Next generation GLP-1/GIP/glucagon triple agonists normalize body weight in obese mice.

OBJECTIVE: Pharmacological strategies that engage multiple mechanisms-of-action have demonstrated synergistic benefits for metabolic disease in preclinical models. One approach, concurrent activation of the glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), and glucagon (Gcg) receptors (i.e. triagonism), combines the anorectic and insulinotropic activities of GLP-1 and GIP with the energy expenditure effect of glucagon. While the efficacy of triagonism in preclinical models is known, the relative contribution of GcgR activation remains unassessed. This work aims to addresses that central question. METHODS: Herein, we detail the design of unimolecular peptide triagonists with an empirically optimized receptor potency ratio. These optimized peptide triagonists employ a protraction strategy permitting once-weekly human dosing. Additionally, we assess the effects of these peptides on weight-reduction, food intake, glucose control, and energy expenditure in an established DIO mouse model compared to clinically relevant GLP-1R agonists (e.g. semaglutide) and dual GLP-1R/GIPR agonists (e.g. tirzepatide). RESULTS: Optimized triagonists normalize body weight in DIO mice and enhance energy expenditure in a manner superior to that of GLP-1R mono-agonists and GLP-1R/GIPR co-agonists. CONCLUSIONS: These pre-clinical data suggest unimolecular poly-pharmacology as an effective means to target multiple mechanisms contributing to obesity and further implicate GcgR activation as the differentiating factor between incretin receptor mono- or dual-agonists and triagonists.

Chemical Synthesis of Phosphorylated Insulin-like Growth Factor Binding Protein 2.

Chemical protein synthesis is a powerful avenue for accessing homogeneously modified proteins. While a significant number of small modified proteins bearing native post-translational modifications and non-natural modifications have been generated to date, access to larger targets has proved challenging. Herein, we describe the use of two ligation manifolds, namely, diselenide-selenoester ligation and native chemical ligation, to assemble a 31.5 kDa phosphorylated insulin-like growth factor binding protein (IGFBP-2) that comprises 290 amino acid residues, a phosphoserine post-translational modification, and nine disulfide bonds.

Synthesis and Utility of ß-Selenophenylalanine and ß-Selenoleucine in Diselenide-Selenoester Ligation.

The synthesis of suitably protected ß-selenophenylalanine and ß-selenoleucine amino acids was accomplished from Garner's aldehyde as a common starting point. These selenoamino acids were incorporated into model peptides and shown to facilitate rapid diselenide-selenoester ligation (DSL) with peptide selenoesters which, when coupled with in situ deselenization, afforded native peptide products. The utility of one-pot DSL-deselenization chemistry at phenylalanine and leucine was demonstrated through the rapid synthesis of a glycosylated interferon-γ fragment and the chemokine-binding protein UL22A, respectively.

Diselenide-selenoester ligation for chemical protein synthesis.

Chemoselective peptide ligation methods have provided synthetic access to numerous proteins, including those bearing native post-translational modifications and unnatural labels. This protocol outlines the chemical synthesis of proteins using a recently discovered reaction (diselenide-selenoester ligation (DSL)) in a rapid, additive-free manner. After ligation, the products can be chemoselectively deselenized to produce native peptide and protein products. We describe methods for the synthesis of suitably functionalized peptide diselenide and peptide selenoester fragments via Fmoc-solid-phase peptide synthesis (SPPS) protocols, fusion of these fragments by DSL, and the chemoselective deselenization of the ligation products to generate native synthetic proteins. We demonstrate the method's utility through the total chemical synthesis of the post-translationally modified collagenous domain of the hormone adiponectin via DSL-deselenization at selenocystine (the oxidized form of selenocysteine) and the rapid preparation of two tick-derived thrombin-inhibiting proteins by DSL-deselenization at ß-selenoaspartate and γ-selenoglutamate. This method should find widespread use for the rapid synthesis of proteins, including cases in which other peptide ligation methods cannot be used (or cannot be used efficiently), e.g., at sterically hindered or deactivated acyl donors. The method's speed and efficiency may render it useful in the generation of synthetic protein libraries. Each protein discussed can be synthesized within 15 working days from resin loading and can be readily produced by practitioners with master's-level experience in organic chemistry. Each synthesis using these protocols was performed independently by two labs (one academic and one industrial), which attained comparable yields of the protein products.

Rapid assembly and profiling of an anticoagulant sulfoprotein library.

Hematophagous organisms produce a suite of salivary proteins which interact with the host's coagulation machinery to facilitate the acquisition and digestion of a bloodmeal. Many of these biomolecules inhibit the central blood-clotting serine proteinase thrombin that is also the target of several clinically approved anticoagulants. Here a bioinformatics approach is used to identify seven tick proteins with putative thrombin inhibitory activity that we predict to be posttranslationally sulfated at two conserved tyrosine residues. To corroborate the biological role of these molecules and investigate the effects of amino acid sequence and sulfation modifications on thrombin inhibition and anticoagulant activity, a library of 34 homogeneously sulfated protein variants were rapidly assembled using one-pot diselenide-selenoester ligation (DSL)-deselenization chemistry. Downstream functional characterization validated the thrombin-directed activity of all target molecules and revealed that posttranslational sulfation of specific tyrosine residues crucially modulates potency. Importantly, access to this homogeneously modified protein library not only enabled the determination of key structure-activity relationships and the identification of potent anticoagulant leads, but also revealed subtleties in the mechanism of thrombin inhibition, between and within the families, that would be impossible to predict from the amino acid sequence alone. The synthetic platform described here therefore serves as a highly valuable tool for the generation and thorough characterization of libraries of related peptide and/or protein molecules (with or without modifications) for the identification of lead candidates for medicinal chemistry programs.

Solid-phase synthesis of peptide selenoesters via a side-chain anchoring strategy.

Peptide selenoesters have recently emerged as key building blocks for the ligation-based assembly of large polypeptides and proteins. Herein, we report an efficient solid-phase method for the high yielding and epimerisation-free synthesis of peptide selenoesters using a side-chain immobilisation strategy.

Examination of mercaptobenzyl sulfonates as catalysts for native chemical ligation: application to the assembly of a glycosylated Glucagon-Like Peptide 1 (GLP-1) analogue.

3/4-Mercaptobenzyl sulfonates were investigated as aryl thiol catalysts for native chemical ligation (NCL). Whilst catalysing NCL processes at a similar rate to 4-mercaptophenyl acetic acid (MPAA), the increased polarity and solubility of 3-mercaptobenzyl sulfonate in particular may favour its selection as NCL catalyst in many instances.

Cysteine promoted C-terminal hydrazinolysis of native peptides and proteins.

Tagging the terminus: N→S acyl transfer in native peptides and proteins can be reliably intercepted with hydrazine. The method allows selective labeling and ligation, without recourse to the use of protein-splicing elements. NCL=native chemical ligation.

Native N-glycopeptide thioester synthesis through N→S acyl transfer.

Peptide thioesters are important tools for the total synthesis of proteins using native chemical ligation (NCL). Preparation of glycopeptide thioesters, that enable the assembly of homogeneously glycosylated proteins, is complicated by the perceived fragile nature of the sugar moiety. Herein, we demonstrate the compatibility of thioester formation via N→S acyl transfer with native N-glycopeptides and report observations that will aid in their preparation.

Shifting Native Chemical Ligation into Reverse through N→S Acyl Transfer.

Peptide thioester synthesis by N→S acyl transfer is being intensively explored by many research groups the world over. Reasons for this likely include the often straightforward method of precursor assembly using Fmoc-based chemistry and the fundamentally interesting acyl migration process. In this review we introduce recent advances in this exciting area and discuss, in more detail, our own efforts towards the synthesis of peptide thioesters through N→S acyl transfer in native peptide sequences. We have found that several peptide thioesters can be readily prepared and, what's more, there appears to be ample opportunity for further development and discovery.