Prolonged reversal of chronic experimental allergic encephalomyelitis using a small molecule inhibitor of alpha4 integrin

The role of α4 integrin in Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease: an infectious animal model for multiple sclerosis (MS)

Natalizumab, which is an antibody against α4 integrin, has been used for the treatment of multiple sclerosis (MS). In the present study, we investigated both the role of α4 integrin and the therapeutic effect of HCA3551, a newly synthesized orally active small-molecule α4 integrin antagonist, in the development of TMEV-induced demyelinating disease (TMEV-IDD). The mRNA levels of α4 integrins were significantly up-regulated in the CNS of mice with TMEV-IDD as compared with naïve mice (*p<0.05). HCA3551 treatment in the effector phase significantly suppressed both the clinical and histological development of TMEV-IDD. The number of infiltrating mononuclear inflammatory cells in the CNS was significantly decreased in the mice treated with HCA3551 (**p<0.01). The labeling indices for CD68 antigen and the absolute cell numbers of TNF-α-producing CD4⁺ T cells and IFN-γ-producing CD8⁺ T cells were significantly decreased in the CNS of mice treated with HCA3551 (*p<0.05). HCA3551 treatment in the effector phase might inhibit the binding of α4 integrin to VCAM-1, thereby decreasing the number of MNCs in the CNS.

Suppression of acute experimental allergic encephalomyelitis with a small molecule inhibitor of α4 integrin

Purpose: To determine the efficacy of a small molecule inhibitor of α4 integrin (CT301) at reversing the clinical, pathological and MR- detectable deficits associated with the acute phase of experimental allergic encephalomyelitis (EAE). Materials and methods: EAE was induced in 36 female Hartley guinea pigs, and the treatment period was from day 11 to day 17 post-immunization. Animals received either saline (n=12), anti-α4 integrin antibody (AN100226m; n=12) or CT301 (n=12). T2-weighted fast spin echo and T1-weighted pre- and post-contrast scans were performed at the beginning (day 11) and end (day 18) of the treatment period, and scored for cerebral inflammation and gadolinium enhancement. T1-weighted images were further analyzed to quantify this enhancement as a measure of blood-brain barrier integrity. Dissected CNS was evaluated for inflammation and demyelination. Results: CT301 successfully reversed two clinical indicators of disease over the course of the treatment period. These animals showed decreased T2-weighted abnormalities, as well as a reduction in gadolinium leakage on T1-weighted images. Meningeal and perivascular inflammation was decreased by anti-α4 integrin treatments. Conclusion: CT301 effectively reverses the clinical, pathological and MR-detectable deficits of acute EAE, and may therefore be a promising therapeutic agent in multiple sclerosis (MS).

Anti-integrin therapy for multiple sclerosis

Integrins are the foremost family of cell adhesion molecules that regulate immune cell trafficking in health and diseases. Integrin alpha4 mediates organ-specific migration of immune cells to the inflamed brain, thereby playing the critical role in the pathogenesis of multiple sclerosis. Anti-alpha4 integrin therapy aiming to block infiltration of autoreactive lymphocytes to the inflamed brain has been validated in several clinical trials for the treatment of multiple sclerosis. This paper provides readers with an overview of the molecular and structural bases of integrin activation as well as rationale for using anti-alpha4 integrin therapy for multiple sclerosis and then chronicles the rise and fall of this treatment strategy using natalizumab, a humanized anti-alpha4 integrin.

A novel, potent, and orally active VLA-4 antagonist with good aqueous solubility: trans-4-[1-[[2-(5-Fluoro-2-methylphenylamino)-7-fluoro-6-benzoxazolyl]acetyl]-(5S)-[methoxy(methyl)amino]methyl-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid

We have carried out the optimization of substituents at the C-3 or the C-5 position on the pyrrolidine ring of VLA-4 antagonist 3 with 2-(phenylamino)-7-fluorobenzoxazolyl moiety for the purpose of improving in vivo efficacy while maintaining good aqueous solubility. As a result, we successfully increased in vitro activity in the presence of 3% human serum albumin and achieved an exquisite lipophilic and hydrophilic balance of compounds suitable for oral administrative regimen. The modification resulted in the identification of zwitterionic compound 7n with (5S)-[methoxy(methyl)amino]methylpyrrolidine, which significantly alleviated bronchial hyper-responsiveness to acetylcholine chloride at 12.5mg/kg, p.o. in a murine asthma model and showed favorable aqueous solubility (JP1, 89 μg/mL; JP2, 462 μg/mL). Furthermore, this compound showed good oral bioavailability (F=54%) in monkeys.

Molecular MRI enables early and sensitive detection of brain metastases

Metastasis to the brain is a leading cause of cancer mortality. The current diagnostic method of gadolinium-enhanced MRI is sensitive only to larger tumors, when therapeutic options are limited. Earlier detection of brain metastases is critical for improved treatment. We have developed a targeted MRI contrast agent based on microparticles of iron oxide that enables imaging of endothelial vascular cell adhesion molecule-1 (VCAM-1). Our objectives here were to determine whether VCAM-1 is up-regulated on vessels associated with brain metastases, and if so, whether VCAM-1-targeted MRI enables early detection of these tumors. Early up-regulation of cerebrovascular VCAM-1 expression was evident on tumor-associated vessels in two separate murine models of brain metastasis. Metastases were detectable in vivo using VCAM-1-targeted MRI 5 d after induction (<1,000 cells). At clinical imaging resolutions, this finding is likely to translate to detection at tumor volumes two to three orders of magnitude smaller (0.3-3 × 10(5) cells) than those volumes detectable clinically (10(7)-10(8) cells). VCAM-1 expression detected by MRI increased significantly (P < 0.0001) with tumor progression, and tumors showed no gadolinium enhancement. Importantly, expression of VCAM-1 was shown in human brain tissue containing both established metastases and micrometastases. Translation of this approach to the clinic could increase therapeutic options and change clinical management in a substantial number of cancer patients.

Experimental autoimmune encephalomyelitis (EAE) as a model for multiple sclerosis (MS)

Experimental autoimmune encephalomyelitis (EAE) is the most commonly used experimental model for the human inflammatory demyelinating disease, multiple sclerosis (MS). EAE is a complex condition in which the interaction between a variety of immunopathological and neuropathological mechanisms leads to an approximation of the key pathological features of MS: inflammation, demyelination, axonal loss and gliosis. The counter-regulatory mechanisms of resolution of inflammation and remyelination also occur in EAE, which, therefore can also serve as a model for these processes. Moreover, EAE is often used as a model of cell-mediated organ-specific autoimmune conditions in general. EAE has a complex neuropharmacology, and many of the drugs that are in current or imminent use in MS have been developed, tested or validated on the basis of EAE studies. There is great heterogeneity in the susceptibility to the induction, the method of induction and the response to various immunological or neuropharmacological interventions, many of which are reviewed here. This makes EAE a very versatile system to use in translational neuro- and immunopharmacology, but the model needs to be tailored to the scientific question being asked. While creating difficulties and underscoring the inherent weaknesses of this model of MS in straightforward translation from EAE to the human disease, this variability also creates an opportunity to explore multiple facets of the immune and neural mechanisms of immune-mediated neuroinflammation and demyelination as well as intrinsic protective mechanisms. This allows the eventual development and preclinical testing of a wide range of potential therapeutic interventions.

Identification of trans-4-[1-[[7-fluoro-2-(1-methyl-3-indolyl)-6-benzoxazolyl]acetyl]-(4S)-fluoro-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid as a potent, orally active VLA-4 antagonist

For the purpose of obtaining orally potent VLA-4 inhibitors, we have carried out structural modification of the (N'-phenylureido)phenyl group in compound 1, where the group was found to be attributed to poor pharmacokinetic profile in our previous research. Through modification, we have identified several compounds with both potent in vitro activity and improved oral exposure. In particular, compound 7e with 7-fluoro-2-(1-methyl-1H-indol-3-yl)-1,3-benzoxazolyl group as a novel replacement of the (N'-phenylureido)phenyl group significantly inhibited eosinophil infiltration into bronchoalveolar lavage fluid at 15mg/kg in an Ascaris-antigen-induced murine bronchial inflammatory model, and its efficacy was comparable to that of the anti-mouse α(4) antibody (R1-2).

Discovery of potential integrin VLA-4 antagonists using pharmacophore modeling, virtual screening and molecular docking studies

Very late antigen-4 (VLA-4) is an integrin protein, and its antagonists are useful as anti-inflammatory drugs. The aim of this study is to discover novel virtual lead compounds to use them in designing potent VLA-4 antagonists. A best pharmacophore model was generated with correlation coefficient of 0.935, large cost difference of 114.078, comprising two hydrogen bond acceptors and three hydrophobic features. It was further validated and used in database screening for potential VLA-4 antagonists. A homology model of VLA-4 was built and employed in molecular docking of screened hit compounds. Finally, two compounds were identified as potential virtual leads to be deployed in the designing of novel potent VLA-4 antagonists.

Discovery of trans-4-[1-[[2,5-Dichloro-4-(1-methyl-3-indolylcarboxamido)phenyl]acetyl]-(4S)-methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid: an orally active, selective very late antigen-4 antagonist

We have focused on optimization of the inadequate pharmacokinetic profile of trans-4-substituted cyclohexanecarboxylic acid 5, which is commonly observed in many small molecule very late antigen-4 (VLA-4) antagonists. We modified the lipophilic moiety in 5 and found that reducing the polar surface area of this moiety results in improvement of the PK profile. Consequently, our efforts have led to the discovery of trans-4-[1-[[2,5-dichloro-4-(1-methyl-3-indolylcarboxamido)phenyl]acetyl]-(4S)-methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid (14e) with potent activity (IC(50) = 5.4 nM) and significantly improved bioavailability in rats, dogs, and monkeys (100%, 91%, 68%), which demonstrated excellent oral efficacy in murine and guinea pig models of asthma. Based on its overall profile, compound 14e was progressed into clinical trails. In a single ascending-dose phase I clinical study, compound 14e exhibited favorable oral exposure as expected and had no serious adverse events.

alpha4-Integrin antagonism with natalizumab: effects and adverse effects

Based on the results of two phase III clinical trials, the humanized recombinant monoclonal antibody natalizumab was approved for the treatment of relapsing forms of multiple sclerosis (MS). Since its initial approval in November 2004, it has been announced that six patients who received natalizumab in the context of clinical studies acquired an infection with the human polyoma virus JC and were diagnosed with progressive multifocal leukoencephalopathy (PML). Two of these individuals had a fatal outcome. Our groups recently showed that natalizumab therapy results in a reduction of CD4(+) T cells within the cerebrospinal fluid (CSF) that is ten-fold more pronounced than the reduction in the number of CD8(+) T lymphocytes. Interestingly, it appears that the effect of natalizumab on cell numbers in the CSF persists for at least 6 months after cessation of treatment. More recently, we studied the expression of major histocompatibility complex (MHC) I and II, and the number and phenotypes of leukocytes in cerebral perivascular spaces (CPVS). We observed that natalizumab therapy was associated with a significant decrease in the cell surface expression of MHC class II molecules, and the numbers of dendritic cells in CPVS. In addition, no CD4(+) T cells were detectable in this compartment. Our observations may explain the differential and prolonged effects of natalizumab therapy on different leukocyte subsets in the central nervous system. They also suggest that natalizumab treatment may result in prolonged immunosuppression in peripheral organs, and the delayed onset of adverse events.

VEGF and angiogenesis in acute and chronic MOG((35-55)) peptide induced EAE

An increased expression of vascular endothelial growth factor (VEGF) is associated with demyelinated lesions in both multiple sclerosis (MS) and its model (EAE), implicating changes in vasculature as a potential component of CNS plaque formation. The purpose of this study was to investigate the vascular changes in acute and chronic EAE in C57BL/6 mice induced with myelin oligodendrocyte glycoprotein (MOG ((35-55))) peptide. We investigated the functional contribution of VEGF to acute and chronic EAE by treating immunized mice with SU5416 (Semaxinib), a potent and selective inhibitor of VEGF receptor 2 (VEGFR2). Animals received seven daily injections of SU5416 (50 mg/kg) or vehicle beginning on the day after disease onset (acute study) or on day 45 post-immunization (chronic study). Spinal cord sections were collected on the day of sacrifice. Modulation of angiogenic gene expression was determined using RNA isolated from 4 acute and 4 non-immunized controls. MOG peptide induction produced extensive demyelination, immune cell infiltration, tissue laminin deposits, and axonal loss in lesions. VEGF expression was extensively increased in the acute mice, which correlated positively with clinical score. In the acute study, SU5416 treatment produced a significant clinical improvement versus vehicle controls (p<0.001), with less demyelination (-37%) and cellular infiltration (-23%) in the spinal cord (p<0.05). Treated animals also had significantly fewer blood vessels per section than controls (56.1+/-6.1 v. 81.6+/-11.5, p<0.05), and significantly reduced laminin abnormalities (28.9% of lesion area v. 46.8%, p<0.05). There was no improvement in clinical score or tissue pathology, and no difference in vessel number or lesion laminin expression, when SU5416 was administered during the chronic disease (all p>0.05). In the acute study only, VEGF staining correlated with demyelination and the extent of cellular infiltration in both control (r=0.723, r=0.665) and treated (r=0.681, r=0.487) animals (all p<0.05). Laminin staining in lesion areas was strongly correlated with tissue pathology for all animals in both the acute and chronic study (all p<0.001). Vascular alterations in MOG peptide-induced EAE in the mouse are accompanied by increased lesion-specific levels of VEGF, extensive laminin deposits in the tissue and altered transcription of numerous angiogenic factors. In the microarray studies, acute mice showed a significant increase in several angiogenic RNA transcripts, six of which were verified by RT-PCR, alanyl aminopeptidase, caspase 8, Hif1a, MMP-19, plasminogen activator inhibitor, and thrombospondin1.

A novel and potent VLA-4 antagonist based on trans-4-substituted cyclohexanecarboxylic acid

During the course of our study, it was revealed that the poor pharmacokinetic properties of a series of benzoic acid derivatives such as 1 should be attributed to the diphenylurea moiety. Thus, we replaced the diphenylurea moiety in 1 with a 2-(2-methylphenylamino)benzoxazole moiety which mimics the diphenylurea structure. However, this modification resulted in a significant decrease (3, IC(50)=19 nM) in VLA-4 inhibitory activity compared to 1 (IC(50)=1.6 nM). To address this discrepancy, we worked on optimization of the carboxylic acid moiety in compound 3. As a result, our efforts have led to the discovery of trans-4-substituted cyclohexanecarboxylic acid derivative 11b (IC(50)=2.8 nM) as a novel and potent VLA-4 antagonist. In addition, compound 11b exhibited favorable pharmacokinetic properties (CL=3.3 ml/min/kg, F=51%) in rats.

Identification of 4-[1-[3-chloro-4-[N'-(5-fluoro-2-methylphenyl)ureido]phenylacetyl]-(4S)-fluoro-(2S)-pyrrolidinylmethoxy]benzoic acid as a potent, orally active VLA-4 antagonist

Optimization of benzoic acid derivatives by introducing substituents into the diphenyl urea moiety led to the identification of compound 20l as a potent VLA-4 antagonist. Compound 20l inhibited eosinophil infiltration into bronchial alveolar lavage fluid in a murine asthma model by oral dosing and its efficacy was comparable to anti-mouse alpha4 antibody (R1-2). Furthermore, this compound significantly blocked bronchial hyper-responsiveness in the model.

Iron-oxide labeling of hematogenous macrophages in a model of experimental autoimmune encephalomyelitis and the contribution to signal loss in fast imaging employing steady state acquisition (FIESTA) images

PURPOSE

To determine the contribution of blood-derived macrophages to the signal loss observed in MR images of inflammatory lesions in experimental autoimmune encephalomyelitis (EAE).

MATERIALS AND METHODS

A relapsing-remitting form of EAE was induced in transgenic mice that express enhanced green fluorescent protein (EGFP) specifically in hematopoietic cells of the myelomonocytic lineage. Animals were injected with Feridex, a superparamagnetic iron oxide (SPIO) nanoparticle, 24 hours prior to in vivo MRI. MRI was performed using a 1.5T whole-body scanner; a high-performance, custom-built gradient coil insert; and a 3D steady-state free precession (SSFP) imaging pulse sequence. Comparisons were made between MR images and corresponding anti-GFP and Perl's Prussian blue (PPB)-stained brain sections.

RESULTS

MR images revealed the presence of discrete regions of signal loss throughout the brains of EAE animals that were administered Feridex. Histological staining showed that regions of signal loss on MR images corresponded anatomically with regions of PPB- and GFP-positive cells.

CONCLUSION

This experiment provides the first direct evidence that macrophages of hematogenous origin are labeled with SPIO after intravenous administration of Feridex, and contribute to the regions of signal loss detected in MR images of EAE brain.

Pharmacological properties, toxicology and scientific rationale for the use of natalizumab (Tysabri) in inflammatory diseases

Natalizumab (Tysabri) was the first adhesion molecule antagonist to make it into clinical trial for patients with multiple sclerosis (MS) and other inflammatory disorders. Natalizumab is a humanized recombinant monoclonal antibody (MAb) that binds to the alpha (alpha)(4) chain of the alpha(4) beta (beta)(1) (very late activating antigen 4; VLA-4) and alpha(4)beta(7) integrins. The scientific rationale for natalizumab therapy is the reduction of leukocyte extravasation into peripheral tissues. Natalizumab, like other VLA-4 antagonists, may also interfere with the activation of T lymphocytes in secondary lymphoid organs and their reactivation in the central nervous system (CNS). Shortly after its approval for the treatment of relapsing-remitting MS (RR-MS), three patients who were treated with natalizumab in the setting of clinical trials developed progressive multifocal leukoencephalopathy (PML), an opportunistic infection of the brain with the polyoma virus JC. It remains to be elucidated why the use of this VLA-4 antagonist is associated with an increased incidence of PML. Natalizumab was recently reapproved for the treatment of relapsing forms of MS. In this review, we outline the scientific rationale for using natalizumab in MS and other inflammatory disorders. In addition, an overview of pharmacological properties, clinical efficacy, safety, and toxicology of natalizumab is provided.

Connexin 43 gap junction proteins are up-regulated in remyelinating spinal cord

Alterations in the expression of gap junction proteins have previously been observed in several diseases affecting the central nervous system; however, the status of connexin 43 (Cx43) has not yet been reported in spinal cord remyelination. We studied Cx43 expression in demyelination and remyelination by using a chronic guinea pig model of experimental allergic encephalomyelitis (EAE). Hartley guinea pigs were immunized with homogenized whole CNS and complete Freund's adjuvant. Animals became chronically ill by day 40 postimmunization, and animals with paralysis were entered into the study. Animals were treated on days 40-60 postimmunization with either saline or drugs that promote remyelination: an adenosine amine congener (100 mug/kg), an anti-alpha4-integrin blocker (CT301; ELN 69299; 30 mg/kg), or a combination of both drugs. Remyelination was induced in all drug-treated groups. Cx43 expression was virtually absent in demyelinated lesions of saline-treated controls compared with healthy tissue and normal appearing white matter (P < 0.001), whereas Cx43 was considerably increased (300-500%) in remyelinating lesions of all treatment groups (P < 0.001), most notably in CT301-treated animals. These changes in Cx43 expression indicate that Cx43 may beimportant for recovery from neuroinflammation.

4-(Pyrrolidinyl)methoxybenzoic acid derivatives as a potent, orally active VLA-4 antagonist

A novel series of benzoic acid derivatives as VLA-4 antagonists were synthesized. Optimization, focusing on activity and lipophilicity needed for cell permeability, resulted in the identification of 15b and 15e with good activity (IC50 = 1.6 nM each) and moderate lipophilicity (Log D = 2.0, 1.8). Furthermore, 15e demonstrated efficacy in murine asthma model by an oral dose of 30 mg/kg.

Synthesis and biological evaluation of benzoic acid derivatives as potent, orally active VLA-4 antagonists

A series of benzoic acid derivatives was synthesized as VLA-4 antagonists. Introduction of chlorine or bromine into the 3-position on the central benzene of the diphenylurea portion as in lead compound 2 led to improvement in the pharmacokinetic properties. In particular, 12l demonstrated an acceptable plasma clearance and bioavailability in mice and rats as well as dogs (mice, CL=18.5 ml/min/kg,F=28%; rats, CL=5.2 ml/min/kg,F=36%; dogs, CL=3.6 ml/min/kg,F=55%). Additionally, 12l exhibited potent activity with an IC50 value of 0.51 nM and efficacy by oral administration at a dosage of 10 mg/kg in a rat pleurisy model.

The role of inflammation in CNS injury and disease

For many years, the central nervous system (CNS) was considered to be 'immune privileged', neither susceptible to nor contributing to inflammation. It is now appreciated that the CNS does exhibit features of inflammation, and in response to injury, infection or disease, resident CNS cells generate inflammatory mediators, including proinflammatory cytokines, prostaglandins, free radicals and complement, which in turn induce chemokines and adhesion molecules, recruit immune cells, and activate glial cells. Much of the key evidence demonstrating that inflammation and inflammatory mediators contribute to acute, chronic and psychiatric CNS disorders is summarised in this review. However, inflammatory mediators may have dual roles, with detrimental acute effects but beneficial effects in long-term repair and recovery, leading to complications in their application as novel therapies. These may be avoided in acute diseases in which treatment administration might be relatively short-term. Targeting interleukin (IL)-1 is a promising novel therapy for stroke and traumatic brain injury, the naturally occurring antagonist (IL-1ra) being well tolerated by rheumatoid arthritis patients. Chronic disorders represent a greater therapeutic challenge, a problem highlighted in Alzheimer's disease (AD); significant data suggested that anti-inflammatory agents might reduce the probability of developing AD, or slow its progression, but prospective clinical trials of nonsteroidal anti-inflammatory drugs or cyclooxygenase inhibitors have been disappointing. The complex interplay between inflammatory mediators, ageing, genetic background, and environmental factors may ultimately regulate the outcome of acute CNS injury and progression of chronic neurodegeneration, and be critical for development of effective therapies for CNS diseases.

Translating the concept of suppressor/regulatory T cells to clinical applications

The in vivo expansion of suppressor/regulatory T cells (Tregs) is a desirable event in autoimmunity and transplantation. Here we summarize the general rules involved in antigen recognition by T cells and describe Tregs and their requirements, discussing different levels of immune intervention.

Reevaluation of P-selectin and alpha 4 integrin as targets for the treatment of experimental autoimmune encephalomyelitis

There has been a great deal of interest in adhesion molecules as targets for the treatment of multiple sclerosis and other inflammatory diseases. In this study, we systematically evaluate alpha(4) integrin and P-selectin as targets for therapy in murine models of multiple sclerosis-for the first time directly measuring the ability of their blockade to inhibit recruitment and relate this to clinical efficacy. Experimental autoimmune encephalomyelitis was induced in C57BL/6 or SJL/J mice and intravital microscopy was used to quantify leukocyte interactions within the CNS microvasculature. In both strains, pretreatment with blocking Abs to either alpha(4) integrin or P-selectin reduced firm adhesion to a similar extent, but did not block it completely. The combination of the Abs was more effective than either Ab alone, although the degree of improvement was more evident in SJL/J mice. Similarly, dual blockade was much more effective at preventing the subsequent accumulation of fluorescently labeled leukocytes in the tissue in both strains. Despite evidence of blockade of leukocyte recruitment mechanisms, no clinical benefit was observed with anti-adhesion molecule treatments or genetic deletion of P-selectin in the C57BL/6 model, or in a pertussis toxin-modified model in SJL/J mice. In contrast, Abs to alpha(4) integrin resulted in a significant delay in the onset of clinical signs of disease in the standard SJL/J model. Despite evidence of a similar ability to block firm adhesion, Abs to P-selectin had no effect. Importantly, combined blockade of both adhesion molecules resulted in significantly better clinical outcome than anti-alpha(4) integrin alone.

Synthesis, biological evaluation, and pharmacokinetic study of prolyl-1-piperazinylacetic acid and prolyl-4-piperidinylacetic acid derivatives as VLA-4 antagonists

A series of prolyl-1-piperazinylacetic acid and prolyl-4-piperidinylacetic acid derivatives were synthesized and evaluated for their activity as VLA-4 antagonists. Of 22 compounds synthesized, 19 compounds showed potent activity with low nanomolar IC50 values. In addition, the representative compounds 11o and 11p with a hydroxy group in the pyrrolidine ring showed moderate plasma clearance in rats (11o, 30 ml/min/kg and 11p, 21 ml/min/kg) and in dogs (11o, 12 ml/min/kg and 11p, 9 ml/min/kg).

Spontaneous remyelination following prolonged inhibition of alpha4 integrin in chronic EAE

Inhibition of alpha(4)beta(1) integrin blocks immune cell influx into the CNS providing benefit to patients with multiple sclerosis and in animal model systems. We have used this mechanism to examine whether the presence of inflammatory cells suppresses spontaneous myelin repair in experimental autoimmune encephalomyelitis. We observed (1) 87% of plaques showed remyelination after 40 days of treatment; (2) myelin repair occurred in half of the total lesion area; (3) half of the animals regained motor function. There was no significant repair or gain of motor function in vehicle-treated animals. Therefore, prolonged inhibition of CNS inflammation, in the absence of targeted myelin repair, facilitates mechanisms of spontaneous remyelination.

Developing therapeutics for the treatment of multiple sclerosis

Multiple sclerosis (MS) is both a complex and chronic neurological disease of the CNS. This poses unique challenges for drug discovery in terms of delineating specific targets related to disease mechanisms and developing safe and effective molecules for clinical application. Preclinical animal models of MS provide the necessary test bed for evaluating the effects of novel therapeutic strategies. Because the clinical manifestations and pathological consequences of disease vary dramatically from individual to individual, as well as treatment response to existing therapies, this creates a significant research endeavor in terms of translating preclinical methodologies to the clinical domain. Potentially exciting treatments have emerged in the form of natalizumab (Tysabri), an alpha4 integrin antagonist, and more recently FTY720, a sphinogosine-1 phosphate receptor modulator, providing a compelling proof-of-principle from bench to bedside. However, further research is required to discharge safety concerns associated with these therapeutic avenues. Future prospects in the guise of disease-modifying therapies that target the inflammatory and neurodegenerative components of disease have come to the forefront of preclinical research with the sole aim of reducing the underlying irreversible progressive disability of MS. Significant progress with novel therapies will be made by implementing biomarker strategies that extrapolate robustly from animal models to the divergent patient populations of MS. The future therapeutic options for MS will depend on improvements in understanding the precise factors involved in disease onset and progression and subsequently the development of oral therapeutics that translate sustained benefit from the preclinical context into clinical reality.

Influence of acid surrogates toward potency of VLA-4 antagonist

A series of VLA-4 antagonist were synthesized wherein carboxylic acid was replaced by various acid surrogates. The effect of these acid surrogates toward potency was evaluated in a binding assay. A number of acid surrogates were potent antagonist of VLA-4, albeit significantly less potent than the corresponding carboxylic acid. Heterocyclic acid surrogate, oxadiazolidinone 3, demonstrated an improved pharmacokinetic property when dosed intravenously.

Identified a morpholinyl-4-piperidinylacetic acid derivative as a potent oral active VLA-4 antagonist

An investigation into the structure-activity relationship of a lead compound, prolyl-5-aminopentanoic acid 4, led to the identification of a novel series of 4-piperidinylacetic acid, 1-piperazinylacetic acid, and 4-aminobenzoic acid derivatives as potent VLA-4 antagonists with low nanomolar IC(50) values. A representative compound morpholinyl-4-piperidinylacetic acid derivative (13d: IC(50)=4.4 nM) showed efficacy in the Ascaris-antigen sensitized murine airway inflammation model by oral administration.

Design, synthesis, and analysis of a polyethelene glycol-modified (PEGylated) small molecule inhibitor of integrin {alpha}4{beta}1 with improved pharmaceutical properties

Integrin alpha4beta1 plays an important role in inflammatory processes by regulating the migration of leukocytes into inflamed tissues. Previously, we identified BIO5192 [2(S)-{[1-(3,5-dichloro-benzenesulfonyl)-pyrrolidine-2(S)-carbonyl]-amino}-4-[4-methyl-2(S)-(methyl-{2-[4-(3-o-tolyl-ureido)-phenyl]-acetyl}-amino)-pentanoylamino]-butyric acid], a highly selective and potent (K(D) of 9 pM) small molecule inhibitor of alpha4beta1. Although BIO5192 is efficacious in various animal models of inflammatory disease, high doses and daily treatment of the compound are needed to achieve a therapeutic effect because of its relatively short serum half-life. To address this issue, polyethylene glycol modification (PEGylation) was used as an approach to improve systemic exposure. BIO5192 was PEGylated by a targeted approach in which derivatizable amino groups were incorporated into the molecule. Two sites were identified that could be modified, and from these, five PEGylated compounds were synthesized and characterized. One compound, 2a-PEG (K(D) of 19 pM), was selected for in vivo studies. The pharmacokinetic and pharmacodynamic properties of 2a-PEG were dramatically improved relative to the unmodified compound. The PEGylated compound was efficacious in a rat model of experimental autoimmune encephalomyelitis at a 30-fold lower molar dose than the parent compound and required only a once-a-week dosing regimen compared with a daily treatment for BIO5192. Compound 2a-PEG was highly selective for alpha4beta1. These studies demonstrate the feasibility of PEGylation of alpha4beta1-targeted small molecules with retention of activity in vitro and in vivo. 2a-PEG, and related compounds, will be valuable reagents for assessing alpha4beta1 biology and may provide a new therapeutic approach to treatment of human inflammatory diseases.

VEGF and vascular changes in chronic neuroinflammation

A vascular component has long been associated with the pathological changes in multiple sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE). Despite the codependence of angiogenesis and many chronic inflammatory disorders, only circumstantial evidence is available to support the existence of angiogenesis in MS or EAE. To determine if angiogenesis occurs in conjunction with clinical and pathological signs of CNS inflammatory disease we evaluated temporal and spatial blood vessel counts, VEGF immunoreactivity, and histopathological changes in the spinal cord of guinea pigs with chronic-progressive (CP)-EAE (day 0-90 post-immunization, n=64) and controls (n=17). The number of vessels per section increased in infiltrated and demyelinated lesions by day 15 post-immunization and remained significantly higher than controls throughout the course of the disease. The number of vessels correlated with both clinical and pathological scores for inflammation, infiltration and demyelination. Vascular endothelial growth factor (VEGF) expression increased during acute disease peaking at day 26, which was the transition from the acute-inflammatory to chronic-demyelinating phase, before gradually returning to baseline levels. These observations implicate angiogenesis as a component of chronic neuroinflammation and demyelination and may suggest alternative therapeutic strategies for multiple sclerosis.

Synthesis, characterization and evaluation of pro-drugs of VLA-4 antagonists

A pro-drug strategy to identify orally efficacious VLA-4 antagonists is described. Potential pro-drugs were evaluated for their physical chemical characteristics and in vitro properties, including solubility, stability, permeability and plasma stability. Based on this characterization, promising compounds were identified for in vivo pharmacokinetic evaluation. These studies resulted in the identification of a pro-drug that exhibited desirable blood levels in PK studies in several different species.

Differential effects of treatment with a small-molecule VLA-4 antagonist before and after onset of relapsing EAE

Interaction of very late antigen-4 (VLA-4) with its ligand vascular cell adhesion molecule-1 (VCAM-1) is required for central nervous system (CNS) migration of encephalitogenic T cells in relapsing experimental autoimmune encephalomyelitis (R-EAE). Anti-VLA-4 monoclonal antibody (mAb) treatment prior to EAE onset inhibits disease induction; however, treatment initiated after the appearance of clinical symptoms increases relapse rates, augments Th1 responses, and enhances epitope spreading perhaps due to the activation of costimulatory signals. To negate the potential costimulatory activity of intact anti-VLA-4, we examined the ability of BIO 5192, a small-molecule VLA-4 antagonist, to regulate active proteolipid protein 139-151 (PLP139-151)-induced R-EAE. BIO 5192 administered one week after peptide priming (ie, before clinical disease onset) delayed the clinical disease onset but led to severe disease exacerbation upon treatment removal. BIO 5192 treatment initiated during disease remission moderately enhanced clinical disease while mice were on treatment and also resulted in posttreatment exacerbation. Interestingly, BIO 5192 treatment begun at the peak of acute disease accelerated entrance into disease remission and inhibited relapses, but treatment removal again exacerbated disease. Enhanced disease was caused by the release of encephalitogenic cells from the periphery and the rapid accumulation of T cells in the CNS. Collectively, these results further demonstrate the complexity of VLA-4/VCAM interactions, particularly in a relapsing-remitting autoimmune disease.

Role of ICAM-1 and P-selectin expression in the development and effector function of CD4+CD25+regulatory T cells

Dynamic regulatory mechanisms prevent autoreactive T cell activation. Upon T cell receptor crosslinking, CD4+CD25+ T regulatory (T(R)) cells block both the proliferation and cytokine production of CD4+CD25- effector cells in an apparent antigen non-specific manner. Within the T(R)population, L-selectin (CD62L)(hi)T(R)cells have been described as more efficient suppressors of T cell proliferation than CD62L(low)T(R)cells. We have previously reported that CD4+CD25+CD62L(hi)T(R)cells express elevated levels of two additional adhesion molecules, ICAM-1 (CD54) and P-selectin (CD62P) in comparison to non-T(R)cells. In the current study, we investigated the functional contribution of CD54 and CD62P expression to the suppressive phenotype of T(R)cells both in vitro and in vivo. While the CD4+CD25+ T(R)cell population was demonstrated to be significantly larger in CD62P-/- mice than in wild-type C57BL/6 mice, CD62P-/- T(R)cell function was deficient in vitro, but not in vivo. Interestingly, we detected no deficiencies in T(R)cell numbers or effector function in CD54-/- mice suggesting that T(R)cells may differ from effector CD4+ T cells in the requirement for CD54 expression within the immunological synapse. Collectively, these findings indicate that CD62P may influence T(R)cell differentiation/development and that T(R)cell activation occurs independently of CD54 expression.