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

Cardiovascular Protective Properties of GLP-1 Receptor Agonists: More than Just Diabetic and Weight Loss Drugs

Owing to their potent glucose-lowering efficacy and substantial weight loss effects, glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are now considered part of the frontline therapeutic options to treat both type 2 diabetes mellitus and nondiabetic overweight/obesity. Stemming from successful demonstration of their cardiometabolic modulation and reduction of major adverse cardiovascular events in clinical outcome trials, GLP-1 RAs have since been validated as agents with compelling cardiovascular protective properties. Studies spanning from the bench to preclinical and large-scale randomised controlled trials have consistently corroborated the cardiovascular benefits of this pharmacological class. Most notably, there is converging evidence that they exert favourable effects on atherosclerotic ischaemic endpoints, with preclinical data indicating that they may do so by directly modifying the burden and composition of atherosclerotic plaques. This narrative review examines the underlying pharmacology and clinical evidence behind the cardiovascular benefits of GLP-1 RAs, with particular focus on atherosclerotic cardiovascular disease. It also delves into the mechanisms that underpin their putative plaque-modifying actions, addresses existing knowledge gaps and therapeutic challenges and looks to future developments in the field, including the use of combination incretin agents for diabetes and weight loss management.

Insight into the role of PCSK9 in glucose metabolism

Diabetes mellitus (DM) is strongly associated with an increased risk of atherosclerotic cardiovascular disease (ASCVD). Proprotein convertase subtilisin/kexin type 9 (PCSK9) was recently identified as an important regulator of circulating low-density lipoprotein-cholesterol (LDL-C) levels via degradation of the LDL receptor, proving to be a valid target to improve lipoprotein profiles and cardiovascular outcomes in patients with ASCVD. Beyond LDL receptor processing and cholesterol homeostasis, the PCSK9 protein has recently been verified to be associated with glucose metabolism. Importantly, clinical trials suggest that treatment with PCSK9 inhibitors for patients with DM is more effective. Hence, in this review, we summarize the current findings derived from experimental, preclinical, and clinical studies regarding the association between PCSK9 and glucose metabolism, including the relationship of PCSK9 genetic mutations to glucose metabolism and diabetes, the link between plasma PCSK9 concentrations and glucose metabolic parameters, the effects of glucose-lowering drugs on plasma PCSK9 levels and the impacts of PCSK9 inhibitors on cardiovascular outcomes of patients with DM. Clinically, exploring this field may improve our understanding regarding the roles of PCSK9 in glucose metabolism and may offer an in-depth interpretation of how PCSK9 inhibitors exert effects on the treatment of patients with DM.

Characterization of a Nanobody-Epitope Tag Interaction and Its Application for Receptor Engineering

Peptide epitope tags offer a valuable means for detection and manipulation of protein targets for which high quality detection reagents are not available. Most commonly used epitope tags are bound by conventional, full-size antibodies (Abs). The complex architecture of Abs complicates their application in protein engineering and intracellular applications. To address these shortcomings, single domain antibodies (nanobodies, Nbs) that recognize short peptide epitopes have become increasingly prized. Here, we characterize the interaction between a Nb (Nb6E) and a 14-mer peptide epitope. We identify residues in the peptide epitope essential for high affinity binding. Using this information in combination with computational modeling we propose a mode of interaction between Nb6E and this epitope. We apply this nanobody-epitope pair to augment the potency of a ligand at an engineered adenosine A2A receptor. This characterization of the nanobody-epitope pair opens the door to diverse applications including mechanistic studies of the G protein-coupled receptor function.

Selective vulnerability of tripartite synapses in amyotrophic lateral sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disorder. Separate lines of evidence suggest that synapses and astrocytes play a role in the pathological mechanisms underlying ALS. Given that astrocytes make specialised contacts with some synapses, called tripartite synapses, we hypothesise that tripartite synapses could act as the fulcrum of disease in ALS. To test this hypothesis, we have performed an extensive microscopy-based investigation of synapses and tripartite synapses in the spinal cord of ALS model mice and post-mortem human tissue from ALS cases. We reveal widescale synaptic changes at the early symptomatic stages of the SOD1^G93a mouse model. Super-resolution microscopy reveals that large complex postsynaptic structures are lost in ALS mice. Most surprisingly, tripartite synapses are selectively lost, while non-tripartite synapses remain in equal number to healthy controls. Finally, we also observe a similar selective loss of tripartite synapses in human post-mortem ALS spinal cords. From these data we conclude that tripartite synaptopathy is a key hallmark of ALS.

GLP-1 receptor agonists in diabetic kidney disease: current evidence and future directions

With the emergence of various classes of blood glucose-lowering agents, choosing the appropriate drug for each patient is emphasized in diabetes management. Among incretin-based drugs, glucagon-like peptide 1 (GLP-1) receptor agonists are a promising therapeutic option for patients with diabetic kidney disease (DKD). Several cardiovascular outcome trials have demonstrated that GLP-1 receptor agonists have beneficial effects on cardiorenal outcomes beyond their blood glucose-lowering effects in patients with type 2 diabetes mellitus (T2DM). The renal protective effects of GLP-1 receptor agonists likely result from their direct actions on the kidney, in addition to their indirect actions that improve conventional risk factors for DKD, such as reducing blood glucose levels, blood pressure, and body weight. Inhibition of oxidative stress and inflammation and induction of natriuresis are major renoprotective mechanisms of GLP-1 analogues. Early evidence from the development of dual and triple combination agents suggests that GLP-1 receptor agonists will probably become popular treatment options for patients with T2DM.

Engineering of an EpCAM-targeting cyclic peptide to improve the EpCAM-mediated cellular internalization and tumor accumulation of a peptide-fused antibody

Fusion of a target-specific peptide to a full-length antibody (Ab) can result in a peptide-Ab fusion protein with additional specificity and enhanced activity. We recently developed an intracellular pan-RAS-targeting cytosol-penetrating antibody, RT22-ep59, in which a tumor-specific targeting ability was achieved via the fusion of an epithelial cell adhesion molecule (EpCAM) targeting cyclic peptide (ep133). Here, the aim was to enhance EpCAM-mediated endocytosis and tumor accumulation of the peptide-fused RAS-targeting Ab. Accordingly, we engineered a cyclic peptide (from ep133) that has stronger affinity for EpCAM by using yeast surface display technology and then rationally designed cyclic peptides in the Ab-fused form to enhance colloidal stability. The finally engineered EpCAM-targeting cyclic peptide (ep₆)-fused Ab, ep₆Ras37, has ∼10-fold stronger affinity (K_D ≈ 1.9 nM) for EpCAM than that of RT22-ep59, without deterioration of biophysical properties. Compared with the parental antibody (RT22-ep59), ep₆Ras37 more efficiently reached the cytosol of EpCAM-expressing cells and showed greater preferential tumor homing and accumulation in mice bearing EpCAM-expressing LoVo xenograft tumors. Thus, the high-affinity EpCAM-targeting peptide ensures efficient cellular internalization and better tumor accumulation of the peptide-fused Ab.

Strategies for targeting cell surface proteins using multivalent conjugates and chemical biology

Proper function of receptors on the cell surface is essential for homeostasis. Compounds that target cell surface receptors to address dysregulation have proven exceptionally successful as therapeutic agents; however, the development of compounds with the desired specificity for receptors, cells, and tissues of choice has proven difficult in some cases. The use of compounds that can engage more than one binding site at the cell surface offers a path toward improving biological specificity or pharmacological properties. In this chapter we summarize historical context for the development of such bivalent compounds. We focus on developments in chemical methods and biological engineering to provide bivalent compounds in which the high affinity and specificity of antibodies are leveraged to create multifunctional conjugates with new and useful properties. The development of methods to meld biological macromolecules with synthetic compounds will facilitate modulation of receptor biology in ways not previously possible.

Increased Valency Improves Inhibitory Activity of Peptides Targeting Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9)

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a clinically validated target for treating hypercholesterolemia. Peptide-based PCSK9 inhibitors have attracted pharmaceutical interest, but the effect of multivalency on bioactivity is poorly understood. Here we designed bivalent and tetravalent dendrimers, decorated with the PCSK9 inhibitory peptides Pep2-8[RRG] or P9-38, to study relationships between peptide binding affinity, peptide valency, and PCSK9 inhibition. Increased valency resulted in improved PCSK9 inhibition for both peptides, with activity improvements of up to 100-fold achieved for the P9-38-decorated dendrimers compared to monomeric P9-38 in in vitro competition binding assays. Furthermore, the P9-38-decorated dendrimers showed improved potency at restoring functional low-density lipoprotein (LDL) receptor levels and internalizing LDL in the presence of PCSK9, demonstrating significant cell-based activity at picomolar concentrations. This study demonstrates the potential of increasing valency as a strategy for increasing the efficacy of peptide-based PCSK9 therapeutics.

Improved GPCR ligands from nanobody tethering

Antibodies conjugated to bioactive compounds allow targeted delivery of therapeutics to cell types of choice based on that antibody's specificity. Here we develop a new type of conjugate that consists of a nanobody and a peptidic ligand for a G protein-coupled receptor (GPCR), fused via their C-termini. We address activation of parathyroid hormone receptor-1 (PTHR1) and improve the signaling activity and specificity of otherwise poorly active N-terminal peptide fragments of PTH by conjugating them to nanobodies (VHHs) that recognize PTHR1. These C-to-C conjugates show biological activity superior to that of the parent fragment peptide in vitro. In an exploratory experiment in mice, a VHH-PTH peptide conjugate showed biological activity, whereas the corresponding free peptide did not. The lead conjugate also possesses selectivity for PTHR1 superior to that of PTH(1-34). This design approach, dubbed "conjugation of ligands and antibodies for membrane proteins" (CLAMP), can yield ligands with high potency and specificity.

Glucagon-like peptide 1 (GLP-1)

BACKGROUND

The glucagon-like peptide-1 (GLP-1) is a multifaceted hormone with broad pharmacological potential. Among the numerous metabolic effects of GLP-1 are the glucose-dependent stimulation of insulin secretion, decrease of gastric emptying, inhibition of food intake, increase of natriuresis and diuresis, and modulation of rodent β-cell proliferation. GLP-1 also has cardio- and neuroprotective effects, decreases inflammation and apoptosis, and has implications for learning and memory, reward behavior, and palatability. Biochemically modified for enhanced potency and sustained action, GLP-1 receptor agonists are successfully in clinical use for the treatment of type-2 diabetes, and several GLP-1-based pharmacotherapies are in clinical evaluation for the treatment of obesity.

SCOPE OF REVIEW

In this review, we provide a detailed overview on the multifaceted nature of GLP-1 and its pharmacology and discuss its therapeutic implications on various diseases.

MAJOR CONCLUSIONS

Since its discovery, GLP-1 has emerged as a pleiotropic hormone with a myriad of metabolic functions that go well beyond its classical identification as an incretin hormone. The numerous beneficial effects of GLP-1 render this hormone an interesting candidate for the development of pharmacotherapies to treat obesity, diabetes, and neurodegenerative disorders.

VHH characterization.Recombinant VHHs: Production, characterization and affinity

Among the biological approaches to therapeutics, are the cells, such as CAR-T cells engineered or not, the antibodies armed or not, and the smaller protein scaffolds that can be modified to render them specific of other proteins, à la façon of antibodies. For several years, we explored ways to substitute antibodies by nanobodies (also known as VHHs), the smallest recognizing part of camelids' heavy-chain antibodies: production of those small proteins in host microorganisms, minute analyses, characterization, and qualification of their affinity towards designed targets. Here, we present three standard VHHs described in the literature: anti-albumin, anti-EGF receptor and anti-HER2, a typical cancer cell surface -associated protein. Because they differ slightly in global structure, they are good models to assess our body of analytical methodologies. The VHHs were expressed in several bacteria strains in order to identify and overcome the bottlenecks to obtain homogeneous preparations of this protein. A large panel of biophysical tools, ranging from spectroscopy to mass spectrometry, was here combined to assess VHH structural features and the impact of the disulfide bond. The routes are now ready to move to more complex VHHs raised against specific targets in numerous areas including oncology.

An update on pharmacotherapies in diabetic dyslipidemia

Hyperlipidemia plays a crucial role in the underlying pathogenesis of multiple cardiovascular diseases (CVD), including coronary artery disease, peripheral arterial disease, carotid stenosis, and heart failure. The risk of developing such diseases in the diabetic population is relatively high. Diabetes mellitus (DM) is an independent risk factor for premature atherosclerosis. The hallmark of DM dyslipidemia is a demonstrably high level of atherogenic triglyceride rich lipids including very low-density lipoprotein, chylomicrons, and small dense low-density lipoprotein (LDL). Moderate to high intensity statins, targeting LDL cholesterol reduction, remain the cornerstone in the management of this unique disorder. Many 'non-statin' drugs have recently been studied in the DM patients who were either on a 'maximally tolerated statin' or 'statin intolerant'. Ezetimibe and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are particularly important and were incorporated in the recent guidelines by the European Society of Cardiology, American College of Cardiology, American Heart Association, and American Diabetes Association. Icosapent Ethyl has garnered huge interest this year following publication of the REDUCE-IT trial. There are several newer hypolipidemic drugs, including Bempedoic acid, Inclisiran and RVX-208, that are in different phases of clinical trials. In this article, we review the underlying pathophysiology of DM dyslipidemia, existing guidelines related to its management, and the potential of newer hypolipidemic and anti-inflammatory drugs being incorporated in the management of DM.