Systemic Blockade of Clever-1 Elicits Lymphocyte Activation Alongside Checkpoint Molecule Downregulation in Patients with Solid Tumors: Results from a Phase I/II Clinical Trial

PURPOSE

Macrophages are critical in driving an immunosuppressive tumor microenvironment that counteracts the efficacy of T-cell-targeting therapies. Thus, agents able to reprogram macrophages toward a proinflammatory state hold promise as novel immunotherapies for solid cancers. Inhibition of the macrophage scavenger receptor Clever-1 has shown benefit in inducing CD8+ T-cell-mediated antitumor responses in mouse models of cancer, which supports the clinical development of Clever-1-targeting antibodies for cancer treatment.

PATIENTS AND METHODS

In this study, we analyzed the mode of action of a humanized IgG4 anti-Clever-1 antibody, FP-1305 (bexmarilimab), both in vitro and in patients with heavily pretreated metastatic cancer (n = 30) participating in part 1 (dose-finding) of a phase I/II open-label trial (NCT03733990). We studied the Clever-1 interactome in primary human macrophages in antibody pull-down assays and utilized mass cytometry, RNA sequencing, and cytokine profiling to evaluate FP-1305-induced systemic immune activation in patients with cancer.

RESULTS

Our pull-down assays and functional studies indicated that FP-1305 impaired multiprotein vacuolar ATPase-mediated endosomal acidification and improved the ability of macrophages to activate CD8+ T-cells. In patients with cancer, FP-1305 administration led to suppression of nuclear lipid signaling pathways and a proinflammatory phenotypic switch in blood monocytes. These effects were accompanied by a significant increase and activation of peripheral T-cells with indications of antitumor responses in some patients.

CONCLUSIONS

Our results reveal a nonredundant role played by the receptor Clever-1 in suppressing adaptive immune cells in humans. We provide evidence that targeting macrophage scavenging activity can promote an immune switch, potentially leading to intratumoral proinflammatory responses in patients with metastatic cancer.

Short-term homing assay reveals a critical role for lymphocyte function-associated antigen-1 in the hepatic recruitment of lymphocytes in graft-versus-host disease

BACKGROUND/AIMS

The liver is a major target organ of graft versus host disease (GvHD) with massive infiltration of alloreactive lymphocytes resulting in hepatitis and hepatocyte injury. Although adhesive mechanisms have been implicated in the biology of GvHD hepatitis, the identity of homing receptors involved in the initial recruitment of cells from the blood is not known.

METHODS

We have developed a short-term homing assay in a model of murine GvHD. Splenocytes from donors at an active stage of GvHD were injected intravenously into adoptive recipients also undergoing GvHD. The recruitment of cells to the liver was assessed 6h after cell transfer.

RESULTS

Activated donor CD8 and CD4 lymphocytes expressed lymphocyte function antigen-1 (LFA-1), alpha4-integrins, and P-selectin binding ligands, and localized more efficiently than naïve T cells. Immunoneutralization of LFA-1 reduced the recruitment of CD8 and CD4 lymphocytes to the liver by more than 60%. Anti-LFA-1 antibody also markedly reduced infiltration of lymphocytes in periportal areas and protected against hepatocellular damage.

CONCLUSIONS

We demonstrate a critical role of LFA-1 in the recruitment of activated lymphocytes to the liver and in immune-cell mediated hepatitis. LFA-1 may be an effective therapeutic target for protecting the liver following bone marrow transplantation.

Immune therapy for autoimmune diseases

Our increasing understanding of the pathophysiology of autoimmune disease has revealed a number of checkpoints that can be targeted with immune therapy, including key mediators of lymphocyte adhesion and migration, destructive cytokines involved in tissue damage, and the complex of molecules critical in the presentation of self-antigen and the activation of autoaggressive T lymphocytes. In many organ-specific autoimmune diseases, the identity of the molecules attacked by T cells and autoantibodies is known and attempts are under way to tolerize the immune system with a high level of specificity to these targets.

Biological therapy in Crohn's disease

The discovery of the central role of tumour necrosis factor-alpha in Crohn's disease and the subsequent introduction of infliximab into routine clinical practice has transformed the treatment of refractory disease. Advances in understanding of the immunopathological basis of Crohn's disease are leading to the development of new biological therapies which are likely to play an increasing role in future.

Enteral feeding preserves mucosal immunity despite in vivo MAdCAM-1 blockade of lymphocyte homing

OBJECTIVE

To determine the influence of route of nutrition on gut mucosal addressin cellular adhesion molecule-1 (MAdCAM-1) expression and the effect of MAdCAM-1 blockade on gut-associated lymphoid tissue (GALT) lymphocyte populations and established respiratory antibacterial immunity.

SUMMARY BACKGROUND DATA

Lymphocytes, sensitized to antigens in Peyer's patches, migrate via mesenteric lymph nodes and home to intestinal lamina propria. MAdCAM-1 located on endothelial cells regulates this trafficking. Experimentally, parenteral nutrition (PN) decreases GALT cell mass and mucosal immunity when compared with enteral feeding.

METHODS

In experiment 1, MAdCAM-1 expression was quantified in 32 mice after 4 days of feeding chow, a complex diet, intragastric (IG)-PN, or PN. In experiment 2, MAdCAM-1 was measured in 102 mice 0, 4, 8, 12, 24, 48, or 72 hours after starting PN and at 0, 4, 8, 12, 24, or 48 hours after reinstituting chow following 5 days of PN. In experiment 3, 56 mice received chow, PN, chow + MECA-367 (anti-MAdCAM-1 mAb), or chow + Isotype control Ab (IsoAb) for 5 days, followed by Peyer's patches, lamina propria, and intraepithelial lymphocyte yield with respiratory and intestinal IgA levels. In experiment 4, 10 days after Pseudomonas immunization, mice received chow + MECA-367 or chow + IsoAb for 4 days followed by 1.2 x 108 Pseudomonas intratracheally.

RESULTS

Diet and route affect MAdCAM-1 expression (chow > complex diet > IG-PN > PN). Decreased MAdCAM-1 expression occurred within hours of starting PN in Peyer's patches, but not mesenteric lymph nodes or the intestine, and recovered quickly with enteral refeeding. MAdCAM-1 blockade reduced all GALT populations. Blockade had little effect on IgA levels and partially impaired the late response of established respiratory immunity.

CONCLUSIONS

Enteral feeding affects MAdCAM-1 expression. Complete MAdCAM-1 blockade reduces GALT lymphocytes to PN levels, but the chow feeding stimulus preserves IgA and early antibacterial resistance, implying the existence of non-MAdCAM-1 mechanisms to preserve mucosal immunity.

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.

Alpha 4 integrin antagonists

The accumulation of leukocytes in various organs contributes to the pathogenesis of a number of human autoimmune diseases such as asthma, rheumatoid arthritis, Crohn s disease, ulcerative colitis, hepatitis C, and multiple sclerosis. The inflammatory processes leading to tissue damage and disease are mediated in part by the alpha4 integrins, alpha4beta1 and alpha4beta7, expressed on the leukocyte cell surface. These glycoprotein receptors modulate cell adhesion via interaction with their primary ligands, vascular cell adhesion molecule (VCAM) and mucosal addressin cell adhesion molecule (MAdCAM), expressed in the affected tissue. Upon binding, the combined integrin/CAM interactions at the cell surface result in firm adhesion of the leukocyte to the vessel wall followed by entry into the affected tissue. Elevated cell adhesion molecule (CAM) expression in various organs has been linked with several autoimmune diseases. Monoclonal antibodies specific for alpha4 integrins or their CAM ligands can moderate inflammation in animal models suggesting such inhibitors may be useful for treating human inflammatory diseases. The alpha4 integrins have become well validated drug targets for pharmaceutical companies and numerous publications describing alpha4 integrin antagonists have recently appeared. This article discusses the rationale for targeting alpha4 integrins for the treatment of autoimmune disorders and reviews some currently known antagonists. The methods used to identify lead molecules and the progress of selected antagonists toward becoming new drugs will is also discussed. (131 references).

Clustering of very late antigen-4 integrins modulates K(+) currents to alter Ca(2+)-mediated monocyte function

Endothelial cell vascular cell adhesion molecule-1 (VCAM-1) activates adherent monocytes by clustering their very late antigen-4 (VLA-4) receptors, resulting in the modulation of the inwardly rectifying (I(ir)) and delayed rectifying (I(dr)) K(+) currents, hyperpolarization of the cells, and enhanced Ca(2+) influx (Colden-Stanfield M and Gallin EK. Am J Physiol Cell Physiol 275: C267-C277, 1998; Colden-Stanfield M and Scanlon M. Am J Physiol Cell Physiol 279: C488-C494, 2000). The present study was undertaken to test the hypothesis that monoclonal antibodies (MAbs) against VLA-4 (MAbVLA-4) mimic VCAM-1 to cluster VLA-4 integrins, which play a key role in signaling an increase in the secretion of the proinflammatory cytokine interleukin-8 (IL-8). Whole cell ionic currents and IL-8 secretion from THP-1 monocytes that were incubated on polystyrene, VCAM-1-immobilized MAbVLA-4 or an isotype-matched MAb against CD45 (MAbCD45) were measured. Clustering of VLA-4 integrins with a cross-linked MAbVLA-4, but not a monovalent MAbVLA-4, modulated the K(+) currents in an identical manner to incubation of cells on VCAM-1. Similarly, cross-linked MAbVLA-4 or VCAM-1 augmented Ca(2+)-mediated IL-8 secretion from THP-1 monocytes and was completely abolished by exposure to CsCl, an I(ir) blocker. Thus VLA-4 integrin clustering by cross-linked MAbVLA-4 mimics VCAM-1/VLA-4 interactions sufficiently to be associated with events leading to monocyte differentiation, enhanced Ca(2+)-mediated macrophage function, and possibly atherosclerotic plaque formation.

Combinatorial approaches to inhibitors of VLA-4: piperazine-peptoid-bisarylureas

A combinatorial approach towards identifying inhibitors of VALA-4 was investigated. A library of piperazine-peptoid-bisarylureas was assembled in solid phase and screening in the novel v-well assay enabled the identification of active compounds.

Identification of potent and novel alpha4beta1 antagonists using in silico screening

The antigen alpha4beta1 (very late antigen-4, VLA-4) plays an important role in the migration of white blood cells to sites of inflammation. It has been implicated in the pathology of a variety of diseases including asthma, multiple sclerosis, and rheumatoid arthritis. We describe a series of potent inhibitors of alpha4beta1 that were discovered using computational screening for replacements of the peptide region of an existing tetrapeptide-based alpha4beta1 inhibitor (1; 4-[N'-(2-methylphenyl)ureido]phenylacetyl-Leu-Asp-Val) derived from fibronectin. The search query was constructed using a model of 1 that was based upon the X-ray conformation of the related integrin-binding region of vascular cell adhesion molecule-1 (VCAM-1). The 3D search query consisted of the N-terminal cap and the carboxyl side chain of 1 because, upon the basis of existing structure-activity data on this series, these were known to be critical for high-affinity binding to alpha4beta1. The computational screen identified 12 reagents from a virtual library of 8624 molecules as satisfying the model and our synthetic filters. All of the synthesized compounds tested inhibit alpha4beta1 association with VCAM-1, with the most potent compound having an IC(50) of 1 nM, comparable to the starting compound. Using CATALYST, a 3D QSAR was generated that rationalizes the variation in activities of these alpha4beta1 antagonists. The most potent compound was evaluated in a sheep model of asthma, and a 30 mg nebulized dose was able to inhibit early and late airway responses in allergic sheep following antigen challenge and prevented the development of nonspecific airway hyperresponsiveness to carbachol. Our results demonstrate that it is possible to rapidly identify nonpeptidic replacements of integrin peptide antagonists. This approach should be useful in identification of nonpeptidic alpha4beta1 inhibitors with improved pharmacokinetic properties relative to their peptidic counterparts.

Alpha(4)beta(7)/alpha(4)beta(1) dual integrin antagonists block alpha(4)beta(7)-dependent adhesion under shear flow

The alpha(4) integrin, alpha(4)beta(7), plays an important role in recruiting circulating lymphocytes to the gastrointestinal tract, where its ligand mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is preferentially expressed on high endothelial venules (HEVs). Dual antagonists of alpha(4)beta(1) and alpha(4)beta(7), N-(2,6-dichlorobenzoyl)-(L)-4-(2',6'-bis-methoxyphenyl)phenylalanine (TR14035) and N-(N-[(3,5-dichlorobenzene)sulfonyl]-2-(R)-methylpropyl)-(D)-phenylalanine (compound 1), were tested for their ability to block the binding of alpha(4)beta(7)-expressing cells to soluble ligand in suspension and under in vitro and in vivo shear flow. Compound 1 and TR14035 blocked the binding of human alpha(4)beta(7) to an (125)I-MAdCAM-Ig fusion protein with IC(50) values of 2.93 and 0.75 nM, respectively. Both compounds inhibited binding of soluble ligands to alpha(4)beta(1) or alpha(4)beta(7) on cells of human or rodent origin with similar potency. Under shear flow in vitro, TR14035 and compound 1 blocked binding of human alpha(4)beta(7)-expressing RPMI-8866 cells or murine mesenteric lymph node lymphocytes to MAdCAM-Ig with IC(50) values of 0.1 and 1 microM, respectively. Intravital microscopy was used to quantitate alpha(4)-dependent adhesion of fluorescent murine lymphocytes in Peyer's patch HEVs. When cells were prestimulated with 2 mM Mn(2+) to activate alpha(4)beta(7) binding to ligand, anti-alpha(4) monoclonal antibody (mAb) [10 mg/kg (mpk) i.v.] blocked adhesion by 95%, and anti-beta(1) mAb did not block adhesion, demonstrating that this interaction was dependent on alpha(4)beta(7). TR14035 blocked adhesion to HEVs [ED(50) of 0.01-0.1 mpk i.v.], and compound 1 blocked adhesion by 47% at 10 mpk i.v. Thus, alpha(4)beta(7)/alpha(4)beta(1) antagonists blocked alpha(4)beta(7)-dependent adhesion of lymphocytes to HEVs under both in vitro and in vivo shear flow.

IFN-gamma-inducible T cell alpha chemoattractant is a potent stimulator of normal human blood T lymphocyte transendothelial migration: differential regulation by IFN-gamma and TNF-alpha

Previous studies have shown that the CXC chemokine, IFN-gamma-inducible T cell alpha chemoattractant (I-TAC), was chemotactic for IL-2-activated human T lymphocytes, which express abundant CXCR3. However, because most memory T lymphocytes are also CXCR3(+), the ability of I-TAC to promote the migration of normal human blood T cells across HUVEC monolayers in Transwell chambers was examined. I-TAC induced a marked (4- to 6-fold) increase in transendothelial migration (TEM) of T cells across unstimulated HUVEC from 5.6 to 28% of input T cells and was substantially more active than IFN-gamma-inducible protein-10, another CXCR3 ligand. I-TAC significantly enhanced TEM of T cells across TNF-alpha, but not across IFN-gamma or IFN-gamma plus TNF-alpha-activated HUVEC. IFN-gamma or IFN-gamma plus TNF-alpha-activated HUVEC produced substantial amounts of I-TAC, in contrast to TNF-alpha-treated EC. Both CD4(+) and CD8(+) T cells migrated in response to I-TAC to a similar extent, while memory T cells migrated several fold better than naive T cells. Blockade of LFA-1 strongly inhibited I-TAC-induced T cell TEM across unstimulated HUVEC, and approximately 50-60% of the TEM across cytokine-activated HUVEC. However, blocking both LFA-1 and very late Ag-4 abolished I-TAC induced T cell TEM. In vivo significant levels of I-TAC were detected in arthritic synovial fluid. Thus, I-TAC is one of the most potent chemoattractants of normal human blood CD4 and CD8 T cell TEM and is likely a major mediator of blood memory T lymphocyte migration to inflammation.

Comparative assessment of the ligand and metal ion binding properties of integrins alpha9beta1 and alpha4beta1

Integrins alpha9beta1 and alpha4beta1 form a distinct structural class, but while alpha4beta1 has been subjected to extensive study, alpha9beta1 remains poorly characterized. We have used the small molecule N-(benzenesulfonyl)-(L)-prolyl-(L)-O-(1-pyrrolidinylcarbonyl)tyrosine (3) to investigate the biochemical properties of alpha9beta1 and directly compare these properties with those of alpha4beta1. Compound 3 has a high affinity for both integrins with K(D) values of < or =3 and 180 pM for alpha9beta1 in 1 mM Mn2+ (activating) and 1 mM Ca2+ and 1 mM Mg2+ (nonactivating) conditions and < or =5 and 730 pM for alpha4beta1 under the corresponding conditions. Ca2+ treatment promoted the binding of 3 to both integrins (EC50 = 30 microM Ca2+ in both cases). Compound 3 binding to both integrins was also stimulated by the addition of the activating monoclonal antibody TS2/16. These findings indicate that the mechanisms by which metal ions and TS2/16 regulate ligand binding to alpha9beta1 and alpha4beta1 are similar. The binding of 3 to both integrins induced the mAb 9EG7 LIBS epitope, a property consistent with occupancy of the receptor's ligand binding site by 3. But whereas EGTA treatment inhibited the binding of 9EG7 to alpha4beta1, it stimulated the binding of 9EG7 to alpha9beta1. The 9EG7 and TS2/16 effects point to contributions of the beta1-chains on binding. Cross-linking data revealed that the integrin alpha-chains are also involved in binding the small molecule, as stable linkages were observed on both the alpha9 chain of alpha9beta1 and the alpha4 chain of alpha4beta1. Extensive structure-activity analyses with natural and synthetic ligands indicate distinct features of the ligand binding pockets. Most notable was the estimated >1000-fold difference in the affinity of the integrins for VCAM-1, which binds alpha4beta1with an apparent K(D) of 10 nM and alpha9beta1 with an apparent K(D) of >10 microM. Differences were also seen in the binding of alpha9beta1 and alpha4beta1 to osteopontin. Compound 3 competed effectively for the binding of VCAM-1 and osteopontin to both integrins. While these studies show many similarities in the biochemical properties of alpha9beta1 and alpha4beta1, they identify important differences in their structure and function that can be exploited in the design of selective alpha9beta1 and alpha4beta1 inhibitors.

Eosinophil adhesion to cholinergic nerves via ICAM-1 and VCAM-1 and associated eosinophil degranulation

In vivo, eosinophils localize to airway cholinergic nerves in antigen-challenged animals, and inhibition of this localization prevents antigen-induced hyperreactivity. In this study, the mechanism of eosinophil localization to nerves was investigated by examining adhesion molecule expression by cholinergic nerves. Immunohistochemical and functional studies demonstrated that primary cultures of parasympathetic nerves express vascular cell adhesion molecule-1 (VCAM-1) and after cytokine pretreatment with tumor necrosis factor-alpha and interferon-gamma intercellular adhesion molecule-1 (ICAM-1). Eosinophils adhere to these parasympathetic neurones after cytokine pretreatment via a CD11/18-dependent pathway. Immunohistochemistry and Western blotting showed that a human cholinergic nerve cell line (IMR-32) expressed VCAM-1 and ICAM-1. Inhibitory experiments using monoclonal blocking antibodies to ICAM-1, VCAM-1, or CD11/18 and with the very late antigen-4 peptide inhibitor ZD-7349 showed that eosinophils adhered to IMR-32 cells via these adhesion molecules. The protein kinase C signaling pathway is involved in this process as a specific inhibitor-attenuated adhesion. Eosinophil adhesion to IMR-32 cells was associated with the release of eosinophil peroxidase and leukotriene C(4). Thus eosinophils adhere to cholinergic nerves via specific adhesion molecules, and this leads to eosinophil activation and degranulation; this may be part of the mechanism of eosinophil-induced vagal hyperreactivity.

Pulmonary eosinophilia in a murine model of allergic inflammation is attenuated by small molecule alpha4beta1 antagonists

Inhibition of alpha4beta1/vascular cell adhesion molecule-1 (VCAM-1) interactions have therapeutic potential in treating allergic airway disease because of the importance of these adhesion molecules in the trafficking of eosinophils, lymphocytes, and monocytes. We examined several small molecule inhibitors of alpha4beta1/VCAM-1 interactions with in vitro potencies (IC(50) values) ranging from 0.52 nM (CP-664511; 3-[3-(1-[2-[3-methoxy-4-(3-O-tolyl-ureido)phenyl]-acetylamino]-3-methyl-butyl)isoxazol-5-yl]-propionic acid) to 38.5 nM (CP-609643; 3-[3-methyl-1-[2-[4-(3-O-tolyl-ureido)-phenyl]-acetylamino]-butyl)-isoxazol-5-yl]-propionic acid). The same compounds were evaluated in vivo using a murine model of ovalbumin-induced pulmonary eosinophilia. In this model, systemic administration of antibodies against alpha4 reduced bronchoalveolar lavage (BAL) eosinophilia approximately 60%. Small molecule alpha4beta1 antagonists were administered by intratracheal instillation and demonstrated dose-dependent inhibition of BAL eosinophil numbers and achieved a maximum inhibition of approximately 60%. In general, the rank order of potency for these compounds in vitro was consistent with that observed in vivo, which confirms that their efficacy is likely via blockade of alpha4beta1/VCAM-1 interactions. The most potent compound, CP-664511, also inhibited BAL eosinophilia following s.c. administration (1-10 mg/kg, s.c.). These data support the utility of small molecule alpha4beta1 antagonists in the treatment of relevant diseases, such as asthma.

Melatonin reduces TNF-a induced expression of MAdCAM-1 via inhibition of NF-kappaB

BACKGROUND

Endothelial MAdCAM-1 (mucosal addressin cell adhesion molecule-1) expression is associated with the oxidant-dependent induction and progress of inflammatory bowel disease (IBD). Melatonin, a relatively safe, potent antioxidant, has shown efficacy in several chronic injury models may limit MAdCAM-1 expression and therefore have a therapeutic use in IBD.

METHODS

We examined how different doses of melatonin reduced endothelial MAdCAM-1 induced by TNF-a in an in vitro model of lymphatic endothelium. Endothelial monolayers were pretreated with melatonin prior to, and during an exposure, to TNF-a (1 ng/ml, 24 h), and MAdCAM-1 expression measured by immunoblotting.

RESULTS

MAdCAM-1 was induced by TNF-a. Melatonin at concentrations over 100 microm (10(-4) M) significantly attenuated MAdCAM-1 expression and was maximal at 1 mM.

CONCLUSIONS

Our data indicate that melatonin may exert therapeutic activity in IBD through its ability to inhibit NF-kappaB dependent induction of MAdCAM-1.

Squaric acid derivatives as VLA-4 integrin antagonists

SAR studies aimed at improving the rate of clearance by the incorporation of a 3,4-diamino-3-cyclobutene-1,2-dione group as an amino acid isostere in a series of VLA-4 integrin antagonists are described.

N-aryl 2,6-dimethoxybiphenylalanine analogues as VLA-4 antagonists

A series of N-arylated phenylalanine derivatives has been synthesized and has been shown to be potent inhibitors of the integrin VLA-4. N-phenyl and N-heteroaryl derivatives with hydrogen bond acceptors in the meta position demonstrated low nanomolar activity against VLA-4.

alpha(4)beta(1) Integrin activation of L-type calcium channels in vascular smooth muscle causes arteriole vasoconstriction

A pathway for the regulation of vascular tone appears to involve coupling between integrins and extracellular matrix proteins or their fragments and the subsequent modulation of ion movement across the smooth muscle cell membrane. Here, we report that the activation of L-type voltage-activated Ca(2+) channels occurs through a novel interaction of alpha(4)beta(1) integrin with peptides containing the Leu-Asp-Val (LDV) integrin--binding sequence, which is found in the CS-1 region of an alternately spliced fibronectin variant. Experiments were conducted on arterioles isolated from rat skeletal muscle. Arterioles exhibited sustained concentration-dependent vasoconstriction to LDV peptides but not to Leu-Glu-Val (LEV) control peptides. The constriction was associated with increased smooth muscle cell [Ca(2+)](i), as measured by using fura 2. The response could be inhibited with a function-blocking anti--alpha(4) integrin antibody. Removal of the endothelium did not alter the vasoconstrictor response. Further experiments demonstrated that the vasoconstriction was abolished by the L-type Ca(2+) channel inhibitor nifedipine and the Src family kinase inhibitor PP2. In studies of isolated smooth muscle cells using whole-cell patch-clamp methods, the L-type current was enhanced by the LDV but not LEV peptide and was blocked by PP2 or antibodies to alpha(4) integrin. Collectively, these data indicate that activation of alpha(4)beta(1) integrin leads to enhanced influx of Ca(2+) through L-type channels by activating a tyrosine kinase pathway, leading to vasoconstriction. Involvement of integrins in the modulation of vascular tone may be particularly important in vascular responses to mechanical signals, such as pressure and flow, and to tissue injury after damage to the extracellular matrix.

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.

The role of E-selectin, P-selectin, and very late activation antigen-4 in T lymphocyte migration to dermal inflammation

T lymphocyte infiltration into inflamed tissues is thought to involve lymphocyte rolling on vascular endothelial cells. Because both selectin and alpha(4) integrin adhesion molecules can mediate leukocyte rolling, the contribution of these receptors to lymphocyte migration to inflammation was examined. The recruitment of (111)In-labeled spleen T cells to intradermal sites injected with IFN-gamma, TNF-alpha, LPS, poly inosine-cytosine, and Con A was measured in the rat, and the effect of blocking mAbs to E-selectin, P-selectin, very late activation Ag-4 (VLA-4), and LFA-1 was determined on this T cell migration in vivo. Anti-E-selectin and anti-P-selectin mAbs each inhibited 10-40 and 20-48%, respectively, of the T lymphocyte migration to the inflammatory sites, depending on the stimulus. Blocking VLA-4 inhibited 50% of the migration to all of the lesions except Con A. Treatment with both anti-VLA-4 and anti-E-selectin mAbs inhibited up to 85% of the lymphocyte accumulation, while P-selectin and VLA-4 blockade in combination was not more effective than VLA-4 blockade alone in TNF-alpha, IFN-gamma, LPS, and poly inosine-cytosine lesions. Inhibiting E-selectin, P-selectin, and VLA-4 together nearly abolished lymphocyte migration to all inflammatory sites. Anti-LFA-1 mAb strongly inhibited lymphocyte accumulation by itself, and this inhibition was not significantly further reduced by E- or P-selectin blockade. Thus, T cell migration to dermal inflammation is dependent on E-selectin, P-selectin, and VLA-4, likely because these three receptors are required for rolling of memory T lymphocytes, but VLA-4 and E-selectin are especially important for lymphocyte infiltration in these tissues.

Blockade of signaling via the very late antigen (VLA-4) and its counterligand vascular cell adhesion molecule-1 (VCAM-1) causes increased T cell apoptosis in experimental autoimmune neuritis

We characterized the early effects of anti-very late antigen (VLA-4) and its counterligand vascular cell adhesion molecule-1 (VCAM-1) antibody therapy on T cell infiltration and apoptosis in adoptive transfer experimental autoimmune neuritis of female Lewis rats. At the peak of disease, animals were treated with anti-VCAM-1 monoclonal antibody (mAb), anti-VLA-4 mAb, or the respective isotype mAb controls 18, 12, or 6 h before perfusion. Anti-VCAM-1 led to a rapid, significant increase of apoptotic T cells in the sciatic nerve with a maximum after 6 h, preceding the significant decrease of T cell infiltration seen after 18 h. This was accompanied by a significant reduction in mRNA levels for IFN-gamma and inducible nitric oxide synthase. The results for anti-VLA-4 treatment showed a similar trend. The early increase of T cell apoptosis following disruption of VLA-4/VCAM-1 interaction may reflect a novel signaling component of proapoptotic pathways.

Alterations in the expression of homing-associated molecules at the maternal/fetal interface during the course of pregnancy

One of the most fascinating immunologic questions is how the genetically distinct fetus is able to survive and develop within the mother without provoking an immune rejection response. The pregnant uterus undergoes rapid morphological and functional changes, and these changes may influence the nature of local immune responses at the maternal/fetal interface at different stages of gestation. We hypothesized that specialized mechanisms exist to control access of maternal leukocyte subsets to the decidua and that these mechanisms are modulated during the course of pregnancy. At the critical period of initial placenta development, the maternal/fetal interface displays an unparalleled compartmentalization of microenvironmental domains associated with highly differentiated vessels expressing vascular addressins in nonoverlapping patterns and with recruitment of specialized leukocyte subsets (monocytes, granulated metrial gland cells, and granulocytes) thought to support, modulate, and regulate trophoblast invasion. One of the most striking observations at this time of gestation is the almost complete exclusion of lymphocytes from the maternal/fetal interface. The second half of pregnancy is characterized by a partial loss of microenvironmental specialization and different switches in vascular specificity within the decidua basalis, paralleling dramatic changes in the populations of recruited leukocytes (e.g., a striking influx of lymphocytes, especially T cells). In the term pregnant uterus, the expression of all vascular addressins decreased dramatically; only weakly staining maternal vascular segments remained. These segments may define sites of extremely low residual traffic in the term decidua, which contains remarkably few maternal leukocytes overall. Our results suggest that the maternal/fetal interface represents a situation in which leukocyte trafficking is exquisitely regulated to allow entry of specialized leukocyte subsets that may play a fundamental role in immune regulation during pregnancy.

N-acyl-L-phenylalanine derivatives as potent VLA-4 antagonists that mimic a cyclic peptide conformation

A series of N-benzylpyroglutamyl-L-phenylalanine derivatives bearing carbamoyl substituents in the 3- or 4-positions was prepared and assayed for inhibition of the interaction between VCAM and VLA-4. Potent inhibition was observed in a number of analogues with substitution in the 4-position favored over the 3-position. A crystal structure of the key intermediate 25 indicates that it accesses a low energy conformation which closely matches key pharmacophores of a structurally characterized cyclic peptide.

The discovery of small molecule carbamates as potent dual alpha(4)beta(1)/alpha(4)beta(7) integrin antagonists

The alpha(4)beta(1) and alpha(4)beta(7) integrins are implicated in several inflammatory disease states. Systematic SAR studies of an alpha(4)beta(1)-specific arylsulfonyl-Pro-Tyr lead led to the identification of a new alpha(4)beta(7) binding site, best captured by O-carbamates of Tyr for this structural class. Several compounds showed a 200- to 400-fold improvement in alpha(4)beta(7) binding affinity while maintaining subnanomolar alpha(4)beta(1) activity, for example 2l, VCAM-Ig alpha(4)beta(1) IC(50)=0.13 nM, VCAM-Ig alpha(4)beta(7) IC(50)=1.92 nM.

Specific and dual antagonists of alpha(4)beta(1) and alpha(4)beta(7) integrins

N-(3,5-Dichlorophenylsulfonyl)-(R)-thioprolyl biarylalanine 10a has been identified as a potent and specific antagonist of the alpha(4)beta(1) integrin. Altering the configuration of thioproline from R to S led to a series of dual antagonists of alpha(4)beta(1) and alpha(4)beta(7), and the N-acetyl analogue 8b was found to be the most potent dual antagonist. A binding site model for alpha(4)beta(1) and alpha(4)beta(7) is proposed to explain the structure-activity relationship.

Effects of VLA-4 antagonists in rat whole embryo culture

BACKGROUND

Pharmacological antagonism of VLA-4 (Very Late Antigen 4, alpha(4)beta(1) integrin) has become an attractive target for the treatment of predominantly eosinophil mediated disease states such as asthma, allergic rhinitis, multiple sclerosis, rheumatoid arthritis, diabetes, and inflammatory bowel disease. Gene knockouts of the alpha(4)-integrin subunit of VLA-4 or its cell surface ligand, VCAM-1, however, have been shown to result in embryo-lethality in homozygous null mice due to defects in chorio-allantoic or epi-myocardial fusion. Although gene knockout phenotypes are not always manifested by pharmacological antagonism, those studies suggested that VLA-4 antagonists might cause embryo-lethality or drug-induced malformations.

METHODS

To test these concepts, early neurulating rat embryos were cultured by the methods of New ('78) after intra-coelomic microinjection of a VLA-4 blocking antibody or in the presence of small molecule VLA-4 antagonists.

RESULTS

Defects in chorio-allantoic fusion were induced after microinjection of VLA4 blocking antibody and after continuous exposure to small molecule antagonists. In a minority of affected embryos chorio-allantoic fusion was completely blocked whereas the majority of affected embryos had only superficial chorio-allantoic fusion and the allantois was enlarged and edematous. Although the allantoic mesoderm covered the trophoblasts of the chorionic plate and contained blood vessels there was only minimal invasion of the trophoblasts by the allantoic mesoderm. The lowest observed effect level generally correlated with the IC(approximately 95), as determined in 90% plasma.

DISCUSSION

Based on these data, VLA-4 antagonism might represent a significant risk to the developing embryo/fetus. In vitro exposure, however, is "constant" and does not take into account the elimination phase of these xenobiotics in vivo. Given the high concentrations required to elicit an effect, therapeutic blood levels in vivo may be several fold lower than those that affect the conceptus, depending on the tissue penetration of the compound and the route of administration. VLA-4 also exists in a range of conformations and activation states in vivo and the gene KOs and present studies do not define whether these developmental processes are dependent upon a particular activation state of VLA-4. Therefore, state-selective antagonists may have an improved embryonic safety profile. Additional studies will be required to determine potential effects of VLA-4 antagonists on embryo/fetal development in vivo.

LC/MS/MS plasma assay for the peptidomimetic VLA4 antagonist I and its major active metabolite II: for treatment of asthma by inhalation

In vitro and in animals, I is a potent and specific peptidomimetic for the potential treatment of airway inflammation in the pathogenesis of asthma. Preclinical studies indicated extensive conversion of I to an active metabolite II, and thus, a very sensitive assay for I and II was needed to support an inhalation ascending-dose study in man. The LC/MS/MS plasma/urine assay method (1.0 ml of sample) involves the following: liquid-liquid extraction of acidified plasma into pentane-ethyl acetate (90:10 v/v); evaporation of the organic extract, reconstitution into methanol; addition of water to the methanolic extract and freezing. After thawing, the extract is centrifuged and the clear supernatant injected for chromatography. Extract is chromatographed on a YMC ODS-AM column (50 x 2.0 mm). For detection, a Sciex 365 LC/MS/MS with an electrospray inlet and used in the positive ion, multiple reaction monitoring mode was used to monitor precursor-->fragment ions of m/z 709-->594 for I and m/z 513-->380 for II. The plasma assay was linear over the concentration range of 0.1-100 ng/ml in plasma for I and II. Accuracy and precision for I ranged from 97.9 to 102.1% of nominal with a 0.84-10.65% CV; similarly for II, 98.0-101.7% and 1.39-9.28% CV, respectively. Extraction recovery averaged 63.7% for I and 64.9% for II. This general assay methodology may be applied to assay small acidic peptides and peptidomimetics from biological fluids by LC/MS/MS.

Discovery and evaluation of piperidinyl carboxylic acid derivatives as potent alpha(4)beta(1) integrin antagonists

Piperidinyl carboxylic acid-based derivatives were prepared as antagonists of the leukocyte cell adhesion process that is mediated through the interaction of the alpha(4)beta(1) integrin (VLA-4, very late antigen 4) and the vascular cell adhesion molecule 1 (VCAM-1). Compounds 2a-h inhibited the adhesion in a cell-based assay in the low and sub micromolar range, a pharmacokinetic study of 2d is reported.

Design and synthesis of potent and selective inhibitors of integrin VLA-4

The synthesis and identification of a novel series of inhibitors of integrin VLA-4 are described. Their in vitro activity and selectivity against closely related integrins are also presented.

The discovery of sulfonylated dipeptides as potent VLA-4 antagonists

Directed screening of a carboxylic acid-containing combinatorial library led to the discovery of potent inhibitors of the integrin VLA-4. Subsequent optimization by solid-phase synthesis afforded a series of sulfonylated dipeptide inhibitors with structural components that when combined in a single hybrid molecule gave a sub-nanomolar inhibitor as a lead for medicinal chemistry. Preliminary metabolic studies led to the discovery of substituted biphenyl derivatives with low picomolar activities. SAR and pharmacokinetic characterization of this series are presented.

Isoxazolyl, oxazolyl, and thiazolylpropionic acid derivatives as potent alpha(4)beta(1) integrin antagonists

A series of isoxazolyl, oxazolyl, and thiazolylpropionic acid derivatives derived from LDV was found to be a potent antagonist of the alpha(4)beta(1) integrin. The synthesis and SAR leading up to 3-[3-(1-[-[3-methoxy-4-(3-o-tolyl-ureido)-phenyl]-acetylamino]-3-methyl-butyl)-isoxazol-5-yl]-propionic acid (22) are reported. In an allergic mouse model, compound 22 was efficacious delivered systemically (58% inhib @ 10 mg/kg, sc) as well as by intra-tracheal instillation (ED(50)=2 microg/kg).

Evidence that ligand and metal ion binding to integrin alpha 4beta 1 are regulated through a coupled equilibrium

We have used the highly selective alpha(4)beta(1) inhibitor 2S-[(1-benzenesulfonyl-pyrrolidine-2S-carbonyl)-amino]-4-[4-methyl-2S-(methyl-[2-[4-(3-o-tolyl-ureido)-phenyl]-acetyl]-amino)-pentanoylamino]-butyric acid (BIO7662) as a model ligand to study alpha(4)beta(1) integrin-ligand interactions on Jurkat cells. Binding of [(35)S]BIO7662 to Jurkat cells was dependent on the presence of divalent cations and could be blocked by treatment with an excess of unlabeled inhibitor or with EDTA. K(D) values for the binding of BIO7662 to Mn(2+)-activated alpha(4)beta(1) and to the nonactivated state of the integrin that exists in 1 mm Mg(2+), 1 mm Ca(2+) were <10 pm, indicating that it has a high affinity for both activated and nonactivated integrin. No binding was observed on alpha(4)beta(1) negative cells. Through an analysis of the metal ion dependences of ligand binding, several unexpected findings about alpha(4)beta(1) function were made. First, we observed that Ca(2+) binding to alpha(4)beta(1) was stimulated by the addition of BIO7662. From solution binding studies on purified alpha(4)beta(1), two types of Ca(2+)-binding sites were identified, one dependent upon and the other independent of BIO7662 binding. Second, we observed that the metal ion dependence of ligand binding was affected by the affinity of the ligand for alpha(4)beta(1). ED(50) values for the metal ion dependence of the binding of BIO7762 and the binding of a lower affinity ligand, BIO1211, differed by 2-fold for Mn(2+), 30-fold for Mg(2+), and >1000-fold for Ca(2+). Low Ca(2+) (ED(50) = 5-10 microm) stimulated the binding of BIO7662 to alpha(4)beta(1). The effects of microm Ca(2+) closely resembled the effects of Mn(2+) on alpha(4)beta(1) function. Third, we observed that the rate of BIO7662 binding was dependent on the metal ion concentration and that the ED(50) for the metal ion dependence of BIO7662 binding was affected by the concentration of the BIO7662. These studies point to an even more complex interplay between metal ion and ligand binding than previously appreciated and provide evidence for a three-component coupled equilibrium model for metal ion-dependent binding of ligands to alpha(4)beta(1).

Diamine containing VLA-4 antagonists

Design and synthesis of a library as potential VLA-4 antagonists has been accomplished, based around a proposed pharmacophoric model. Compounds possessing submicromolar potency were identified and structure-activity relationships were seen across the library. Further derivatisation produced compounds with IC(50)'s <10 nmol for inhibiting the VLA-4 mediated binding of fibronectin to RAMOS cells, providing an ideal starting point for a lead optimisation Programme.

A homogeneous fluorometric assay for measuring cell adhesion to immobilized ligand using V-well microtiter plates

We have developed a homogeneous high-capacity assay format for measuring integrin- and selectin-dependent cell binding to immobilized ligand using V-well microtiter plates. 2',7'-Bis(2-carboxyethyl)-5-(and-6)-carboxylfluorescence, acetoxymethylester-labeled cells are added to ligand-coated V-shaped microtiter wells. Bound cells are separated from free cells using centrifugal force to produce shear stress. Nonadherent cells accumulate in the nadir of the well and are measured using a fluorescence plate reader. Antibody or low-molecular-weight inhibitors of either the ligand or the cell surface receptor result in less cell binding, more cells in the pellet, and increased signal. The optimization and validation of the very late antigen-4/vascular cell adhesion molecule-1 assay is described in detail. We demonstrate that this assay can be rapidly adapted to measure other integrin- and selectin-mediated interactions. This assay format has several advantages over conventional assays. The centrifugal process is biologically relevant and eliminates the washing steps to remove nonadherent cells that can cause well-to-well and plate-to-plate variation. Because the assay is robust with a high signal-to-noise ratio and low variability, it is ideally suited for studying multiple parameters of cell adhesion and for high capacity screening.

Inhibition of TNF-alpha-induced sickle RBC retention in retina by a VLA-4 antagonist

PURPOSE

Patients with sickle cell disease have elevated circulating levels of cytokines including tumor necrosis factor (TNF) alpha. TNF-alpha stimulates expression by endothelial cells of adhesion molecules, including vascular cell adhesion molecule (VCAM) 1. Others have demonstrated that VLA-4 (alpha(4)beta(1)), a ligand for VCAM-1 or fibronectin, is present on a fraction of sickle reticulocytes. The intent of this study was to determine, using a rat model, if TNF-alpha increases retention of sickle erythrocytes in retina and if that retention can be inhibited.

METHODS

TNF-alpha was given intraperitoneally to rats 5 hours before IV administration of FITC-labeled, density-separated sickle erythrocytes. After 5 minutes, rats were exsanguinated, and retinas were excised and incubated for ADPase activity, permitting the determination of the number and location of retained cells.

RESULTS

TNF-alpha caused a three- to fourfold increase in retention of sickle erythrocytes in retinal capillaries (P < 0.05) but not of normal human erythrocytes. Preincubation of sickle erythrocytes with TBC772, a peptide that blocks the binding of alpha(4)beta(1) and alpha(4)beta(7), or a monoclonal antibody against VLA-4 (19H8), significantly inhibited the TNF-alpha-induced retention (P < or = 0.02), whereas a control cyclic peptide and antibody had no effect. IV TBC772 also inhibited sickle erythrocyte retention (P = 0.01). Two intravenously administered anti-fibronectin antibodies inhibited sickle cell retention as well, but an anti-rat VCAM-1 antibody did not inhibit retention.

CONCLUSIONS

The authors conclude that TNF-alpha stimulates retention of sickle erythrocytes in the retinal vasculature. This increased retention can be blocked by a VLA-4 antagonist, suggesting that the cells retained after cytokine stimulation are reticulocytes. The counter-receptor for VLA-4 in this rat retina model appears to be fibronectin and not VCAM-1, based on data obtained using antibodies against these molecules.

Combining G-CSF with a blockade of adhesion strongly improves the reconstitutive capacity of mobilized hematopoietic progenitor cells

OBJECTIVE

Mobilization of hematopoietic progenitor cells is achieved mainly by application of growth factors and, more recently, by blockade of adhesion. In this report, we describe the advantages of a combined treatment with granulocyte colony-stimulating factor (G-CSF) and anti-VLA4 (CD49d)/anti-CD44 as compared to treatment with the individual components.

MATERIALS AND METHODS

Mobilization by intravenous injection of anti-CD44, anti-VLA4, or G-CSF was controlled in spleen and bone marrow with regard to frequencies of multipotential colony-forming unit (C-CFU), marrow repopulating ability, long-term reconstitution, recovery of myelopoiesis, and regain of immunocompetence.

RESULTS

Mobilization by anti-CD44 had a strong effect on expansion of early progenitor cells in the bone marrow, while the recovery in the spleen was poor. In anti-CD49d-mobilized noncommitted and committed progenitors, progenitor expansion was less pronounced, but settlement in the spleen was quite efficient. Thus, anti-CD44 and anti-CD49d differently influenced mobilization. Accordingly, mobilization and recovery after transfer were improved by combining anti-CD44 with anti-CD49d treatment. Mobilization by G-CSF was most efficient with respect to recovery of progenitor cells in the spleen. However, when transferring G-CSF-mobilized cells, regain of immunocompetence was strongly delayed. This disadvantage could be overridden when progenitor cells were mobilized via blockade of adhesion and when expansion of these mobilized progenitor cells was supported by low-dose G-CSF only during the last 24 hours before transfer.

CONCLUSION

Mobilization of pluripotent progenitor cells via antibody blockade of CD44 or CD49d or via G-CSF relies on distinct mechanisms. Therefore, the reconstitutive capacity of a transplant can be significantly improved by mobilization regimens combining antibody with low-dose G-CSF treatment.

Synthesis, conformational analysis and biological activities of lanthionine analogs of a cell adhesion modulator

Cell adhesion is critical for many biological processes, such as hemostasis, wound healing, tumor metastasis and inflammation. Integrins are important mediators of cell adhesion. The integrin alpha4beta1, also known as VLA-4, is a cell surface receptor involved in inflammation. A cyclic peptide, 1-FCA-Arg-c[Cys-Asp-Thz-Cys]-OH, is a potent antagonist to VLA-4 with an IC50 of 2.4 nM. In the current study, we synthesized the lanthionine analogs of 1-FCA-Arg-c[Cys-Asp-Thz-Cys]-OH and determined the conformations of both the parent compound and its lanthionine analog in solution by NMR and computer simulations. The lanthionine analog retains its selectivity to VLA-4 with high nanomolar potency. Both molecules adopt similar topological arrangements in their conformations, while some important differences remain in the sulfur bridge region, which may cause the difference in potency.

Imide and lactam derivatives of N-benzylpyroglutamyl-L-phenylalanine as VCAM/VLA-4 antagonists

A series of imides and lactams derived from 4-amino-N-benzylpyroglutamyl-L-phenylalanine was prepared and evaluated for activity as VCAM/VLA-4 antagonists. Imides were more potent than the corresponding lactams; several had subnanomolar IC50s in an ELISA based assay and were also highly effective at blocking VLA-4 expressing Ramos cell binding to VCAM coated plates.

Inhibition of phosphodiesterase 4 attenuates airway hyperresponsiveness and airway inflammation in a model of secondary allergen challenge

We compared for the first time the therapeutic potential of a specific phosphodiesterase 4 (PDE4) inhibitor, rolipram, with anti-VLA-4 and anti-IL-5 in a model of secondary allergen exposure of previously sensitized and challenged mice. To address these issues, mice were sensitized and challenged with ovalbumin (OVA) (primary challenge). Six weeks later, sensitized/challenged mice were reexposed to OVA (secondary challenge) and airway response (resistance [RL] and dynamic compliance [Cdyn]) to inhaled methacholine was monitored. After secondary OVA challenge, RL significantly increased as did the number of lung inflammatory cells and IL-4 and IL-5 production in bronchoalveolar lavage fluid (BALF). Administration of rolipram, in a dose-dependent manner, significantly prevented both changes in RL and Cdyn, as well as eosinophil, lymphocyte, and neutrophil accumulation in the BALF; IL-4 and IL-5 levels in BALF were also significantly reduced. In contrast, treatment with anti-VLA-4 and anti-IL-5 only prevented changes in RL and eosinophil numbers and IL-5 production in BALF. Further, goblet cell hyperplasia was suppressed only by treatment with rolipram. None of the treatments affected OVA-specific antibody levels. These studies confirm that IL-5 dependent eosinophilic inflammation plays an essential role in the development of certain aspects of airway function after rechallenge of sensitized mice and that lymphocytes and neutrophils are also important in the development of altered airway function. The use of agents that inhibit PDE4 may have an important role in the treatment of asthma in previously sensitized mice.

Antibody to the alpha4 integrin decreases infarct size in transient focal cerebral ischemia in rats

BACKGROUND AND PURPOSE

Inflammation, a process that involves neutrophils, lymphocytes, and monocytes, contributes to cerebral ischemic injury. Blockade of neutrophil adhesion to endothelium improves outcome after experimental stroke. In this study we sought to assess the contribution of lymphocytes and monocytes to ischemic brain injury.

METHODS

Male Lewis rats underwent 3 hours of middle cerebral artery occlusion followed by 45 hours of reperfusion. Two hours after the onset of ischemia, one group of animals received an intraperitoneal injection of antibodies to the alpha(4) integrin (n=16); another group was injected with an isotype control antibody (n=11). Neurological examination, body temperature, and body weight were assessed at different time points after stroke. Animals were killed 48 hours after the onset of ischemia for determination of infarct volume and leukocyte counts.

RESULTS

There were no significant differences in body temperature or weight at any time. Neurological scores (deficits) were significantly less in animals treated with anti-alpha(4) antibodies at 24 (2.0+/-1.2 versus 3. 0+/-0.4; P:=0.006) and 48 (2.0+/-1.2 versus 3.0+/-0.8; P:=0.011) hours after ischemia. Peripheral blood leukocyte counts were significantly higher in anti-alpha(4)-treated animals (6.8+/-2.2 x 10(9) versus 2.9+/-1.9 x 10(9); P:=0.001) and revealed a lymphocyte/monocyte predominance (86.0+/-16.2% versus 71.0+/-15.6%; P:=0.008). Infarct volume was significantly less in animals treated with antibodies to alpha(4) (120.1+/-51.21 versus 173.7+/-42.29 mm(3); P:=0.012).

CONCLUSIONS

These data support a role for lymphocytes and monocytes in cerebral ischemic injury and show that blockade of alpha(4), even when instituted after the onset of ischemia, can improve neurological outcome and decrease infarct volume.

Ligation of alpha4ss1 integrin on human intestinal mucosal mesenchymal cells selectively Up-regulates membrane type-1 matrix metalloproteinase and confers a migratory phenotype

Human intestinal lamina propria mesenchymal cells show high surface expression of the alpha4ss1 integrin. Ligation of alpha4ss1 on mesenchymal cell lines with an activating monoclonal anti-alpha4 antibody or vascular cell adhesion molecule-immunoglobulin (VCAM-IgG) leads to the appearance of activated forms of gelatinase A in culture supernatants, and the de novo expression of activated membrane type-1-matrix metalloproteinase (MT1-MMP). In functional assays, signaling through alpha4ss1 results in an increased capacity of mesenchymal cells to migrate through an artificial extracellular matrix, an effect inhibitable by excess tissue inhibitor of metalloproteinase-2. In organ cultures of human intestine, VCAM-IgG also up-regulates MT1-MMP, and in mucosal ulcers of inflammatory bowel disease patients, MT1-MMP transcripts are abundant, coincident with expression of VCAM-1 on cells at the ulcer margin. Collectively these results suggest that alpha4ss1-induced up-regulation of MT1-MMP may be a crucial factor in the migration of mesenchymal cells into ulcer beds during restitution of diseased gut mucosa.

Timing of administration of anti-VLA-4 differentiates airway hyperresponsiveness in the central and peripheral airways in mice

The development of airway hyperresponsiveness (AHR) is correlated with the infiltration into the lungs of activated eosinophils and T lymphocytes. In large part, influx of eosinophils into the lung is dependent on very late activating antigen-4 (VLA-4) expression. However, the kinetics of eosinophil recruitment and the development of AHR are not fully delineated. Airway function was monitored by changes in lung resistance (RL) and dynamic compliance (Cdyn) to methacholine (MCh) inhalation after anti-VLA-4. After ovalbumin (OVA) sensitization and airway challenge of BALB/c mice, AHR increased as did the number of lung inflammatory cells. Administration of anti-VLA-4 to sensitized mice 2 h before the first (of three) OVA airway challenges significantly prevented changes in RL. Moreover, injection of the antibody from 2 h before the first challenge to 42 h after the last challenge significantly prevented the increases in RL, as well as eosinophil and lymphocyte numbers in the bronchoalveolar lavage fluid (BALF); interleukin-5 (IL-5) and leukotriene concentrations in BALF were also significantly inhibited. Interestingly, treatment with anti-VLA-4 only prevented changes in Cdyn and goblet cell hyperplasia when administered 2 h before the first challenge. These studies demonstrate that the timing of anti-VLA-4 administration can selectively affect pathologic processes that contribute to altered airway function in the central and peripheral airways after allergen challenge.

Potent cyclic peptide inhibitors of VLA-4 (alpha4beta1 integrin)-mediated cell adhesion. Discovery of compounds like cyclo(MePhe-Leu-Asp-Val-D-Arg-D-Arg) (ZD7349) compatible with depot formulation

Additional structure-activity relationship studies on potent cyclic peptide inhibitors of very late antigen-4 (VLA-4) are reported. The new N- to C-terminal cyclic hexa-, hepta- and octapeptide inhibitors like cyclo(MeIle/MePhe-Leu-Asp-Val-X) (X = 2-4 amino acids containing hydrophobic and/or basic side chains) were synthesized using solid phase peptide synthesis methods. The peptides were evaluated in in vitro cell adhesion assays and in in vivo inflammation models. Many of the peptides like cyclo(MePhe-Leu-Asp-Val-D-Arg-D-Arg) (ZD7349) (17), cyclo(MeIle-Leu-Asp-Val-D-Arg-D-Arg-D-Phe) (20), cyclo(MeIle-Leu-Asp-Val-D-Arg-D-Arg-MePhe) (21) and cyclo(MePhe-Leu-Asp-Val-D-Arg-D-Arg-D-Ala-D-Ala) (23) were potent inhibitors of VLA-4-mediated cell adhesion and inhibited ovalbumin-induced delayed type hypersensitivity (DTH) response in mice. The more potent compounds were highly selective and did not affect U937 cell adhesion to fibronectin (VLA-5), phorbolmyristate acetate or PMA-differentiated U937 cell adhesion to intercellular cell adhesion molecule-1 (ICAM-1)-expressing Chinese hamster ovary cells (LFA-1) and adenosine diphosphate (ADP)-induced platelet aggregation (GPIIb/IIIa). In contrast to the inhibitors like Ac-cyclo(D-Lys-D-Ile-Leu-Asp-Val) and cyclo(CH2CO-Ile-Leu-Asp-Val-Pip-CH2CO-Ile-Leu-Asp-Val-Pip) described earlier, the new compounds were much more compatible with the depot formulations based on poly(DL-lactide-co-glycolide) polymers. The hexapeptide cyclo(MePhe-Leu-Asp-Val-D-Arg-D-Arg) (ZD7349) (17) inhibited MOLT-4 cell adhesion to fibronectin and vascular cell adhesion molecule-1 (VCAM-1) with IC50 values of 260 and 330 nM, respectively, and did not show any significant effect against other integrins (IC50 > 300 microM). ZD7349 inhibited ovalbumin-induced DTH response in mice when administered continuously using a mini-pump (ED50 0.01 mg/kg/day) or when given as an s.c. or i.v. bolus injection at a dose of 1-10 mg/kg. ZD7349 was also active in type II collagen-induced arthritis (CIA) and experimental autoimmune encephalomyelitis (EAE) tests at a dose of 3-10 mg/kg. The peptide was released from some formulations over a period of 10-20 days. ZD7349 is currently undergoing pre-clinical investigation.

Cell adhesion antagonists: synthesis and evaluation of a novel series of phenylalanine based inhibitors

Several phenylalanine based inhibitors were synthesized as antagonists of the leukocyte cell adhesion process that is mediated through the interactions of the mucosal addressin cell adhesion molecule (MAdCAM) and the integrin alpha4beta7. Analogues 20, 21, 22 and 24 displayed inhibition of adhesion in a cell based assay in the low micromolar range.

Potent cyclic monomeric and dimeric peptide inhibitors of VLA-4 (alpha4beta1 integrin)-mediated cell adhesion based on the Ile-Leu-Asp-Val tetrapeptide

Potent monomeric and dimeric cyclic peptide very late antigen-4 (VLA-4) inhibitors have been designed based on a tetrapeptide (Ile-Leu-Asp-Val) sequence present in a 25-amino acid peptide (CS-1) reported in the literature. The peptides, synthesized by the SPPS techniques, were evaluated in the in vitro cell adhesion assays and in the in vivo inflammation models. The N- to C-terminal cyclic peptides such as cyclo(Ile-Leu-Asp-Val-NH-(CH2)2-S-(CH2)2-CO) (28) and cyclo(MeIle-Leu-Asp-Val-D-Ala-D-Ala) (31), monomeric and dimeric peptides containing piperazine (Pip) or homopiperazine (hPip) residues as linking groups, e.g. cyclo(MeIle-Leu-Asp-Val-Pip-CH2CO-NH-(CH2)2-S-CH2-CO) (49) and cyclo(MeIle-Leu-Asp-Val hPip-CH2CO-MeIle-Leu-Asp-Val-hPip-CH2CO) (58) and cyclic peptides containing an amide bond between the side chain amino group of an amino acid such as Lys and the C-terminal Val carboxyl group, e.g. Ac-cyclo(D-Lys-D-Ile-Leu-Asp-Val) (62) and beta-Ala-cyclo(D-Lys-D-Leu-Leu-Asp-Val) (68) were more potent than CS-1 in inhibiting the adhesion of the VLA-4-expressing MOLT-4 cells to fibronectin. The more potent compounds were highly selective and did not affect U937 cell adhesion to fibronectin (VLA-5), PMA-differentiated U937 cell adhesion to intercellular cell adhesion molecule- 1-expressing Chinese hamster ovary cells (LFA-1) and ADP-induced platelet aggregation (GPIIb/IIIa). A number of the more potent compounds inhibited ovalbumin-induced delayed type hypersensitivity in mice and some were 100-300 times more potent (ED50 = 0.003-0.009 mg/kg/day, s.c.) than CS-1. Two peptides, Ac-cyclo(D-Lys D-Ile-Leu-Asp-Val) (62) and cyclo(CH2CO-Ile-Leu-Asp-Val-Pip-CH2CO-Ile-Leu-Asp-Val-Pip) (55), were formulated in poly(DL-lactide-co-glycolide) depots and the release profile was investigated in vitro over a 30-day period.

Carbacyclic peptide mimetics as VCAM-VLA-4 antagonists

Substitution of carbon for sulfur in a potent 13-membered cyclic disulfide containing peptide was accomplished via an intramolecular Wittig reaction and resulted in a series of 'carba' analogues. Potency in the VCAM-VLA-4 assay was sensitive to ring size and lower than that of the parent disulfide.

The design and synthesis of potent cyclic peptide VCAM-VLA-4 antagonists incorporating an achiral Asp-Pro mimetic

The Asp-Pro sequence of the cyclic peptide Ac-HN-Tyr-Cys*-Asp-Pro-Cys*-OH (1) could be replaced with the achiral dipeptide mimetic 1-(2-aminoethyl)cyclpentylcarboxylic acid with retention of potent inhibition of the VCAM-VLA-4 interaction.

Cyclic thioether peptide mimetics as VCAM-VLA-4 antagonists

Selective substitution of a sulfur atom by carbon in a highly potent 13-membered cyclic disulfide was accomplished by intramolecular displacement of a bromide. The potency of the resulting thioethers in the VCAM/VLA-4 assay was dependent on ring size and the position of the sulfur atom.