Evaluation of the effect of multiple-dose administration of R411, a dual α4β1–α4β7 integrin antagonist on the major CYP isoform activities in healthy volunteers

Integrin signaling in cancer: bidirectional mechanisms and therapeutic opportunities

Integrins are transmembrane receptors that possess distinct ligand-binding specificities in the extracellular domain and signaling properties in the cytoplasmic domain. While most integrins have a short cytoplasmic tail, integrin β4 has a long cytoplasmic tail that can indirectly interact with the actin cytoskeleton. Additionally, 'inside-out' signals can induce integrins to adopt a high-affinity extended conformation for their appropriate ligands. These properties enable integrins to transmit bidirectional cellular signals, making it a critical regulator of various biological processes.Integrin expression and function are tightly linked to various aspects of tumor progression, including initiation, angiogenesis, cell motility, invasion, and metastasis. Certain integrins have been shown to drive tumorigenesis or amplify oncogenic signals by interacting with corresponding receptors, while others have marginal or even suppressive effects. Additionally, different α/β subtypes of integrins can exhibit opposite effects. Integrin-mediated signaling pathways including Ras- and Rho-GTPase, TGFβ, Hippo, Wnt, Notch, and sonic hedgehog (Shh) are involved in various stages of tumorigenesis. Therefore, understanding the complex regulatory mechanisms and molecular specificities of integrins are crucial to delaying cancer progression and suppressing tumorigenesis. Furthermore, the development of integrin-based therapeutics for cancer are of great importance.This review provides an overview of integrin-dependent bidirectional signaling mechanisms in cancer that can either support or oppose tumorigenesis by interacting with various signaling pathways. Finally, we focus on the future opportunities for emergent therapeutics based on integrin agonists. Video Abstract.

α4β7 integrin inhibitors: a patent review

INTRODUCTION

The α₄β₇ integrin is heterodimeric cell surface receptors expressed on most leukocytes. Mucosal addressing cell adhesion molecule 1(MAdCAM-1) is an exclusive ligand for α₄β₇ integrin. Areas covered: This article will highlight the progress that has been made in the discovery and development of α₄β₇ integrin inhibitors, and their use in the treatment of inflammatory bowel diseases, multiple sclerosis, asthma, hepatic disorders, human immunodeficiency virus, allergic conjunctivitis and type 1 diabetes. Expert opinion: α₄β₇ integrin inhibitors have attracted much interest for their clinical implication. Natalizumab and Vedolizumab are monoclonal antibodies (mAbs) successfully utilized clinically. Natalizumab is a mAbs of α₄-subunit blocking both α₄β₁ and α₄β₇ integrin. Vedolizumab selectively targets the α₄β₇ integrin. Several mAbs are still in the process of research and development. Among these mAbs, etrolizumab selectively against the β₇-subunit and AMG-181 specifically against the α₄β₇ integrin are the most promising anti-α₄β₇ integrin antibodies. Despite the unclear development stage of TR-14035 and R411, several low molecular compounds show bright future of further development, such as AJM300 and CDP323. In addition, results from laboratory data show that peptide inhibitors, such as peptide X, are effective α₄β₇ integrin inhibitors.

Role of integrin alpha4 in drug resistance of leukemia

Chemotherapeutic drug resistance in acute lymphoblastic leukemia (ALL) is a significant problem, resulting in poor responsiveness to first-line treatment or relapse after transient remission. Classical anti-leukemic drugs are non-specific cell cycle poisons; some more modern drugs target oncogenic pathways in leukemia cells, although in ALL these do not play a very significant role. By contrast, the molecular interactions between microenvironment and leukemia cells are often neglected in the design of novel therapies against drug resistant leukemia. It was shown however, that chemotherapy resistance is promoted in part through cell–cell contact of leukemia cells with bone marrow (BM) stromal cells, also called cell adhesion-mediated drug resistance (CAM-DR). Incomplete response to chemotherapy results in persistence of resistant clones with or without detectable minimal residual disease (MRD). Approaches for how to address CAM-DR and MRD remain elusive. Specifically, studies using anti-functional antibodies and genetic models have identified integrin alpha4 as a critical molecule regulating BM homing and active retention of normal and leukemic cells. Pre-clinical evidence has been provided that interference with alpha4-mediated adhesion of ALL cells can sensitize them to chemotherapy and thus facilitate eradication of ALL cells in an MRD setting. To this end, Andreeff and colleagues recently provided evidence of stroma-induced and alpha4-mediated nuclear factor-κB signaling in leukemia cells, disruption of which depletes leukemia cells of strong survival signals. We here review the available evidence supporting the targeting of alpha4 as a novel strategy for treatment of drug resistant leukemia.

Discontinued drugs in 2006: pulmonary-allergy, dermatological, gastrointestinal and arthritis drugs

This perspective is the second in a series discussing drugs dropped from development in 2006, with a focus on pulmonary-allergy, dermatological, gastrointestinal and arthritis drugs. A survey of discontinued drugs from 2006 is provided, based on data from the Pharmaprojects database, along with an analysis of biology, mechanisms of action and economic considerations in developing new drugs.

Targeting integrin structure and function in disease

Initially linked to the pathogenesis of inflammatory and hematologic diseases, integrins have become validated drug targets with the approval of five drugs. Moreover, there are several promising drug candidates in preclinical and clinical stages of development for multiple clinical indications. Integrins are attractive drug targets as their antagonism can block several steps in disease progression or maintenance. Integrin inhibitors can block the proliferation, migration, or tissue localization of inflammatory, angiogenic, and tumor cells, as well as signaling and gene expression contributing to disease. There has been a rapid increase in the elucidation of integrin structure, their allosteric mechanisms of bidirectional signaling, and the structure of complexes with drugs. This information brings greater focus to how integrins support various cellular functions and how they have been and may be targeted to develop novel drugs. Here we review conformational switches, including an internal ligand, which allosterically regulate the transition from low- to high-affinity ligand binding. We address some of the successes, disappointments, and challenges in targeting competitive or allosteric sites to develop therapeutics. We also discuss new opportunities, including a structure-based approach to discover novel drugs to treat inflammatory and other diseases. This approach targets structural relatives of the von Willebrand factor A-domain present in integrins and many functionally diverse proteins.