Selective alpha4beta7 integrin antagonists and their potential as antiinflammatory agents

Exploring Integrin α5β1 as a Potential Therapeutic Target for Pulmonary Arterial Hypertension: Insights from Comprehensive Multicenter Preclinical Studies

Pulmonary arterial hypertension (PAH) is characterized by obliterative vascular remodeling of the small pulmonary arteries (PA) and progressive increase in pulmonary vascular resistance (PVR) leading to right ventricular (RV) failure. Although several drugs are approved for the treatment of PAH, mortality remains high. Accumulating evidence supports a pathological function of integrins in vessel remodeling, which are gaining renewed interest as drug targets. However, their role in PAH remains largely unexplored. We found that the arginine-glycine-aspartate (RGD)-binding integrin α5β1 is upregulated in PA endothelial cells (PAEC) and PA smooth muscle cells (PASMC) from PAH patients and remodeled PAs from animal models. Blockade of the integrin α5β1 or depletion of the α5 subunit resulted in mitotic defects and inhibition of the pro-proliferative and apoptosis-resistant phenotype of PAH cells. Using a novel small molecule integrin inhibitor and neutralizing antibodies, we demonstrated that α5β1 integrin blockade attenuates pulmonary vascular remodeling and improves hemodynamics and RV function in multiple preclinical models. Our results provide converging evidence to consider α5β1 integrin inhibition as a promising therapy for pulmonary hypertension.

One sentence summary

The α5β1 integrin plays a crucial role in pulmonary vascular remodeling.

Alpha4 beta7 integrin controls Th17 cell trafficking in the spinal cord leptomeninges during experimental autoimmune encephalomyelitis

Th1 and Th17 cell migration into the central nervous system (CNS) is a fundamental process in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis (MS). Particularly, leptomeningeal vessels of the subarachnoid space (SAS) constitute a central route for T cell entry into the CNS during EAE. Once migrated into the SAS, T cells show an active motility behavior, which is a prerequisite for cell-cell communication, in situ reactivation and neuroinflammation. However, the molecular mechanisms selectively controlling Th1 and Th17 cell trafficking in the inflamed leptomeninges are not well understood. By using epifluorescence intravital microscopy, we obtained results showing that myelin-specific Th1 and Th17 cells have different intravascular adhesion capacity depending on the disease phase, with Th17 cells being more adhesive at disease peak. Inhibition of αLβ2 integrin selectively blocked Th1 cell adhesion, but had no effect on Th17 rolling and arrest capacity during all disease phases, suggesting that distinct adhesion mechanisms control the migration of key T cell populations involved in EAE induction. Blockade of α4 integrins affected myelin-specific Th1 cell rolling and arrest, but only selectively altered intravascular arrest of Th17 cells. Notably, selective α4β7 integrin blockade inhibited Th17 cell arrest without interfering with intravascular Th1 cell adhesion, suggesting that α4β7 integrin is predominantly involved in Th17 cell migration into the inflamed leptomeninges in EAE mice. Two-photon microscopy experiments showed that blockade of α4 integrin chain or α4β7 integrin selectively inhibited the locomotion of extravasated antigen-specific Th17 cells in the SAS, but had no effect on Th1 cell intratissue dynamics, further pointing to α4β7 integrin as key molecule in Th17 cell trafficking during EAE development. Finally, therapeutic inhibition of α4β7 integrin at disease onset by intrathecal injection of a blocking antibody attenuated clinical severity and reduced neuroinflammation, further demonstrating a crucial role for α4β7 integrin in driving Th17 cell-mediated disease pathogenesis. Altogether, our data suggest that a better knowledge of the molecular mechanisms controlling myelin-specific Th1 and Th17 cell trafficking during EAE delevopment may help to identify new therapeutic strategies for CNS inflammatory and demyelinating diseases.

Liposomal Targeting Modifies Endosomal Escape: Design and Mechanistic Implications

Development of effective targeted nanoparticle (TNP) therapeutics requires rational design of targeted and endosomolytic moieties. Nevertheless, endosomal escape of TNPs is poorly understood, relying on extrapolation of knowledge from nontargeted (NP) systems. Here, we describe how incorporation of targeting elements on endosomolytic nanoparticles alters the endosomal escape mechanism. We demonstrated that NP and TNP systems react differently to addition of precise length oligohistidines and showcase the effects of alternating spatial arrangements of targeting and endosomolytic elements. The results established that these elements act cooperatively and must be incorporated as individual moieties, rather than a single multifunctional moiety, for optimal internalization by target cells.

Identification and optimization of tunable endosomal escape parameters for enhanced efficacy in peptide-targeted prodrug-loaded nanoparticles

Endosomal escape of nanoparticles (NPs) is a weighty consideration for engineering successful nanomedicines. Although it is well-established that incorporation of histidine (His) in particle design improves endosomal escape for NPs, our understanding of its effects for ligand-targeted nanoparticles (TNPs) remains incomplete. Here, we systematically evaluated the cooperativity between targeting ligands and endosomolytic elements using liposomal TNPs with precise stoichiometric control over functional moieties (>90% loading efficiency). We synthesized endosomolytic lipid conjugates consisting of 1 to 10 consecutive His residues presented at the end of linkers between 2 to 45 repeating units of ethylene glycol (His_n-EG_m). His_n-EG_m had minimal effect on NP size (∼115 nm) and had no significant effect on the receptor specificity of TNPs (>90% inhibition by competing peptide). We evaluated various formulations with 8 different targeting ligands relevant to two disease models. Incorporation of His₁-EG₈ resulted in up to ∼170- and ∼12.9-fold enhancement in intracellular accumulation relative to non-endosomolytic NP and TNP, respectively. These observations were time-dependent, targeted receptor-dependent, and showed different trends for NPs and TNPs. Further evaluation demonstrated short linkers (EG_2-4) significantly enhanced nanoparticle internalization compared to EG₈ or longer by up to ∼2.5-fold. Finally, rationally optimized formulation, His₁-EG₂-TNP, improved in vitro toxicity of a DM1 prodrug to SK-BR-3 cells by ∼4.2-fold, with IC₅₀ ∼8.5 nM compared to ∼36 nM for no-His TNP, and >100 nM for non-targeted/no-His NP. This study uncovers an intricate relationship between endosomal escape and ligand-targeted drug delivery, as well as tunable parameters. Furthermore, our findings highlight the value of rational design and systematic analysis for optimization of multifunctional NPs.

Novel inhibitors of leukocyte transendothelial migration

Leukocyte transendothelial migration is one of the most important step in launching an inflammatory immune response and chronic inflammation can lead to devastating diseases. Leukocyte migration inhibitors are considered as promising and potentially effective therapeutic agents to treat inflammatory and auto-immune disorders. In this study, based on previous trioxotetrahydropyrimidin based integrin inhibitors that suboptimally blocked leukocyte adhesion, twelve molecules with a modified scaffold were designed, synthesized, and tested in vitro for their capacity to block the transendothelial migration of immune cells. One of the molecules, namely, methyl 4-((2-(tert-butyl)-6-((2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene) methyl) phenoxy) methyl) benzoate, (compound 12), completely blocked leukocyte transendothelial migration, without any toxic effects on immune or endothelial cells (IC₅₀ = 2.4 µM). In vivo, compound 12 exhibited significant therapeutic effects in inflammatory bowel disease (IBD)/Crohn's disease, multiple sclerosis, fatty liver disease, and rheumatoid arthritis models. A detailed acute and chronic toxicity profile of the lead compound in vivo did not reveal any toxic effects. Such a type of molecule might therefore provide a unique starting point for designing a novel class of leukocyte transmigration blocking agents with broad therapeutic applications in inflammatory and auto-immune pathologies.

Optimizing design parameters of a peptide targeted liposomal nanoparticle in an in vivo multiple myeloma disease model after initial evaluation in vitro

Despite ligand-targeted liposomes long garnering interest as drug delivery vehicles for cancer therapeutics, inconsistency in successful outcomes have hindered their translation into the clinic. This is in part due to discrepancies between in vitro design evaluations and final in vivo outcomes. By employing a multifaceted synthetic strategy to prepare peptide-targeted nanoparticles of high purity, reproducibility, and with precisely controlled quantity of functionalities, we systematically evaluated the individual roles that peptide-linker length, peptide hydrophilicity, peptide density, and nanoparticle size play on cancer cell uptake and tumor targeting both in vitro and in vivo, and how the results correlated and contrasted. These parameters were analyzed using a VLA-4-targeted liposome system in a multiple myeloma mouse xenograft model to evaluate in vivo biodistribution and tumor cell uptake. The results showed that using in vitro models to optimize targeted-nanoparticles for maximum cellular uptake was helpful in narrowing down the particle characteristics. However, in vitro optimization fell short of achieving enhanced results in animal models, rather had negative consequences for in vivo targeting. This outcome is not surprising considering that the receptor being targeted is also present on healthy lymphocytes and increasing targeting peptide valency on particle surfaces results in an increase in non-selective, off-target binding to healthy cells. Hence, further optimization using in vivo models was absolutely necessary, through which we were able to increase the uptake of peptide-targeted liposomes by cancerous cells overexpressing VLA-4 to 15-fold over that of non-targeted liposomes in vivo. The results highlighted the importance of creating a comprehensive understanding of the effect of each liposome design parameter on multifactorial biological endpoints including both in vitro and in vivo in determining the therapeutic potential of peptide-targeted liposomes.

Dual-receptor targeted strategy in nanoparticle design achieves tumor cell selectivity through cooperativity

Targeted liposomal nanoparticles are commonly used drug delivery vehicles for targeting cancer cells that overexpress a particular cell surface receptor. However, typical target receptors are also expressed at variable levels in healthy tissue, leading to non-selective targeting and systemic toxicity. Here, we demonstrated that the selectivity of peptide-targeted liposomes for their target cells can be significantly enhanced by employing a dual-receptor targeted approach to simultaneously target multiple tumor cell surface receptors. The dual-receptor targeted approach can be tuned to create cooperativity in binding only for the cancer cells, therefore leaving the healthy cells and tissue unharmed. We evaluated this strategy in a multiple myeloma disease model where the liposomes were functionalized with two distinct peptide antagonists to target VLA-4 and LPAM-1, two receptors with increasing relevance in multiple myeloma. By employing a multifaceted strategy to synthesize dual-receptor targeted liposomes with high purity, reproducibility, and precisely controlled stoichiometry of functionalities, we identified optimal design parameters for enhanced selectivity via systematic analysis. Through control of the liposomal formulation and valency of each targeting peptide, we identified that the optimal dual-receptor targeted liposome consisted of a peptide density of 0.75% VLA4pep and 1% LPAM1pep, resulting in an 8-fold and 12-fold increased cellular uptake over VLA-4 and LPAM-1 single targeted liposomes respectively. This formulation resulted in a cooperative ratio of 4.3 and enhanced uptake for myeloma cells that simultaneously express both VLA-4 and LPAM-1 receptors, but displayed no increase in uptake for cells that express only one or neither of the receptors, resulting in a 28-fold selectivity of the dual-targeted liposomes for cells displaying both targeted receptors over cells displaying neither receptor. These results demonstrated that through refined design and well-characterized nanoparticle formulations, dual-receptor targeted liposomes have the potential to improve cancer therapy by providing enhanced selectivity over conventional single-receptor targeted approaches.

Liver fibrosis: Direct antifibrotic agents and targeted therapies

Liver fibrosis and in particular cirrhosis are the major causes of morbidity and mortality of patients with chronic liver disease. Their prevention or reversal have become major endpoints in clinical trials with novel liver specific drugs. Remarkable progress has been made with therapies that efficiently address the cause of the underlying liver disease, as in chronic hepatitis B and C. Highly effective antiviral therapy can prevent progression or even induce reversal in the majority of patients, but such treatment remains elusive for the majority of liver patients with advanced alcoholic or nonalcoholic steatohepatitis, genetic or autoimmune liver diseases. Moreover, drugs that would speed up fibrosis reversal are needed for patients with cirrhosis, since even with effective causal therapy reversal is slow or the disease may further progress. Therefore, highly efficient and specific antifibrotic agents are needed that can address advanced fibrosis, i.e., the detrimental downstream result of all chronic liver diseases. This review discusses targeted antifibrotic therapies that address molecules and mechanisms that are central to fibrogenesis or fibrolysis, including strategies that allow targeting of activated hepatic stellate cells and myofibroblasts and other fibrogenic effector cells. Focus is on collagen synthesis, integrins and cells and mechanisms specific including specific downregulation of TGFbeta signaling, major extracellular matrix (ECM) components, ECM-crosslinking, and ECM-receptors such as integrins and discoidin domain receptors, ECM-crosslinking and methods for targeted delivery of small interfering RNA, antisense oligonucleotides and small molecules to increase potency and reduce side effects. With an increased understanding of the biology of the ECM and liver fibrosis and an improved preclinical validation, the translation of these approaches to the clinic is currently ongoing. Application to patients with liver fibrosis and a personalized treatment is tightly linked to the development of noninvasive biomarkers of fibrosis, fibrogenesis and fibrolysis.

South African HIV-1 subtype C transmitted variants with a specific V2 motif show higher dependence on α4β7 for replication

Background

The integrin α4β7 mediates the trafficking of immune cells to the gut associated lymphoid tissue (GALT) and is an attachment factor for the HIV gp120 envelope glycoprotein. We developed a viral replication inhibition assay to more clearly evaluate the role of α4β7 in HIV infection and the contribution of viral and host factors.

Results

Replication of 60 HIV-1 subtype C viruses collected over time from 11 individuals in the CAPRISA cohort were partially inhibited by antibodies targeting α4β7. However, dependence on α4β7 for replication varied substantially among viral isolates from different individuals as well as over time in some individuals. Among 8 transmitted/founder (T/F) viruses, α4β7 reactivity was highest for viruses having P/SDI/V tri-peptide binding motifs. Mutation of T/F viruses that had LDI/L motifs to P/SDI/V resulted in greater α4β7 reactivity, whereas mutating P/SDI/V to LDI/L motifs was associated with reduced α4β7 binding. P/SDI/V motifs were more common among South African HIV subtype C viruses (35%) compared to subtype C viruses from other regions of Africa (<8%) and to other subtypes, due in part to a founder effect. In addition, individuals with bacterial vaginosis (BV) and who had higher concentrations of IL-7, IL-8 and IL-1α in the genital tract had T/F viruses with higher α4β7 dependence for replication, suggesting that viruses with P/SDI/V motifs may be preferentially transmitted in the presence of BV in this population.

Conclusions

Collectively, these data suggest a role for α4β7 in HIV infection that is influenced by both viral and host factors including the sequence of the α4β7 binding motif, the cytokine milieu and BV in the genital tract. The higher frequency of P/SDI/V sequences among South African HIV-1 subtype C viruses may have particular significance for the role of α4β7 in this geographical region.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-015-0183-3) contains supplementary material, which is available to authorized users.

Dehydro-β-proline Containing α4β1 Integrin Antagonists: Stereochemical Recognition in Ligand-Receptor Interplay

A novel class of dehydro-β-proline-containing peptidomimetics, designed to be effective as α4β1 integrin ligands, has been developed on the basis of the fundamental requirements for the interactions of these transmembrane receptors with bioactive ligands. Dehydro-β-proline ring has been synthesized through an original pathway, involving ring closing metathesis of a diallylamino derivative. The synthesized products showed to be effective and selective as α4β1 integrin antagonists and displayed IC50 values in the nanomolar range in cell adhesion inhibition assays and in VCAM-1-induced phosphorylation of extracellular-signal-regulated kinases. Significant activity was observed also toward the homologous integrin α4β7, while they did not display any activity toward selected members of β1, β2, and β3 families. A strong dependence on the stereochemistry of the heterocyclic central core could be observed. The great importance of α4β1 integrin in chronic inflammatory and autoimmune diseases suggests a possible exploitation of these ligands as lead compounds for therapeutic tools development.

Changes in the integrins expression are related with the osteoarthritis severity in an experimental animal model in rats

We identify changes in the expression and localization of α5, α4, and α2 integrins during osteoarthritis (OA) pathogenesis in a rat experimental model. The changes were concomitant with variations in the extracellular matrix (ECM) content and the increase of metalloproteinases (MMPs) activity during OA pathogenesis, which were analyzed by immunofluorescence and Western blot assays. Our results showed an increased expression of α5 and α2 integrins at OA late stages, which was co-related with changes in the ECM content, as a consequence of the MMPs activity. In addition, this is the first report that has shown the presence of α4 integrin since OA early stages, which was co-related with the loss of proteoglycans and clusters formation. However, at late OA stages, the increased expression of α4 integrin in the middle and deep zones of the cartilage was also co-related with the abnormal endochondral ossification of the cartilage through its interaction with osteopontin. Finally, we conclude that ECM-chondrocytes interaction through specific cell receptors is essential to maintain the cartilage homeostasis. However, due to integrins cell signaling is ligand-dependent; changes in the ECM contents could induce activation of either anabolic or catabolic processes, which limits the reparative capacity of chondrocytes, favoring OA severity.

Role of integrins in fibrosing liver diseases

Integrins and other cell adhesion molecules regulate numerous physiological and pathological mechanisms by mediating the interaction between cells and their extracellular environment. Although the significance of integrins in the evolution and progression of certain cancers is well recognized, their involvement in nonmalignant processes, such as organ fibrosis or inflammation, is only beginning to emerge. However, accumulating evidence points to an instrumental role of integrin-mediated signaling in a variety of chronic and acute noncancerous diseases, particularly of the liver.

Both Th1 and Th17 are immunopathogenic but differ in other key biological activities

The role of Th17 lymphocytes in immunopathogenic processes has been well established, but little is known about their basic cell features. In this study, we compared polarized Th1 and Th17 for key biological activities related to pathogenicity and trafficking. Th1 and Th17 lineages were derived from TCR-transgenic CD4 murine cells specific against hen egg lysozyme. When adoptively transferred into mice expressing hen egg lysozyme in their eyes, both Th1 and Th17 induced ocular inflammation but with slight differences in histological pathology. PCR analysis revealed selective expression of IFN-gamma or IL-17 in eyes of Th1 or Th17 recipients, respectively. Additionally, Th1 and Th17 were found to differ in three other key activities: 1) Th17 cells were inferior to Th1 cells in their capacity to trigger massive lymphoid expansion and splenomegaly; 2) the proportion of Th1 cells among infiltrating cells in inflamed recipient eyes declined rapidly, becoming a minority by day 7, whereas Th17 cells remained in the majority throughout this period; and 3) remarkable differences were noted between Th1 and Th17 cells in their expression of certain surface markers. In particular, reactivated Th1 expressed higher levels of CD49d and alpha(4)beta(7) (mucosal homing) in vitro and higher levels of CXCR3 (Th1 trafficking) in vivo. Reactivated Th17, however, expressed higher levels of alpha(E)beta(7) (epithelial tissue homing) and CD38 (activation, maturation and trafficking) in vitro, but in vivo Th17 expressed higher levels of alpha(4)beta(7) and CCR6 (lymphocyte trafficking). These data reveal that Th1 and Th17 cells differ in several key biological activities influencing migration and pathogenic behavior during inflammatory disease.

An in vivo approach to structure activity relationship analysis of peptide ligands

PURPOSE

The goals in this study were several-fold. First, to optimize the in vivo phage display methodology by incorporating phage pharmacokinetic properties, to isolate peptides that target the brain microvasculature, and then to build focused libraries to obtain structure activity relationship information in vivo to identify the optimal targeting motif.

MATERIALS AND METHODS

The blood pharmacokinetics of filamentous and T7 phage were evaluated to choose the optimal platform. A randomized peptide library with a motif CX(10)C was constructed in T7 phage and used for in vivo panning. Focused peptide libraries around each structural element of the brain-specific peptide were constructed to perform kinetic structure activity relationship (kSAR) analysis in vivo. To determine potential function, sepsis was induced in mice by LPS administration and four hours later the effect of GST-peptide on adhesion of rhodamine-labelled lymphocytes or CFDA-labelled platelets to pial microvasculature was observed by intravital microscopy.

RESULTS

The blood phamacokinetics of T7 was rapid (half-life of 12 min) which aids the clearance of non-specific phage. In vivo panning in brain enriched for isolates expressing the motif CAGALCY. Kinetic analysis of focused libraries built around each structural element of the peptide provided for rapid pharmacophore mapping. The computer modeling data suggested the peptide showed similarities to peptide mimetics of adhesion molecule ligands. GST-CAGALCY but not GST control protein was able to inhibit the rolling and adhesion of labeled platelets to inflamed pial vasculature. GST-CAGALCY had no effect on lymphocyte adhesion.

CONCLUSIONS

Incorporating normal blood phamacokinetics of T7 phage into in vivo phage display improves the ability to recover targeting peptide motifs and allows effective lead optimization by kSAR. This approach led to the isolation of a brain-specific peptide, CAGALCY, which appears to function as an effective antagonist of platelet adhesion to activated pial microvasculature.

The alpha4bbeta7-integrin is dynamically expressed on murine eosinophils and involved in eosinophil trafficking to the intestine

BACKGROUND

Of the numerous adhesion molecules expressed by eosinophils, the alpha4-integrin has been identified as critically involved in eosinophil trafficking in the lung. Most studies have focused on the role of the alpha4beta1-adhesion complex, but eosinophils also express the alpha4beta7-integrin complex.

OBJECTIVE

To investigate the role of alpha4beta7, by assessing its membrane expression on eosinophils from different compartments using allergen-challenged mice and IL-4/IL-5 bi-transgenic mice. In addition, we aim to determine the impact of beta7-integrin deficiency on eosinophil recruitment to the lungs and intestine in specific experimental allergic models.

RESULTS

Evaluation of alpha4beta7 expression on bronchoalveolar lavage fluid (BALF) and lung tissue eosinophils revealed a down-regulation of this integrin as eosinophils migrate through the lungs. Indeed eosinophils isolated from the BALF and lung of allergic mice had low expression of the alpha4beta7-complex. While expression of the alpha4-chain remained unchanged, a significant decrease in beta7-surface expression was observed. Intestinal eosinophils, isolated from Peyer's patches, also displayed a down-regulation of the alpha4beta7-integrin, albeit only modest. In contrast, circulating eosinophils, isolated from the blood and spleen, expressed high levels of the alpha4beta7-integrin. However, eosinophil trafficking into the lungs of beta7-integrin-deficient mice was not significantly impaired in response to respiratory allergen challenges. In contrast, beta7-deficient mice had impaired eosinophil recruitment to the intestine.

CONCLUSION

Taken together, these results identify differential expression of the alpha4beta7-integrin on eosinophils and its critical role in regulating eosinophil responses in the intestine.

Bioactive peptides from libraries

New ligands for a variety of biological targets can be selected from biological or synthetic combinatorial peptide libraries. The use of different libraries to select novel peptides with potential therapeutic applications is reviewed. The possible combination of molecular diversity provided by combinatorial libraries and a rational approach derived from computational modeling is also considered. Advantages and disadvantages of different approaches are compared. Possible strategies to bypass loss of peptide bioactivity in the transition from ligand selection to in vivo use are discussed.

Integrin α4β1 function is required for cell survival in developing retina

In the retina, integrins in the beta1 family have been shown to be important in many phases of neuronal development, particularly neuroblast migration and axon outgrowth. However, the functions of specific integrin heterodimers are not well defined. In this study, we investigated the functions of beta1 integrins in developing chicken retina by expression of a dominant-negative beta1A construct using a replication-competent retrovirus. Inhibition of integrins using this approach resulted in alteration of cell morphology and increased apoptosis, but did not preclude migration and axon elongation. In an attempt to identify which specific beta1 heterodimer was important, expression and function of the alpha4beta1 heterodimer were also investigated. At early developmental stages, alpha4 protein and mRNA were detected in undifferentiated neuroblasts throughout the retina. At later stages, expression was confined to retinal ganglion cells (RGCs) and amacrine cells. A small molecule antagonist of alpha4 integrins was shown to inhibit neurite outgrowth on recombinant soluble vascular cell adhesion molecule-1 (VCAM-1), a known ligand of alpha4beta1. Introduction of alpha4 antagonist in vivo gave rise to increased apoptosis and led to a thinning of the retina and reduced numbers of retinal ganglion cells (RGCs). We conclude that the integrin alpha4beta1 is important for survival of developing retinal neurons, including RGCs.

Phage display of random peptide libraries: applications, limits, and potential

The identification of ligands from large biological libraries by phage display has now been used for almost 15 years. Most of the successful reports on high-affinity ligand identification originated from work with different antibody libraries. In contrast, the progress of applying phage display to random peptide libraries was relatively slow. However, in the last few years several improvements have led to an increasing number of published peptide ligands identified by phage display from such libraries and which exhibited good biological activity and high affinity. This review summarizes the current state and the technical progress of the application of random peptide libraries using filamentous phage for ligand identification.

Leukocyte and endothelial cell adhesion molecules as targets for therapeutic interventions in inflammatory disease

Inflammation is a fundamental response to tissue injury and invasion of pathogens, but it is detrimental in clinically important inflammatory disorders. Leukocytes are key players in the inflammatory response because of their antimicrobial, secretory and phagocytic activities. They are recruited to the inflamed tissue by sequential adhesive interactions between leukocytes and the endothelium that are mediated by cell-adhesion molecules (CAMs) on the surface of the interacting cells. The effects of many anti-inflammatory drugs can be ascribed, in part, to inhibition of the expression of CAMs. However, in the search for more selective and potent drugs for clinically important diseases such as multiple sclerosis, asthma, rheumatoid arthritis, inflammatory bowel disease, allergies and atherosclerosis, direct inhibition of the function of CAMs has attracted increasing interest. In recent years, the development of synthetic antagonists has provided better opportunities for drug targeting. Future advances in this field hold new prospects for therapeutic intervention in human inflammatory disorders.

Solid-phase synthesis of dual α4β1/α4β7 integrin antagonists: two scaffolds with overlapping pharmacophores

Two structural classes of dual alpha4beta1/alpha4beta7 integrin antagonists were investigated via solid-phase parallel synthesis. Using an acylated amino acid backbone, lead compounds containing biphenylalanine or tyrosine carbamate scaffolds were optimized for inhibition of alpha4beta1/VCAM and alpha4beta7/MAdCAM. A comparison of the structure-activity relationships in the inhibition of the alpha4beta7/MAdCAM interaction for substituted amines employed in both scaffolds suggests a similar binding mode for the compounds.