118 Current Immunology Reviews, 2012, 8, 118-134

Integrin
47 Antagonists: Activities, Mechanisms of Action and Therapeutic Prospects Dulce Soler-Ferran*,1 and Michael J. Briskin2

1Former Affiliation: Millennium Pharmaceuticals. Currently at Centers for Therapeutic Innovation (CTI), Pfizer, Inc., 3 Blackfan Circle, Boston, MA 02115, USA 2Former Affiliation: Millennium Pharmaceuticals and Merrimack Pharmaceuticals; Currently at Biotechnology Consulting, 28 Harbell Street, Lexington, MA 02421, USA

Abstract: The
47 integrin is a leukocyte homing receptor with selective tissue tropism for the gastrointestinal tract through its interaction with MAdCAM-1, an adhesion receptor expressed on the endothelium of the gut mucosa. Crohn’s disease (CD) and ulcerative colitis (UC), two inflammatory bowel diseases resulting from intestinal immune- dysregulation, are associated with pronounced infiltration of
47 positive lymphocytes. This has triggered the development of inhibitors of the
47/MAdCAM-1 homing pathway. Vedolizumab is a humanized monoclonal antibody selective for
47 that demonstrated efficacy in early clinical studies for the treatment of CD and UC and is currently in phase 3 clinical trials. Targeting of
47 is also achieved by less selective therapeutic modalities which also block one of the two other leukocyte integrins that share a subunit with
47, namely,
41 and
E7. Natalizumab is an anti-
4

monoclonal antibody and dual
41 and
47 antagonist approved for the treatment of multiple sclerosis and CD. Other therapies in development include antibodies targeting the 7 subunit of
47 and
E7, MAdCAM-1, and dual
4 small molecule antagonists. This review will focus on the mechanism of action, pharmacology, efficacy and safety properties as well as future opportunities that may arise from this unique class of leukocyte anti-adhesion antagonists.

Keywords:
47,
41, and
E7, integrin, inflammatory bowel disease (IBD), mucosal addressin cell adhesion molecule 1 (MAdCAM-1), natalizumab, progressive multifocal leukoencephalopathy (PML), vedolizumab.

INTRODUCTION tissue-tropism is most elegantly illustrated in the gastro- intestinal tract by the imprinting of the gut-homing Chronic inflammatory diseases arise from dysregulated lymphocyte receptors, the integrin
47 and the chemokine innate and adaptive immune responses and are characterized receptor CCR9. These homing receptors are induced via by large inflammatory infiltrates, which come about as a interaction with dendritic cells of the inductive gut result of expansion and excessive trafficking of particular associated lymphoid tissues (GALT), the Peyer’s patches leukocyte subsets [1]. Regulation of lymphocyte trafficking (PPs) and mesenteric lymph nodes (MLNs) [5-7]. The into lymphoid and non-lymphoid tissues involves a complex expression of
47 is associated with homing to both the multi-step process that requires the sequential engagement of hi + large and small intestine while
47 CCR9 lymphocyte unique combinations of particular adhesive and signaling populations preferentially migrate to the small intestine [8- molecules on the surface of the lymphocyte with their 10]. The regulation of these receptors during memory respective ligands/receptors on the endothelial cell at the acquisition dictates the specification and segregation of sites of leukocyte extravasation [2, 3]. This molecular intestinal versus systemic (or non intestinal) immune diversity provides a mechanism for the regional responses. specialization of adaptive immune responses. Targeting the Increased expression of MAdCAM-1 and associated molecular mechanisms that confer tissue-selectivity to the hi trafficking of lymphocytes is a novel therapeutic strategy for trafficking of
47 subsets in the gastrointestinal tract have modulating pathogenic adaptive immune responses and long suggested that these receptors might play a role in treating organ-specific chronic inflammatory diseases induction and maintenance of intestinal inflammation. The without causing significant systemic immunosuppression. two major forms of inflammatory bowel diseases (IBD) Crohn’s disease (CD) and ulcerative colitis (UC), are still Naïve lymphocytes exert their immune surveillance fraught with lack of understanding of etiology and function by circulating continuously between the blood and mechanism but are both characterized by amplified cellular the lymphoid organs in search of cognate antigens. Upon hi infiltrates consisting of
47 lymphocytes and increased antigen encounter and activation in different regional expression of MAdCAM-1 [11-15]. It is thought that lymphoid organs, lymphocytes acquire homing receptors initiation of these diseases partially results from defects in which imprint them with capacities to migrate to the tissues innate immunity which cause altered adaptive immune where antigen was first encountered [4]. This selective responses which lead to the chronic inflammatory states that characterize these debilitating disorders [1, 16]. Crohn’s disease can affect the entire gastrointestinal tract; it is *Address correspondence to this author at the Centers for Therapeutic Innovation (CTI), Pfizer, Inc., 3 Blackfan Circle, Boston, MA 02115, USA; characterized by discontinuous lesions, transmural pathology Tel: 617-599-7377; and often granulomas and fistulae. UC pathology however, is E-mails: [email protected], [email protected] restricted to the large bowel and is characterized by

1875-631X/12 $58.00+.00 © 2012 Bentham Science Publishers Integrin
47 Antagonists Current Immunology Reviews, 2012, Vol. 8, No. 2 119 continuous superficial lesions of the mucosal layer. Current and mediate important immune cell functions.
41 binding management of CD and UC is often unsatisfactory because to its endothelial receptor, VCAM-1 (vascular cell adhesion of either lack of efficacy and durable response or side molecule-1) mediates lymphocyte recruitment into several effects. Recently, anti-TNF
biologics have been shown to inflamed tissues outside the gastrointestinal tract including be effective for induction and maintenance of response in the brain, the lung, synovium and the heart. The predominant IBD [17]. However, a significant proportion of patients fail ligand for
47, mucosal addressin cell adhesion molecule to respond or become refractory to anti-TNF therapy. In (MAdCAM-1), exhibits a more restricted tissue expression. addition, anti-TNF agents are frequently associated with It is preferentially and constitutively expressed at sites of serious complications [18]. Consequently, there is a need for extravasation of intestinal lymphoid tissue and intestinal new therapies for IBD that induce and maintain remission lamina propria where it mediates the migration of gut- and cause minimal immunosuppression or other complications. homing lymphocyte subsets. A number of studies discussed below suggest that integrin
 interacting with MAdCAM- Decreasing immune cell infiltration in the chronically 4 7 1 plays a critical role in lymphocyte recirculation to inflamed gut tissue by blocking the interaction of the gut intestinal tissues but not to non-intestinal tissues. homing
47 integrin on circulating leukocytes with its endothelial counter receptor, MAdCAM-1, represents a promising novel therapeutic modality for the treatment of

IBD. Current antagonists of
47 in development include a selective anti-
47 monoclonal antibody, vedolizumab; a selective MAdCAM-1 antibody; and dual anti-
4 (
41and
47) and anti-7 (
47 and
E7) monoclonal antibodies. Natalizumab, the dual
4 antibody, is used clinically for the treatment of multiple sclerosis and in the US for Crohn’s disease. This review will focus on the current status in the development of these novel anti-adhesive therapeutics as well as their mechanism of action and pharmacologic properties. We will also discuss potential efficacy and safety advantages and disadvantages, small molecule antagonists of
47 as well as other potential therapeutic indications for therapies targeting the
 /MAdCAM-1 pathway. 4 7

ROLE OF
47 AND MADCAM-1 IN LYMPHOCYTE RECRUITMENT TO THE GASTROINTESTINAL TRACT The intestinal adaptive immune system plays an essential role in protecting against constant exposure to pathogens and in maintaining tolerance to commensal antigens and normal flora. Lymphocytes in the intestine are found in the gut- associated lymphoid tissues (GALT) (e.g. Peyer’s patches, Fig. (1). Classical view of multistep adhesion cascade. Initial mesenteric lymph nodes (MNL)), diffused through the lymphocyte endothelial cell interactions characterized by leukocyte lamina propria and embedded in the epithelium (IELs rolling, are typically mediated by selectin family members and intraepithelial lymphocytes), reaching these sites by various carbohydrate containing glycoprotein ligands. Some species extravasation from the vasculature. of MAdCAM-1 are also decorated with selectin binding determi- Leukocyte migration from the circulation into lymphoid nants and can bind L-selectin.
47 can thus mediate leukocyte and non-lymphoid tissues takes place following a sequence rolling as well, but upon chemokine triggering it mediates firm of molecular events (Fig. 1). The first is the tethering or adhesion to MAdCAM-1 on the vessel wall after which rolling of the leukocyte along the vessel wall through a series transmigration ensues. of weak and reversible interactions typically mediated by members of the selectin family of proteins and their
47 Integrin carbohydrate ligands on the endothelium. This allows for sampling of signaling molecules such as chemokines which
47 initially was termed LPAM-1 (lymphocyte Peyer’s activate their respective receptors and induce increased patch (PP) adhesion molecule-1) as it was shown to mediate the integrin adhesiveness, causing them to firmly bind to their adhesion of lymphocytes to the high endothelial cells of post- endothelial receptor and arrest the cell. Diapedesis and capillary venules (HEVs) of PPs [22, 23]. The critical role of transendothelial migration then ensues in the direction of a
47 in mediating the migration of lymphocytes to Peyer’s chemotactic gradient [2, 19]. patches and the small and large intestinal lamina propria was first demonstrated by in vivo homing studies with antibodies Integrins are heterodimeric cell surface proteins that specific for the
47 heterodimer, and anti-
4, anti-7 and anti- mediate many important cellular functions including MAdCAM-1 antibodies [24, 25] and with studies with 7 adhesion, migration, proliferation, hematopoiesis and deficient mice or immune cells. Antibodies to 7 preferentially survival by binding to their counter-receptors on cells or inhibited in vivo homing to Peyer’s patches, partially inhibited extracellular matrix proteins [20, 21]. The
4 integrins,
41 homing to MLN, and were ineffective in blocking homing to and
47 are expressed on many types of hematopoietic cells peripheral nodes; a pattern that is consistent with the progressive 120 Current Immunology Reviews, 2012, Vol. 8, No. 2 Soler-Ferran and Briskin decreased expression of MAdCAM-1 at these respective sites. preferentially, but not exclusively, expressed at anatomic 7 deficient mice are healthy and develop normally but contain sites of lymphocyte extravasation in gastrointestinal tissues. hypocellular PPs (but no change in their numbers); they have It is constitutively expressed in high endothelial cells of greatly decreased numbers of B cells, plasma cells, and helper T post-capillary venules of intestinal lymphoid tissues, PPs and cells in the lamina propria and decreased numbers of IELs. Firm mesenteric MLNs, and in endothelial cells of post-capillary adhesion and migration of 7 -/- lymphocytes to PPs was venules of the small and large intestinal lamina propria. mostly abrogated and it was reduced in MLNs [26]. Another MAdCAM-1 is also expressed in follicular dendritic cells of study with 7 -/- mice demonstrated a requirement for this Peyer’s patches [11, 44]. integrin in the migration of naïve CD8+ T cells and B cells to While MAdCAM-1 is the predominant ligand for
 , PPs but not to MLNs. In this study, migration of activated CD8+ 4 7 this integrin can also bind to VCAM-1 and fibronectin but T cells during an anti-viral immune response was impaired in with much lower affinity. These additional interactions do PPs and MLNs, and in large and small intestinal lamina propria not appear to play a role in extravasation but rather, may be [9]. Lastly, a study that showed the requirement of 7 for B involved in intra-tissue interactions with stromal cells or lymphocyte migration into isolated lymphoid follicles (ILF) extracellular matrix.
4-VCAM-1 interactions appear to be within intestinal mucosa (but not for cryptopatch formation) dominated by
41 even when adhesion is performed with added further proof to the selectivity of this pathway [27]. hi
47 lymphocytes (which also express low levels of
41) An important role for
47 in the migration of leukocytes to [4, 45]. the gut was also suggested by several studies that established a MAdCAM-1 gene-deficient mice are healthy, fertile and correlation between
 expression and lymphocyte 4 7 with no obvious alterations. PPs developed normally until recirculation into the gut and not into other peripheral tissues, day 3 of birth, but became hypocellular as a result of a including the lung or the skin [28]. Consistent with a role of homing defect, a phenotype reminiscent of the 7-deficient
47 in intestinal immunity, protective adaptive immune mice. These mice have decreased numbers of B cells and responses to enteric pathogens are also associated with high plasma cells in the LP, likely due to a homing failure of expression of
 in pathogen-specific lymphocytes [28, 29]. 4 7 these cells as shown by adoptive transfer experiments. In In addition, a subset of dendritic cells (CD103+) derived agreement with this, IgA plasma cells in blood and spleen from LP, PPs and MLNs, but not DCs from other were elevated and humoral immune responses to oral but not microenvironments, induce expression of
47 and CCR9 --a systemic antigen immunizations were compromised, small intestine-tropic chemokine receptor for CCL25 (a emphasizing the role of MAdCAM-1/
47 in regional chemokine expressed by small intestine epithelium)-- on T and immunity [46]. B cells in a retinoic acid dependent manner [5-7, 30-33]. The strength of the RA signal appears to regulate large versus small
47/MAdCAM-1 Interactions Mediate Migration of intestinal tropism by inducing expression of
47 without or Lymphocytes to Intestinal Lymphoid and Non-Lymphoid with concomitant CCR9 expression respectively; while hi + hi - Tissue
47 CCR9 migrate to the small intestine,
47 CCR9 lymphocytes migrate to and induce inflammation in the large
47/MAdCAM-1 interactions mediate not only firm intestine but can also migrate to the small intestine, presumably adhesion but also L-selectin independent lymphocyte rolling through activation by other chemokine receptors [10, 34]. [47]. The topographical location of the
4 integrins on Importantly, conservation of this mechanism was also shown as microvillus tips makes this interaction possible. In addition, CD103+ DCs with similar functional properties were isolated the mucin domain of MAdCAM-1 on HEVs of intestinal from human MLNs and from MLNs of CD patients [35]. lymphoid tissues (but not intestinal non-lymphoid venules) is decorated with L-selectin carbohydrate ligands and can In human peripheral blood leukocytes,
47 is expressed + + support L-selectin mediated interactions (Fig. 1). This most highly in a subset of memory CD4 T lymphocytes (CD4 hi unique property of MAdCAM-1 confers this molecule with
 ), which also express low levels of
 , and represents 4 7 4 1 the ability to mediate leukocyte rolling and homing of naïve approximately a fourth of the entire population [36]. The rest of + + L-selectin lymphocytes to intestinal lymphoid tissues [48]. memory CD4 T cells do not express
47 but the majority + Naïve cells, which express low levels of
 , extravasate in express high levels of
 . Memory CD8 T cells have a 4 7 4 1 PPs through rolling mediated by MAdCAM-1 interacting similar pattern of
 expression, albeit at lower levels, while 4 7 with L-selectin and
 , and firm adhesion mediated by naïve T and B lymphocytes and NK cells express intermediate 4 7
 /MAdCAM-1 and LFA-1/ICAM interactions [24].
 hi to low
 . Neutrophils are negative for this integrin; a small 4 7 4 7 4 7 memory lymphocytes can extravasate into GI lymphoid percentage of monocytes (15%) express very low levels, while Eosinophils are relatively bright in
 expression [37, 38]. In organs or lamina propria by
47/MAdCAM-1 interactions 4 7 alone [4]. human intestinal lamina propria, most T and B lymphocytes, blasts and plasma cells were positive for
47 expression while MAdCAM-1 is also expressed on endothelial cells of the most IELs were negative but expressed the other 7 integrin, gastric mucosa and lymphocyte activation by antigens in the
E7 as did some dendritic cells [14]. stomach or the intestine microenvironments results in
47 expression and homing to the gastric mucosa [49, 50]. In Mucosal Addressin Cell Adhesion Molecule-1 (MAdCAM-1) addition to directing the trafficking of lymphocytes,
47 has been implicated in GI mucosa trafficking of other leukocytes
47 was shown to bind to MAdCAM-1 [39], a cell important in immune responses to parasitic infections, such adhesion molecule of the immunoglobulin (Ig) domain super as certain intestinal helminths. Studies with gene-deficient family of integrin receptors [40-43]. MAdCAM-1 is mice and neutralizing antibodies demonstrated a critical role Integrin
47 Antagonists Current Immunology Reviews, 2012, Vol. 8, No. 2 121 for
47 in directing the selective migration of mast cell cell migration into the brain is likely mediated by progenitors and eosinophils to the intestine in these settings
41/VCAM-1 but not
47/MAdCAM-1 interactions. [51, 52]. Blockade with monoclonal antibodies against
4 and VCAM-1, but not against 7 or
47, inhibited development of experimental autoimmune encephalomyelitis (EAE); (the
47/MAdCAM-1 Interactions in Intestinal Inflammation and Preclinical Models of IBD encephalitogenic T cells expressed both
4 integrins) [70- 73]. Furthermore, studies in a rat model of EAE showed MAdCAM-1 expression is increased in CD and UC [11- equal efficacy (and a similar pharmacological effect on 13] and is generally not associated with other inflamed circulating lymphocytes) of an
41 selective small molecule tissues with a few exceptions such as the inflamed pancreas antagonist and a dual anti-
4 antibody, suggesting the and liver (these two will be discussed in the section on other mechanism of action for the dual inhibitor was the inhibition therapeutic indications for antagonists of
47). of
41 and not
47 [74]. In addition, the expression of 1 in encephalitogenic T cells was shown to be required for A number of studies demonstrating effectiveness of development of experimental autoimmune encephalomyelitis function-blocking antibodies selective for
 or 4 7 in mice as 1 was required for T cell trafficking to the brain MAdCAM-1 in preclinical models of IBD supported a but not for T cell proliferation or activation [75]. In spite of potential therapeutic role in human IBD for antagonists of
 /MAdCAM-1 mediated interactions. Act-1 (the selective these data some studies have suggested that antibodies 4 7 against MAdCAM-1 and 7, as well as 7-deficient mice,
 murine antibody from which vedolizumab was derived) 4 7 partially protected against murine EAE. In these studies and a dual anti-
4 antibody antagonist, were effective in however, disease inhibition was greater with anti-
4 resolving disease symptoms in cotton top tamarins, a non- blockade when compared to the effect of anti-7 antibodies. human primate model of spontaneous colitis [53, 54]. A Lastly anti-
4 mAbs inhibited EAE induced in the 7 number of rodent gut inflammation models (via antibody blockade or deficiency of the
 /MAdCAM-1 pathway) deficient mice suggesting a predominant role for
41 [76, 4 7 77]. Importantly, no MAdCAM-1 expression was detected in resulted in attenuation of disease including: 1) colitis normal or inflamed brain from control and MS human induced in immunodeficient mice by adoptive transfer of hi samples [78] or in the CNS of normal humans or CD45RB T cells [55-58]; 2) murine DSS-induced colitis + cynomolgus monkeys or EAE cynomolgus monkeys [11, [59, 60]; 3) granulomatous colitis in rats [61]; 4) CD8 T-cell 79]. dependent ileitis in the TNF(DeltaARE) mouse [62]; 5) ileitis in SAMP1/Yit mice [63]; 6) and in TNBS-induced colitis (in this case was treated with antisense oligos against BIOLOGIC THERAPIES TARGETING INTEGRIN MAdCAM-1) [64].
47 FUNCTION FOR THE TREATMENT OF INFLAMMATORY BOWEL DISEASE

47/MAdCAM-1 Interactions are not Generally There are currently four monoclonal antibodies targeting Involved in Migration of Lymphocytes to Non-Intestinal blockade of
47- MAdCAM-1 interactions which are either Tissues in the clinic or in clinical studies for the treatment of IBD. Of the three antibodies that bind the integrin
 and block Despite the role of MAdCAM-1/
 interactions in 4 7 4 7 its function, only vedolizumab (previously known as intestinal mucosal immunity, they appear to play no or little MLN0002, MLN02, LDP02; Millennium Pharmaceuticals role in immunity to other mucosal tissues such as the lung or Inc.: The Takeda Oncology Company, Cambridge, MA) pulmonary tissues, oral, and nasal mucosa, although contradicting reports suggest a potential role in some selectively inhibits this heterodimer. The other two antibodies that bind also bind either
 (Natalizumab, infections of the genitourinary tract [4, 28, 65, 66]. These
47 4 1 Tysabri, formerly known as Antegren, Elan Pharmaceuticals interactions may also play a role in oral infections as a study [Elan; San Francisco, CA] and Biogen Idec [Biogen; with HIV patients with oropharyngeal candidiasis showed Cambridge, MA]) or
E7 (rhuMAb beta7, Genentech, CA) significantly increased expression of MAdCAM-1 in (Table 1 and Fig. 2). The fourth monoclonal antibody that infected patients versus those not infected, as well as expression of
 in infiltrating lymphocytes [67]. In mice, was in clinical development, PF-00547659, selectively binds 4 7 to human MAdCAM-1 and inhibits its binding to
 nasal associated lymphoid tissue (NALT) MAdCAM-1 4 7 (Pfizer, Groton, CT). expression appears to be associated with follicular dendritic cells which are not involved in extravasation but perhaps in Natalizumab (Tysabri) is a humanized IgG4 monoclonal
47 dependent B cell adhesion and activation in germinal antibody in clinical use for the treatment of relapsing forms centers [68]. of multiple sclerosis and moderate to severe active Crohn’s disease. It binds to the
4 subunit of the integrins
 and Natalizumab is likely effective in the treatment of MS 4 1
 and as mentioned before, blocks adhesion to VCAM-1 because of inhibition of leukocyte infiltration into the brain 4 7 and MAdCAM-1, respectively, thereby inhibiting by blocking
 binding to VCAM-1 [69]. In the midst of 4 1 lymphocyte infiltration into the brain (and other tissues) and this success, inhibition of effector T cell migration into the into GI tract, respectively. Natalizumab also blocks brain has also been implicated as one of the potential causes in the reactivation of the JC virus and PML development leukocyte cell adhesion to the extracellular matrix by disrupting binding of the
4 integrins to one of the protein during natalizumab treatment (discussed in the next section). components of the ECM, a fibronectin splice variant Although natalizumab inhibits both
 and
 -mediated 4 1 4 7 containing the CS-1 peptide. Natalizumab was shown to be interactions with VCAM-1 and MAdCAM-1 respectively, effective for the treatment of multiple sclerosis [80, 81] and the following evidence briefly discussed here, suggests T 122 Current Immunology Reviews, 2012, Vol. 8, No. 2 Soler-Ferran and Briskin

Table 1.
47 Antagonist Programs in Clinical Development

Target Mechanism Clinical Company Name Inhibitor Type Disease of Action Status

® Biogen/Elan Natalizumab (Tysabri ) MAb (humanized IgG4) 4 (41/47) MS, CD Marketed Vedolizumab (LDP-02, MLN-02, Millennium/Takeda MAb (humanized IgG1)   UC, CD Phase 3 MLN0002) 4 7

Genentech/Roche rhuMAbBeta7 (RG7413) MAb (humanized IgG2) 7 (41/47) UC Phase 1

ELAN ELND-004 Small molecule 47? UC, CD Phase 1

Ajinomoto AJM-300 Small molecule 41/47 CD Phase 3

Ajinomoto AJM-300 Small molecule 41/47 UC Phase 2

GSK Mitsubishi/Tanabe pharma SB-683699 (Firategrast) Small molecule 41/47 MS, CD Phase 2

UCB, Inc./Biogen IDEC CDP-323 Small molecule 41/47 MS Phase 2 Encysive/Schering TBC-4746 Small molecule   /  Asthma Phase 1 Plough/Merck 4 1 4 7 gained accelerated FDA approval for the treatment of the induction trial, 905 moderately to severe active Crohn’s relapsing forms of MS in November 2004. disease patients were randomly assigned to receive 3 doses at 0, 4 and 8 weeks in a 4:1 ratio of 300 mg of natalizumab IBD IBD??/?? or placebo. The primary end point was induction of response RA/MS as measured by a decrease of
70 points in the CDAI Tysabri MLN0002 (Crohn’s Disease Activity Index) score at week 10. A rhuMAb Beta7 secondary outcome was disease remission, marked by a CDAI below 150. The natalizumab and placebo groups had similar rates of response (56 percent and 49 percent, respectively; P=0.05) and remission (37 percent and 30 percent, respectively; P=0.12). In contrast, statistically significant differences in rates of response or remission for natalizumab versus placebo were achieved in subgroups of a4 b1 a4 b7 aE b7 patients with either an elevated concentration of C-reactive Fig. (2). Delineation of relevant integrin pairs related to protein (CRP) at baseline (660 patients), or that had mucosal and non-mucosal homing/retention. The 4 integrin can previously received anti-TNF- therapy (358 patients), or pair with two beta chains, namely 1 and 7. Expression of 41 with active disease despite the use of immunosuppressants correlates with homing to non-intestinal lymphoid tissues as well as (330). The rates of response or remission where higher non-intestinal sites of inflammation, while 47 homing is largely among patients receiving natalizumab that those receiving restricted to the GI tract. Antibodies that inhibit 4 function, such placebo in the patient groups that did not receive prior anti- as Tysabri, can block migration of both of these heterodimers, and TNF- therapy or were not concomitantly treated with as shown in the clinic, have therapeutic utility in a wider range of immunosuppressants, but these differences were not disease indications; albeit with potentially greater risks of significant. No differences between the natalizumab and immunosuppression. Blocking 47 specifically, as in the case of placebo groups were observed in patients with normal vedolizumab, will largely target GI homing lymphocytes (as well as concentrations of CRP. For the maintenance trial, 339 other leukocytes that express 47) and in doing so has more limited patients that had a response to natalizumab in the induction therapeutic utility, but with perhaps a greater safety profile. The 7 trial were randomly reassigned to either 300 mg of integrin can also pair with another alpha chain, namely
E. E7 natalizumab or placebo every 4 weeks through week 56. The expression is associated with mucosal associated leukocytes primary outcome was a sustained response through week 36. including intraepithelial lymphocytes (as well as a subset of A secondary outcome was sustained remission through week dendritic cells that are associated with education of gut-homing 36. The rates of sustained response (61 percent versus 28 lymphocytes, some with potential regulatory properties). MAbs that percent; P<0.001) and disease remission (44 percent versus target the 7 chain alone, like rhuMAbBeta7, may affect both 47 26 percent, P=0.003) through week 36 were significantly interactions with MAdCAM-1 as well as E7 interactions with its higher in the patients that continued on natalizumab versus counter-ligand E-cadherin. Whether or not this approach has greater the ones that were switched to placebo. therapeutic utility than specific 47 inhibition remains to be seen. In another induction phase 3 study, Encore (Efficacy of Early clinical studies had also suggested that Natalizumab in Crohn’s Disease Response and Remission), Natalizumab may be effective for the treatment of Crohn’s 509 patients with moderate to severe active Crohn’s disease disease [82, 83]. The phase 3 study ENACT, consisted of an and active inflammation characterized by elevated induction trial, ENACT-1 (Efficacy of Natalizumab as concentrations of CRP (> 2.87 mg/L), were randomly Active Crohn’s Therapy) and a maintenance trial, ENACT-2 assigned to receive 300 mg of natalizumab or placebo in a (Evaluation of Natalizumab as Continuous Therapy) [84]. In 1:1 ratio at weeks 0, 4 or 8 [85]. The primary outcome was Integrin
47 Antagonists Current Immunology Reviews, 2012, Vol. 8, No. 2 123 induction of response (
70 point decrease from baseline in the clinical benefits of using Tysabri outweigh its potential CDAI at week 8 and sustained through week 12). Secondary risks. efficacy end points included induction of sustained remission PML is a rare and often fatal demyelinating disease of (CDAI <150) and response or remission over time. Rates of the white matter of the brain caused by lytic infection of sustained response and remission were significantly higher oligodendrocytes by the JC polyoma virus. Exposure to the in patients that received natalizumab as compared to those JC virus occurs in childhood and is widespread in the adult that received placebo (48 percent vs 32 percent; P=0.001 and population as indicated by the high incidence of JC virus 26 percent vs 16 percent; P=0.002) respectively. seropositivity (~80%). Viral latency and reactivation are Natalizumab induced response and remission at weeks 4, 8 poorly understood, but reactivation occurs only in severely and 12, demonstrating early and sustained efficacy as immune-compromised patients such as the HIV population, induction therapy for active Crohn’s disease patients with which carries the highest incidence of PML (~3-5%); organ elevated CRP. transplant recipients; or those with hematologic Natalizumab was well tolerated in moderate to severe CD malignancies, although the incidence in these populations is patients with no increased rates of serious adverse events. In much lower than that in the HIV population [94]. In addition combined safety data for several MS or CD natalizumab to the cases described above for natalizumab, PML in studies there was no increased incidence of lymphomas or patients with autoimmune disease has newly emerged in the other cancers, autoimmune or cardiovascular disease in the setting of other new biological immune-modulatory natalizumab-treated patients [80-87]. However, one CD therapies. PML cases have been reported in severe plaque patient in an open-label extension study in the ENACT trial, psoriasis patients treated with efalizumab (Raptiva®), another who had been treated with 8 doses of natalizumab over 18 anti-integrin antibody (CD11a) which inhibits migration of T months and received multiple immunosuppressant therapies, cells into tissues, and in patients with rheumatoid arthritis and two MS patients in clinical trials, who had been treated and lymphomas treated with rituximab (Rituxan®), a B-cell with combined natalizumab and interferon beta-1 therapy lytic anti-CD20 antibody [95, 96]. for over 2 years, developed progressive multifocal The mechanisms by which natalizumab may reactivate leukoencephalopathy (PML), a rare but frequently fatal brain the JC virus and cause PML are not fully understood but disease caused by the JC polyomavirus [88-92]. Two of several mechanisms have been proposed. It is likely that a these patients died and Tysabri was voluntarily removed combination of factors related to the mechanism of action of from the market in February 2005. Early investigations natalizumab and to the biology and pathogenicity of the JC determined the risk for PML to be 1 in 1000 patients. virus come into play. Decreased immunosurveillance in the Natalizumab was reintroduced to the market in June 2006 CNS and other tissues and mobilization of hematopoietic and was also approved for treatment of moderate to severe cells with a latent infection from the bone marrow might active Crohn’s disease in the United States (but not in come together to reactivate the virus. Ransohoff was the first Europe) in January 2008. Natalizumab is approved only as to propose that the effects of nataluzimab on the bone monotherapy and its distribution restricted by a risk marrow might be one of the key contributing factors to viral minimization program called TOUCH (Tysabri Outreach reactivation [97]. Cumulative evidence suggests lymphoid Unified Commitment to Health) prescribing program. The + tissues and bone marrow cells including B cells and CD34 program restricts distribution and closely monitors patients hematopoietic stem cells are sites of viral latency and for the occurrence of PML and other serious opportunistic important players in the pathogenesis of JCV [94, 98-102]. infections. New safety information released by the FDA in Virus recovered from hematopoietic infected cells infects early February 2010 [93] will be included in the Tysabri glial cells suggesting that a plausible mechanism for the label and the patient medication guide to maximize the safe pathogenesis of JCV brain infection is a reactivation of the use of Tysabri. This new information is based on 31 new bone marrow reservoir under conditions of immune confirmed cases of PML worldwide in natalizumab-treated suppression with resulting viremia and brain infiltration of patients (8 of these have died) since marketing resumption in either cell-bound or free virus. July 2006 and through January 21, 2010. The risk of acquiring PML increases with the number of infusions Natalizumab administration to primates and humans received. No PML cases have been reported in patients with results in a rapid, sustained and significant elevation in the less than 12 months of therapy. In patients treated for 24 to numbers of all cells that express 41 in the circulation 36 months (24 to 36 infusions), the overall rates of including B, CD4+ and CD8+ T lymphocytes, NK cells, developing PML worldwide and in the U.S. are 1.3 and 0.8 monocytes, basophils and eosinophils. Neutrophils-- which in 1000 patients respectively; the rate in Europe is 1.9 in do not express 41, are not elevated [81, 82, 84, 92]. This 1000; the reason for this difference is not understood. There leukocytosis might result from inhibition of leukocyte is scant clinical experience beyond 36 month either from extravasation and retention into multiple tissues including clinical trials or in the postmarketing setting. Approximately, the bone marrow. Inhibition of migration to the bone marrow 66,000 people worldwide have received at least one infusion as well as mobilization of cells retained in the bone marrow of Tysabri since resumption of marketing and through the by 41/VCAM-1 adhesion is also likely to contribute to this end of 2009. The new label includes a warning and elevation. A wide body of scientific evidence points to a precaution on the occurrence of IRIS (Immune predominant role for 41/VCAM-1 interactions in Reconstitution Inflammatory Syndrome) in patients that hematopoiesis, homing and retention of hematopoietic develop PML and who undergo subsequent removal of progenitors, B and T lymphocytes, and dendritic cells in the Tysabri. Based on current information, the FDA believes that bone marrow [103-105]: 1) Conditional VCAM-1 deletion in mice (conventional VCAM-1 deficiency in mice results in 124 Current Immunology Reviews, 2012, Vol. 8, No. 2 Soler-Ferran and Briskin embryonic lethality) resulted in decreased numbers of number of cerebrospinal fluid (CFS) mononuclear cells immature B cells and mature B and T cells in the bone including CD4+, CD8+, B lymphocytes and plasma cells marrow with a concomitant increase in immature B cells and [123]. So it is possible that natalizumab may cause PML leukocytosis in blood. These mice exhibited a profound from impaired lymphocyte responses in the brain in impairment of bone marrow homing of transferred mature T combination with viral reactivation at other sites. and B lymphocytes and a defect in T-cell dependent humoral Elan Pharmaceuticals is directing an observational study response [106, 107]. 2) Furthermore,
4 deficiency in the (CD INFORM NCT00707512) to determine the incidence of hematopoietic compartment of chimeric mice resulted in a serious infections, malignancies or other SAEs (serious severe defect in B cell development as well as compromised adverse events) in Crohn’s disease patients treated with general lymphopoiesis. These mice had decreased B cell natalizumab. The molecular mechanisms proposed for viral progenitors in the bone marrow, hematopoietic progenitors reactivation and PML development by natalizumab implicate in the circulation, and lymphocytosis [108]. 3) Mouse and
 /VCAM-1 interactions and not
 due to the latter's human hematopoietic progenitors and lymphocyte precursors 4 1 4 7 more restricted tissue-tropism to the GI tract. Consequently, bind to VCAM-1 expressed on bone marrow stromal cells selective
 inhibitor therapies in IBD treatment might and anti-VCAM-1 and anti-
4 antibodies inhibit 4 7 carry less risk of opportunistic infections while still lymphopoiesis and erythropoiesis in bone marrow cultures achieving a comparable level of efficacy. [109-113]. Attachment of hematopoietic progenitors to bone marrow stroma also occurs through binding of
41 to the Vedolizumab is a humanized IgG1 monoclonal antibody connecting segment 1 (CS-1) of alternatively spliced selective for the integrin
47 currently in phase 3 clinical fibronectin in the extracellular matrix (ECM). Binding is development for the treatment of UC and CD sponsored by blocked by anti-
4 and anti-1 MAbs. Anti-1 1 antibodies Millennium Pharmaceuticals Inc and the Takeda also block medullary hematopoiesis in vivo following Pharmaceutical Company. The implied mechanism of action infusion of bone marrow cells [114]. A role for
4 integrin in of vedolizumab is the inhibition of adhesion and migration hi the attachment of hematopoietic progenitors to stromal cells of
47 memory T lymphocytes to MAdCAM-1 expressed in the bone marrow was confirmed by the release of on endothelial cells of the GI tract and associated lymphoid progenitors to the circulation upon
4 blockade in mice and tissues. Vedolizumab was engineered from the murine primates [105, 115]. Accordingly, natalizumab treatment antibody Act-1 which was shown to bind an epitope that is + mobilizes CD34 hematopoietic progenitors in humans [116, accessible only to the heterodimer
47 and fails to bind to 117]. Furthermore, the bone marrow has been shown to be a the other two integrins expressing the
4 or 7 subunits, major reservoir and site of activation for central memory namely
41 and
E7, respectively (Fig. 2). Vedolizumab CD8+ T lymphocytes by dendritic cells and induction of was shown to exhibit the same ligand specificity, affinity and recall responses as well as a site of long-term persistence of inhibitory potency and selectivity as Act-1 [37]. It binds antiviral memory cells [103, 104, 118]. Intravital microscopy most brightly to a small subset (approximately 25%) of + demonstrated a major role for
41 (but not
47) adhesion to memory CD4 T lymphocytes (which contain some T-helper VCAM-1 on bone marrow microvessels in homing of 17 lymphocytes expressing IL17, a cytokine recently memory CTLs and dendritic cells. Disruption of
41 binding implicated in IBD pathogenesis). Vedolizumab does not bind to VCAM-1 by a dual
4 antagonist such as natalizumab the vast majority of memory helper T cells, nor does it bind might result in viral reactivation not only by the release of neutrophils or the vast majority of monocytes in human infected bone marrow B cells and CD34+ progenitors but by peripheral blood. Vedolizumab also binds at high levels to interfering with a CTL response in the bone marrow that peripheral blood eosinophils and to a lesser extent naive T- might be critical to keep the virus in check. Long-term helper, naïve and memory cytotoxic T and B lymphocytes as persistence of anti-viral T cell responses might also explain well as natural killer cells and basophils. Vedolizumab binds hi why it takes over a year of Tysabri infusions for the virus to to peripheral blood
47 memory CD4 cells and B cells with be reactivated. The rate of viral reactivation associated with high affinity (EC50=0.05 μg/ml) and inhibits binding of hi natalizumab as well as the proposed increased JC viremia human MAdCAM to whole blood activated
47 CD4 associated with natalizumab administration [119] may be memory cells with similar potency [37]. It also blocks
47 explained by one or several of these effects of the adhesion to fibronectin but not to VCAM-1. Vedolizumab mechanism of action of natalizumab. In addition, PML does not mediate complement dependent cytotoxicity (CDC) development may occur because of inhibition of CNS or antibody dependent cellular cytotoxicity (ADCC). immune surveillance. JC virus specific CD8+ Cytotoxic T + Phase 2 clinical trials have demonstrated therapeutic lymphocyte (CTL) and CD4 Helper T lymphocyte immune activity of vedolizumab in ulcerative colitis (UC) and responses correlate with control of PML disease progression Crohn’s disease (CD). Vedolizumab is currently in phase 3 [120-122]. It has then been proposed that blockade of + clinical development for the treatment of UC and CD. In an infiltration of effector virus-specific CTL and CD4 cells into exploratory Phase 2 study in patients with mild to the brain, the effector site of action, and inhibition of CNS moderately active ulcerative colitis, treatment with 2 mg/kg immune surveillance are likely to be key mechanisms of vedolizumab was well tolerated and induced complete contributing to PML development by natalizumab. remission in some patients [124]. A second well-powered Consistent with the major role that
41/VCAM-1 phase 2 study demonstrated that treatment with vedolizumab interactions play in migration of lymphocytes to the brain, was safe and efficacious in the induction of clinical and natalizumab has been shown to interfere with lymphocyte endoscopic remission [125]. This randomized, double-blind infiltration into the brain [69, 73]. Additionally, Stuve and placebo-controlled multicenter study was carried out in 181 colleagues demonstrated that natalizumab reduces the patients with moderately to severely active ulcerative colitis Integrin
47 Antagonists Current Immunology Reviews, 2012, Vol. 8, No. 2 125

(ulcerative colitis clinical score from 5 to 9 on a scale differences in laboratory results were identified among the ranging from 0 to 12, that included a score of at least 1 for treatment groups. Importantly, no changes were observed in rectal bleeding or stool frequency; in addition patients had to the total blood lymphocyte, T and B lymphocyte counts have a baseline modified Baron score (endoscopic between patients receiving vedolizumab or placebo, a evaluation) of at least 2 on a scale of 0 to 4). Patients were noteworthy finding that informs on the mechanism of action randomly assigned to receive intravenous infusions of either of MLN-02 as compared to that of natalizumab. Human anti- 0.5 or 2 mg/kg of body weight of MLN-02 (a vedolizumab human antibodies were observed in 44 percent of patients precursor with identical potency and binding specificity) or that received MLN-02 with 24 percent (11 percent in the 2 placebo at days 1 and 29. Some patients also received mg/kg group and 38 percent in the 0.5 mg/kg group) concomitant mesalamine. developing high enough antibody titers to affect saturation of + Patients were evaluated at 6 weeks, the primary study 47 receptors in the memory CD4 population. Patients who lost saturation of   receptors in the memory CD4+ end point, by ulcerative colitis clinical scores (clinical 4 7 population, not surprisingly, lost the statistically significant activity) and modified Baron score (endoscopic activity). benefit on efficacy versus patients receiving placebo (12 The primary outcome was clinical remission at week 6, as percent in clinical remission vs 14 percent in the placebo defined by an ulcerative colitis clinical score of 0 to 1 and a group). In contrast, in the 76 percent of patients with modified Baron score of 0 to 1 with no rectal bleeding. Secondary outcomes included the proportion of patients with undetectable or low antibody titers, receptor saturation was greater than 90 percent, and the rates of clinical remission a clinical response (a decrease of at least 3 points on the were 42 percent versus 14 percent in the placebo group). The ulcerative colitis clinical score), endoscopically evident serum half -lives were 9 and 12 days for the 0.5 and 2 mg/kg remission (modified Baron score of 0), endoscopic response doses, respectively. (an improvement of the modified Baron score of at least 2) at weeks 4 and 6. Other secondary end points were changes in A phase 2 study in patients with active Crohn’s disease the ulcerative colitis clinical scores, modified Baron scores, suggested a dose dependent beneficial effect of vedolizumab Riley’s histopathology score (from 0 to 7 on biopsies) and in inducing clinical remission [18]. Vedolizumab was well the scores on the inflammatory bowel disease questionnaire tolerated in this patient population. Patients with moderate to on health-related quality of life (32 to 224). Clinical severe active Crohn’s disease (CDAI ranging from 220 to remission rates at week 6 were 33 percent, 32 percent and 14 400 on a scale from 0 to 600) were randomly assigned to percent for the groups receiving 0.5 mg/kg of MLN-02, 2 receive an intravenous infusion of 0.5 mg/kg vedolizumab, 2 mg/kg of MLN-02 and placebo respectively (P=0.03). The mg/kg vedolizumab or placebo at days 1 and 29. Patients corresponding proportion of patients that experienced were stratified by mesalamine usage, the only permitted clinical response (a minimum 3 points improvement in concomitant medication in addition to antibiotics. The ulcerative colitis clinical scores), were 66 percent, 53 percent primary efficacy endpoint was clinical response, defined as a and 33 percent (P=0.002). Endoscopically evident remission decrease in the CDAI of 70 points on day 57. Secondary was achieved by 28 percent, 12 percent and 8 percent of efficacy end points included clinical remission (absolute those receiving 0.5 mg of vedolizumab, 2 mg of CDAI
150 points) and enhanced clinical response (defined vedolizumab and placebo, respectively (P=0.007). by a decrease of 100 points in the CDAI) at day 57 among Furthermore, patients who received 0.5 or 2 mg/kg of MLN- others. The proportions of patients with clinical response at 02 were more likely to improve 2 or more points in their day 57 were 49 percent, 53 percent and 41 percent in the 0.5 endoscopic scores than patients who received placebo (48 mg/kg vedolizumab, 2 mg/kg vedolizumab and placebo percent and 35 percent respectively, vs 16 percent; P=0.001). groups respectively. These differences however, were not Patients receiving MLN-02 had greater improvements in the statistically significant. At day 15 a statistically significant inflammatory bowel disease questionnaire (IBDQ), the difference in the rate of clinical response of the 2 mg/kg ulcerative colitis clinical score and the Riley score. vedolizumab group as compared to the placebo group was Moreover, endoscopic, histopathological improvements, and observed, however this difference was not sustained over health-related quality of life questionnaire improvements time despite a continued rising rate of MLN-02 treated were more frequent among patients that were assigned to patients achieving response, as the delta was reduced due to active treatment. In summary, treatment with vedolizumab placebo patients achieving clinical response at later time resulted in a clinically significant benefit in the induction of points. In addition, the median time to clinical response was clinical remission in this short study with patients with active significantly different in the 2 mg/kg group as compared to ulcerative colitis. No significant differences in adverse the placebo group (17 days vs 42 days; P=0.04). effects were observed among the three groups including no A clinically relevant benefit of vedolizumab was further deaths, cancers or opportunistic infections. Most common suggested by the dose-dependent trend in the more stringent adverse events were exacerbations of ulcerative colitis, secondary end points of enhanced clinical response and nausea and headache. Serious adverse events included an clinical remission. The proportions of patients in clinical infusion reaction which occurred only in one patient of the remission at day 57 were 30 percent, 37 percent and 21 103 that received MLN-02. This patient tested positive for percent for the 0.5 mg/kg vedolizumab, 2 mg/kg high titers of anti-MLN-02 antibodies. Another patient vedolizumab and placebo groups, respectively (P=0.04 for developed a primary cytomegalovirus infection which the 2 mg/kg vs placebo comparison). Statistically significant resolved without treatment and was not consistent with a differences in remission rates between the 2 mg/kg viral reactivation that might be seen in a setting of vedolizumab and the placebo groups occurred also at days compromised immunity. Lobar pneumonia developed 15 and 29. The proportions of patients achieving the more postoperatively in a patient and was successfully treated. No stringently defined enhanced clinical response at day 57 126 Current Immunology Reviews, 2012, Vol. 8, No. 2 Soler-Ferran and Briskin were 43 percent, 47 percent and 31 percent for the 0.5 mg/kg Additionally, a study with 23 volunteers receiving either 300 vedolizumab, 2 mg/kg vedolizumab and placebo groups mg of vedolizumab or placebo demonstrated no increases in respectively (P=0.05 for the 2 mg/kg vs placebo the relative frequency of CD34+ hematopoietic progenitors in comparison). At day 113 (84 days after the final dose of the peripheral circulation. This report also included data for study drug) the corresponding rates of enhanced clinical serum JC virus by quantitative PCR (limit of detection 30 response were 32 percent, 43 percent, and 27 percent copies/mL; ViraCor Laboratotires, Lee’s Summit, MO) (P=0.05 for the 2 mg/kg group vs placebo), indicative of the showing no association between exposure to vedolizumab prolonged pharmacokinetic and pharmacodynamic effects of and JC viremia. This study involved ~5000 serum samples: this agent. Statistically significant differences between the 2 1089 were retrospective samples from 296 patients from mg/kg vedolizumab and placebo groups were also found in early phase 2 studies (exposure 0 to 4 months) and 3,950 the mean decrease in CDAI scores and in the proportion of samples were from a prospective, longitudinal study with patients with normal CRP concentrations at day 57. No 1,132 subjects from recent phase 1, 2 and 3 studies (included statistically significant differences among the groups were samples with variable exposure ranging from 0 to 36 months found in the IBDQ scores. The proportions of patients that and blinded samples from pivotal studies). Approximately 90 developed HAHA titers affecting saturation were 12 percent patients had been exposed to vedolizumab for longer than 18 and 34 percent in the groups receiving 2 mg/kg and 0.5 months. The results regarding reactivation of the JC virus by mg/kg vedolizumab, respectively. Clinical efficacy observed natalizumab are mixed and therefore controversial. High with the higher dose correlated with higher rates of
47 viremia was observed in a Crohn’s patient on natalizumab saturation. No significant differences in the rates of adverse treatment who eventually succumbed to PML [90]. Another events were observed among the treatment groups, with study including 19 MS patients receiving chronic higher serious adverse effects actually observed in the natalizumab therapy showed a subclinical reactivation of the placebo group. The most frequent were exacerbations of JC virus after 12 months in kidney and after 18 months in Crohn’s disease. Other adverse effects were small bowel blood [119]. In yet another study involving 24 MS patients, obstruction (1 patient in each group) and renal nephrolitiasis no JC viremia was detected up to 18 months. It is currently (1 patient in each of the MLN-02 groups). No opportunistic unclear whether or not viremia in any way predicts infections occurred. No lymphocytosis or differences in total development of PML, however, comparisons of larger blood lymphocyte, B or T cells were observed. datasets for patients treated with natalizumab or vedolizumab might confirm differences in viral reactivation It is noteworthy that these Phase 2 studies described above were affected by high degrees of immunogenicity in resulting from treatment with each of these therapeutic antibodies. response to treatment with a vedolizumab precursor (referred to as LDP-02, MLN02 or MLN002). It is therefore possible As of May 2010, approximately 1200 subjects had been that improvements in the manufacturing process and exposed to vedolizumab. The exposure was quite varied and formulation of the version of vedolizumab that will be used ranged from 1 to 24 doses of 0.15 to 10 mg/kg for up to 3 in Phase 3 studies may contribute to a decrease in the years (the vast majority received 2 or more doses in the 2 to observed incidence of HAHA and even higher clinical 6 mg/kg range); many received vedolizumab in combination responses. In more recent clinical studies, additional with corticosteroids or immunomodulatory therapies. strategies to minimize HAHA include a dosing regime with Although this is a limited dataset containing a small number upfront loading, administration of a higher dose of the of patients treated for longer than 18 months, and it is too antibody, and scheduled maintenance dosing. In addition, preliminary to draw any definitive conclusions, no patients potential future use of concomitant immunosuppressive exposed to vedolizumab treatment have developed PML to drugs with first doses of the antibody might further decrease this date. An integrated safety analysis performed with data HAHA incidence. Hitherto, a total of nine clinical studies from 9 clinical trials (8 placebo controlled) in 579 patients have been completed or initiated with vedolizumab produced with IBD and healthy subjects (including 57 patients with under the new manufacturing process. Some of these include more than 12 months of exposure) showed that vedolizumab phase 1 and 2 trials to evaluate safety, PK, PD, was well tolerated, with no increases in serious adverse immunogenicity and efficacy as well as phase 3 trials for events, systemic gastrointestinal or lower respiratory tract or more conclusive safety and efficacy evaluation including the systemic infections. No opportunistic infections were use of vedolizumab as maintenance therapy in IBD. reported in these studies. Early aggregate data seems to indicate that vedolizumab may be associated with increased Important distinctions in the mechanism of action of rates of non-serious upper respiratory and vaginal and oral natalizumab and vedolizumab underscore vedolizumab’s GI mucosal infections, which may be reflective of its tract selectivity which may potentially confer a safety advantage without loss of efficacy. The absence of systemic mechanism of action [65-67]. immunosuppressive effects of vedolizumab could translate Studies in non-human primates further illustrated into a lower risk for development of opportunistic infections interesting mechanistic differences between natalizumab and such as PML for this novel therapy as compared to vedolizumab. Fedyk, Parikh and colleagues reported the natalizumab, a pan-
4 inhibitor. Lymphocytosis and pharmacologic profile of vedolizumab in a series of studies mobilization of CD34+ progenitors are two on Cynomolgus macaques given up to 100 mg/kg (23 fold pharmacodynamic effects of the mechanism of natalizumab higher than the clinical dose) of vedolizumab biweekly for implicated in JC virus reactivation. Parikh and colleagues up to 6 months [127, 128]. Vedolizumab was well tolerated recently reported aggregate data from several clinical studies with no overt signs of toxicity or histopathological effects in showing that vedolizumab does not induce lymphocytosis, non GI tissues (35 tissues including spleen). Vedolizumab which confirmed data from earlier clinical studies [126]. inhibited migration of lymphocytes into the gastrointestinal Integrin
47 Antagonists Current Immunology Reviews, 2012, Vol. 8, No. 2 127 tract and caused a variable and mild asymptomatic lymphoid the gastrointestinal tract and of retention of intraepithelial depletion in Peyer’s Patches. Consistent with inhibition of lymphocytes, by blocking
47 interactions with MAdCAM-1 lymphocyte infiltration of the GI tissues, vedolizumab on endothelial cells, and of
E7 with E-cadherin on epithelial increased the frequency of a small subset of GI-tropic cells, respectively. Information on the development status of this memory helper lymphocytes expressing
47 in peripheral biologic was obtained from the Genentech website (http:// + + hi blood (CD4 CD45RA
47 ; ~1% of total leukocyte www.gene.com/gene/pipeline/status/immunology/rhumab-beta7/ population) by 2 to 3 fold without affecting circulating levels and http://www.gene.com/gene/pipeline/status/and clinicaltrials. of memory helper cells lacking expression of
47 in org NCT00694980) and updates of April 2010 which indicate peripheral blood. No alterations in other peripheral blood that rhuMAb Beta7 is currently being evaluated in a phase 1 leukocyte subsets including total neutrophil, B cell, helper or study assessing safety, PK/PD and immunogenicity in cytotoxic T lymphocytes, basophils, eosinophils or natural ulcerative colitis patients. Safety, PK/PD studies in Cynomolgus killer cell populations were noted. In addition, no changes monkeys dosed with rhuMAbBeta7 demonstrated that gut- were observed in CSF lymphocyte counts or CD4/CD8 ratios homing lymphocytes are specifically targeted by this antibody upon exaggerated vedolizumab exposure for 6 months. [132]. Dosing of Cynomolgus monkeys with rhuMAbBeta7 Vedolizumab administration of 10, 30 or 100 mg/kg for 10 (intravenously with 5 or 25 mg/Kg with 4 weekly doses or IV weeks did not have any effect on an adaptive T cell- with 5, 15 and 50 mg/Kg or intraperitoneally with 15 and 50 dependent antibody response (TDAR = IgM and IgG mg/kg doses administered weekly for 12 weeks) resulted in 3 to production in response to neoantigen KLH) nor innate 6 fold elevations in the peripheral blood 7hi memory CD4+ immune responses (natural killer cell-mediated cytolysis). In lymphocyte population and no changes in the 7low memory or contrast, a single dose of natalizumab of 10 or 30 mg/kg (2 7int naïve 7int CD4+ lymphocyte populations, which was hi + and 7 fold the clinical dose, respectively) induced a rapid somewhat higher than the
47 memory CD4 lymphocyte leukocytosis as well as splenic abnormalities (increased elevation in the periphery seen in the similar study with weight and white pulp hyperplasia) in 2 weeks and inhibited vedolizumab. These changes were reversible with clearance of the IgM T cell dependent antibody response [127]. Increases the antibody and correlated with PK and saturation of 7 sites. in leukocyte counts and spleen weights in monkeys exposed This PD effect is consistent with the mechanism of action of this chronically to natalizumab were also reported in a series of antibody, the inhibition of homing and retention of lymphocytes studies by other investigators. These studies also reported a to the gut via
47 and
E7 respectively. Whether simultaneous mild and variable effect on IgM TDAR responses and no blockade of
47 and
E7 in the gut will result in either greater effect on in vitro effector cell functions in blood or spleen efficacy in the treatment of UC and CD than blockade of
47 lymphocytes [129]. Effects on TDAR responses by alone, or will have greater toxicity, will be determined by natalizumab but not vedolizumab suggest that this effect is clinical studies.
E7 (
E is also termed CD103) is expressed by + likely to be mediated by
41, a hypothesis supported by >90% of mucosal intraepithelial CD8 lymphocytes and a small studies in mice with genetic deficiencies for
4, 1 and percentage of mucosal CD4+ lymphocytes and binds to E- VCAM-1 [107, 130, 131] but not MAdCAM-1 [46]. These cadherin (epithelial cell expressed cadherin, a cell adhesion studies highlight that the more restricted target and tissue protein) [133, 134]. It is thought that this interaction contributes selectivity of vedolizumab suggests important mechanistic to the localization and retention of lymphocytes in the epithelial distinctions with natalizumab that may translate into a safety layer. In peripheral blood,
E7 is expressed in 1-2% of advantage for vedolizumab. Ongoing clinical studies will lymphocytes which comprise a small subset of the memory hi ultimately establish the benefit-to-risk ratio in patients with
47 lymphocytes.
E 7 however, does not appear to play a IBD treated with
47 selective therapies. Ongoing pivotal role in homing and extravasation [9]. Increased
E7 expression clinical trials are investigating the role of vedolizumab as in intestinal tissues is partially a result of
47 dependent induction therapy and maintenance therapy in both ulcerative lymphocyte homing to the lamina propria, followed by down colitis and Crohn’s disease (clinicaltrial.org identifiers regulation of
4 and subsequent increase in
E. These changes NCT00783718 and NCT00783692). The long term safety of are thought to be a response to locally expressed TGF and/or this drug is also being investigated (NCT00790933). In the epithelial cell-expressed CCL25, the ligand for CCR9 [134- time that elapsed since this review was written in 2010, a news 136].
E-deficient mice have substantially decreased numbers release on February 21, 2012 from Takeda Pharmaceutical of intraepithelial and lamina propria CD8+ cells in intestinal and Company Limited announced top-line results from the vagina mucosal tissues [137].
E7 is also expressed in some GEMINI I pivotal Phase 3 trial evaluating vedolizumab in dendritic cells and regulatory T cells although its function 895 patients with moderately to severely active ulcerative beyond being a marker in these cells is not known [138-140]. colitis who had failed at least one conventional therapy As mentioned in other sections of this review, CD103+ DCs in including anti-TNFa agents. Primary endpoints were met for the intestine play an important role in the imprinting of gut both the induction and maintenance phases of the study. homing receptors; they have also shown to play a role in Statistical significance was achieved in clinical response in intestinal regulatory T cell development [141].
E7-Ecadherin the induction phase and clinical remission in the mainte- interactions occur in intraepithelial lymphocytes in the gut and nance phase. Most common adverse events in both the pla- other tissues such as the lung, the genitourinary tract or the skin cebo and vedolizumab arms were colitis, headaches and na- [142-144], (which might explain the somewhat higher sopharyngitis. http://www.takeda.com/press/article_45046.html peripheral 7 counts in the cynomolgus study with rhuMAb Beta7 is a humanized IgG1 monoclonal antibody rhuMAbBeta7 than with vedolizumab). It is possible that this dual 7 antibody may have effects in other tissues besides the targeting the 7 integrin subunit of the two integrin adhesion gut, imposing a greater safety monitoring hurdle for this receptors,
 and
E (Fig. 2). The mechanism of action of 4 7 7 biologic. If proven to be safe, perhaps there may be other rhuMAbBeta7 is the inhibition of lymphocyte trafficking into 128 Current Immunology Reviews, 2012, Vol. 8, No. 2 Soler-Ferran and Briskin therapeutic opportunities for this antibody. Ultimately, the elevation paralleled PK. The elevation occurred similarly in + + impact of blocking E7 in addition to 47 on safety and total T cells and subsets of T cells (CD3 as well as CD4 efficacy clinical studies will determine the efficacy and safety and CD8+) and B cells, but not NK cells. The 7-expressing ratio of this biologic. naïve, central memory and effector CD4+ T cells were elevated 2, 3 and 2.5 fold respectively. The effect on the PF-00547659, an Anti-Human MAdCAM-1 Monoclonal central memory T cell population was the most consistent Antibody and robust with a greater degree of variability in the response of the naïve and effector populations. The central memory Inhibition of 47 mediated lymphocyte migration into population devoid of 7 expression was unchanged by anti- the gastrointestinal tract can also be achieved by agents that human MAdCAM-1 treatment. This PD effect is in marked hi bind to MAdCAM-1 expressed on endothelial cells and contrast to the more selective effect on 47 memory T cells block its binding to 47 on lymphocytes. PF-00547659 is a resulting from blockade by beta7-specific antibodies fully human IgG2 monoclonal antibody selective for human discussed above. It is possible that some of the additional PD MAdCAM-1 that was in clinical development for the effects on lymphocyte subpopulations resulting from treatment of ulcerative colitis (clinicalTrials.gov identifier MAdCAM-1 inhibition, that are not observed in beta7 NCT00928681). Pfizer has completed a randomized, double- blockade, might be due to disruption of MAdCAM-1 binding blind, placebo controlled, dose escalating, multi-center phase to other molecules different from 47. As previously I study to investigate the safety, toleration, pharmacokinetics mentioned, MAdCAM-1 has been reported to interact with and pharmacodynamics of single and multiple L-selectin and to support lymphocyte rolling [47]. Disruption intravenous/sub-cutaneous doses of anti-human MAdCAM-1 of MAdCAM-1/L-selectin interactions alone or in mAb in 80 patients with ulcerative colitis (active UC with a combination with inhibition of additional interactions with score
6). This study was started in 2005 and completed in 47 might contribute to some of the observed PD effects on 2008. PF-00547659 binds to human MAdCAM with high lymphocyte populations. Whether this broader effect on affinity (Kd=16 pM) and inhibits binding of 47 leukocytes lymphocyte trafficking occurs in humans and what its with similar high affinity [79]. Immunonohistochemical significance is on efficacy and safety will be ascertained as tissue-reactivity studies with a panel of human and data from clinical studies becomes available when and if cynomolgus macaque tissues with PF-00547659 Pfizer reactivates the program. A Pfizer pipeline update of demonstrated a pattern of staining consistent with February 28 2008 lists PF-00547659 as a program in phase 2 MAdCAM-1-specific staining of endothelial cells of discontinued from development. The program is not listed as gastrointestinal tract tissues and associated lymphoid tissues, active in subsequent updates of September 2008, March 31, as previously reported [11]. The pattern and intensity of 2009 or February 2010. staining was similar for both species. Specific MAdCAM-1 staining was identified in esophagus (LP), stomach (LP, SMALL MOLECULE ANTAGONISTS of
47 FOR GALT, submucosa), small intestine (LP, GALT, submucosa) THE TREATMENT OF INFLAMMATORY BOWEL and colon (LP, GALT) and in lymph nodes, spleen, and DISEASE pancreas, very much in agreement with previous studies [11]. Exceptions were occasional staining of endothelial cells For over 15 years, many pharmaceutical and within bone marrow and tonsils of macaques and of lung, biotechnology companies have undertaken the development liver, uterus and bladder of 1 of 3 human samples. Notably, of small molecule antagonists for the 4 integrin. Small no staining was found in CNS tissues (brain, choroid plexus, molecule antagonists offer several potential advantages for cortex, cerebellum, eye, pituitary, spinal cord). A separate patients over biologics such as convenience of study with PF-00547659 and other commercial anti- administration and quick and easy drug removal for fast MAdCAM-1 antibodies in control and MS human samples recovery of receptor sites and function, a particularly demonstrated no MAdCAM-1 protein expression in normal important characteristic when suspecting an opportunistic or inflamed brain [78]. VCAM-1 protein was however infection such as PML. Cost of manufacturing is another expressed in unaffected and inflamed brain tissue and its consideration as they can be considerably less to make than expression was increased in acute MS plaque brain. biologics. For a comprehensive historical summary and MAdCAM-1 protein expression was absent in meninges, update up to 2007 of the various small molecule 4 inhibitor white or gray matter, choroid plexus and ependyma CNS drugs in development see Davenport and Munday review of samples. In the ileum, the positive control tissue however, 2007 [145]. They discuss these drugs’ chemical structures, MAdCAM-1 expression was found associated with the SAR, medicinal chemistry approaches to address potency membrane and cytoplasm of the endothelium, perivascular and ADME challenges, and development stage and outcome. space and leukocyte aggregates of the mucosa, submucosa Some of the programs that were active in 2007 have since and Peyer’s Patches. VCAM-1 but not MAdCAM-1 protein been discontinued. This review will focus only on current expression in unaffected and control brain reinforces a role programs still in development and specifically, on those in for 41/VCAM-1 but not 47/MAdCAM-1 interactions in development for IBD that target 47 as the major immune surveillance and inflammatory cell infiltration in mechanism of action (Table 1). No selective 47 small MS pathogenesis. molecule antagonists have reached clinical development although a limited number have been described in various Cynomolgus macaques dosed intravenously with PF- publications and patent literature [146-150]. Elan’s web page 00547659 (0.1 to 1 mg/kg) were found to have states they have small molecule antagonists which block approximately 1.5 fold statistically significant elevations of selectively a subset of the
4 interactions. One of these total lymphocyte counts at the highest dose of 1 mg/kg; this compounds, ELND-004 is an orally available small molecule Integrin
47 Antagonists Current Immunology Reviews, 2012, Vol. 8, No. 2 129 therapeutic currently in phase 1 and being developed for CD sclerosing cholangitis (PSC), and diabetes, chronic and UC, which suggests it might selectively block
47 inflammatory diseases of the liver, and the pancreas interactions. The other compound mentioned to exhibit respectively. Liver and gut manifestations of graft versus selectivity, ELND-002, is a PEGylated small molecule host disease (GVHD), a devastating chronic inflammatory administered subcutaneously and currently in phase 1 for disorder resulting from allogeneic hematopoietic cell development for secondary progressive MS and transplantation for the treatment of hematologic hematological malignancies, suggesting that the selectivity malignancies, have also been shown to involve attributed to it is likely for
41-mediated interactions. All
47/MAdCAM-1 interactions. other reported
 small molecule antagonists are dual
4 4 7 Primary sclerosing cholangitis is a chronic inflammatory inhibitors and consequently, also inhibit
 function. The 4 1 disease of the liver characterized by progressive bile duct furthest advanced and currently active program is from the destruction. PSC has been proposed to be an extra-intestinal Japanese company Ajinomoto, which is evaluating AJM300, manifestation of IBD [153]. There is a strong association of a dual
 /
 inhibitor. AJM300 is currently in a phase 3 4 1 4 7 PSC with IBD, with more than 70 percent of patients with study in patients with Crohn’s disease and in a phase 2a PSC also experiencing IBD. Inflammation in the liver study in patients with ulcerative colitis (New drug pipeline however, can occur in the absence of bowel inflammation as May 2009 www.ajinomoto.com/ir/pdf/FY08dataE.pdf - well as long after the colon has been removed. Adams and 2009-05-18 and http://www.clinicaltrials.jp/user/showCte colleagues first hypothesized that PSC might be caused by DetailE.jsp?japicId=JapicCTI-090925). AJM300 was shown long-term memory cells initially activated during active IBD to be orally active in preventing the development of in gut inductive lymphoid tissue which, under certain experimental colitis induced in immunedeficient mice by conditions, can also be recruited to the liver in addition to the adoptive transfer of IL10-deficient CD4+ cells [151] and in a gut [154, 155]. Several lines of evidence support this murine model of colitis induced by DNBS [145]. SB683699 + enterohepatic lymphocyte recirculation hypothesis: 1)
47 (firategrast) is a dual
4 small molecule antagonist being lymphocytes are present in PSC liver but not in non- developed by Glaxo Smithkline (GSK) in collaboration with inflamed liver lymphocyte infiltrates [156, 157]; 2) Mitsubishi Tanabe Pharma. A phase 2 trial to evaluate the MAdCAM-1 is aberrantly expressed on the endothelium of efficacy and safety of SB683699 in moderately to severely portal veins of chronically inflamed liver (PSC and active Crohn’s disease was started at the end of 2004 and has autoimmune hepatitis) and in dendritic cells of lymphoid been completed. A product development pipeline update by aggregates in areas of chronic portal inflammation; in GSK dated February 2010 however, does not list Crohn’s as addition, studies of interactions of isolated lymphocytes with an indication for which firategrast is being developed; it frozen tissue have shown that vessels from PSC hepatic does, however, list MS. Two phase 2 studies have been + tissue supported selective adhesion of
47 lymphocytes completed in MS and a third one is underway isolated from gut lamina propria from IBD patients, or from (clinicaltrial.org identifier NCT00395317). One of the PSC liver, via
 MAdCAM-1 interactions (as shown with completed studies evaluated the efficacy and safety of a 3 4 7/ function-blocking antibodies) [157]; 3) PSC liver infiltrating month administration of firategrast in patients with relapsing lymphocytes (LIL) are enriched for CCR9 expression as multiple sclerosis. The second completed phase 2 trial was + compared to peripheral blood, with all CCR9 LIL also an open-label study of leukocyte counts in the expressing
 . CCL25, the ligand for CCR9, a gut homing cererebrospinal fluid and blood following a 6 month 4 7 chemokine receptor, is aberrantly expressed by PSC liver treatment with firategrast. The current phase 2 study is and supports activation and adhesion to MAdCAM-1 of LIL evaluating the efficacy and safety of a 6 month and blood lymphocytes expressing CCR9 and
47 [158] and administration of firategrast in relapsing multiple sclerosis 4) human and mice gut-derived dendritic cells but not liver- patients. TBC-4647 is a dual
4 inhibitor in phase I for derived DCs or stellate cells imprint naïve T cells with gut asthma developed by Merck/Schering Plough in homing molecules
47 and CCR9 in a retinoic acid collaboration with Encysive Pharmaceuticals (originator of + + dependent manner indicating that
4 7 CCR9 LILs are the compound and previously Texas Biotechnology and primed in the gut [159]. Other inflammatory liver diseases acquired by Pfizer in 2008) BIOWORLD Today, Nov 2009 with a strong association with IBD such as autoimmune [152]. UCB/Biogen IDEC are evaluating the efficacy and hepatitis (AIH) might also benefit from therapeutic targeting safety of a dual
4 inhibitor, CDP-323, in a phase 2 study of
 . with patients with relapsing forms of multiple sclerosis 4 7 (clinicaltrial.org NCT00484536). Diabetes is a T cell dependent chronic inflammation of the pancreas resulting in destruction of beta cells of the islets OTHER POTENTIAL THERAPEUTIC INDICATIONS due to an autoimmune response to beta cell autoantigens. A FOR
 ANTAGONISTS role for MAdCAM-1/
47 interactions in diabetes is 4 7 suggested by several studies briefly described here. In the Therapeutic targeting of
47 function might be beneficial non-obese diabetic mice (NOD), both
47 and MAdCAM-1 for other immune-mediated diseases in which
47-mediated were shown to be expressed in inflamed islets; MAdCAM-1 tissue infiltration of lymphocytes or other leukocytes has expression correlated with insulitis development and the vast been suggested to be involved in pathogenesis of disease. majority of infiltrating T cells expressed
47. Moreover, Within the gut,
47/MAdCAM-1 interactions might play a treatment with neutralizing antibodies specific for either functional role in eosinophil-associated gastrointestinal MAdCAM-1 or
47 led to a durable protection against disorders [52]. This homing system may govern some extra spontaneous development of insulitis and diabetes [160- intestinal inflammatory disorders as well such as primary 162]. MAdCAM-1 blockade inhibited diabetes development in neonatal NOD mice upon adoptive transfer of a 130 Current Immunology Reviews, 2012, Vol. 8, No. 2 Soler-Ferran and Briskin diabetogenic T cell clone [163]. In addition, antibodies targeted biologic therapies that have increased therapeutic against MAdCAM-1 and
47 inhibited infiltration of options for those afflicted with disorders such as RA, MS pancreatic lymph nodes by peripheral blood B cells which and IBD. While these treatments are more selective than are known to play a crucial role as antigen presenting cells broad immunosuppression with steroids, recent for the induction of islet beta cell autoreactive T cells in the complications with promising approved drugs such as early phase of diabetes development [164]. In humans, islet Tysabri and Rituxan illustrate the needs for safety cell antigen specific T cell clones from patients with IDDM monitoring as well as the desire to develop even more hi were shown to be of the
47 phenotpype [165]. Some of selective therapies. The next few years will see an these studies suggest an early role for MAdCAM-1
47 emergence of new therapies for IBD targeting the molecular interactions in diabetes development. VCAM-1/
41 mechanism of cell adhesion and transmigration at the interactions have been also shown to play a role in diabetes leukocyte-endothelium interface. The 47 system illustrates in the NOD mice so a dual 4 inhibitor might be more one of the more selective and apparently efficacious means efficacious than a selective one [166, 167]. of targeting intestinal disease. We will witness the results of clinical studies comparing biologics targeting anti , The success of allogeneic hematopoietic stem cell
47 anti- 7 and MAdCAM-1 as well as potentially, small transplantation (allo-HSCT) for the treatment of a variety of  molecule antagonists targeting this integrin as well as . malignant and not malignant conditions is hampered by the 41 development of graft versus host disease (GVHD), a life- It is expected that more selective therapies that target the gut, such as may represent major strides in fulfilling the threatening complication. GVHD can develop in multiple 47 promise of safe effective targeted therapies; data to come in tissues but is particularly severe when it develops acutely in the years ahead will hopefully substantiate this promise. the intestine. Therapeutic strategies that preserve graft versus tumor (GVT) responses but prevent GVHD complications are desirable. Scientific evidence points to a role for ACKNOWLEDGEMENTS
 /MAdCAM-1 interactions in the intestinal 4 7 We thank Drs. Asit Parikh, Eric Fedyk and Irving Fox manifestations of GVHD. In a murine model of allogeneic from Millennium Pharmaceuticals, Takeda, for helpful bone marrow transfer, recipients of 7 deficient cells discussions, suggestions and review of this manuscript. developed significantly less morbidity and mortality associated with GVHD --which correlated with decreased donor T cell infiltration and less severe GVHD in the gut and CONFLICT OF INTEREST the liver but not in skin or thymus—than recipients of wild Declared none. type cells. Importantly, graft versus tumor (GVT) activity of 7-deficient cell was preserved [168, 169]. MAdCAM-1 blockade in two models of intestinal GVHD resulted in REFERENCES significant protection from GVHD without affecting GVT [1] Xavier RJ, Podolsky DK. Unravelling the pathogenesis of responses [170]. inflammatory bowel disease. Nature 2007; 448(7152): 427-34. A number of recent studies demonstrated the crucial role [2] Butcher EC. Leukocyte-endothelial cell recognition: three (or more) steps to specificity and diversity. Cell 1991; 67(6): 1033-6. that dendritic cells play in imprinting donor T cells with [3] Dustin ML, Springer TA. Role of lymphocyte adhesion receptors in organ-specific homing receptors in HCT. In an adoptive transient interactions and cell locomotion. Annu Rev Immunol transfer GVHD model, in vitro priming of alloreactive donor 1991; 9: 27-66. naïve T cells with gut-derived dendritic cells induced gut- [4] Butcher EC, Williams M, Youngman K, Rott L, Briskin M. Lymphocyte trafficking and regional immunity. Adv Immunol homing receptors
47 and CCR9 and caused more severe 1999; 72: 209-53. GVHD than when dendritic cells were from other organs [5] Stagg AJ, Kamm MA, Knight SC. Intestinal dendritic cells increase [171]. In another murine study, amelioration of GVHD by T cell expression of alpha4beta7 integrin. Eur J Immunol 2002; anti-CD3 preconditioning was associated with a decrease in 32(5): 1445-54. gut homing receptors
 and CCR9 on donor T cells. These [6] Johansson-Lindbom B, Svensson M, Wurbel MA, Malissen B, 4 7 Marquez G, Agace W. Selective generation of gut tropic T cells in changes were thought to be a consequence of decreased host gut-associated lymphoid tissue (GALT): requirement for GALT dendritic cell priming and homing receptor imprinting of dendritic cells and adjuvant. J Exp Med 2003; 198(6): 963-9. alloreactive T cells as a result of decreased trafficking of [7] Mora JR, Bono MR, Manjunath N, et al. Selective imprinting of DCs from tissues to LNs [172]. These studies suggest that gut-homing T cells by Peyer's patch dendritic cells. Nature 2003; 424(6944): 88-93. inhibition of recruitment of alloreactive T cells to the GI [8] Kunkel EJ, Campbell JJ, Haraldsen G, et al. Lymphocyte CC tract by inhibiting gut-homing molecules could prevent gut chemokine receptor 9 and epithelial thymus-expressed chemokine GVHD and preserve GVT responses. (TECK) expression distinguish the small intestinal immune compartment: Epithelial expression of tissue-specific chemokines Other potential uses of antibodies targeting
47 are as an organizing principle in regional immunity. J Exp Med 2000; selective drug delivery to gut lymphocytes by nanoparticle 192(5): 761-8. targeting [173] and radioimmunodetection of IBD for [9] Lefrancois L, Parker CM, Olson S, et al. The role of beta7 integrins diagnosis, evaluation and monitoring response to therapy in CD8 T cell trafficking during an antiviral immune response. J Exp Med 1999; 189(10): 1631-8. [174]. [10] Wang C, Kang SG, HogenEsch H, Love PE, Kim CH. Retinoic acid determines the precise tissue tropism of inflammatory Th17 CONCLUSION AND FUTURE PERSPECTIVES cells in the intestine. J Immunol 2010; 184(10): 5519-26. [11] Briskin M, Winsor-Hines D, Shyjan A, et al. Human mucosal addressin cell adhesion molecule-1 is preferentially expressed in Immunology research in autoimmune disease and intestinal tract and associated lymphoid tissue. Am J Pathol 1997; inflammation over the past 2 decades has brought forth novel 151(1): 97-110. Integrin
47 Antagonists Current Immunology Reviews, 2012, Vol. 8, No. 2 131

[12] Souza HS, Elia CC, Spencer J, MacDonald TT. Expression of [34] Johansson-Lindbom B, Agace WW. Generation of gut-homing T lymphocyte-endothelial receptor-ligand pairs, alpha4beta7/MAd cells and their localization to the small intestinal mucosa. Immunol CAM-1 and OX40/OX40 ligand in the colon and jejunum of Rev 2007; 215: 226-42. patients with inflammatory bowel disease. Gut 1999; 45(6): 856- [35] Jaensson E, Uronen-Hansson H, Pabst O, et al. Small intestinal 63. CD103+ dendritic cells display unique functional properties that [13] Arihiro S, Ohtani H, Suzuki M, et al. Differential expression of are conserved between mice and humans. J Exp Med 2008; 205(9): mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in 2139-49. ulcerative colitis and Crohn's disease. Pathol Int 2002; 52(5-6): [36] Schweighoffer T, Tanaka Y, Tidswell M, et al. Selective 367-74. expression of integrin alpha 4 beta 7 on a subset of human CD4+ [14] Farstad IN, Halstensen TS, Lien B, Kilshaw PJ, Lazarovits AI, memory T cells with Hallmarks of gut-trophism. J Immunol 1993; Brandtzaeg P. Distribution of beta 7 integrins in human intestinal 151(2): 717-29. mucosa and organized gut-associated lymphoid tissue. [37] Soler D, Chapman T, Yang LL, Wyant T, Egan R, Fedyk ER. The Immunology 1996; 89(2): 227-37. binding specificity and selective antagonism of vedolizumab, an [15] Meenan, J, SpaansJ, Grool TA, Pals ST, Tytgat GN, van Deventer anti-alpha4beta7 integrin therapeutic antibody in development for SJ. Altered expression of alpha 4 beta 7, a gut homing integrin, by inflammatory bowel diseases. J Pharmacol Exp Ther 2009; 330(3): circulating and mucosal T cells in colonic mucosal inflammation. 864-75. Gut 1997; 40(2): 241-6. [38] Erle DJ, Briskin MJ, Butcher EC, Garcia-Pardo A, Lazarovits AI, [16] Strober W, Fuss I, Mannon P. The fundamental basis of Tidswell M. Expression and function of the MAdCAM-1 receptor, inflammatory bowel disease. J Clin Invest 2007; 117(3): 514-21. integrin alpha 4 beta 7, on human leukocytes. J Immunol 1994; [17] Rutgeerts P, Vermeire S, Van Assche G. Biological therapies for 153(2): 517-28. inflammatory bowel diseases. Gastroenterology 2009; 136(4): [39] Berlin C, Berg EL, Briskin MJ, et al. Alpha 4 beta 7 integrin 1182-97. mediates lymphocyte binding to the mucosal vascular addressin [18] Feagan BG, Greenberg GR, Wild G, et al. Treatment of active MAdCAM-1. Cell 1993; 74(1): 185-95. Crohn's disease with MLN0002, a humanized antibody to the [40] Briskin MJ, McEvoy LM, Butcher EC. MAdCAM-1 has homology alpha4beta7 integrin. Clin Gastroenterol Hepatol 2008; 6(12): to immunoglobulin and mucin-like adhesion receptors and to IgA1. 1370-7. Nature 1993; 363(6428): 461-4. [19] Butcher EC, Picker LJ. Lymphocyte homing and homeostasis. [41] Briskin MJ, Rott L, Butcher EC. Structural requirements for Science 1996; 272(5258): 60-6. mucosal vascular addressin binding to its lymphocyte receptor [20] Luo BH, Carman CV, Springer TA. Structural basis of integrin alpha 4 beta 7. Common themes among integrin-Ig family regulation and signaling. Annu Rev Immunol 2007; 25: 619-47. interactions. J Immunol 1996; 156(2): 719-26. [21] Pribila JT, Quale AC, Mueller KL, Shimizu Y. Integrins and T cell- [42] Shyjan AM, Bertagnolli M, Kenney CJ, Briskin MJ. Human mediated immunity. Annu Rev Immunol 2004; 22: 157-80. mucosal addressin cell adhesion molecule-1 (MAdCAM-1) [22] Holzmann B, McIntyre BW, Weissman IL. Identification of a demonstrates structural and functional similarities to the alpha 4 murine Peyer's patch--specific lymphocyte homing receptor as an beta 7-integrin binding domains of murine MAdCAM-1, but integrin molecule with an alpha chain homologous to human VLA- extreme divergence of mucin-like sequences. J Immunol 1996; 4 alpha. Cell 1989; 56(1): 37-46. 156(8): 2851-7. [23] Hu MC, Crowe DT, Weissman IL, Holzmann B. Cloning and [43] Streeter PR, Berg EL, Rouse BT, Bargatze RF, Butcher EC. A expression of mouse integrin beta p(beta 7): a functional role in tissue-specific endothelial cell molecule involved in lymphocyte Peyer's patch-specific lymphocyte homing. Proc Natl Acad Sci U S homing. Nature 1988; 331(6151): 41-6. A 1992; 89(17): 8254-8. [44] Szabo MC, Butcher EC, McEvoy LM. Specialization of mucosal [24] Bargatze RF, Jutila MA, Butcher EC. Distinct roles of L-selectin follicular dendritic cells revealed by mucosal addressin-cell and integrins alpha 4 beta 7 and LFA-1 in lymphocyte homing to adhesion molecule-1 display. J Immunol 1997; 158(12): 5584-8. Peyer's patch-HEV in situ: the multistep model confirmed and [45] Rott LS, Briskin MJ, Andrew DP, Berg EL, Butcher EC. A refined. Immunity 1995; 3(1): 99-108. fundamental subdivision of circulating lymphocytes defined by [25] Hamann A, Andrew DP, Jablonski-Westrich D, Holzmann B, adhesion to mucosal addressin cell adhesion molecule-1. Butcher EC. Role of alpha 4-integrins in lymphocyte homing to Comparison with vascular cell adhesion molecule-1 and correlation mucosal tissues in vivo. J Immunol 1994; 152(7): 3282-93. with beta 7 integrins and memory differentiation. J Immunol 1996; [26] Wagner N, Lohler J, Kunkel EJ, et al. Critical role for beta7 156(10): 3727-36. integrins in formation of the gut-associated lymphoid tissue. Nature [46] Schippers A, Leuker C, Pabst O, et al. Mucosal addressin cell- 1996; 382(6589): 366-70. adhesion molecule-1 controls plasma-cell migration and function in [27] Wang C, McDonough JS, McDonald KG, Huang C, Newberry RD. the small intestine of mice. Gastroenterology 2009; 137(3): 924-33. Alpha4beta7/MAdCAM-1 interactions play an essential role in [47] Berlin C, Bargatze RF, Campbell JJ, et al. alpha 4 integrins transitioning cryptopatches into isolated lymphoid follicles and a mediate lymphocyte attachment and rolling under physiologic flow. nonessential role in cryptopatch formation. J Immunol 2008; Cell 1995; 80(3): 413-22. 181(6): 4052-61. [48] Berg EL, McEvoy LM, Berlin C, Bargatze RF, Butcher EC. L- [28] Abitorabi MA, Mackay CR, Jerome EH, Osorio O, Butcher EC, selectin-mediated lymphocyte rolling on MAdCAM-1. Nature Erle DJ. Differential expression of homing molecules on 1993; 366(6456): 695-8. recirculating lymphocytes from sheep gut, peripheral, and lung [49] Quiding-Jarbrink M, Ahlstedt I, Lindholm C, Johansson EL, lymph. J Immunol 1996; 156(9): 3111-7. Lonroth H. Homing commitment of lymphocytes activated in the [29] Rott LS, Rose JR, Bass D, Williams MB, Greenberg HB, Butcher human gastric and intestinal mucosa. Gut 2001; 49(4): 519-25. EC. Expression of mucosal homing receptor alpha4beta7 by [50] Quiding-Jarbrink M, Lonroth H, Ahlstedt I, Holmgren J, circulating CD4+ cells with memory for intestinal rotavirus. J Clin Svennerholm AM. Human gastric B cell responses can be induced Invest 1997; 100(5): 1204-8. by intestinal immunisation. Gut 2001; 49(4): 512-8. [30] Johansson-Lindbom B, Svensson M, Pabst O, et al. Functional [51] Gurish MF, Tao H, Abonia JP, et al. Intestinal mast cell specialization of gut CD103+ dendritic cells in the regulation of progenitors require CD49dbeta7 (alpha4beta7 integrin) for tissue- tissue-selective T cell homing. J Exp Med 2005; 202(8): 1063-73. specific homing. J Exp Med 2001; 194(9): 1243-52. [31] Mora JR, Iwata M, Eksteen B, et al. Generation of gut-homing [52] Brandt EB, Zimmermann N, Muntel EE, et al. The alpha4bbeta7- IgA-secreting B cells by intestinal dendritic cells. Science 2006; integrin is dynamically expressed on murine eosinophils and 314(5802): 1157-60. involved in eosinophil trafficking to the intestine. Clin Exp Allergy [32] Iwata M, Hirakiyama A, Eshima Y, Kagechika H, Kato C, Song 2006; 36(4): 543-53. SY. Retinoic acid imprints gut-homing specificity on T cells. [53] Hesterberg PE, Winsor-Hines D, Briskin MJ, et al. Rapid Immunity 2004; 21(4): 527-38. resolution of chronic colitis in the cotton-top tamarin with an [33] Hammerschmidt SI, Ahrendt M, Bode U, et al. Stromal mesenteric antibody to a gut-homing integrin alpha 4 beta 7. Gastroenterology lymph node cells are essential for the generation of gut-homing T 1996; 111(5): 1373-80. cells in vivo. J Exp Med 2008; 205(11): 2483-90. 132 Current Immunology Reviews, 2012, Vol. 8, No. 2 Soler-Ferran and Briskin

[54] Podolsky DK, Lobb R, King N, et al. Attenuation of colitis in the encephalomyelitis in the mouse requires alpha4-integrin but not cotton-top tamarin by anti-alpha 4 integrin monoclonal antibody. J alpha4beta7-integrin. J Clin Invest 1998; 102(12): 2096-105. Clin Invest 1993; 92(1): 372-80. [74] Leone DR, Giza K, Gill A, et al. An assessment of the mechanistic [55] Sydora BC, Wagner N, Lohler J, et al. beta7 Integrin expression is differences between two integrin alpha 4 beta 1 inhibitors, the not required for the localization of T cells to the intestine and monoclonal antibody TA-2 and the small molecule BIO5192, in rat colitis pathogenesis. Clin Exp Immunol 2002; 129(1): 35-42. experimental autoimmune encephalomyelitis. J Pharmacol Exp [56] Shigematsu T, Specian RD, Wolf RE, Grisham MB, Granger DN. Ther 2003; 305(3): 1150-62. MAdCAM mediates lymphocyte-endothelial cell adhesion in a [75] Bauer M, Brakebusch C, Coisne C, et al. Beta1 integrins murine model of chronic colitis. Am J Physiol Gastrointest Liver differentially control extravasation of inflammatory cell subsets Physiol 2001; 281(5): G1309-15. into the CNS during autoimmunity. Proc Natl Acad Sci U S A [57] Picarella D, Hurlbut P, Rottman J, Shi X, Butcher E, Ringler DJ. 2009; 106(6): 1920-5. Monoclonal antibodies specific for beta 7 integrin and mucosal [76] Kanwar JR, Harrison JE, Wang D, et al. Beta7 integrins contribute addressin cell adhesion molecule-1 (MAdCAM-1) reduce to demyelinating disease of the central nervous system. J inflammation in the colon of scid mice reconstituted with Neuroimmunol 2000; 103(2): 146-52. CD45RBhigh CD4+ T cells. J Immunol 1997; 158(5): 2099-106. [77] Kanwar JR, Kanwar RK, Wang D, Krissansen GW. Prevention of a [58] Park EJ, Mora JR, Carman CV, et al. Aberrant activation of chronic progressive form of experimental autoimmune integrin alpha4beta7 suppresses lymphocyte migration to the gut. J encephalomyelitis by an antibody against mucosal addressin cell Clin Invest 2007; 117(9): 2526-38. adhesion molecule-1, given early in the course of disease [59] Kato S, Hokari R, Matsuzaki K, et al. Amelioration of murine progression. Immunol Cell Biol 2000; 78(6): 641-5. experimental colitis by inhibition of mucosal addressin cell [78] Allavena R, Noy S, Andrews M, Pullen N. CNS elevation of adhesion molecule-1. J Pharmacol Exp Ther 2000; 295(1): 183-9. vascular and not mucosal addressin cell adhesion molecules in [60] Farkas S, Hornung M, Sattler C, et al. Blocking MAdCAM-1 in patients with multiple sclerosis. Am J Pathol 2010; 176(2): 556-62. vivo reduces leukocyte extravasation and reverses chronic [79] Pullen N, Molloy E, Carter D, et al. Pharmacological inflammation in experimental colitis. Int J Colorectal Dis 2006; characterization of PF-00547659, an anti-human MAdCAM 21(1): 71-8. monoclonal antibody. Br J Pharmacol 2009; 157(2): 281-93. [61] Hokari R, Kato S, Matsuzaki K, et al. Involvement of mucosal [80] Polman CH, O'Connor PW, Havrdova E, et al. A randomized, addressin cell adhesion molecule-1 (MAdCAM-1) in the placebo-controlled trial of natalizumab for relapsing multiple pathogenesis of granulomatous colitis in rats. Clin Exp Immunol sclerosis. N Engl J Med 2006; 354(9): 899-910. 2001; 126(2): 259-65. [81] Miller DH, Khan OA, Sheremata WA, et al. A controlled trial of [62] Apostolaki M, Manoloukos M, Roulis M, et al. Role of beta7 natalizumab for relapsing multiple sclerosis. N Engl J Med 2003; integrin and the chemokine/chemokine receptor pair CCL25/CCR9 348(1): 15-23. in modeled TNF-dependent Crohn's disease. Gastroenterology [82] Ghosh S, Goldin E, Gordon FH, et al. Natalizumab for active 2008; 134(7): 2025-35. Crohn's disease. N Engl J Med 2003; 348(1): 24-32. [63] Matsuzaki K, Tsuzuki Y, Matsunaga H, et al. In vivo demonstration [83] Gordon FH, Lai CW, Hamilton MI, et al. A randomized placebo- of T lymphocyte migration and amelioration of ileitis in intestinal controlled trial of a humanized monoclonal antibody to alpha4 mucosa of SAMP1/Yit mice by the inhibition of MAdCAM-1. Clin integrin in active Crohn's disease. Gastroenterology 2001; 121(2): Exp Immunol 2005; 140(1): 22-31. 268-74. [64] Goto A, Arimura Y, Shinomura Y, Imai K, Hinoda Y. Antisense [84] Sandborn WJ, Colombel JF, Enns R, et al. Natalizumab induction therapy of MAdCAM-1 for trinitrobenzenesulfonic acid-induced and maintenance therapy for Crohn's disease. N Engl J Med 2005; murine colitis. Inflamm Bowel Dis 2006; 12(8): 758-65. 353(18): 1912-25. [65] Kelly KA, Rank RG. Identification of homing receptors that [85] Targan SR, Feagan BG, Fedorak RN, et al. Natalizumab for the mediate the recruitment of CD4 T cells to the genital tract treatment of active Crohn's disease: results of the ENCORE Trial. following intravaginal infection with Chlamydia trachomatis. Infect Gastroenterology 2007; 132(5): 1672-83. Immun 1997; 65(12): 5198-208. [86] Rudick RA, Stuart WH, Calabresi PA, et al. Natalizumab plus [66] Perry LL, Feilzer K, Portis JL, Caldwell HD. Distinct homing interferon beta-1a for relapsing multiple sclerosis. N Engl J Med pathways direct T lymphocytes to the genital and intestinal 2006; 354(9): 911-23. mucosae in Chlamydia-infected mice. J Immunol 1998; 160(6): [87] Tubridy N, Behan PO, Capildeo R, et al. The effect of anti-alpha4 2905-14. integrin antibody on brain lesion activity in MS. The UK Antegren [67] McNulty KM, Plianrungsi J, Leigh JE, Mercante D, Fidel PL, Jr. Study Group. Neurology 1999; 53(3): 466-72. Characterization of CD8+ T cells and microenvironment in oral [88] Kleinschmidt-DeMasters BK, Tyler KL. Progressive multifocal lesions of human immunodeficiency virus-infected persons with leukoencephalopathy complicating treatment with natalizumab and oropharyngeal candidiasis. Infect Immun 2005; 73(6): 3659-67. interferon beta-1a for multiple sclerosis. N Engl J Med 2005; [68] Csencsits KL, Jutila MA, Pascual DW. Nasal-associated lymphoid 353(4): 369-74. tissue: phenotypic and functional evidence for the primary role of [89] Langer-Gould A, Atlas SW, Green AJ, Bollen AW, Pelletier D. peripheral node addressin in naive lymphocyte adhesion to high Progressive multifocal leukoencephalopathy in a patient treated endothelial venules in a mucosal site. J Immunol 1999; 163(3): with natalizumab. N Engl J Med 2005; 353(4): 375-81. 1382-9. [90] Van Assche G, Van Ranst M, Sciot R, et al. Progressive multifocal [69] Coisne C, Mao W, Engelhardt B. Cutting edge: Natalizumab blocks leukoencephalopathy after natalizumab therapy for Crohn's disease. adhesion but not initial contact of human T cells to the blood-brain N Engl J Med 2005; 353(4): 362-8. barrier in vivo in an animal model of multiple sclerosis. J Immunol [91] Yousry TA, Major EO, Ryschkewitsch C, et al. Evaluation of 2009; 182(10): 5909-13. patients treated with natalizumab for progressive multifocal [70] Engelhardt B, Martin-Simonet MT, Rott LS, Butcher EC, Michie leukoencephalopathy. N Engl J Med 2006; 354(9): 924-33. SA. Adhesion molecule phenotype of T lymphocytes in inflamed [92] Tysabri [package insert]. San Diego, C.E., and Cambridge, MA: CNS. J Neuroimmunol 1998; 84(1): 92-104. Biogen Idec. [71] Steffen BJ, Butcher EC, Engelhardt B. Evidence for involvement of [93] FDA, FDA Drug Safety Communication: Risk of Progressive ICAM-1 and VCAM-1 in lymphocyte interaction with endothelium Multifocal Leukoencephalopathy (PML) with the use of Tysabri in experimental autoimmune encephalomyelitis in the central (natalizumab) in http://www.fiercebiotech.com/press-releases/fda- nervous system in the SJL/J mouse. Am J Pathol 1994; 145(1): drug-safety-communication-risk-progressive-multifocal-leukoence 189-201. phalopathy-pml-use#ixzz0nRj7uGAb. [72] Engelhardt B, Conley FK, Kilshaw PJ, Butcher EC. Lymphocytes [94] Major EO. Progressive multifocal leukoencephalopathy in patients infiltrating the CNS during inflammation display a distinctive on immunomodulatory therapies. Annu Rev Med 2010; 61: 35-47. phenotype and bind to VCAM-1 but not to MAdCAM-1. Int [95] Allison M. PML problems loom for Rituxan. Nat Biotechnol 2010; Immunol 1995; 7(3): 481-91. 28(2): 105-6. [73] Engelhardt B, Laschinger M, Schulz M, Samulowitz U, Vestweber [96] Molloy ES, Calabrese LH. Therapy: Targeted but not trouble-free: D, Hoch G. The development of experimental autoimmune efalizumab and PML. Nat Rev Rheumatol 2009; 5(8): 418-9. Integrin
47 Antagonists Current Immunology Reviews, 2012, Vol. 8, No. 2 133

[97] Ransohoff RM. Natalizumab and PML. Nat Neurosci 2005; 8(10): [119] Chen Y, Bord E, Tompkins T, et al. Asymptomatic reactivation of 1275. JC virus in patients treated with natalizumab. N Engl J Med 2009; [98] Dubois V, Dutronc H, Lafon ME, et al. Latency and reactivation of 361(11): 1067-74. JC virus in peripheral blood of human immunodeficiency virus [120] Du Pasquier RA, Kuroda J, Zheng Y, Jean-Jacques J, Letvin ND, type 1-infected patients. J Clin Microbiol 1997; 35(9): 2288-92. Koralnik IJ. A prospective study demonstrates an association [99] Houff SA, Major EO, Katz DA, et al. Involvement of JC virus- between JC virus-specific cytotoxic T lymphocytes and the early infected mononuclear cells from the bone marrow and spleen in the control of progressive multifocal leukoencephalopathy. Brain 2004; pathogenesis of progressive multifocal leukoencephalopathy. N 127(Pt 9): 1970-8. Engl J Med 1988; 318(5): 301-5. [121] Du Pasquier RA, Schmitz JE, Jean-Jacques J, et al. Detection of JC [100] Monaco MC, Atwood WJ, Gravell M, Tornatore CS, Major EO. JC virus-specific cytotoxic T lymphocytes in healthy individuals. J virus infection of hematopoietic progenitor cells, primary B Virol 2004; 78(18): 10206-10. lymphocytes, and tonsillar stromal cells: implications for viral [122] Gasnault J, Kahraman M, de Goer de Herve MG, Durali D, latency. J Virol 1996; 70(10): 7004-12. Delfraissy JF, Taoufik Y. Critical role of JC virus-specific CD4 T- [101] Monaco MC, Shin J, Major EO. JC virus infection in cells from cell responses in preventing progressive multifocal lymphoid tissue. Dev Biol Stand 1998; 94: 115-22. leukoencephalopathy. AIDS 2003; 17(10): 1443-9. [102] Tan CS, Dezube BJ, Bhargava P, et al. Detection of JC virus DNA [123] Stuve O, Marra CM, Bar-Or A, et al. Altered CD4+/CD8+ T-cell and proteins in the bone marrow of HIV-positive and HIV-negative ratios in cerebrospinal fluid of natalizumab-treated patients with patients: implications for viral latency and neurotropic multiple sclerosis. Arch Neurol 2006; 63(10): 1383-7. transformation. J Infect Dis 2009; 199(6): 881-8. [124] Feagan B, McDonald J, Greenberg G, et al. An ascending dose trial [103] Cavanagh LL, Bonasio R, Mazo IB, et al. Activation of bone of a humanised a4b7 antibody in ulcerative colitis. marrow-resident memory T cells by circulating, antigen-bearing Gastroenterology 2000; 118(Suppl): A874. dendritic cells. Nat Immunol 2005; 6(10): 1029-37. [125] Feagan BG, Greenberg GR, Wild G, et al. Treatment of ulcerative [104] Mazo IB, Honczarenko M, Leung H, et al. Bone marrow is a major colitis with a humanized antibody to the alpha4beta7 integrin. N reservoir and site of recruitment for central memory CD8+ T cells. Engl J Med 2005; 352(24): 2499-507. Immunity 2005; 22(2): 259-70. [126] Parikh A, Wyant T, Clifford DB, et al. No increase in JC viremia, [105] Papayannopoulou T, Craddock C, Nakamoto B, Priestley GV, Wolf lymphocyte count, or circulating CD34+ hematopoietic progenitor NS. The VLA4/VCAM-1 adhesion pathway defines contrasting cells after treatment with vedolizumab, a humanized monoclonal mechanisms of lodgement of transplanted murine hemopoietic antibody to a4b7 integrin. Gastroenterology 2010; 138(5 (S1)): progenitors between bone marrow and spleen. Proc Natl Acad Sci S145-S146. U S A 1995; 92(21): 9647-51. [127] Fedyk E, Yang H, Wyant T, et al. The pharmacologic and [106] Koni PA, Joshi SK, Temann UA, Olson D, Burkly L, Flavell RA. toxicologic profile of the gastrointestinal-selective, anti- Conditional vascular cell adhesion molecule 1 deletion in mice: inflammatory drug vedolizumab in cynomolgus macaques. J. impaired lymphocyte migration to bone marrow. J Exp Med 2001; Crohn's Colitis 2010; 4(1): S6,9. 193(6): 741-54. [128] Parikh A, Fedyk E, Soler D, et al. Gastrointestinal selectivity of [107] Leuker CE, Labow M, Muller W, Wagner N. Neonatally induced vedolizumab (MLN0002), a humanized monoclonal antibody to the inactivation of the vascular cell adhesion molecule 1 gene impairs a4b7 integrin. J. Crohn's Colitis 2009; 5 (1) B cell localization and T cell-dependent humoral immune response. [129] Wehner NG, Gasper C, Shopp G, et al. Immunotoxicity profile of J Exp Med 2001; 193(6): 755-68. natalizumab. J Immunotoxicol 2009; 6(2): 115-29. [108] Arroyo AG, Yang JT, Rayburn H, Hynes RO. Differential [130] Banerjee ER, Latchman YE, Jiang Y, Priestley GV, requirements for alpha4 integrins during fetal and adult Papayannopoulou T. Distinct changes in adult lymphopoiesis in hematopoiesis. Cell 1996; 85(7): 997-1008. Rag2-/- mice fully reconstituted by alpha4-deficient adult bone [109] Teixido J, Hemler ME, Greenberger JS, Anklesaria P. Role of beta marrow cells. Exp Hematol 2008; 36(8): 1004-13. 1 and beta 2 integrins in the adhesion of human CD34hi stem cells [131] Brakebusch C, Fillatreau S, PotocnikAJ, et al. Beta1 integrin is not to bone marrow stroma. J Clin Invest 1992; 90(2): 358-67. essential for hematopoiesis but is necessary for the T cell- [110] Miyake K, Medina K, Ishihara K, Kimoto M, Auerbach R, Kincade dependent IgM antibody response. Immunity 2002; 16(3): 465-77. PW. A VCAM-like adhesion molecule on murine bone marrow [132] Stefanich E, Fuh F, David C, et al. Gut-homing CD4+ stromal cells mediates binding of lymphocyte precursors in culture. Lymphocytes are Specifically Targeted in Cynomolgus Monkeys J Cell Biol 1991; 114(3): 557-65. Dosed with Anti-Beta7 Antibody. Clinical Immunology 2008; [111] Miyake K, Weissman IL, Greenberger JS, Kincade PW. Evidence 127(S1): S118-S119. for a role of the integrin VLA-4 in lympho-hemopoiesis. J Exp [133] Cepek KL, Shaw SK, Parker CM, et al. Adhesion between Med 1991; 173(3): 599-607. epithelial cells and T lymphocytes mediated by E-cadherin and the [112] Simmons PJ, Masinovsky B, Longenecker BM, Berenson R, alpha E beta 7 integrin. Nature 1994; 372(6502): 190-3. Torok-Storb B, Gallatin WM. Vascular cell adhesion molecule-1 [134] Cepek KL, Parker CM, Madara JL, Brenner MB. Integrin alpha E expressed by bone marrow stromal cells mediates the binding of beta 7 mediates adhesion of T lymphocytes to epithelial cells. J hematopoietic progenitor cells. Blood 1992; 80(2): 388-95. Immunol 1993; 150(8 Pt 1): 3459-70. [113] Yanai N, Sekine C, Yagita H, Obinata M. Roles for integrin very [135] Ericsson A, Arya A, Agace W. CCL25 enhances CD103-mediated late activation antigen-4 in stroma-dependent erythropoiesis. Blood lymphocyte adhesion to E-cadherin. Ann N Y Acad Sci 2004; 1994; 83(10): 2844-50. 1029: 334-6. [114] Williams DA, Rios M, Stephens C, Patel VP. Fibronectin and [136] Ericsson A, Svensson M, Arya A, Agace WW. CCL25/CCR9 VLA-4 in haematopoietic stem cell-microenvironment interactions. promotes the induction and function of CD103 on intestinal Nature 1991; 352(6334): 438-41. intraepithelial lymphocytes. Eur J Immunol 2004; 34(10): 2720-9. [115] Papayannopoulou T, Nakamoto B. Peripheralization of [137] Schon MP, Arya A, Murphy EA, et al. Mucosal T lymphocyte hemopoietic progenitors in primates treated with anti-VLA4 numbers are selectively reduced in integrin alpha E (CD103)- integrin. Proc Natl Acad Sci U S A 1993; 90(20): 9374-8. deficient mice. J Immunol 1999; 162(11): 6641-9. [116] Zohren F, Toutzaris D, Klarner V, Hartung HP, Kieseier B, Haas [138] Lehmann J, Huehn J, de la Rosa M, et al. Expression of the integrin R. The monoclonal anti-VLA-4 antibody natalizumab mobilizes alpha Ebeta 7 identifies unique subsets of CD25+ as well as CD25- CD34+ hematopoietic progenitor cells in humans. Blood 2008; regulatory T cells. Proc Natl Acad Sci U S A 2002; 99(20): 13031- 111(7): 3893-5. 6. [117] Bonig H, Wundes A, Chang KH, Lucas S, Papayannopoulou T. [139] Schon MP, Schon M, Parker CM, Williams IR. Dendritic Increased numbers of circulating hematopoietic stem/progenitor epidermal T cells (DETC) are diminished in integrin cells are chronically maintained in patients treated with the CD49d alphaE(CD103)-deficient mice. J Invest Dermatol 2002; 119(1): blocking antibody natalizumab. Blood 2008; 111(7): 3439-41. 190-3. [118] Slifka MK, Whitmire JK, Ahmed R. Bone marrow contains virus- [140] Bedoui S, Whitney PG, Waithman J, et al. Cross-presentation of specific cytotoxic T lymphocytes. Blood 1997; 90(5): 2103-8. viral and self antigens by skin-derived CD103+ dendritic cells. Nat Immunol 2009; 10(5): 488-95. 134 Current Immunology Reviews, 2012, Vol. 8, No. 2 Soler-Ferran and Briskin

[141] Coombes JL, Siddiqui KR, Arancibia-Carcamo CV, et al. A [158] Eksteen B, Grant AJ, Miles A, et al. Hepatic endothelial CCL25 functionally specialized population of mucosal CD103+ DCs mediates the recruitment of CCR9+ gut-homing lymphocytes to the induces Foxp3+ regulatory T cells via a TGF-beta and retinoic liver in primary sclerosing cholangitis. J Exp Med 2004; 200(11): acid-dependent mechanism. J Exp Med 2007; 204(8): 1757-64. 1511-7. [142] de Vries IJ, Langeveld-Wildschut EG, van Reijsen FC, Bihari IC, [159] Eksteen B, Mora JR, Haughton EL, et al. Gut homing receptors on Bruijnzeel-Koomen CA, Thepen T. Nonspecific T-cell homing CD8 T cells are retinoic acid dependent and not maintained by liver during inflammation in atopic dermatitis: expression of cutaneous dendritic or stellate cells. Gastroenterology 2009; 137(1): 320-9. lymphocyte-associated antigen and integrin alphaE beta7 on skin- [160] Yang XD, Sytwu HK, McDevitt HO, Michie SA. Involvement of infiltrating T cells. J Allergy Clin Immunol 1997; 100(5): 694-701. beta 7 integrin and mucosal addressin cell adhesion molecule-1 [143] Pauls K, Schon M, Kubitza RC, et al. Role of integrin (MAdCAM-1) in the development of diabetes in obese diabetic alphaE(CD103)beta7 for tissue-specific epidermal localization of mice. Diabetes 1997; 46(10): 1542-7. CD8+ T lymphocytes. J Invest Dermatol 2001; 117(3): 569-75. [161] Hanninen A, Jaakkola I, Jalkanen S. Mucosal addressin is required [144] Picker LJ, Martin RJ, Trumble A, et al. Differential expression of for the development of diabetes in nonobese diabetic mice. J lymphocyte homing receptors by human memory/effector T cells in Immunol 1998; 160(12): 6018-25. pulmonary versus cutaneous immune effector sites. Eur J Immunol [162] Hanninen A, Taylor C, Streeter PR, et al. Vascular addressins are 1994; 24(6): 1269-77. induced on islet vessels during insulitis in nonobese diabetic mice [145] Davenport RJ, Munday JR. Alpha4-integrin antagonism--an and are involved in lymphoid cell binding to islet endothelium. J effective approach for the treatment of inflammatory diseases? Clin Invest 1993; 92(5): 2509-15. Drug Discov Today 2007; 12(13-14): 569-76. [163] Phillips JM, Haskins K, Cooke A. MAdCAM-1 is needed for [146] Dubree NJ, Artis DR, Castanedo G, et al. Selective alpha4beta7 diabetes development mediated by the T cell clone, BDC-2.5. integrin antagonists and their potential as antiinflammatory agents. Immunology 2005; 116(4): 525-31. J Med Chem 2002; 45(16): 3451-7. [164] Xu B, Cook RE, Michie SA. alpha(4)beta(7) integrin/MAdCAM-1 [147] Boer J, Gottschling D, Schuster A, Semmrich M, Holzmann B, adhesion pathway is crucial for B cell migration into pancreatic Kessler H. Design and synthesis of potent and selective lymph nodes in nonobese diabetic mice. J Autoimmun 2010. alpha(4)beta(7) integrin antagonists. J Med Chem 2001; 44(16): [165] Paronen J, Klemetti P, Kantele JM, et al. Glutamate decarboxylase- 2586-92. reactive peripheral blood lymphocytes from patients with IDDM [148] Harriman GC, Brewer M, Bennett R, et al. Selective cell adhesion express gut-specific homing receptor alpha4beta7-integrin. inhibitors: Barbituric acid based alpha4beta7--MAdCAM Diabetes 1997; 46(4): 583-8. inhibitors. Bioorg Med Chem Lett 2008; 18(7): 2509-12. [166] Jakubowski A, Ehrenfels BN, Pepinsky RB, Burkly LC. Vascular [149] Harriman GC, Schwender CF, Gallant D, Cochran NA, Briskin MJ. cell adhesion molecule-Ig fusion protein selectively targets Cell adhesion antagonists: synthesis and evaluation of a novel activated alpha 4-integrin receptors in vivo. Inhibition of series of phenylalanine based inhibitors. Bioorg Med Chem Lett autoimmune diabetes in an adoptive transfer model in nonobese 2000; 10(14): 1497-9. diabetic mice. J Immunol 1995; 155(2): 938-46. [150] Shroff HN, Schwender CF, Baxter AD, et al. Novel modified [167] Hanninen A, Nurmela R, Maksimow M, Heino J, Jalkanen S, Kurts tripeptide inhibitors of alpha 4 beta 7 mediated lymphoid cell C. Islet beta-cell-specific T cells can use different homing adhesion to MAdCAM-1. Bioorg Med Chem Lett 1998; 8(13): mechanisms to infiltrate and destroy pancreatic islets. Am J Pathol 1601-6. 2007; 170(1): 240-50. [151] Sugiura T, Kuribayashi K, Kageyama S. An orally active alpha 4 [168] Petrovic A, Alpdogan O, Willis LM, et al. LPAM (alpha 4 beta 7 integring antagonist AJM300 prevents the developmente of integrin) is an important homing integrin on alloreactive T cells in experimental colitis induced by adoptive transfer of IL-10 deficient the development of intestinal graft-versus-host disease. Blood CD4+ T cells in mice. GASTRO 2009, London 2009. 2004; 103(4): 1542-7. [152] Sharm P, Halayko AJ. Emerging molecular targets for the [169] Waldman E, Lu SX, Hubbard VM, et al. Absence of beta7 integrin treatment of asthma. Indian J Biochem Biophys 2009; 46(6): 447- results in less graft-versus-host disease because of decreased 60. homing of alloreactive T cells to intestine. Blood 2006; 107(4): [153] Chapman RW. Aetiology and natural history of primary sclerosing 1703-11. cholangitis--a decade of progress? Gut 1991; 32(12): 1433-5. [170] Ueha S, Murai M, Yoneyama H, et al. Intervention of MAdCAM-1 [154] Grant AJ, Lalor PF, Salmi M, Jalkanen S, Adams DH. Homing of or fractalkine alleviates graft-versus-host reaction associated mucosal lymphocytes to the liver in the pathogenesis of hepatic intestinal injury while preserving graft-versus-tumor effects. J complications of inflammatory bowel disease. Lancet 2002; Leukoc Biol 2007; 81(1): 176-85. 359(9301): 150-7. [171] Kim TD, Terwey TH, Zakrzewski JL, et al. Organ-derived [155] Adams DH, Eksteen B. Aberrant homing of mucosal T cells and dendritic cells have differential effects on alloreactive T cells. extra-intestinal manifestations of inflammatory bowel disease. Nat Blood 2008; 111(5): 2929-40. Rev Immunol 2006; 6(3): 244-51. [172] Li N, Chen Y, He W, et al. Anti-CD3 preconditioning separates [156] Ponsioen CY, Kuiper H, Ten Kate FJ, van Milligen M, de Wit SJ. GVL from GVHD via modulating host dendritic cell and donor T- van Deventer, and G.N. Tytgat. Immunohistochemical analysis of cell migration in recipients conditioned with TBI. Blood 2009; inflammation in primary sclerosing cholangitis. Eur J Gastroenterol 113(4): 953-62. Hepatol 1999; 11(7): 769-74. [173] Peer D, Park EJ, Morishita Y, Carman CV, Shimaoka M. Systemic [157] Grant AJ, Lalor PF, Hubscher SG, Briskin M, Adams DH. leukocyte-directed siRNA delivery revealing cyclin D1 as an anti- MAdCAM-1 expressed in chronic inflammatory liver disease inflammatory target. Science 2008; 319(5863): 627-30. supports mucosal lymphocyte adhesion to hepatic endothelium [174] Dearling JL, Park EJ, Dunning P, et al. Detection of intestinal (MAdCAM-1 in chronic inflammatory liver disease). Hepatology inflammation by MicroPET imaging using a (64)Cu-labeled anti- 2001; 33(5): 1065-72. beta(7) integrin antibody. Inflamm Bowel Dis 2010.

Received: August 24, 2010 Revised: June 24, 2011 Accepted: July 8, 2011