In vitro
This study presents a novel chemical platform for installing carbon-14 (¹⁴C) or tritium (³H) radiolabeled lysine residues directly onto solid-supported peptides, circumventing the high cost and complexity of traditional radiolabeling methods. The researchers developed a two-step workflow: first, a mild hydroformylation reaction converts allylglycine residues — already incorporated into the peptide on a solid support — into a labeled allysine intermediate using either ¹⁴CO (generated from solid precursors) or ³H₂ gas. Second, reductive amination converts allysine into a radiolabeled lysine residue, with the final labeled peptide released upon cleavage from the solid support. The study reports that the optimized conditions are compatible with diverse peptide sequences and were successfully applied to analogs of semaglutide, a complex pharmaceutical peptide. The platform's key advantages highlighted by the authors include late-stage isotope introduction, flexibility in choosing the radiolabel, and avoidance of lengthy multi-step synthesis. Limitations include that this is a synthetic chemistry methods paper with no biological or clinical testing; all work was conducted in vitro at the bench-chemistry level. No pharmacological, pharmacokinetic, or efficacy data in animals or humans are reported.
Nature communications · 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 study investigated whether five FDA-approved glucagon-like peptide-1 receptor agonists (GLP-1RAs) — semaglutide, tirzepatide, liraglutide, and two others — could directly inhibit the aggregation of the 42-residue amyloid-β peptide (Aβ42), a key process implicated in Alzheimer's disease (AD). Using in vitro aggregation kinetics and microscopic analysis, researchers found that semaglutide, tirzepatide, and liraglutide inhibited Aβ42 aggregation, primarily by targeting the primary nucleation step — the initial formation of amyloid seeds. Semaglutide and tirzepatide delayed aggregation with submicromolar potency, while liraglutide showed the strongest suppression of primary nucleation and additionally modestly inhibited secondary nucleation. Liraglutide also altered fibril structure — producing less mature, more tortuous, and longer fibrils — and reduced the ability of fibrils to self-replicate (template). The study was conducted entirely in vitro (no cell, animal, or human data), which is a significant limitation for clinical translation. The authors conclude that certain GLP-1RAs can directly interfere with molecular steps of Aβ42 aggregation, and call for further studies to determine whether these mechanisms contribute to potential AD-protective effects observed in preclinical and clinical research.
Journal of the American Chemical Society · 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 investigated the metabolic profiles of three amylin receptor agonists — pramlintide, cagrilintide, and KBP-066 — in the context of sports anti-doping research. Motivated by growing concerns about misuse of weight-loss peptide hormones in athletic disciplines where weight management is performance-relevant, researchers used comprehensive in vitro models (human skin and kidney S9 fractions, biological fluids) to characterize how these compounds are broken down. High-resolution tandem mass spectrometry (HRMS/MS) was used to identify metabolites, and authentic post-administration rat plasma samples were analyzed for cagrilintide to assess in vivo relevance. The study found that all three peptides underwent N-terminal and C-terminal degradation, producing multiple stable metabolites considered suitable as analytical detection targets. Metabolites predicted from in vitro experiments for cagrilintide were confirmed in rat plasma samples. The researchers developed and validated an LC-MS/MS-based detection method applicable to anti-doping screening. Limitations include the primary reliance on in vitro models; the only in vivo data came from rat samples, not humans. This represents the first systematic metabolic characterization of these three compounds in an anti-doping context and lays groundwork for future human monitoring programs.
Journal of pharmaceutical and biomedical analysis · Feb 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 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 ↗