Exploring N-Arylsulfonyl-l-proline Scaffold as a Platform for Potent and Selective αvβ1 Integrin Inhibitors

Small molecule- and peptide-drug conjugates addressing integrins: A story of targeted cancer treatment

Targeted cancer treatment should avoid side effects and damage to healthy cells commonly encountered during traditional chemotherapy. By combining small molecule or peptidic ligands as homing devices with cytotoxic drugs connected by a cleavable or non-cleavable linker in peptide-drug conjugates (PDCs) or small molecule-drug conjugates (SMDCs), cancer cells and tumours can be selectively targeted. The development of highly affine, selective peptides and small molecules in recent years has allowed PDCs and SMDCs to increasingly compete with antibody-drug conjugates (ADCs). Integrins represent an excellent target for conjugates because they are overexpressed by most cancer cells and because of the broad knowledge about native binding partners as well as the multitude of small-molecule and peptidic ligands that have been developed over the last 30 years. In particular, integrin αVβ3 has been addressed using a variety of different PDCs and SMDCs over the last two decades, following various strategies. This review summarises and describes integrin-addressing PDCs and SMDCs while highlighting points of great interest.

Design and Discovery of a Potent and Selective Inhibitor of Integrin αvβ1

Selective inhibition of the RGD (Arg-Gly-Asp) integrin αvβ1 has been recently identified as an attractive therapeutic approach for the treatment of liver fibrosis given its function, target expression, and safety profile. Our identification of a non-RGD small molecule lead followed by focused, systematic changes to the core structure utilizing a crystal structure, in silico modeling, and a tractable synthetic approach resulted in the identification of a potent small molecule exhibiting a remarkable affinity for αvβ1 relative to several other integrin isoforms measured. Azabenzimidazolone 25 demonstrated antifibrotic efficacy in an in vivo rat liver fibrosis model and represents a tool compound capable of further exploring the biological consequences of selective αvβ1 inhibition.

Discovery of the novel Benzo[b]thiophene 1,1-dioxide derivatives as a potent STAT3 inhibitor against idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disease of unknown aetiology with limited treatment options. Currently, only two drugs, nintedanib and pirfenidone, are approved for the clinical treatment of IPF, but their efficacies are not satisfactory. Previous studies have shown that STAT3 might be a promising therapeutic target for IPF. Here, we designed several series of compounds and finally synthesized a total of 48 novel compounds as potential STAT3 inhibitors. Notably, compound 10K was the most promising compound with excellent inhibitory activity against STAT3 phosphorylation. Subsequently, the anti-pulmonary fibrosis effect of 10K was further investigated by TGF-β1-stimulated in vitro cell assay and bleomycin (BLM)-induced pulmonary fibrosis animal models. Specifically, compound 10K inhibited the TGF-β1 induced fibrotic response and blocked the epithelial-mesenchymal transition (EMT) of A549 cells, and its inhibitory effect was significantly better than that of Stattic. In addition, after oral administration of 10K, the symptoms of IPF in the lung tissue in the prevention and treatment mouse models were significantly reversed, and the efficacy was comparable to that of nintedanib. Moreover, 10K improved BLM-induced imbalance of immune microenvironment in lung tissue. Taken together, these results suggest that 10K could be a potential STAT3 inhibitor for the treatment of IPF.

Emerging therapeutic opportunities for integrin inhibitors

Integrins are cell adhesion and signalling proteins crucial to a wide range of biological functions. Effective marketed treatments have successfully targeted integrins αIIbβ3, α4β7/α4β1 and αLβ2 for cardiovascular diseases, inflammatory bowel disease/multiple sclerosis and dry eye disease, respectively. Yet, clinical development of others, notably within the RGD-binding subfamily of αv integrins, including αvβ3, have faced significant challenges in the fields of cancer, ophthalmology and osteoporosis. New inhibitors of the related integrins αvβ6 and αvβ1 have recently come to the fore and are being investigated clinically for the treatment of fibrotic diseases, including idiopathic pulmonary fibrosis and nonalcoholic steatohepatitis. The design of integrin drugs may now be at a turning point, with opportunities to learn from previous clinical trials, to explore new modalities and to incorporate new findings in pharmacological and structural biology. This Review intertwines research from biological, clinical and medicinal chemistry disciplines to discuss historical and current RGD-binding integrin drug discovery, with an emphasis on small-molecule inhibitors of the αv integrins.

Integrins are key signalling molecules that are present on the surface of subsets of cells and are therefore good potential therapeutic targets. In this Review, Hatley and colleagues discuss the development of integrin inhibitors, particularly the challenges in developing inhibitors for integrins that contain an αv-subunit, and suggest how these challenges could be addressed.

Inhibition of Cancer Cell Adhesion, Migration and Proliferation by a Bispecific Antibody that Targets two Distinct Epitopes on αv Integrins

Members of the αv family of integrins regulate activation of transforming growth factor beta (TGFβ) and are directly involved in pro-tumorigenic phenotypes. Thus, αv integrins may be therapeutic targets for fibrosis and cancer, yet the isolation of selective inhibitors is currently a challenge. We generated synthetic antibodies selective for αv integrins by phage display selections on cell lines that displayed integrin heterodimers. We identified antibodies that targeted two distinct epitopes on cell-surface αv integrins and partially inhibited cell adhesion mediated by interactions between integrins and the latency-associated peptide, part of the pro-form of TGFβ. Using the isolated antibody paratope sequences we engineered a bispecific antibody capable of binding to both epitopes simultaneously; this antibody potently and completely inhibited cell adhesion mediated by integrins αvβ1, αvβ3 and αvβ5. In addition, the bispecific antibody inhibited proliferation and migration of lung carcinoma lines, where the highest and lowest potencies observed correlated with integrin-αv cell surface expression levels. Taken together, our results demonstrate that phage display selections with live cells can yield high quality anti-integrin antibodies, which we used as biparatopic building blocks to construct a bispecific antibody that strongly inhibited integrin function and may be a therapeutic candidate for cancer and fibrosis.

Targeting the TGF-β signaling pathway for fibrosis therapy: a patent review (2015-2020)

INTRODUCTION

Fibrosis is a serious disease that occurs in many organs, such as kidney, liver and lung. The deterioration of these organs ultimately leads to death. Due to the complex mechanisms of fibrosis, research and development of antifibrotic drugs is difficult. One solution is to focus on core pathways, one of which is the TGF-β signaling pathway. In virtually every type of fibrosis, TGF-β signaling is recognized as a critical pathway.

AREA COVERED

This review discusses patents on active molecules related to the TGF-β signaling. Molecules targeting components related to the activation of TGF-β are introduced. Several strategies preventing signal propagation from active TGF-β to downstream targets are also introduced, including TGF-β antibodies, TGF-β ligand traps, and inhibitors of TGF-β receptor kinases. Finally, molecules affecting downstream targets in both canonical and noncanonical TGF-β signaling pathways are described.

EXPERT OPINION

Since the approval of pirfenidone, targeting TGF-β signaling has been anticipated as an effective therapy for fibrosis. The potential of this therapy has been further supported by emerging patents on the TGF-β signaling. This pathway can be entirely inhibited, from the activation of TGF-β to downstream signaling. Inhibiting TGF-β signaling is expected to provide more effective treatments for fibrosis.

Dual antagonists of α5β1/αvβ1 integrin for airway hyperresponsiveness

Inhibition of integrin α5β1 emerges as a novel therapeutic option to block transmission of contractile forces during asthma attack. We designed and synthesized novel inhibitors of integrin α5β1 by backbone replacement of known αvβ1 integrin inhibitors. These integrin α5β1 inhibitors also retain the nanomolar potency against αvβ1 integrin, which shows promise for developing dual integrin α5β1/αvβ1 inhibitor. Introduction of hydrophobic adamantane group significantly boosted the potency as well as selectivity over integrin αvβ3. We also demonstrated one of the inhibitors (11) reduced airway hyperresponsiveness in ex vivo mouse tracheal ring assay. Results from this study will help guide further development of integrin α5β1 inhibitors as potential novel asthma therapeutics.

Therapeutic molecular targets of SSc-ILD

Systemic sclerosis is a fibrosing chronic connective tissue disease of unknown etiology. A major hallmark of systemic sclerosis is the uncontrolled and persistent activation of fibroblasts, which release excessive amounts of extracellular matrix, lead to organ dysfunction, and cause high mobility and motility of patients. Systemic sclerosis–associated interstitial lung disease is one of the most common fibrotic organ manifestations in systemic sclerosis and a major cause of death. Treatment options for systemic sclerosis–associated interstitial lung disease and other fibrotic manifestations, however, remain very limited. Thus, there is a huge medical need for effective therapies that target tissue fibrosis, vascular alterations, inflammation, and autoimmune disease in systemic sclerosis–associated interstitial lung disease. In this review, we discuss data suggesting therapeutic ways to target different genes in distinct tissues/organs that contribute to the development of SSc.

The Design of Potent, Selective and Drug-Like RGD αvβ1 Small-Molecule Inhibitors Derived from non-RGD α4β1 Antagonists

Up to 45 % of deaths in developed nations can be attributed to chronic fibroproliferative diseases, highlighting the need for effective therapies. The RGD (Arg-Gly-Asp) integrin αvβ1 was recently investigated for its role in fibrotic disease, and thus warrants therapeutic targeting. Herein we describe the identification of non-RGD hit small-molecule αvβ1 inhibitors. We show that αvβ1 activity is embedded in a range of published α4β1 (VLA-4) ligands; we also demonstrate how a non-RGD integrin inhibitor (of α4β1 in this case) was converted into a potent non-zwitterionic RGD integrin inhibitor (of αvβ1 in this case). We designed urea ligands with excellent selectivity over α4β1 and the other αv integrins (αvβ3, αvβ5, αvβ6, αvβ8). In silico docking models and density functional theory (DFT) calculations aided the discovery of the lead urea series.

Initial osteoblast adhesion and subsequent differentiation on zirconia surfaces are regulated by integrins and heparin-sensitive molecule

Purpose

It is well known that zirconia materials have good biocompatibility; however, little is known regarding the mechanism by which cells attach to these materials. The purpose of this study is to elucidate the mechanism of cell attachment.

Materials and methods

In this study, we examined the surface characteristics of ceria-stabilized zirconia/alumina nanocomposite (NANOZR), yttria-stabilized zirconia (Y-TZP) and commercially pure titanium (CpTi), and we evaluated the initial response of osteoblast-like cells to them with different inhibitors.

Results

Under the same polishing treatment, the three materials, NANOZR, Y-TZP and CpTi, show similar surface wettability but different surface roughness. Osteoblasts could adhere to the surface of all three materials, and spindle shapes were clearer in serum-containing media compared to PBS and serum-free culture media, suggesting that serum-contained proteins are helpful for the initial cell adhesion and spreading. Cell adhesion and proliferation were disrupted in the presence of EDTA. RGD-peptide interfered with cell proliferation by affecting cell protrusion and stress fibers. Monoclonal antibody against non-RGD type integrin α₂β₁ enhanced proliferation in Y-TZP, CpTi and culture dish but not in NANOZR. Cell proliferation on NANOZR was specifically inhibited in the presence of heparin. Furthermore, under heparin administration, spindle shape formation was maintained but actin cytoskeleton was disrupted, resulting in loose cellular spreading.

Conclusion

These results suggest that RGD type integrins and heparin-sensitive protein in coordination regulate cell morphology and proliferation on NANOZR, through the regulation of cell polarity and stress fiber formation, respectively.

Thrombospondin-1 regulation of latent TGF-β activation: A therapeutic target for fibrotic disease

Transforming growth factor-β (TGF-β) is a central player in fibrotic disease. Clinical trials with global inhibitors of TGF-β have been disappointing, suggesting that a more targeted approach is warranted. Conversion of the latent precursor to the biologically active form of TGF-β represents a novel approach to selectively modulating TGF-β in disease, as mechanisms employed to activate latent TGF-β are typically cell, tissue, and/or disease specific. In this review, we will discuss the role of the matricellular protein, thrombospondin 1 (TSP-1), in regulation of latent TGF-β activation and the use of an antagonist of TSP-1 mediated TGF-β activation in a number of diverse fibrotic diseases. In particular, we will discuss the TSP-1/TGF-β pathway in fibrotic complications of diabetes, liver fibrosis, and in multiple myeloma. We will also discuss emerging evidence for a role for TSP-1 in arterial remodeling, biomechanical modulation of TGF-β activity, and in immune dysfunction. As TSP-1 expression is upregulated by factors induced in fibrotic disease, targeting the TSP-1/TGF-β pathway potentially represents a more selective approach to controlling TGF-β activity in disease.

Rhodium(III)-Catalyzed Oxadiazole-Directed Alkenyl C-H Activation for Synthetic Access to 2-Acylamino and 2-Amino Pyridines

We report herein a Rh(III)-catalyzed alkenyl C-H activation protocol for the coupling of oxadiazoles with alkynes and synthesis of 2-acylamino and 2-amino pyridines, an important heterocyclic scaffold for various naturals products and synthetic pharmaceuticals bearing a readily reacting functional group. The selective protection/deprotection of amino groups through simple solvent switching, good functional group compatibility, superior product yield, and high regioselectivity are some of the notable synthetic features witnessed in this reaction protocol.

RGD-Binding Integrins in Head and Neck Cancers

Alterations in integrin expression and function promote tumour growth, invasion, metastasis and neoangiogenesis. Head and neck cancers are highly vascular tumours with a tendency to metastasise. They express a wide range of integrin receptors. Expression of the αv and β1 subunits has been explored relatively extensively and linked to tumour progression and metastasis. Individual receptors αvβ3 and αvβ5 have proved popular targets for diagnostic and therapeutic agents but lesser studied receptors, such as αvβ6, αvβ8, and β1 subfamily members, also show promise. This review presents the current knowledge of integrin expression and function in squamous cell carcinoma of the head and neck (HNSCC), with a particular focus on the arginine-glycine-aspartate (RGD)-binding integrins, in order to highlight the potential of integrins as targets for personalised tumour-specific identification and therapy.