Multifunctional Antibody Agonists Targeting Glucagon-like Peptide-1, Glucagon, and Glucose-Dependent Insulinotropic Polypeptide Receptors

Customizable Click Biochemistry Strategy for the Design and Preparation of Glucagon-like Peptide-1 Conjugates and Coagonists

The development of oligomeric glucagon-like peptide-1 (GLP-1) and GLP-1-containing coagonists holds promise for enhancing the therapeutic potential of the GLP-1-based drugs for treating type 2 diabetes mellitus (T2DM). Here, we report a facile, efficient, and customizable strategy based on genetically encoded SpyCatcher-SpyTag chemistry and an inducible, cleavable self-aggregating tag (icSAT) scheme. icSAT-tagged SpyTag-fused GLP-1 and the dimeric or trimeric SpyCatcher scaffold were designed for dimeric or trimeric GLP-1, while icSAT-tagged SpyCatcher-fused GLP-1 and the icSAT-tagged SpyTag-fused GIP were designed for dual GLP-1/GIP (glucose-dependent insulinotropic polypeptide) receptor agonist. These SpyCatcher- and SpyTag-fused protein pairs were spontaneously ligated directly from the cell lysates. The subsequent icSAT scheme, coupled with a two-step standard column purification, resulted in target proteins with authentic N-termini, with yields ranging from 35 to 65 mg/L and purities exceeding 99%. In vitro assays revealed 3.0- to 4.1-fold increased activities for dimeric and trimeric GLP-1 compared to mono-GLP-1. The dual GLP-1/GIP receptor agonist exhibited balanced activity toward the GLP-1 receptor or the GIP receptor. All the proteins exhibited 1.8- to 3.0-fold prolonged half-lives in human serum compared to mono-GLP-1 or GIP. This study provides a generally applicable click biochemistry strategy for developing oligomeric or dual peptide/protein-based drug candidates.

Conjugation of a peptide to an antibody engineered with free cysteines dramatically improves half-life and activity

The long circulating half-life and inherently bivalent architecture of IgGs provide an ideal vehicle for presenting otherwise short-lived G-protein-coupled receptor agonists in a format that enables avidity-driven enhancement of potency. Here, we describe the site-specific conjugation of a dual agonist peptide (an oxyntomodulin variant engineered for potency and in vivo stability) to the complementarity-determining regions (CDRs) of an immunologically silent IgG4. A cysteine-containing heavy chain CDR3 variant was identified that provided clean conjugation to a bromoacetylated peptide without interference from any of the endogenous mAb cysteine residues. The resulting mAb-peptide homodimer has high potency at both target receptors (glucagon receptor, GCGR, and glucagon-like peptide 1 receptor, GLP-1R) driven by an increase in receptor avidity provided by the spatially defined presentation of the peptides. Interestingly, the avidity effects are different at the two target receptors. A single dose of the long-acting peptide conjugate robustly inhibited food intake and decreased body weight in insulin resistant diet-induced obese mice, in addition to ameliorating glucose intolerance. Inhibition of food intake and decrease in body weight was also seen in overweight cynomolgus monkeys. The weight loss resulting from dosing with the bivalently conjugated dual agonist was significantly greater than for the monomeric analog, clearly demonstrating translation of the measured in vitro avidity to in vivo pharmacology.

Rapid selection of a novel GLP-1/GIP dual receptor agonist with prolonged glycemic control and weight loss in rodent animals

BACKGROUND

Glucagon-like peptide-1 receptor (GLP-1R) and glucose-dependent insulinotropic polypeptide receptor (GIPR) co-agonists have emerged as treatment options for reversing diabetes and obesity. Here, we screened the high potency receptor-biased GLP-1R agonists via a newly designed high-throughput GLP-1R extracellular domain (ECD)-based system and demonstrated its in vitro and in vivo therapeutic characters.

METHODS

Twelve 9-mer peptides (named XEL1-XEL12) which were screened from a large phage-displayed peptide library were fused to the N-terminus of GIP (3-30) to generate another twelve fusion peptides, termed XEL13-24. Using the six lysine-altered XEL17 as leading sequences, eighteen fatty chain modified fusion peptides were further assessed via in vitro GLP-1R/GIPR-based cell assay. Moreover, the acute and long-acting in vivo effects of selected candidate on diabetic db/db mice and diet-induced obesity (DIO) rats were both carefully evaluated.

RESULTS

XEL17 exhibited balanced activation potency on GLP-1R/GIPR in stable cell lines, and further assessment was performed to evaluate the XEL32, a fatty chain modified XEL17 derivative. Preclinical pharmacodynamic results in diabetic db/db mice demonstrated that XEL32 held outstanding insulinotropic and glucose-lowering activities. In addition, protracted antidiabetic effects of XEL32 were also proved by the hypoglycemic test and multiple oral glucose tolerance test. Furthermore, chronic treatment of XEL32 in DIO rats exhibited outstanding beneficial effects on body weight control, fat loss, food intake control, hemoglobin A1C (HbA1C) reduction as well as the glucose tolerance.

CONCLUSIONS

XEL32, as a novel GLP-1/GIP dual receptor agonist, may supply efficient glycemic control and weight loss.

Pyrazolone ligation-mediated versatile sequential bioconjugations

Bioconjugation chemistries are critical tools in biotherapeutics discovery. The past efforts have been exclusively focused on two-segment conjugations. However, emerging research directions, such as polypharmacy biotherapeutics, desire multiple-component bioconjugations where more than two pharmacologically related biomolecules can be assembled into a single construct in high efficiency. We present here a set of sequential bioconjugation chemistries centered on a pyrazolone structural motif. It starts with a clickable “pyrazolone ligation” between a hydrazine group and a β-ketoester moiety followed by the conjugation between the newly formed pyrazolone core and an aldehyde-bearing biomolecule through a Knoevenagel reaction forming a Michael addition acceptor that can effectively capture a thiol-bearing biomolecule. When utilized intermolecularly, it quickly assembles four segments together forming a quadruple functional construct. When applied intramolecularly, it offers a set of highly diverse biomolecule scaffolds including stapled peptides and poly-macrocyclic peptides. We envision broad utilities of such sequential ligation chemistries.

A multiple component sequential bioconjugation chemistry establishes upon the joined force of hydrazine, β-keto ester, thiol and aldehyde.

A novel thrombin-based triagonist with diabetes-protective and weight-lowering potential

AIMS

To investigate the diabetes-protective effect and weight-lowering potential of a novel long-acting triagonist at three metabolically related hormone receptors including glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), glucagon receptors.

MAIN METHODS

Triagonist were designed in an iterative manner from native GLP-1, GIP and Glucogan. Main peptide chain (termed TG peptides) and subsequently modified LTG peptides were synthesized via solid phase synthesis. In vitro receptor activity assay was performed to screen the TG peptide with most balanced potency on all three receptors. The in vitro biological activities of modified TG peptides were further investigated by albumin-binding measurement and proteolytic cleavage test. Subsequently, oral glucose tolerance test (OGTT), pharmacokinetic test and chronic study were subjected to the acute and long-term efficacy evaluation of selected fusion peptide, LTG-6.

KEY FINDINGS

TG-8 exhibited equally aligned constituent efficacy and supraphysiological potency on corresponding receptor without cross-reactivity. Modified TG-8, termed LTG-6, exerted the great binding affinity for human serum albumin and the enhanced rational controlled-release of TG-8 in vitro. Further OGTT in different gene knockout mice and diabetic mice demonstrated the promising hypoglycemic and insulinotropic abilities of LTG-6. After long-term treatment for 8 weeks, LTG-6 was proved superior to co-agonists to decrease the body weight and %HbA1c, improve reverse dyslipidemia and glycemic control in the DIO models.

SIGNIFICANCE

LTG-6, as a newly designed long-acting triagonist, holds potential to correct the obesity related metabolic disorders.

Design and characterization of novel oxyntomodulin derivatives with potent dual GLP-1/glucagon receptor activation and prolonged antidiabetic effects

AIMS

To investigate the combination of dimerization and PEGylation to enhance the receptor activation and in vivo stability of Oxyntomodulin (OXM).

MAIN METHODS

All LDM peptides were produced by using standard method of solid phase synthesis. The in vitro effects of LDM peptides were assessed by glucagon-like peptide-1 receptor (GLP-1R) and glucagon receptor (GcgR) binding test and Proteolytic stability test. Subsequently, saline, Liraglutide and three doses of LDM-3 treated groups were subjected to the evaluation of aute and long-term efficacy.

KEY FINDINGS

Five long-acting OXM conjugates, termed LDM-1 to LDM-5, were designed using cysteine (Cys)-specific modification reaction including the activated PEG, bisMal-NH₂, and OXM-Cys, and all prepared with high purity. LDM-3 exhibited greater GLP-1R and GcgR activation and ameliorative serum stability. In addition, LDM-3 was identified with enhanced insulinotropic and glycemic abilities in the gene knockout mice. The prolonged glucose-lowering effects of the LDM-3 were proved by hypoglycemic duration test and multiple oral glucose tolerance tests (OGTTs) in the diet-induced obesity (DIO) mice. Furthermore, the pharmacokinetic tests in Sprague Dawley (SD) rat and cynomolgus monkey exhibited the lifespans of LDM-3 at 90 nmol·kg^-1 were 101.5 h and 119.4 h, respectively. Nevertheless, consecutive 8-week administration of LDM-3 improved the cumulative body weight gain, food intake, % HbA1c, glucose tolerance and the pancreatic of the obese mice.

SIGNIFICANCE

LDM-3, as a dual GLP-1R and GcgR agonist, holds potential to be developed as a promising therapeutic candidate for both diabetes and obesity.

Selection and progression of unimolecular agonists at the GIP, GLP-1, and glucagon receptors as drug candidates

The continued global growth in the prevalence of obesity coupled with the limited number of efficacious and safe treatment options elevates the importance of innovative pharmaceutical approaches. Combinatorial strategies that harness the metabolic benefits of multiple hormonal mechanisms have emerged at the preclinical and more recently clinical stages of drug development. A priority has been anti-obesity unimolecular peptides that function as balanced, high potency poly-agonists at two or all the cellular receptors for the endocrine hormones glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon. This report reviews recent progress in this area, with emphasis on what the initial clinical results demonstrate and what remains to be addressed.

Gut Peptide Agonism in the Treatment of Obesity and Diabetes

Obesity is a global healthcare challenge that gives rise to devastating diseases such as the metabolic syndrome, type-2 diabetes (T2D), and a variety of cardiovascular diseases. The escalating prevalence of obesity has led to an increased interest in pharmacological options to counteract excess weight gain. Gastrointestinal hormones such as glucagon, amylin, and glucagon-like peptide-1 (GLP-1) are well recognized for influencing food intake and satiety, but the therapeutic potential of these native peptides is overall limited by a short half-life and an often dose-dependent appearance of unwanted effects. Recent clinical success of chemically optimized GLP-1 mimetics with improved pharmacokinetics and sustained action has propelled pharmacological interest in using bioengineered gut hormones to treat obesity and diabetes. In this article, we summarize the basic biology and signaling mechanisms of selected gut peptides and discuss how they regulate systemic energy and glucose metabolism. Subsequently, we focus on the design and evaluation of unimolecular drugs that combine the beneficial effects of selected gut hormones into a single entity to optimize the beneficial impact on systems metabolism. © 2020 American Physiological Society. Compr Physiol 10:99-124, 2020.

New Insights into Beta-Cell GLP-1 Receptor and cAMP Signaling

Harnessing the translational potential of the GLP-1/GLP-1R system in pancreatic beta cells has led to the development of established GLP-1R-based therapies for the long-term preservation of beta cell function. In this review, we discuss recent advances in the current research on the GLP-1/GLP-1R system in beta cells, including the regulation of signaling by endocytic trafficking as well as the application of concepts such as signal bias, allosteric modulation, dual agonism, polymorphic receptor variants, spatial compartmentalization of cAMP signaling and new downstream signaling targets involved in the control of beta cell function.

Anti-Obesity Therapy: from Rainbow Pills to Polyagonists

With their ever-growing prevalence, obesity and diabetes represent major health threats of our society. Based on estimations by the World Health Organization, approximately 300 million people will be obese in 2035. In 2015 alone there were more than 1.6 million fatalities attributable to hyperglycemia and diabetes. In addition, treatment of these diseases places an enormous burden on our health care system. As a result, the development of pharmacotherapies to tackle this life-threatening pandemic is of utmost importance. Since the beginning of the 19th century, a variety of drugs have been evaluated for their ability to decrease body weight and/or to improve deranged glycemic control. The list of evaluated drugs includes, among many others, sheep-derived thyroid extracts, mitochondrial uncouplers, amphetamines, serotonergics, lipase inhibitors, and a variety of hormones produced and secreted by the gastrointestinal tract or adipose tissue. Unfortunately, when used as a single hormone therapy, most of these drugs are underwhelming in their efficacy or safety, and placebo-subtracted weight loss attributed to such therapy is typically not more than 10%. In 2009, the generation of a single molecule with agonism at the receptors for glucagon and the glucagon-like peptide 1 broke new ground in obesity pharmacology. This molecule combined the beneficial anorectic and glycemic effects of glucagon-like peptide 1 with the thermogenic effect of glucagon into a single molecule with enhanced potency and sustained action. Several other unimolecular dual agonists have subsequently been developed, and, based on their preclinical success, these molecules illuminate the path to a new and more fruitful era in obesity pharmacology. In this review, we focus on the historical pharmacological approaches to treat obesity and glucose intolerance and describe how the knowledge obtained by these studies led to the discovery of unimolecular polypharmacology.

Engineering of a GLP-1 analogue peptide/anti-PCSK9 antibody fusion for type 2 diabetes treatment

Type 2 diabetes (T2D) is a complex and progressive disease requiring polypharmacy to manage hyperglycaemia and cardiovascular risk factors. However, most patients do not achieve combined treatment goals. To address this therapeutic gap, we have developed MEDI4166, a novel glucagon-like peptide-1 (GLP-1) receptor agonist peptide fused to a proprotein convertase subtilisin/kexin type 9 (PCSK9) neutralising antibody that allows for glycaemic control and low-density lipoprotein cholesterol (LDL-C) lowering in a single molecule. The fusion has been engineered to deliver sustained peptide activity in vivo in combination with reduced potency, to manage GLP-1 driven adverse effects at high dose, and a favourable manufacturability profile. MEDI4166 showed robust and sustained LDL-C lowering in cynomolgus monkeys and exhibited the anticipated GLP-1 effects in T2D mouse models. We believe MEDI4166 is a novel molecule combining long acting agonist peptide and neutralising antibody activities to deliver a unique pharmacology profile for the management of T2D.

Targeting the Incretin/Glucagon System With Triagonists to Treat Diabetes

Glucagonlike peptide 1 (GLP-1) receptor agonists have been efficacious for the treatment of type 2 diabetes due to their ability to reduce weight and attenuate hyperglycemia. However, the activity of glucagonlike peptide 1 receptor-directed strategies is submaximal, and the only potent, sustainable treatment of metabolic dysfunction is bariatric surgery, necessitating the development of unique therapeutics. GLP-1 is structurally related to glucagon and glucose-dependent insulinotropic peptide (GIP), allowing for the development of intermixed, unimolecular peptides with activity at each of their respective receptors. In this review, we discuss the range of tissue targets and added benefits afforded by the inclusion of each of GIP and glucagon. We discuss considerations for the development of sequence-intermixed dual agonists and triagonists, highlighting the importance of evaluating balanced signaling at the targeted receptors. Several multireceptor agonist peptides have been developed and evaluated, and the key preclinical and clinical findings are reviewed in detail. The biological activity of these multireceptor agonists are founded in the success of GLP-1-directed strategies; by including GIP and glucagon components, these multireceptor agonists are thought to enhance GLP-1's activities by broadening the tissue targets and synergizing at tissues that express multiple receptors, such at the brain and pancreatic islet β cells. The development and utility of balanced, unimolecular multireceptor agonists provide both a useful tool for querying the actions of incretins and glucagon during metabolic disease and a unique drug class to treat type 2 diabetes with unprecedented efficacy.

Are peptide conjugates the golden therapy against obesity?

Obesity is a worldwide pandemic, which can be fatal for the most extremely affected individuals. Lifestyle interventions such as diet and exercise are largely ineffective and current anti-obesity medications offer little in the way of significant or sustained weight loss. Bariatric surgery is effective, but largely restricted to only a small subset of extremely obese patients. While the hormonal factors mediating sustained weight loss and remission of diabetes by bariatric surgery remain elusive, a new class of polypharmacological drugs shows potential to shrink the gap in efficacy between a surgery and pharmacology. In essence, this new class of drugs combines the beneficial effects of several independent hormones into a single entity, thereby combining their metabolic efficacy to improve systems metabolism. Such unimolecular drugs include single molecules with agonism at the receptors for glucagon, glucagon-like peptide 1 and the glucose-dependent insulinotropic polypeptide. In preclinical studies, these specially tailored multiagonists outperform both their mono-agonist components and current best in class anti-obesity medications. While clinical trials and vigorous safety analyses are ongoing, these drugs are poised to have a transformative effect in anti-obesity therapy and might hopefully lead the way to a new era in weight-loss pharmacology.

Gut hormone polyagonists for the treatment of type 2 diabetes

Chemical derivatives of the gut-derived peptide hormone glucagon-like peptide 1 (GLP-1) are among the best-in-class pharmacotherapies to treat obesity and type 2 diabetes. However, GLP-1 analogs have modest weight lowering capacity, in the range of 5-10%, and the therapeutic window is hampered by dose-dependent side effects. Over the last few years, a new concept has emerged: combining the beneficial effects of several key metabolic hormones into a single molecular entity. Several unimolecular GLP-1-based polyagonists have shown superior metabolic action compared to GLP-1 monotherapies. In this review article, we highlight the history of polyagonists targeting the receptors for GLP-1, GIP and glucagon, and discuss recent progress in expanding of this concept to now allow targeted delivery of nuclear hormones via GLP-1 and other gut hormones, as a novel approach towards more personalized pharmacotherapies.

Polypharmacy through Phage Display: Selection of Glucagon and GLP-1 Receptor Co-agonists from a Phage-Displayed Peptide Library

A promising emerging area for the treatment of obesity and diabetes is combinatorial hormone therapy, where single-molecule peptides are rationally designed to integrate the complementary actions of multiple endogenous metabolically-related hormones. We describe here a proof-of-concept study on developing unimolecular polypharmacy agents through the use of selection methods based on phage-displayed peptide libraries (PDL). Co-agonists of the glucagon (GCG) and GLP-1 receptors were identified from a PDL sequentially selected on GCGR- and GLP1R-overexpressing cells. After two or three rounds of selection, 7.5% of randomly picked clones were GLP1R/GCGR co-agonists, and a further 1.53% were agonists of a single receptor. The phages were sequenced and 35 corresponding peptides were synthesized. 18 peptides were potent co-agonists, 8 of whom showed EC₅₀ ≤ 30 pM on each receptor, comparable to the best rationally designed co-agonists reported in the literature. Based on literature examples, two sequences were engineered to stabilize against dipeptidyl peptidase IV cleavage and prolong the in vivo half-life: the engineered peptides were comparably potent to the parent peptides on both receptors, highlighting the potential use of phage-derived peptides as therapeutic agents. The strategy described here appears of general value for the discovery of optimized polypharmacology paradigms across several metabolically-related hormones.

GLP-1/glucagon receptor co-agonism for treatment of obesity

Over a relatively short period, obesity and type 2 diabetes have come to represent a large medical and economic burden to global societies. The epidemic rise in the prevalence of obesity has metabolic consequences and is paralleled by an increased occurrence of other diseases, such as diabetes, cancer and cardiovascular complications. Together, obesity and type 2 diabetes constitute one of the more preventable causes of premature death and the identification of novel, safe and effective anti-obesity drugs is of utmost importance. Pharmacological attempts to treat obesity have had limited success, with notable adverse effects, rendering bariatric surgery as the only current therapy for substantially improving body weight. Novel unimolecular, multifunctional peptides have emerged as one of the most promising medicinal approaches to enhance metabolic efficacy and restore normal body weight. In this review, we will mainly focus on the discovery and translational relevance of dual agonists that pharmacologically function at the receptors for glucagon and glucagon-like peptide-1. Such peptides have advanced to clinical evaluation and inspired the pursuit of multiple related approaches to achieving polypharmacy within single molecules.

New Modalities for Challenging Targets in Drug Discovery

Our ever-increasing understanding of biological systems is providing a range of exciting novel biological targets, whose modulation may enable novel therapeutic options for many diseases. These targets include protein-protein and protein-nucleic acid interactions, which are, however, often refractory to classical small-molecule approaches. Other types of molecules, or modalities, are therefore required to address these targets, which has led several academic research groups and pharmaceutical companies to increasingly use the concept of so-called "new modalities". This Review defines for the first time the scope of this term, which includes novel peptidic scaffolds, oligonucleotides, hybrids, molecular conjugates, as well as new uses of classical small molecules. We provide the most representative examples of these modalities to target large binding surface areas such as those found in protein-protein interactions and for biological processes at the center of cell regulation.

Opportunities for therapeutic antibodies directed at G-protein-coupled receptors

G-protein-coupled receptors (GPCRs) are activated by a diverse range of ligands, from large proteins and proteases to small peptides, metabolites, neurotransmitters and ions. They are expressed on all cells in the body and have key roles in physiology and homeostasis. As such, GPCRs are one of the most important target classes for therapeutic drug discovery. The development of drugs targeting GPCRs has therapeutic value across a wide range of diseases, including cancer, immune and inflammatory disorders as well as neurological and metabolic diseases. The progress made by targeting GPCRs with antibody-based therapeutics, as well as technical hurdles to overcome, are presented and discussed in this Review. Antibody therapeutics targeting C-C chemokine receptor type 4 (CCR4), CCR5 and calcitonin gene-related peptide (CGRP) are used as illustrative clinical case studies.

The New Biology and Pharmacology of Glucagon

In the last two decades we have witnessed sizable progress in defining the role of gastrointestinal signals in the control of glucose and energy homeostasis. Specifically, the molecular basis of the huge metabolic benefits in bariatric surgery is emerging while novel incretin-based medicines based on endogenous hormones such as glucagon-like peptide 1 and pancreas-derived amylin are improving diabetes management. These and related developments have fostered the discovery of novel insights into endocrine control of systemic metabolism, and in particular a deeper understanding of the importance of communication across vital organs, and specifically the gut-brain-pancreas-liver network. Paradoxically, the pancreatic peptide glucagon has reemerged in this period among a plethora of newly identified metabolic macromolecules, and new data complement and challenge its historical position as a gut hormone involved in metabolic control. The synthesis of glucagon analogs that are biophysically stable and soluble in aqueous solutions has promoted biological study that has enriched our understanding of glucagon biology and ironically recruited glucagon agonism as a central element to lower body weight in the treatment of metabolic disease. This review summarizes the extensive historical record and the more recent provocative direction that integrates the prominent role of glucagon in glucose elevation with its under-acknowledged effects on lipids, body weight, and vascular health that have implications for the pathophysiology of metabolic diseases, and the emergence of precision medicines to treat metabolic diseases.