include the in vitro nature of the biological activity assessments and the absence of in vivo or clinical data. The study provides a detailed analytical framework for characterizing charge heterogeneity in complex biopharmaceuticals.
International journal of biological macromolecules · Sep 2025DOI ↗ In vitro
This study reports the first-in-class design of unimolecular "tetra-agonists" — single peptide molecules engineered to simultaneously activate four metabolically relevant receptors: GLP-1R, GIPR, GcgR (all class B GPCRs), and Y2R (a class A GPCR). Prior work had yielded dual and triple agonists exploiting sequence homology among class B GPCR ligands, but incorporating Y2R agonism was considered a major challenge due to the structural and sequence divergence between class A and class B GPCRs. The researchers used rational chimeric peptide design to overcome these topological constraints, producing high-potency tetra-agonists. They further showed that lipidation of the scaffold was well tolerated, potentially improving therapeutic viability. The study also explored biased agonism at GLP-1R, demonstrating that cAMP signaling could be selectively amplified while minimizing β-arrestin recruitment — a mechanism that may reduce receptor desensitization. A tunable framework for modulating β-arrestin engagement without compromising cAMP potency is also described. Limitations include that all experiments appear to be conducted in vitro (cell-based receptor activation and signaling assays), with no animal or human efficacy data reported. The work is primarily a molecular pharmacology and peptide chemistry study establishing proof-of-concept at the receptor level.
Journal of the American Chemical Society · Jun 2025DOI ↗ In vitroPreprint
This preprint describes a computational study aimed at designing improved semaglutide analogues — variants of the GLP-1 receptor agonist used in weight-loss and diabetes treatment — in the context of the underperforming CagriSema Phase III trial. The researchers used an automated "natural amino acid scanning" approach, systematically introducing single amino acid mutations across the semaglutide peptide backbone. Using the crystal structure of the GLP-1–GLP-1R complex (PDB: 4ZGM) as a structural template, they performed high-throughput computational modeling with Modeller and estimated binding affinities (Kd) using the Prodigy tool. From this pipeline, the study identified 564 computationally designed semaglutide analogues predicted to show improved binding affinity to the extracellular domain (ECD) of GLP-1R. The authors propose a conceptual "interfacial electrostatic scaffold" consisting of four salt bridges at the peptide–receptor interface as a framework for next-generation GLP-1R agonist development, drawing an analogy to the century-long iterative optimization of insulin. Key limitations include the fully computational nature of the study — no experimental validation (biochemical, cellular, or in vivo) is presented — and reliance on a single structural template and computational binding affinity estimators, which may not fully capture dynamic receptor behavior.
Unknown journal · Apr 2025DOI ↗