VLA-4 Antagonists Research Articles

Sulphonamide-based small molecule VLA-4 antagonists.

The discovery of a sulphonamide by-product with VLA-4 antagonistic activity led to a series of potent, small molecule VLA-4 antagonists. Synthesis, SAR and in vivo evaluation of the selected compound will be presented.

Corrigendum to “N-Isonicotinoyl-(l)-4-aminophenylalanine Derivatives as Tight Binding VLA-4 Antagonists”[Bioorg. Med. Chem. Lett. 13 (2003) 1891

Corrigendum to “N-Isonicotinoyl-(l)-4-aminophenylalanine Derivatives as Tight Binding VLA-4 Antagonists”[Bioorg. Med. Chem. Lett. 13 (2003) 1891

3-D-QSAR CoMFA and CoMSIA studies on tetrahydrofuroyl- l-phenylalanine derivatives as VLA-4 antagonists

Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were performed on tetrahydrofuroyl- l-phenylalanine derivatives as VLA-4 antagonists. The best CoMFA and CoMSIA models that were generated using atom based alignment from a training set of twenty five tetrahydrofuroyl- l-phenylalanine derivatives, are six-component models with good statistics; CoMFA: r 2 cv=0.366, r 2=0.983, s=0.099, F=172.661 and PRESS=4.435; CoMSIA: r 2 cv=0.528, r 2=0.995, s=0.054, F=577.87 and PRESS=3.563. Both of these 3-D-QSAR models were validated using a test set of eleven compounds, whose predicted pIC 50 values fall within one log unit of the actual pIC 50. The contour diagrams obtained for the various CoMFA and CoMSIA field contributions can be mapped back onto structural features to explain the activity trends of the molecules analysed. Based on the spatial arrangement of the various field contributions, novel molecules with improved activity can be designed.

Efficient synthesis of 3-aminocyclobut-2-en-1-ones: squaramide surrogates as potent VLA-4 antagonists.

A novel series of uniquely functionalized 3-aminocyclobut-2-en-1-ones has been prepared by facile condensation of a variety of cyclobuta-1,3-diones with a phenylalanine-derived primary amine. These systems subsequently lend themselves to substitution at C-2 by reaction with a variety of electrophilic reagents including N-halosuccinimides, sulfenyl chlorides, and Eschenmoser's salt. Compounds from this novel series are potent antagonists of VLA-4. [reaction: see text]

N-isonicotinoyl-(L)-4-aminophenylalanine derivatives as tight binding VLA-4 antagonists.

A series of isonicotinoyl-(L)-aminophenylalanine derivatives was prepared and evaluated as VLA-4 antagonists. These compounds exhibit subnanomolar binding affinity to VLA-4 and significant off-rates. The interplay between off-rate, protein binding and pharmacokinetics is discussed.

Dehydrophenylalanine derivatives as VLA-4 integrin antagonists

We describe a series of dehydrophenylalanine derivatives where the Z isomers are potent VLA-4 antagonists but are subject to rapid biliary clearance and the E isomers have poor activity but have a slower rate of clearance. These configurationally constrained molecules have led to the design of a novel class of benzodiazepine VLA-4 antagonists.

N-(3-Phenylsulfonyl-3-piperidinoyl)-phenylalanine derivatives as potent, selective VLA-4 antagonists

The SAR of 1-sulfonyl-cyclopentyl carboxylic acid amides, ligands for the VLA-4 integrin, was investigated. This effort resulted in the identification of N-(3-phenylsulfonyl-3-piperidinoyl)-( l)-4-(2′,6′-dimethoxyphenyl)phenylalanine 52 as a potent, selective VLA-4 antagonist (IC 50=90 pM). Expansion of the SAR demonstrated that this structural unit can be used to identify a diverse series of sub-nanomolar antagonists.

Aromatic β-Amino Acids as Asp-Phg Mimics in LDV Derived VLA-4 Antagonists­

Aromatic β-amino acid esters 2a-h were prepared in racemic and enantiomerically pure form by the Radionow reaction or based on the method described by Davis and used as mimics of the Asp-Phg C-terminus in LDV derived VLA-4 antagonists. As a promising β-amino acid ester, 11 was identified and used for the synthesis of the highly potent VLA-4 antagonist S9059 with an IC50 of 1.6 nM in a cell attachment assay.

Substituted 3-amino biaryl propionic acids as potent VLA-4 antagonists

A series of substituted N-(3,5-dichlorobenzenesulfonyl)-( l)-prolyl- and ( l)-azetidyl-β-biaryl β-alanine derivatives was prepared as selective and potent VLA-4 antagonists. The 2,6-dioxygenated biaryl substitution pattern is important for optimizing potency. Oral bioavailability was variable and may be a result of binding to circulating plasma proteins.

N-(Arylacetyl)-biphenylalanines as Potent VLA-4 Antagonists

A series of potent N-(aralkyl-, arylcycloalkyl-, and heteroaryl-acyl)-4-biphenylalanine VLA-4 antagonists was prepared by rapid analogue methods using solid-phase chemistry. Further optimization led to several highly potent compounds (IC 50 <1 nM). Evaluation of rat pharmacokinetic revealed generally high clearance.

N-Aryl-prolyl-dipeptides as potent antagonists of VLA-4

The design, synthesis, and biological evaluation of N-arylprolyl-dipeptide derivatives as small molecule VLA-4 antagonists is described. Potency against VLA-4 and α 4β 7 and rat pharmacokinetic evaluation revealed some advantages over the related N-(arylsulfonyl)-prolyl-dipeptide analogues.

N-(Pyrimidin-4-yl) and N-(Pyridin-2-yl) phenylalanine derivatives as VLA-4 integrin antagonists

The SAR studies to optimise both potency and rate of clearance in the rat for a series of pyrimidine and pyridine based VLA-4 antagonists are described.

Substituted tetrahydrofuroyl-1-phenylalanine derivatives as potent and specific VLA-4 antagonists

A series of substituted tetrahydrofuroyl-1-phenylalanine derivatives was prepared and evaluated as VLA-4 antagonists. Substitution of the α carbon of the tetrahydrofuran with aryl groups increased the specificity for VLA-4 versus α 4β 7 while amide substitution increased the potency of the series without increasing the specificity. Substitution of the β carbon of the tetrahydrofuran with keto or amino groups slightly improved the specificity for VLA-4 versus α 4β 7 but with a significant loss in binding affinity for VLA-4.

N-Tetrahydrofuroyl-( l)-phenylalanine derivatives as potent VLA-4 antagonists

Given the proposed involvement of VLA-4 in inflammatory processes, a program to identify orally active VLA-4 antagonists was initiated. Herein, we report the discovery of a N-tetrahydrofuroyl-( l)-phenylalanine derivative ( 17) and related analogues as potent VLA-4 antagonists with good oral bioavailability.

Inhibition of LFA-1/ICAM-1 and VLA-4/VCAM-1 as a therapeutic approach to inflammation and autoimmune diseases.

This review focuses on providing insights into the structural basis and clinical relevance of LFA-1 and VLA-4 inhibition by peptides and small molecules as adhesion-based therapeutic strategies for inflammation and autoimmune diseases. Interactions of cell adhesion molecules (CAM) play central roles in mediating immune and inflammatory responses. Leukocyte function-associated antigen (LFA-1, alpha(L)beta(2), and CD11a/CD18) and very late antigen (VLA-4, alpha(4)beta(1), and CD49d/CD29) are members of integrin-type CAM that are predominantly involved in leukocyte trafficking and extravasation. LFA-1 is exclusively expressed on leukocytes and interacts with its ligands ICAM-1, -2, and -3 to promote a variety of homotypic and heterotypic cell adhesion events required for normal and pathologic functions of the immune systems. VLA-4 is expressed mainly on lymphocyte, monocytes, and eosinophils, but is not found on neutrophils. VLA-4 interacts with its ligands VCAM-1 and fibronectin (FN) CS1 during chronic inflammatory diseases, such as rheumatoid arthritis, asthma, psoriasis, transplant-rejection, and allergy. Blockade of LFA-1 and VLA-4 interactions with their ligands is a potential target for immunosuppression. LFA-1 and VLA-4 antagonists (antibodies, peptides, and small molecules) are being developed for controlling inflammation and autoimmune diseases. The therapeutic intervention of mostly mAb-based has been extensively studied. However, due to the challenging relative efficacy/safety ratio of mAb-based therapy application, especially in terms of systemic administration and immunogenic potential, strategic alternatives in the forms of peptide, peptide mimetic inhibitors, and small molecule non-peptide antagonists are being sought. Linear and cyclic peptides derived from the sequences of LFA-1, ICAM-1, ICAM-2, VCAM-1, and FN C1 have been shown to have inhibitory effects in vitro and in vivo. Finally, understanding the mechanism of LFA-1 and VLA-4 binding to their ligands has become a fundamental basis in developing therapeutic agents for inflammation and autoimmune diseases.

Identification of Unique VLA-4 Antagonists from a Combinatorial Library

A combinatorial library of 28 pools of 180 compounds (345 diastereomers) was designed and prepared in support of the delineation of the SAR of two prototypical VLA-4 antagonists. Deconvolution of the active pools led to the identification of three novel series of VLA-4 antagonists with low nanomolar potencies.

3D QSAR (COMFA) of a series of potent and highly selective VLA-4 antagonists.

The integrin VLA-4 (alpha4,beta1) is involved in the migration of white blood cells to sites of inflammation, and is implicated in the pathology of a variety of diseases including asthma and multiple sclerosis. We report the structure-activity relationships of a series of VLA-4 antagonists that were based upon the integrin-binding sequence of the connecting segment peptide of fibronectin (Leu-Asp-Val), and of VCAM-1 (Ile-Asp-Ser), both natural ligands of VLA-4. We explore variation in the ligand derived peptide portion of these antagonists and also in the novel N-terminal cap, which have discovered through chemical optimization, and which confers high affinity and selectivity. Using the X-ray derived conformation of the Ile-Asp-Ser region of VCAM-1, we rationalize the structure-activity relationships of these antagonists using 3D QSAR (COMFA). The COMFA model was found to be highly predictive with a cross-validated R2CV of 0.7 and a PRESS of 0.49. The robustness of the model was confirmed by testing the influence of various parameters, including grid size, column filtering, as well as the role of orientation of the aligned molecules. Our results suggest that the VCAM-1 structure is useful in generating highly predictive models of our VLA-4 antagonists. The COMFA model coupled with the knowledge that the peptide amides are tolerant to methylation should prove useful in future peptidomimetic design studies.

Mechanisms for sickle red blood cell retention in choroid

Purpose. Although sickle (SS) red cell-mediated vaso-occlusion in retina and resultant retinopathy is well documented, the effects of SS red cells on choroidal vasculature are poorly understood. The intent of this study was to determine, using a rat model, the conditions under which retention of sickle erythrocytes in choroid occur and if that retention can be inhibited. Methods. Sickle red cells were density separated into high density (SS4) or normal density, reticulocyte-enriched fractions (SS2). Red cells were labeled with FITC and administered IV to anesthetized Sprague Dawley rats. Rats were made either hypoxic or were given TNF-a intraperitoneally 5 hours before intravenous administration of red cells. Five minutes after administration of red cells, rats were exsanguinated, the retinas removed, and choroids prepared as flat-mounts. The number of red cells retained in five high power fields of choroid was then determined. In other experiments, SS red cells were preincubated with the cyclic peptide TBC772 [inhibits binding of a4ß1 (VLA-4) and a4ß7 to their ligands], a control peptide TBC1194, or a VLA-4 neutralizing antibody before administration to the rat or antibodies against VLA-4 ligands were delivered IV before administration of SS red cells. Results. Hypoxic conditions before administration of SS red cells significantly stimulated retention of SS4 cells (P = 0.0003), but did not significantly increase retention of SS2 cells. Administration of TNF-a significantly increased retention of all types of SS red cells (P < 0.001). Preincubation of cells with anti-VLA-4 or TBC 772 inhibited retention of SS red cells in choriocapillaris of TNF-a-treated rats (P < 0.0001). Complete inhibition of cytokine-stimulated retention was also accomplished by IV administration of mono-clonal antibodies against fibronectin or its CS-1 domain, a ligand for VLA-4. Conclusions. The mechanisms for retention of SS red cells in retina and choroid appear identical: hypoxia-mediated retention of dense red cells and adherence of red cells in reticulocyte-rich fractions after cytokine stimulation. TNF-a-stimulated retention of SS red cells in choroid appears to be mediated by VLA-4, presumably on the surface of some reticulocytes. This increased retention was inhibited by a VLA-4 antagonist (TBC772), a VLA-4 neutralizing antibody or by blocking one of VLA-4's ligands, the CS-1 portion of fibronectin.

The Discovery of acylated β-Amino acids as potent and orally bioavailable VLA-4 antagonists

Acylated β-amino acids are described as potent, specific and orally bioavailable antagonists of VLA-4. The initial lead was identified from a combinatorial library. Subsequent optimization using a traditional medicinal chemistry approach led to significant improvement in potency (up to 8-fold) while maintaining good pharmacokinetic properties.

Substituted N-(3,5-Dichlorobenzenesulfonyl)- l-prolyl-phenylalanine analogues as potent VLA-4 antagonists

A series of substituted N-(3,5-dichlorobenzenesulfonyl)- l-prolyl- and α-methyl- l-prolyl-phenylalanine derivatives was prepared as VLA-4/VCAM antagonists. The compounds showed excellent potency with a wide variety of neutral, polar, electron withdrawing or donating groups on the phenylalanine ring (IC 50∼1 nM). Heteroaryl ring substitution for phenylalanine was also well tolerated. Pharmacokinetic studies in rat were performed on a representative set of compounds in both series.