Development and preclinical characterization of a humanized antibody targeting CXCL12.

PURPOSE: Our goal was to develop a potent humanized antibody against mouse/human CXCL12. This report summarized its in vitro and in vivo activities. EXPERIMENTAL DESIGN: Cell surface binding and cell migration assays were used to select neutralizing hamster antibodies, followed by testing in several animal models. Monoclonal antibody (mAb) 30D8 was selected for humanization based on its in vitro and in vivo activities. RESULTS: 30D8, a hamster antibody against mouse and human CXCL12α, CXCL12ß, and CXCL12γ, was shown to dose-dependently block CXCL12α binding to CXCR4 and CXCR7, and CXCL12α-induced Jurkat cell migration in vitro. Inhibition of primary tumor growth and/or metastasis was observed in several models. 30D8 alone significantly ameliorated arthritis in a mouse collagen-induced arthritis model (CIA). Combination with a TNF-α antagonist was additive. In addition, 30D8 inhibited 50% of laser-induced choroidal neovascularization (CNV) in mice. Humanized 30D8 (hu30D8) showed similar in vitro and in vivo activities as the parental hamster antibody. A crystal structure of the hu30D8 Fab/CXCL12α complex in combination with mutational analysis revealed a "hot spot" around residues Asn(44)/Asn(45) of CXCL12α and part of the RFFESH region required for CXCL12α binding to CXCR4 and CXCR7. Finally, hu30D8 exhibited fast clearance in cynomolgus monkeys but not in rats. CONCLUSION: CXCL12 is an attractive target for treatment of cancer and inflammation-related diseases; hu30D8 is suitable for testing this hypothesis in humans.

Identification of C-2 hydroxyethyl imidazopyrrolopyridines as potent JAK1 inhibitors with favorable physicochemical properties and high selectivity over JAK2.

Herein we report on the structure-based discovery of a C-2 hydroxyethyl moiety which provided consistently high levels of selectivity for JAK1 over JAK2 to the imidazopyrrolopyridine series of JAK1 inhibitors. X-ray structures of a C-2 hydroxyethyl analogue in complex with both JAK1 and JAK2 revealed differential ligand/protein interactions between the two isoforms and offered an explanation for the observed selectivity. Analysis of historical data from related molecules was used to develop a set of physicochemical compound design parameters to impart desirable properties such as acceptable membrane permeability, potent whole blood activity, and a high degree of metabolic stability. This work culminated in the identification of a highly JAK1 selective compound (31) exhibiting favorable oral bioavailability across a range of preclinical species and robust efficacy in a rat CIA model.

CRIg mediates early Kupffer cell responses to adenovirus.

Whereas adenoviral vectors are known to activate the complement cascade, leading to fixation of C3 proteins to the viral capsid, the consequences of this activation for viral clearance from the circulation are not known. Liver KCs, the macrophage population responsible for early uptake and elimination of many blood-borne pathogens, express CRIg, a complement receptor for C3 proteins. Here, we find that CRIg is important for the early elimination of C3-coated adenoviral vectors from the sinusoidal bloodstream by KCs. We further demonstrate that by acting as a critical receptor for adenovirus phagocytosis, CRIg plays an important role in regulating virus-induced KC death and depletion of these cells from the liver sinusoidal lumen. Our study thus identifies a critical pathway regulating KC function and survival in response to systemic viral infection.

Specific Btk inhibition suppresses B cell- and myeloid cell-mediated arthritis.

Bruton's tyrosine kinase (Btk) is a therapeutic target for rheumatoid arthritis, but the cellular and molecular mechanisms by which Btk mediates inflammation are poorly understood. Here we describe the discovery of CGI1746, a small-molecule Btk inhibitor chemotype with a new binding mode that stabilizes an inactive nonphosphorylated enzyme conformation. CGI1746 has exquisite selectivity for Btk and inhibits both auto- and transphosphorylation steps necessary for enzyme activation. Using CGI1746, we demonstrate that Btk regulates inflammatory arthritis by two distinct mechanisms. CGI1746 blocks B cell receptor-dependent B cell proliferation and in prophylactic regimens reduces autoantibody levels in collagen-induced arthritis. In macrophages, Btk inhibition abolishes FcγRIII-induced TNFα, IL-1ß and IL-6 production. Accordingly, in myeloid- and FcγR-dependent autoantibody-induced arthritis, CGI1746 decreases cytokine levels within joints and ameliorates disease. These results provide new understanding of the function of Btk in both B cell- or myeloid cell-driven disease processes and provide a compelling rationale for targeting Btk in rheumatoid arthritis.

Targeted depletion of lymphotoxin-alpha-expressing TH1 and TH17 cells inhibits autoimmune disease.

Uncontrolled T helper type 1 (T(H)1) and T(H)17 cells are associated with autoimmune responses. We identify surface lymphotoxin-alpha (LT-alpha) as common to T(H)0, T(H)1 and T(H)17 cells and employ a unique strategy to target these subsets using a depleting monoclonal antibody (mAb) directed to surface LT-alpha. Depleting LT-alpha-specific mAb inhibited T cell-mediated models of delayed-type hypersensitivity and experimental autoimmune encephalomyelitis. In collagen-induced arthritis (CIA), preventive and therapeutic administration of LT-alpha-specific mAb inhibited disease, and immunoablated T cells expressing interleukin-17 (IL-17), interferon-gamma and tumor necrosis factor-alpha (TNF-alpha), whereas decoy lymphotoxin-beta receptor (LT-betaR) fusion protein had no effect. A mutation in the Fc tail, rendering the antibody incapable of Fcgamma receptor binding and antibody-dependent cellular cytotoxicity activity, abolished all in vivo effects. Efficacy in CIA was preceded by a loss of rheumatoid-associated cytokines IL-6, IL-1beta and TNF-alpha within joints. These data indicate that depleting LT-alpha-expressing lymphocytes with LT-alpha-specific mAb may be beneficial in the treatment of autoimmune disease.

A novel inhibitor of the alternative pathway of complement reverses inflammation and bone destruction in experimental arthritis.

Complement is an important component of the innate and adaptive immune response, yet complement split products generated through activation of each of the three complement pathways (classical, alternative, and lectin) can cause inflammation and tissue destruction. Previous studies have shown that complement activation through the alternative, but not classical, pathway is required to initiate antibody-induced arthritis in mice, but it is unclear if the alternative pathway (AP) plays a role in established disease. Previously, we have shown that human complement receptor of the immunoglobulin superfamily (CRIg) is a selective inhibitor of the AP of complement. Here, we present the crystal structure of murine CRIg and, using mutants, provide evidence that the structural requirements for inhibition of the AP are conserved in human and mouse. A soluble form of CRIg reversed inflammation and bone loss in two experimental models of arthritis by inhibiting the AP of complement in the joint. Our data indicate that the AP of complement is not only required for disease induction, but also disease progression. The extracellular domain of CRIg thus provides a novel tool to study the effects of inhibiting the AP of complement in established disease and constitutes a promising therapeutic with selectivity for a single complement pathway.

Importance of cellular microenvironment and circulatory dynamics in B cell immunotherapy.

B cell immunotherapy has emerged as a mainstay in the treatment of lymphomas and autoimmune diseases. Although the microenvironment has recently been demonstrated to play critical roles in B cell homeostasis, its contribution to immunotherapy is unknown. To analyze the in vivo factors that regulate mechanisms involved in B cell immunotherapy, we used a murine model for human CD20 (hCD20) expression in which treatment of hCD20(+) mice with anti-hCD20 mAbs mimics B cell depletion observed in humans. We demonstrate in this study that factors derived from the microenvironment, including signals from the B cell-activating factor belonging to the TNF family/BLyS survival factor, integrin-regulated homeostasis, and circulatory dynamics of B cells define distinct in vivo mechanism(s) and sensitivities of cells in anti-hCD20 mAb-directed therapies. These findings provide new insights into the mechanisms of immunotherapy and define new opportunities in the treatment of cancers and autoimmune diseases.

Quantification of cortical bone loss and repair for therapeutic evaluation in collagen-induced arthritis, by micro-computed tomography and automated image analysis.

OBJECTIVE: Ex vivo and in vivo micro-computed tomography (micro-CT) combined with a novel image analysis algorithm were used to quantify cortical bone loss and periosteal new bone formation for therapeutic evaluation in a murine model of collagen-induced arthritis. METHODS: An automated algorithm was created to locate 5 metatarsophalangeal and 3 metacarpophalangeal joints in 3-dimensional micro-CT images of mouse paws for evaluation of joint cortical bone volume (JCBV) within close proximity of the joints as well as cortical bone mineral density and periosteal new bone formation within the paws. For validation, automated estimates of JCBV were compared with radiographic visual scores (RVS) in 4 treatment groups (n = 9 per group): rat anti-mouse CD11a monoclonal antibody, methotrexate (MTX), anti-CD11a plus MTX, and saline only. In a separate study, serial images of hind limbs were evaluated in 2 treatment groups: murine tumor necrosis factor receptor II-Fc fusion protein (mTNFRII; n = 10) and control antibody (n = 7). RESULTS: Automated estimates of the JCBV were significantly correlated with the RVS (hind paws R = -0.94, front paws R = -0.81, combined R = -0.87). The anti-CD11a group had significantly higher JCBV compared with controls. In the serial study, the automated estimate of JCBV detected significant treatment effects in the mTNFRII-Fc group compared with controls. Cortical bone mineral density was significantly higher in all treatment groups compared with controls. CONCLUSION: Micro-CT combined with a novel image analysis technique (estimation of JCBV) provides a fully automated means to quantify bone destruction in a mouse model of rheumatoid arthritis.

A novel in vivo role for osteoprotegerin ligand in activation of monocyte effector function and inflammatory response.

Osteoprotegerin Ligand (OPGL) is a member of the tumor necrosis factor ligand superfamily and has been shown to be involved in interactions between T cells and dendritic cells. Its role in monocyte effector function, however, has not been defined. In the present study a role for OPGL in activating monocytes/macrophages has been characterized. OPGL was found to up-regulate receptor activator of NF-kappaB (RANK) receptor expression on monocytes, regulate their effector function by inducing cytokine and chemokine secretion, activate antigen presentation through up-regulation of co-stimulatory molecule expression, and promote survival. This activation is mediated through the MAPK pathway as evidenced by activation of p38 and p42/44 MAPK and up-regulation of BCL-XL protein levels. A physiological role for OPGL in monocyte activation and effector function was tested in a model of lipopolysaccharide-induced endotoxic shock. Administration of receptor activator of NF-kappaB (RANK)-Fc to block OPGL activity in vivo was able to protect mice from death induced by sepsis, indicating a hitherto undescribed role for OPGL in monocyte function and in mediating inflammatory response. This was further tested in an animal model of inflammation-mediated arthritis. Treatment with RANK-Fc significantly ameliorated disease development and attenuated bone destruction. Thus, our study strongly suggests that administration of receptor fusion proteins to specifically block OPGL activity in vivo may result in blocking development of monocyte/macrophage-mediated diseases.