Engineering PEG-fatty acid stapled, long-acting peptide agonists for G protein-coupled receptors

Glucagon-like peptide-1 analogs: Miracle drugs are blooming?

Glucagon-like peptide-1 (GLP-1), secreted by L cells in the small intestine, assumes a central role in managing type 2 diabetes mellitus (T2DM) and obesity. Its influence on insulin secretion and gastric emptying positions it as a therapeutic linchpin. However, the limited applicability of native GLP-1 stems from its short half-life, primarily due to glomerular filtration and the inactivating effect of dipeptidyl peptidase-IV (DPP-IV). To address this, various structural modification strategies have been developed to extend GLP-1's half-life. Despite the commendable efficacy displayed by current GLP-1 receptor agonists, inherent limitations persist. A paradigm shift emerges with the advent of unimolecular multi-agonists, such as the recently introduced tirzepatide, wherein GLP-1 is ingeniously combined with other gastrointestinal hormones. This novel approach has captured the spotlight within the diabetes and obesity research community. This review summarizes the physiological functions of GLP-1, systematically explores diverse structural modifications, delves into the realm of unimolecular multi-agonists, and provides a nuanced portrayal of the developmental prospects that lie ahead for GLP-1 analogs.

Venom peptides - A comprehensive translational perspective in pain management

Venom peptides have been evolving complex therapeutic interventions that potently and selectively modulate a range of targets such as ion channels, receptors, and signaling pathways of physiological processes making it potential therapeutic. Several venom peptides were deduced in vivo for clinical development targeting pain management, diabetes, cardiovascular diseases, antimicrobial activity. Several contributions have been detailed for a clear perspective for a better understanding of venomous animals, their venom, and their pharmacological effects. Here we unravel and summarize the recent advances in wide venom peptides across varieties of species for their therapeutics prospects.

Sustained Release Systems for Delivery of Therapeutic Peptide/Protein

Peptide/protein therapeutics have been significantly applied in the clinical treatment of various diseases such as cancer, diabetes, etc. owing to their high biocompatibility, specificity, and therapeutic efficacy. However, due to their immunogenicity, instability stemming from its complex tertiary and quaternary structure, vulnerability to enzyme degradation, and rapid renal clearance, the clinical application of protein/peptide therapeutics is significantly confined. Though nanotechnology has been demonstrated to prevent enzyme degradation of the protein therapeutics and thus enhance the half-life, issues such as initial burst release and uncontrollable release kinetics are still unsolved. Moreover, the traditional administration method results in poor patient compliance, limiting the clinical application of protein/peptide therapeutics. Exploiting the sustained-release formulations for more controllable delivery of protein/peptide therapeutics to decrease the frequency of injection and enhance patient compliance is thus greatly meaningful. In this review, we comprehensively summarize the substantial advancements of protein/peptide sustained-release systems in the past decades. In addition, the advantages and disadvantages of all these sustained-release systems in clinical application together with their future challenges are also discussed in this review.

Impact of non-proteinogenic amino acids in the discovery and development of peptide therapeutics

With the development of modern chemistry and biology, non-proteinogenic amino acids (NPAAs) have become a powerful tool for developing peptide-based drug candidates. Drug-like properties of peptidic medicines, due to the smaller size and simpler structure compared to large proteins, can be changed fundamentally by introducing NPAAs in its sequence. While peptides composed of natural amino acids can be used as drug candidates, the majority have shown to be less stable in biological conditions. The impact of NPAA incorporation can be extremely beneficial in improving the stability, potency, permeability, and bioavailability of peptide-based therapies. Conversely, undesired effects such as toxicity or immunogenicity should also be considered. The impact of NPAAs in the development of peptide-based therapeutics is reviewed in this article. Further, numerous examples of peptides containing NPAAs are presented to highlight the ongoing development in peptide-based therapeutics.

Engineering of a Potent, Long-Acting NPY2R Agonist for Combination with a GLP-1R Agonist as a Multi-Hormonal Treatment for Obesity

Bariatric surgery results in increased intestinal secretion of hormones GLP-1 and anorexigenic PYY, which is believed to contribute to the clinical efficacy associated with the procedure. This observation raises the question whether combination treatment with gut hormone analogs might recapitulate the efficacy and mitigate the significant risks associated with surgery. Despite PYY demonstrating excellent efficacy and safety profiles with regard to food intake reduction, weight loss, and glucose control in preclinical animal models, PYY-based therapeutic development remains challenging given a low serum stability and half-life for the native peptide. Here, combined peptide stapling and PEG-fatty acid conjugation affords potent PYY analogs with >14 h rat half-lives, which are expected to translate into a human half-life suitable for once-weekly dosing. Excellent efficacy in glucose control, food intake reduction, and weight loss for lead candidate 22 in combination with our previously reported long-acting GLP-1 analog is demonstrated in a diet-induced obesity mouse model.

Recombinant Expression and Stapling of a Novel Long-Acting GLP-1R Peptide Agonist

Owing to their pleiotropic metabolic benefits, glucagon-like peptide-1 receptor (GLP-1R) agonists have been successfully utilized for treating metabolic diseases, such as type 2 diabetes and obesity. As part of our efforts in developing long-acting peptide therapeutics, we have previously reported a peptide engineering strategy that combines peptide side chain stapling with covalent integration of a serum protein-binding motif in a single step. Herein, we have used this strategy to develop a second generation extendin-4 analog rigidified with a symmetrical staple, which exhibits an excellent in vivo efficacy in an animal model of diabetes and obesity. To simplify the scale-up manufacturing of the lead GLP-1R agonist, a semisynthesis protocol was successfully developed, which involves recombinant expression of the linear peptide followed by attachment of a polyethylene glycol (PEG)-fatty acid staple in a subsequent chemical reaction step.

Construction of a Stapled α-Helix Peptide Library Displayed on Phage for the Screening of Galectin-3-Binding Peptide Ligands

A stapled α-helix peptide library was designed and constructed using a chemically modified phage display system for screening stapled-peptide ligands against target proteins. The α-helix peptide library, with two cysteine residues on the opposite side of the randomized face, was modified with a rigid hydrocarbon staple linker on a phage. The stapled α-helix peptide phage library was screened against galectin-3 (Gal-3), a cancer-related galactose-binding protein. The obtained stapled peptides showed a high binding affinity (K _d = 0.45 μM) despite being nonsugar ligands. The stapled modification played important roles in stabilizing the α-helical structure that contributed to the high binding affinity to Gal-3. In addition, the best stapled peptide ligands showed specific binding to Gal-3 among various carbohydrate-binding proteins. Thus, the designed α-helix peptide phage library with a constrained structure by the staple linker will advance the discovery of peptide ligands with improved specificity and affinity.

Engineering an enhanced thrombin-based GLP-1 analog with long-lasting glucose-lowering and efficient weight reduction

Peptides are considered as potent therapeutic drugs primarily due to the exquisite potency and selectivity to targets. However, the development and clinical application of peptide drugs were severely limited by the poor in vivo lifespans. Here, we designed an improved small albumin-binding polypeptide that can associate with human serum albumin (HSA) and liberate the bioactive peptide. Using glucagon-like peptide-1 (GLP-1) as a model, two new long-lasting GLP-1 analogs (termed XTS1 and XTS2) containing an albumin-binding domain, a protease-cleavable linker and a mutated GLP-1(A8Aib) were designed to demonstrate the sustained release of GLP-1 due to the plasma thrombin (TBN) digestion. Two XTS peptides were prepared of high purity (>99%) and accurate molecular weight determined by reversed high-performance liquid chromatography and mass spectrometry, respectively. In vitro measurements of surface plasmon resonance indicated that XTS1 associate with serum albumins of all species with higher affinity compared with XTS2. Metabolic stability of XTS1 in vitro in human plasma was also better than that of XTS2. Protease cleavage assay results of XTS peptides demonstrated the controlled-release of transient GLP-1 from the XTS1 and XTS2 mixture after thrombin-catalyzed hydrolysis. Then the intraperitoneal glucose tolerance test (IPGTT) showed that the glucose-lowering efficacies of XTS1 were in a dosage-dependent manner within the range of 0.1–0.9 mg kg⁻¹. In addition, XTS1 showed similar hypoglycemic intensity and significantly longer action duration compared to Liraglutide in both multiple IPGTTs and hypoglycemic duration test. Apparently extended plasma half-lives of ∼2.3 and ∼3.5 days were observed after a single subcutaneous administration of XTS1 (0.9 mg kg⁻¹) in rats and cynomolgus monkeys, respectively. Furthermore, twice-weekly subcutaneously dosed XTS1 in db/db mice achieved long-term beneficial effects on body weight, hemoglobin A1C (HbA1C) lowering and the function of pancreatic beta cells. These studies support that XTS1 exerts potential as a therapeutic drug for the treatment of T2DM.

Peptides are considered as potent therapeutic drugs primarily due to the exquisite potency and selectivity to targets.

Design of a Long-Acting and Selective MEG-Fatty Acid Stapled Prolactin-Releasing Peptide Analog

Anorexigenic peptides offer promise as potential therapies targeting the escalating global obesity epidemic. Prolactin-releasing peptide (PrRP), a novel member of the RFamide family secreted by the hypothalamus, shows therapeutic potential by decreasing food intake and body weight in rodent models via GPR10 activation. Here we describe the design of a long-acting PrRP using our recently developed novel multiple ethylene glycol-fatty acid (MEG-FA) stapling platform. By incorporating serum albumin binding fatty acids onto a covalent side chain staple, we have generated a series of MEG-FA stapled PrRP analogs with enhanced serum stability and in vivo half-life. Our lead compound 18-S4 exhibits good in vitro potency and selectivity against GPR10, improved serum stability, and extended in vivo half-life (7.8 h) in mouse. Furthermore, 18-S4 demonstrates a potent body weight reduction effect in a diet-induced obesity (DIO) mouse model, representing a promising long-acting PrRP analog for further evaluation in the chronic obesity setting.