Modulating T cell responses for the treatment of psoriasis: a focus on efalizumab

Protein-protein interactions as drug targets

Modulation of protein-protein interactions (PPIs) is becoming increasingly important in drug discovery and chemical biology. While a few years ago this 'target class' was deemed to be largely undruggable an impressing number of publications and success stories now show that targeting PPIs with small, drug-like molecules indeed is a feasible approach. Here, we summarize the current state of small-molecule inhibition and stabilization of PPIs and review the active molecules from a structural and medicinal chemistry angle, especially focusing on the key examples of iNOS, LFA-1 and 14-3-3.

Concordance of preclinical and clinical pharmacology and toxicology of therapeutic monoclonal antibodies and fusion proteins: cell surface targets

Monoclonal antibodies (mAbs) and fusion proteins directed towards cell surface targets make an important contribution to the treatment of disease. The purpose of this review was to correlate the clinical and preclinical data on the 15 currently approved mAbs and fusion proteins targeted to the cell surface. The principal sources used to gather data were: the peer reviewed Literature; European Medicines Agency 'Scientific Discussions'; and the US Food and Drug Administration 'Pharmacology/Toxicology Reviews' and package inserts (United States Prescribing Information). Data on the 15 approved biopharmaceuticals were included: abatacept; abciximab; alefacept; alemtuzumab; basiliximab; cetuximab; daclizumab; efalizumab; ipilimumab; muromonab; natalizumab; panitumumab; rituximab; tocilizumab; and trastuzumab. For statistical analysis of concordance, data from these 15 were combined with data on the approved mAbs and fusion proteins directed towards soluble targets. Good concordance with human pharmacodynamics was found for mice receiving surrogates or non-human primates (NHPs) receiving the human pharmaceutical. In contrast, there was poor concordance for human pharmacodynamics in genetically deficient mice and for human adverse effects in all three test systems. No evidence that NHPs have superior predictive value was found.

Aplastic anemia: immunosuppressive therapy in 2010

Acquired aplastic anemia (AA) is the typical bone marrow failure syndrome characterized by an empty bone marrow; an immune-mediated pathophysiology has been demonstrated by experimental works as well as by clinical observations. Immunusuppressive therapy (IST) is a key treatment strategy for aplastic anemia; since 20 years the standard IST for AA patients has been anti-thymocyte globuline (ATG) plus cyclosporine A (CyA), which results in response rates ranging between 50% and 70%, and even higher overall survival. However, primary and secondary failures after IST remain frequent, and to date all attempts aiming to overcome this problem have been unfruitful. Here we review the state of the art of IST for AA in 2010, focusing on possible strategies to improve current treatments. We also discuss very recent data which question the equality of different ATG preparations, leading to a possible reconsideration of the current standards of care for AA patients.

Immunosuppressive therapies in the management of immune-mediated marrow failures in adults: where we stand and where we are going

Immunosuppression is a key treatment strategy for aplastic anaemia (AA) and the related immune-mediated bone marrow failure syndromes (BMFS). For the last 20 years the standard immunosuppressive regimen for AA patients has been anti-thymocyte globulin (ATG) plus ciclosporin A (CyA), which results in response rates ranging between 50% and 70%, and even higher overall survival. However, primary and secondary failures after immunosuppressive therapy remain frequent, and to date all attempts aiming to overcome this problem have been unfruitful. This article reviews the state of the art of current immunosuppressive therapies for AA, focusing on open questions linked to standard immunosuppressive treatment, and on experimental immunosuppressive strategies which could lead to future improvement of current treatments. Specific immunosuppressive strategies employed for other BMFS, such as lineage-restricted marrow failures, myelodysplastic syndromes and large granular lymphocyte leukaemia-associated cytopenias, are also briefly discussed.

Discovery of tetrahydroisoquinoline (THIQ) derivatives as potent and orally bioavailable LFA-1/ICAM-1 antagonists

This letter describes the discovery of a novel series of tetrahydroisoquinoline (THIQ)-derived small molecules that potently inhibit both human T-cell migration and super-antigen induced T-cell activation through disruption of the binding of integrin LFA-1 to its receptor, ICAM-1. In addition to excellent in vitro potency, 6q shows good pharmacokinetic properties and its ethyl ester (6t) demonstrates good oral bioavailability in both mouse and rat. Either intravenous administration of 6q or oral administration of its ethyl ester (6t) produced a significant reduction of neutrophil migration in a thioglycollate-induced murine peritonitis model.

Small molecule antagonist of leukocyte function associated antigen-1 (LFA-1): structure-activity relationships leading to the identification of 6-((5S,9R)-9-(4-cyanophenyl)-3-(3,5-dichlorophenyl)-1-methyl-2,4-dioxo-1,3,7-triazaspiro[4.4]nonan-7-yl)nicotinic acid (BMS-688521)

Leukocyte function-associated antigen-1 (LFA-1), also known as CD11a/CD18 or alpha(L)beta(2), belongs to the beta(2) integrin subfamily and is constitutively expressed on all leukocytes. The major ligands of LFA-1 include three intercellular adhesion molecules 1, 2, and 3 (ICAM 1, 2, and 3). The interactions between LFA-1 and the ICAMs are critical for cell adhesion, and preclinical animal studies and clinical data from the humanized anti-LFA-1 antibody efalizumab have provided proof-of-concept for LFA-1 as an immunological target. This article will detail the structure-activity relationships (SAR) leading to a novel second generation series of highly potent spirocyclic hydantoin antagonists of LFA-1. With significantly enhanced in vitro and ex vivo potency relative to our first clinical compound (1), as well as demonstrated in vivo activity and an acceptable pharmacokinetic and safety profile, 6-((5S,9R)-9-(4-cyanophenyl)-3-(3,5-dichlorophenyl)-1-methyl-2,4-dioxo-1,3,7-triazaspiro-[4.4]nonan-7-yl)nicotinic acid (2e) was selected to advance into clinical trials.

Molecular regulation of JC virus tropism: insights into potential therapeutic targets for progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a growing concern for patients undergoing immune modulatory therapies for treatment of autoimmune diseases such as multiple sclerosis. Currently, there are no drugs approved for the treatment of PML that have been demonstrated in the patient to effectively and reproducibly alter the course of disease progression. The human polyoma virus JC is the causative agent of PML. JC virus (JCV) dissemination is tightly controlled by regulation of viral gene expression from the promoter by cellular transcription factors expressed in cells permissive for infection. JCV infection likely occurs during childhood, and latent virus containing PML-associated promoter sequences is maintained in lymphoid cells within the bone marrow. Because development of PML is tightly linked to suppression and or modulation of the immune system as in development of hematological malignancies, AIDS, and monoclonal antibody treatments, further scrutiny of the course of JCV infection in immune cells will be essential to our understanding of development of PML and identification of new therapeutic targets.

LFA-1 antagonists as agents limiting human immunodeficiency virus type 1 infection and transmission and potentiating the effect of the fusion inhibitor T-20

Adhesion molecules are known to play major roles in the initiation and stabilization of cell-to-cell contacts during the immunological response. Human immunodeficiency virus type 1 (HIV-1) exploits those interactions to facilitate infection and propagation processes. The primary objective of the present study was to investigate the ability of antagonists specific for lymphocyte function-associated antigen 1 (LFA-1) to diminish HIV-1 infection and transmission. We demonstrate here that LFA-1 antagonists can significantly reduce HIV-1 replication in primary human cells and virus propagation by affecting cell-to-cell interactions. Moreover, the inhibition of LFA-1-mediated adhesion events also potentiates the antiviral efficacy of the peptide fusion inhibitor T-20. Altogether, our data suggest that LFA-1 antagonists represent promising antiviral agents. Antiadhesion therapy could be considered a complementary strategy targeting cellular functions essential for HIV-1 spreading and against which the combined therapy currently used displays a limited efficacy.

Efalizumab discontinuation: a practical strategy

Efalizumab is a recombinant, humanized IgG1 monoclonal antibody used in the treatment of plaque psoriasis. Efalizumab specifically targets T cells, leading to the subsequent inhibition of T-cell activation. The recent cases (three confirmed and one unconfirmed but suspected case) of the demyelinating disease progressive multifocal leukoencephalopathy (PML) have resulted in efalizumab being pulled from the market by European and Canadian regulatory agencies. Furthermore, manufacturer Genentech, Inc. has voluntarily withdrawn efalizumab from the United States market as of April 2009. In light of these events, this report is a practical guide to transitioning patients from efalizumab to alternative psoriasis therapies. The major consideration is the possibility for efalizumab-associated rebound of psoriasis. According to limited available literature and in the experience of the authors, the most effective agent for minimizing or preventing rebound is cyclosporine at the maximum dermatologic dose of 5 mg/kg per day.

[The lymphocyte: protagonism in the new era of the biological therapies]

Psoriasis is a systemic type T cell mediated immune system chronic inflammatory skin disease. These cells play an important role in the immune system and in the inflammatory response that determines the development and maintenance of the psoriasis lesions. However, greater understanding of the pathophysiology of this disease has led to the development of specific and selective biological treatments. Efalizumab is a humanized IgG1 monoclonal antibody that binds to the Leukocyte-Function-Associated Antigen 1 (LFA-1). When it binds to the CD11a--alpha subunit of LFA1--it inhibits the binding of this ligand to the intercellular adhesion molecule 1. This inhibits several processes related with the T cells that are fundamental in the pathogenesis of psoriasis: activation of the T cells in the lymph nodes, the migration of the T cells towards the dermis and epidermis and finally the reactivation of these in the inflammatory focus. The clinical studies have demonstrated that efalizumab, administered subcutaneously only once a week, provides a clinical benefit as well as improvement in the quality of life in patients with psoriasis with chronic, moderate or severe plaques. Long-term treatment studies suggest that continuous therapy with efalizumab is more beneficial in the maintenance of the improvement of the response and demonstrate that efalizumab may be administered safely for prolonged periods. Given its efficacy, rapid onset action, safety profile due to its selective action mechanism and convenience in its subcutaneous self-administration weekly, efalizumab offers a new therapeutic option, especially of interest for the treatment of psoriasis.

[Efficacy of short- and long-term efalizumab]

T cells play an important role in the immune system and in the inflammatory response that determines the development and maintenance of psoriasis plaques. Better understanding of the pathophysiology of this disease has led to the development of specific biological treatments aimed at patients with extensive psoriasis. Traditionally, psoriasis has been treated with drugs which, in spite of their efficacy, have a toxicity associated to their long-term use. Thus, they cannot be used safely, comfortably or efficiently in many patients. Efalizumab, a biological agent specifically and selectively directed towards blocking the key steps in the pathogenesis of psoriasis, has been shown to be effective and safe in the short and long term in the treatment of psoriasis in more than 15 phase I, II and III clinical trials. In this article, the results of efficacy at 12 weeks, 6 months and three years are reviewed. Efalizumab arises as an important addition to the dermatological pharmacopoeia for the long-term treatment of psoriasis.

Update on the natural history and systemic treatment of psoriasis

The onset of psoriatic disease and its associated comorbidities involves the interplay among a myriad of genetic and environmental risk factors. As we gain further insight into the immunopathogenesis of psoriasis, we hope it will provide the basis for the development of safer, more efficacious, and more durable therapeutics in the future. Given its enormous toll on patient health and quality of life, steps should be taken to prevent or decrease the risk for psoriasis-associated comorbidities through behavior modification and use of preventative health screenings and treatments. Future studies will need to be performed to determine if successful treatment of psoriasis will lead to a decreased risk for developing psoriasis-associated comorbidities over time.

Sequence recognition of alpha-LFA-1-derived peptides by ICAM-1 cell receptors: inhibitors of T-cell adhesion

Blocking the T-cell adhesion signal from intercellular adhesion molecule-1/leukocyte function-associated antigen-1 interactions (Signal-2) can suppress the progression of autoimmune diseases (i.e. type-1 diabetes, psoriasis) and prevent allograph rejection. In this study, we determined the active region(s) of cLAB.L peptide [cyclo(1,12)Pen-ITDGEATDSGC] by synthesizing and evaluating the biologic activity of hexapeptides in inhibiting T-cell adhesion. A new heterotypic T-cell adhesion assay was also developed to provide a model for the T-cell adhesion process during lung inflammation. Two hexapeptides, ITDGEA and DGEATD, were found to be more active than the other linear hexapeptides. The cyclic derivative of ITDGEA [i.e. cyclo(1,6)ITDGEA] has similar activity than the parent linear peptide and has lower activity than cLAB.L peptide. Computational-binding experiments were carried out to explain the possible mechanism of binding of these peptides to intercellular adhesion molecule-1. Both ITDGEA and DGEATD bind the same site on intercellular adhesion molecule-1 and they interact with the Gln34 and Gln73 residues on D1 of intercellular adhesion molecule-1. In the future, more potent derivatives of cyclo(1,6)ITDGEA will be designed by utilizing structural and binding studies of the peptide to intercellular adhesion molecule-1. The heterotypic T-cell adhesion to Calu-3 will also be used as another assay to evaluate the selectivity of the designed peptides.

Potential Complications Associated with the Use of Biologic Agents for Psoriasis

The biologic agents are effective drugs to treat psoriasis. They provide physicians with additional options for patients who cannot tolerate traditional therapies or for whom traditional therapies are not sufficient. While these new TNF-alpha inhibitors and anti-T-cell agents have potential complications, they are generally safe with proper monitoring. Both physicians and patients should be aware of the risks involved with each medicine so that the correct drug is chosen to suit each patient.

Eruptive papules during efalizumab (anti-CD11a) therapy of psoriasis vulgaris: a case series

Background

Newer biological therapies for moderate-to-severe psoriasis are being used more frequently, but unexpected effects may occur.

Case presentations

We present a group of 15 patients who developed inflammatory papules while on efalizumab therapy (Raptiva, Genentech Inc, anti-CD11a). Immunohistochemistry showed that there were increased CD11b⁺, CD11c⁺ and iNOS⁺ cells (myeloid leukocytes) in the papules, with relatively few CD3⁺ T cells. While efalizumab caused a decreased expression of CD11a on T cells, other circulating leukocytes from patients receiving this therapy often showed increased CD11b and CD11c. In the setting of an additional stimulus such as skin trauma, this may predispose to increased trafficking into the skin using these alternative β2 integrins. In addition, there may be impaired immune synapse formation, limiting the development of these lesions to small papules. There is little evidence for these papular lesions being "allergic" in nature as there are few eosinophils on biopsy, and they respond to minimal or no therapy even if efalizumab is continued.

Conclusion

We hypothesize that these papules may represent a unique type of "mechanistic" inflammatory reaction, seen only in the context of drug-induced CD11a blockade, and not during the natural disease process.

Design of LFA-1 antagonists based on a 2,3-dihydro-1H-pyrrolizin-5(7aH)-one scaffold

A new class of lymphocyte function-associated antigen-1 (LFA-1) antagonists is described. Elaboration of the 2,3-dihydro-1H-pyrrolizin-5(7aH)-one scaffold resulted in the synthesis of potent inhibitors of the LFA-1/ICAM-1 interaction. Along with the in vitro activity, we present the X-ray crystal structure of the complex of compound 9b, in a novel binding mode to the I-domain of LFA-1.

The CD11a Binding Site of Efalizumab in Psoriatic Skin Tissue as Analyzed by Multi-Epitope Ligand Cartography Robot Technology

Efalizumab (Raptiva) is an immunomodulating recombinant humanized IgG1 monoclonal antibody that binds to CD11a, the alpha-subunit of leukocyte function antigen-1 (LFA-1). By blocking the binding of LFA-1 to ICAM-1, efalizumab inhibits the adhesion of leukocytes to other cell types and interferes with the migration of T lymphocytes to sites of inflammation (including psoriatic skin plaques). Analysis of the response in patients treated with efalizumab to date shows that distinct groups of responders and nonresponders to the drug exist. It would therefore be of great practical value to be able to predict which patients are most likely to respond to treatment, by identifying key parameters in the mechanism of action of efalizumab. Detailed investigation and detection of multiple epitopes in microcompartments of skin tissue has until recently been restricted by the available technology. However, the newly developed technique of Multi-Epitope Ligand Cartography (MELC) robot technology combines proteomics and biomathematical tools to visualize protein networks at the cellular and subcellular levels in situ, and to decipher cell functions. The MELC technique, which is outlined in this paper, was used to help characterize the binding of efalizumab to affected and unaffected psoriatic skin as compared to normal control skin under ex vivomodel conditions. Efalizumab was labeled with fluorescein isothiocyanate and integrated into a MELC library of more than 40 antibodies. These antibodies were selected for their potential to detect epitopes which may be indicative of (a) various cell types, (b) structural components of the extracellular matrix, or (c) the processes of cell proliferation, activation and adhesion. Efalizumab bound to CD11a in affected psoriatic skin by a factor 15x and 32x higher than in unaffected psoriatic skin and normal control skin, respectively. CD11a and the efalizumab binding site were primarily expressed in the extravascular dermis, whereas CD54 (ICAM-1) as its ligand was most prevalent in the dermal vessels. T lymphocytes (for which the markers were CD3, CD8, CD4, and CD45R0) were the major cellular targets of efalizumab. In contrast, NK cells were only a minor target of efalizumab. Our study demonstrated that efalizumab represents a treatment for psoriasis that primarily targets memory CD4+ and CD8+ T cells and has a high specificity for psoriatic disease activity. Moreover, we hereby introduce the novel principle of a biological drug-binding biochip assay being especially useful for the future monitoring of psoriatic skin lesions under efalizumab treatment conditions.

Incidence of infection during efalizumab therapy for psoriasis: analysis of the clinical trial experience

BACKGROUND

Because many therapies for psoriasis disrupt the normal inflammatory cascade and could theoretically impair the body's ability to respond to external pathogens, a possible increase in the incidence of infection is a concern with any new psoriasis therapy that affects the immune system. Efalizumab is a biologic therapy targeted to inhibit T cells. Its efficacy has been shown in clinical trials encompassing >3500 patients with psoriasis.

OBJECTIVES

The aims of this article were to review the incidence of infection observed in efalizumab-treated patients during 12-week, Phase III clinical trials, compare the incidence rate with that in patients receiving placebo, and evaluate the incidence of infection observed in patients with extended (>12-week) efalizumab use.

METHODS

Adverse events (AEs) of infection were tabulated from a pooled data set of 2335 patients enrolled to receive 12 weeks of subcutaneous (SC) efalizumab 1 or 2 mg/kg . wk or placebo in 4 randomized, double-blind, placebo-controlled, Phase III efalizumab clinical studies. The incidence of infection was further evaluated using pooled data from 1115 patients who received up to 24 weeks of efalizumab therapy during 5 clinical trials with treatment extension arms and from 170 patients who received up to 108 weeks (27 months) of continuous therapy in an open-label, Phase III efalizumab trial of 36 months' total duration.

RESULTS

The incidence and severity of AEs of infection during 12 weeks of efalizumab therapy were comparable to those observed in patients receiving placebo (overall, 28.6% vs 26.3%). Infections did not appear to increase with extended therapy of up to 27 months. Serious infections requiring hospitalization occurred in 1.1% of efalizumab-treated patients.

CONCLUSION

The present review of the available Phase III clinical trial suggests that efalizumab is not associated with an increased risk for infection in patients receiving initial or long-term (27-month) treatment for moderate to severe chronic plaque psoriasis.

A small molecule agonist of an integrin, alphaLbeta2

The binding of integrin alpha(L)beta(2) to its ligand intercellular adhesion molecule-1 is required for immune responses and leukocyte trafficking. Small molecule antagonists of alpha(L)beta(2) are under intense investigation as potential anti-inflammatory drugs. We describe for the first time a small molecule integrin agonist. A previously described alpha/beta I allosteric inhibitor, compound 4, functions as an agonist of alpha(L)beta(2) in Ca(2+) and Mg(2+)and as an antagonist in Mn(2+). We have characterized the mechanism of activation and its competitive and noncompetitive inhibition by different compounds. Although it stimulates ligand binding, compound 4 nonetheless inhibits lymphocyte transendothelial migration. Agonism by compound 4 results in accumulation of alpha(L)beta(2) in the uropod, extreme uropod elongation, and defective de-adhesion. Small molecule integrin agonists open up novel therapeutic possibilities.

A favourable benefit/risk ratio with efalizumab: a review of the clinical evidence

Moderate to severe plaque psoriasis has traditionally been treated with agents that have toxicities associated with long-term use. Many patients therefore cannot be treated safely, conveniently or effectively with traditional therapies. Recent phase 3 clinical trials for efalizumab, a biological agent targeted specifically at the T-cell-based pathology of psoriasis, have demonstrated its short- and long-term efficacy and safety for the treatment of psoriasis. This article reviews results from 12-week, six-month, and three-year trials, focusing on the drug's safety, efficacy, and therapeutic response time, as well as the phenomenon of rebound in non-responding patients. Efalizumab emerges as an important addition to the dermatological pharmacopeia for the long-term treatment of psoriasis.

Psoriasis vulgaris flare during efalizumab therapy does not preclude future use: a case series

Background

Severe psoriasis vulgaris can be extremely difficult to treat in some patients, even with the newer biological therapies available today.

Case presentations

We present two patients with severe chronic plaque psoriasis who received numerous systemic anti-psoriatic therapies with varied results. Both responded well to initial treatment with efalizumab (anti-CD11a), but then experienced a flare of their disease after missing a dose. However, after disease stablization, both patients responded well to re-introduction of efalizumab, one patient requiring concurrent treatment with infliximab (anti-TNF-α).

Conclusion

These cases are presented to characterize this "flare" reaction, and to inform health care providers that efalizumab can still be administered after disease flare, and again may be a successful therapy.

Emerging drugs for moderate-to-severe psoriasis

Psoriasis is a chronic, incurable, disabling skin disease characterised by red, scaly plaques. Approximately 23% of psoriasis patients also have an accompanying arthritis that can become debilitating. Psoriasis has a stigmatising effect on its victims, who often feel socially isolated. Although the exact aetiology of psoriasis is still unknown, it is clearly an immune-mediated disease. Traditional therapies for psoriasis include topical drugs, such as corticosteroids, retinoids and vitamin D3 analogues; systemic drugs, such as methotrexate, ciclosporin and retinoids; and phototherapy. These mainstays of treatment are efficacious for the treatment of severe disease; however, most are associated with toxicities or are inconvenient. Recent advances in biotechnology have produced new pharmaceuticals that interfere with immune responses thought to be involved in the pathogenesis of psoriasis and other inflammatory diseases. The immunobiologicals, one new family of drugs, consist of monoclonal antibodies and fusion proteins. Many have demonstrated efficacy in treating psoriasis. Some appear to offer safety benefits over traditional therapies; further monitoring and surveillance of these agents is required to adequately establish safety profiles. This article discusses existing and emerging treatments for moderate-to-severe psoriasis.

Efalizumab: continuous therapy for chronic psoriasis

Efalizumab is a humanised monoclonal antibody targeting the CD11a subunit of lymphocyte function-associated antigen-1, specifically developed for psoriasis. Indicated for patients with moderate-to-severe plaque psoriasis, efalizumab is FDA-approved in the US for patients aged > or = 18, as well as being approved in several other European countries. Clinical studies have proven the efficacy of efalizumab for a majority of patients, improving quality of life with continuous maintenance therapy by means of weekly subcutaneous self-injections. Controlled trials have demonstrated the safety and tolerability of efalizumab. Clinical trials have established that approximately 30% of patients can achieve a PASI-75 response within 12 weeks of initiating treatment, with further clinical benefit noted with continued therapy up to 24 and even 36 months of therapy. Efalizumab may thus potentially offer patients a safe option for long-term safe control in managing their disease.

De novo design, synthesis, and in vitro activity of LFA-1 antagonists based on a bicyclic[5.5]hydantoin scaffold

LFA-1 (leukocyte function-associated antigen-1), is a member of the beta(2)-integrin family and is expressed on all leukocytes. The LFA-1/ICAM interaction promotes tight adhesion between activated leukocytes and the endothelium, as well as between T cells and antigen-presenting cells. Evidence from both animal models and clinical trials provides support for LFA-1 as a target in several different inflammatory diseases. This paper describes the de novo design, synthesis and in vitro activity of LFA-1 antagonists based on a bicyclic[5.5]hydantoin scaffold.

Antisense oligonucleotide treatments for psoriasis

Antisense oligonucleotides are emerging as an exciting therapeutic strategy for treating skin diseases such as psoriasis. Potential antisense targets are proteins upregulated in psoriatic skin, in particular those associated with inflammation (intercellular adhesion molecule [ICAM]-1, IL-2 and -8), proliferation (insulin-like growth factor type I receptor [IGF-IR], epidermal growth factor) and hyperangiogenesis (vascular endothelial growth factor [VEGF]). Whereas topical application and subsequent penetration of large oligonucleotides into normal skin is problematic, the impaired barrier function of psoriatic lesions permits the uptake of antisense drugs. Studies to date indicate that topically applied antisense molecules can be delivered to target cells in the epidermis and dermis of psoriatic skin. Antisense-mediated suppression of target mRNA and protein has been demonstrated in models of human skin grafted to immunosuppressed mice and in hairless mouse models of skin inflammation. In a xenograft model of human psoriasis, treatment with repeated intradermal injections of IGF-IR antisense caused a normalisation of the epidermal hyperproliferation. This class of drug, therefore, holds much potential for the successful treatment of psoriasis in the clinical setting.

Inhibition of ICAM-1/LFA-1-mediated heterotypic T-cell adhesion to epithelial cells: design of ICAM-1 cyclic peptides

In this work, we have designed cyclic peptides (cIBL, cIBR, cIBC, CH4 and CH7) derived from the parent IB peptide (ICAM-1(1-21)) that are inhibitors of ICAM-1/LFA-1-mediated T-cell adhesion to Caco-2 cell monolayers. Cyclic peptide cIBR has the best activity of any of the peptides evaluated. The active ICAM-1 peptides have a common Pro-Arg-Gly sequence that may be important for binding to LFA-1.

Therapeutic antagonists and conformational regulation of integrin function

Integrins are a structurally elaborate family of adhesion molecules that transmit signals bi-directionally across the plasma membrane by undergoing large-scale structural rearrangements. By regulating cell-cell and cell-matrix contacts, integrins participate in a wide range of biological processes, including development, tissue repair, angiogenesis, inflammation and haemostasis. From a therapeutic standpoint, integrins are probably the most important class of cell-adhesion receptors. Recent progress in the development of integrin antagonists has resulted in their clinical application and has shed new light on integrin biology. On the basis of their mechanism of action, small-molecule integrin antagonists fall into three different classes. Each of these classes affect the equilibria that relate integrin conformational states, but in different ways.