Determination of Ochratoxin A in Currants, Raisins, Sultanas, Mixed Dried Fruit, and Dried Figs by Immunoaffinity Column Cleanup with Liquid Chromatography: Interlaboratory Study

An interlaboratory study was performed on behalf of the Food Standards Agency to evaluate the effectiveness of an affinity column cleanup liquid chromatographic (LC) method for the determination of ochratoxin A in a variety of dried fruit at European regulatory limits. To ensure homogeneity before analysis, laboratory samples are normally slurried with water in the ratio of 5 parts fruit to 4 parts water, and test materials in this form were used in the study. The test portion was extracted with acidified methanol. The extract was filtered, diluted with phosphate-buffered saline, and applied to an affinity column. The column was washed and ochratoxin A was eluted with methanol. Ochratoxin A was quantified by reversed-phase LC. The use of post-column pH shift to enhance the fluorescence of ochratoxin A by the addition of 1.1M ammonia solution to the column eluant is optional. Determination was by fluorescence. Currants, sultanas, raisins, figs, and mixed fruit (comprising dried pineapple, papaya, sultanas, prunes, dates, and banana chips), both naturally contaminated and blank (very low level), were sent to 24 collaborators in 7 European countries. Participants were asked to spike test portions of all test samples at a level equivalent to 5 ng/g ochra toxin A. Average recoveries ranged from 69 to 74%. Based on results for 5 naturally contaminated test samples (blind duplicates) the relative standard deviation for repeatability (RSDr) ranged from 4.9 to 8.7%, and the relative standard deviation for reproducibility (RSDR)rangedfrom14to28%. The method showed acceptable within-and be-tween-laboratory precision for all 5 matrixes, as evidenced by HORRAT values <1.3.

Membrane-Proximal Epitope Facilitates Efficient T Cell Synapse Formation by Anti-FcRH5/CD3 and Is a Requirement for Myeloma Cell Killing

The anti-FcRH5/CD3 T cell-dependent bispecific antibody (TDB) targets the B cell lineage marker FcRH5 expressed in multiple myeloma (MM) tumor cells. We demonstrate that TDBs trigger T cell receptor activation by inducing target clustering and exclusion of CD45 phosphatase from the synapse. The dimensions of the target molecule play a key role in the efficiency of the synapse formation. The anti-FcRH5/CD3 TDB kills human plasma cells and patient-derived myeloma cells at picomolar concentrations and results in complete depletion of B cells and bone marrow plasma cells in cynomolgus monkeys. These data demonstrate the potential for the anti-FcRH5/CD3 TDB, alone or in combination with inhibition of PD-1/PD-L1 signaling, in the treatment of MM and other B cell malignancies.

Two Escape Mechanisms of Influenza A Virus to a Broadly Neutralizing Stalk-Binding Antibody

Broadly neutralizing antibodies targeting the stalk region of influenza A virus (IAV) hemagglutinin (HA) are effective in blocking virus infection both in vitro and in vivo. The highly conserved epitopes recognized by these antibodies are critical for the membrane fusion function of HA and therefore less likely to be permissive for virus mutational escape. Here we report three resistant viruses of the A/Perth/16/2009 strain that were selected in the presence of a broadly neutralizing stalk-binding antibody. The three resistant viruses harbor three different mutations in the HA stalk: (1) Gln387Lys; (2) Asp391Tyr; (3) Asp391Gly. The Gln387Lys mutation completely abolishes binding of the antibody to the HA stalk epitope. The other two mutations, Asp391Tyr and Asp391Gly, do not affect antibody binding at neutral pH and only slightly reduce binding at low pH. Interestingly, they enhance the fusion ability of the HA, representing a novel mechanism that allows productive membrane fusion even in the presence of antibody and hence virus escape from antibody neutralization. Therefore, these mutations illustrate two different resistance mechanisms used by IAV to escape broadly neutralizing stalk-binding antibodies. Compared to the wild type virus, the resistant viruses release fewer progeny viral particles during replication and are more sensitive to Tamiflu, suggesting reduced viral fitness.

IAV causes seasonal epidemics and periodic pandemics that result in significant morbidity and mortality worldwide. The effectiveness of influenza vaccines is highly variable because the virus evolves rapidly and causes antibody mismatch. The use of neuraminidase inhibitors, the current standard of treatment for IAV infection, is limited by their lack of efficacy beyond 48 hours of symptom onset and by the emergence of drug resistant viruses. Recently, broadly neutralizing antibodies targeting the conserved stalk region of IAV HA have been discovered. These antibodies are able to block the infection of many or even all IAV strains, and hold great promise as the next generation of anti-flu treatment. Nonetheless, virus resistance to these antibodies has not been thoroughly studied despite the common view that broadly neutralizing stalk-binding antibodies are less permissive for mutational escape due to the functional importance of their highly conserved epitopes. In this study, we isolated three resistant viruses to a stalk-binding antibody that was previously shown to neutralize all IAV tested. Interestingly, they use two distinct mechanisms to escape the antibody, abolishing antibody binding or enhancing membrane fusion. Our study emphasizes the need to consider novel escape mechanisms when studying virus resistance to broadly neutralizing stalk-binding antibodies.

Depletion of major pathogenic cells in asthma by targeting CRTh2

Eosinophilic inflammation and Th2 cytokine production are central to the pathogenesis of asthma. Agents that target either eosinophils or single Th2 cytokines have shown benefits in subsets of biomarker-positive patients. More broadly effective treatment or disease-modifying effects may be achieved by eliminating more than one inflammatory stimulator. Here we present a strategy to concomitantly deplete Th2 T cells, eosinophils, basophils, and type-2 innate lymphoid cells (ILC2s) by generating monoclonal antibodies with enhanced effector function (19A2) that target CRTh2 present on all 4 cell types. Using human CRTh2 (hCRTh2) transgenic mice that mimic the expression pattern of hCRTh2 on innate immune cells but not Th2 cells, we demonstrate that anti-hCRTh2 antibodies specifically eliminate hCRTh2⁺ basophils, eosinophils, and ILC2s from lung and lymphoid organs in models of asthma and Nippostrongylus brasiliensis infection. Innate cell depletion was accompanied by a decrease of several Th2 cytokines and chemokines. hCRTh2-specific antibodies were also active on human Th2 cells in vivo in a human Th2-PBMC-SCID mouse model. We developed humanized hCRTh2-specific antibodies that potently induce antibody-dependent cell cytotoxicity (ADCC) of primary human eosinophils and basophils and replicated the in vivo depletion capacity of their murine parent. Therefore, depletion of hCRTh2⁺ basophils, eosinophils, ILC2, and Th2 cells with h19A2 hCRTh2-specific antibodies may be a novel and more efficacious treatment for asthma.

Novel antibody-antibiotic conjugate eliminates intracellular S. aureus

Staphylococcus aureus is considered to be an extracellular pathogen. However, survival of S. aureus within host cells may provide a reservoir relatively protected from antibiotics, thus enabling long-term colonization of the host and explaining clinical failures and relapses after antibiotic therapy. Here we confirm that intracellular reservoirs of S. aureus in mice comprise a virulent subset of bacteria that can establish infection even in the presence of vancomycin, and we introduce a novel therapeutic that effectively kills intracellular S. aureus. This antibody-antibiotic conjugate consists of an anti-S. aureus antibody conjugated to a highly efficacious antibiotic that is activated only after it is released in the proteolytic environment of the phagolysosome. The antibody-antibiotic conjugate is superior to vancomycin for treatment of bacteraemia and provides direct evidence that intracellular S. aureus represents an important component of invasive infections.

Novel antibody-antibiotic conjugate eliminates intracellular S. aureus

Staphylococcus aureus is considered to be an extracellular pathogen. However, survival of S. aureus within host cells may provide a reservoir relatively protected from antibiotics, thus enabling long-term colonization of the host and explaining clinical failures and relapses after antibiotic therapy. Here we confirm that intracellular reservoirs of S. aureus in mice comprise a virulent subset of bacteria that can establish infection even in the presence of vancomycin, and we introduce a novel therapeutic that effectively kills intracellular S. aureus. This antibody-antibiotic conjugate consists of an anti-S. aureus antibody conjugated to a highly efficacious antibiotic that is activated only after it is released in the proteolytic environment of the phagolysosome. The antibody-antibiotic conjugate is superior to vancomycin for treatment of bacteraemia and provides direct evidence that intracellular S. aureus represents an important component of invasive infections.

Sustained Brown Fat Stimulation and Insulin Sensitization by a Humanized Bispecific Antibody Agonist for Fibroblast Growth Factor Receptor 1/βKlotho Complex

Dissipating excess calories as heat through therapeutic stimulation of brown adipose tissues (BAT) has been proposed as a potential treatment for obesity-linked disorders. Here, we describe the generation of a humanized effector-less bispecific antibody that activates fibroblast growth factor receptor (FGFR) 1/βKlotho complex, a common receptor for FGF21 and FGF19. Using this molecule, we show that antibody-mediated activation of FGFR1/βKlotho complex in mice induces sustained energy expenditure in BAT, browning of white adipose tissue, weight loss, and improvements in obesity-associated metabolic derangements including insulin resistance, hyperglycemia, dyslipidemia and hepatosteatosis. In mice and cynomolgus monkeys, FGFR1/βKlotho activation increased serum high-molecular-weight adiponectin, which appears to contribute over time by enhancing the amplitude of the metabolic benefits. At the same time, insulin sensitization by FGFR1/βKlotho activation occurs even before the onset of weight loss in a manner that is independent of adiponectin. Together, selective activation of FGFR1/βKlotho complex with a long acting therapeutic antibody represents an attractive approach for the treatment of type 2 diabetes and other obesity-linked disorders through enhanced energy expenditure, insulin sensitization and induction of high-molecular-weight adiponectin.

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A humanized bispecific antibody that selectively activates FGFR1/βKlotho complex was generated.

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Anti-FGFR1/βKlotho agonist antibody induced sustained thermogenesis in brown fat and induced weight loss.

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Anti-FGFR1/βKlotho agonist antibody improved insulin sensitivity even before the onset of weight loss.

Abstract S1-07: HER2 T cell dependent bispecific antibody (HER2-TDB) for treatment of HER2 positive breast cancer

Based on recent clinical success of tumor immunotherapies that block immune suppressive mechanisms to restore T cell function, there is a profound interest in the clinical development of T cell targeted therapies. We have produced a trastuzumab-based HER2 T cell dependent bispecific antibody (HER2-TDB) that conditionally activates T cells resulting in lysis of HER2 expressing cancer cells at low picomolar concentrations. Due to its unique mechanism of action, which is unrelated to HER2 signaling or sensitivity to chemotherapeutic agents, HER2-TDB can eliminate cells refractory to currently approved HER2 therapies. The potent anti-tumor activity of HER2-TDB was demonstrated using four model systems including MMTV-huHER2 and huCD3 transgenic mice. We demonstrate inhibitory effect of PD-L1 expression on the activity of bispecific T cell recruiting antibodies. This resistance mechanism is reversed by anti-PD-L1 treatment and combination of HER2-TDB with anti-PD-L1 immune therapy resulted in enhanced inhibition of tumor growth, increased response rates and durable responses.

Significance:

This report presents a new immunotherapy for HER2+ breast cancer with an alternative, extremely potent mechanism of action that is effective in cells resistant to current HER2 targeted therapies. Several significant advances are provided to bispecific T cell recruiting antibodies: we characterize a critical resistance mechanism, a potential diagnostic marker, a novel transgenic efficacy model and significantly improve the drug-like properties by using technology based on full length antibodies with natural architecture. Finally we demonstrate the benefit of combining two immune therapies: direct polyclonal recruitment of T cell activity together with inhibiting the T cell suppressive PD-1/PD-L1 signaling results in enhanced and durable long term responses.

Citation Format: Teemu T Junttila, Ji Li, Jennifer Johnston, Maria Hristopoulos, Robyn Clark, Diego Ellerman, Bu-Er Wang, Yijin Li, Mary Mathieu, Guangmin Li, Judy Young, Elizabeth Luis, Gail Lewis Phillips, Eric Stefanich, Cristoph Spiess, Andrew Polson, Bryan Irving, Justin M Scheer, Melissa R Junttila, Mark S Dennis, Robert Kelley, Klara Totpal, Allen Ebens. HER2 T cell dependent bispecific antibody (HER2-TDB) for treatment of HER2 positive breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr S1-07.

An Antibody-Drug Conjugate Directed against Lymphocyte Antigen 6 Complex, Locus E (LY6E) Provides Robust Tumor Killing in a Wide Range of Solid Tumor Malignancies

PURPOSE

Chemotherapies are limited by a narrow therapeutic index resulting in suboptimal exposure of the tumor to the drug and acquired tumor resistance. One approach to overcome this is through antibody-drug conjugates (ADC) that facilitate greater potency via target-specific delivery of highly potent cytotoxic agents.

EXPERIMENTAL DESIGN

In this study, we used a bioinformatics approach to identify the lymphocyte antigen 6 complex locus E (LY6E), an IFN-inducible glycosylphosphatidylinositol (GPI)-linked cell membrane protein as a promising ADC target. We developed a monoclonal anti-LY6E antibody and characterized in situ LY6E expression in over 750 cancer specimens and normal tissues. Target-dependent anti-LY6E ADC killing was investigated both in vitro and in vivo using patient-derived xenograft models.

RESULTS

Using in silico approaches, we found that LY6E was significantly overexpressed and amplified in a wide array of different human solid tumors. IHC analysis revealed high LY6E protein expression in a number of tumor types, such as breast, lung, gastric, ovarian, pancreatic, kidney and head/neck carcinomas. Characterization of the endocytic pathways for LY6E revealed that the LY6E-specific antibody is internalized into cells leading to lysosomal accumulation. Consistent with this, a LY6E-specific ADC inhibited in vitro cell proliferation and produced durable tumor regression in vivo in clinically relevant LY6E-expressing xenograft models.

CONCLUSIONS

Our results identify LY6E as a highly promising molecular ADC target for a variety of solid tumor types with current unmet medical need.

Abstract 4494: A clinical candidate anti-mesothelin-MMAE antibody-drug conjugate (ADC) for therapy of mesothelin-expressing cancers

Mesothelin (MSLN) is a cell surface glycoprotein widely expressed in a variety of cancers, with prevalence levels by IHC of 85% in ovarian, 75% in pancreatic and 45% in mesothelioma, and normal expression limited to the mesothelia, suggesting it could be an ideal target for antibody-drug conjugate therapy of these cancers. We have generated a high affinity (subnanomolar), humanized antibody to MSLN and conjugated it to auristatin anti-mitotic drugs (monomethylauristatin E and F, Seattle Genetics) via an uncleavable linker (anti-MSLN-mc-MMAF) or a cathepsin-cleavable valine-citrulline linker (anti-MSLN-mc-vc-PAB-MMAE/F) for comparison. The in vivo efficacy obtained in an ovarian transplant model was superior with the anti-MSLN-MMAE ADC. Anti-MSLN-MMAE was specifically internalized by MSLN-expressing cells in vitro, resulting in cell death compared to control ADCs. Pancreatic, ovarian and mesothelioma tumor cell lines endogenously expressing physiological levels of MSLN were identified and established as xenografts in mice. A single dose of anti-MSLN ADC was sufficient to inhibit or shrink tumor growth in models of each of the three indications in vivo, as well as inducing complete regressions in primary human pancreatic models, even those expressing low levels of MSLN typical of most human pancreatic tumors. Additionally, anti-MSLN-MMAE (at suboptimal doses) appeared to synergize with gemcitabine at clinically relevant doses in an HPAC xenograft model. Furthermore, anti-MSLN-MMAE was well tolerated in non-clinical toxicity studies (see accompanying abstract by Gupta et al.). Our data suggest that anti-MSLN-vc-MMAE is a promising clinical candidate for the treatment of several types of mesothelin-positive cancers.

Citation Format: Suzie J. Scales, Nidhi Gupta, Glenn Pacheco, Ron Firestein, Dorothy M. French, Josefa Chuh, Yin Zhang, Leanne Berry, Jenny Bostrom, Elizabeth Luis, Aimee Fourie O'Donohue, Katherine R. Kozak, Sarajane Ross, Mark S. Dennis, Jay Tibbitts, Susan D. Spencer. A clinical candidate anti-mesothelin-MMAE antibody-drug conjugate (ADC) for therapy of mesothelin-expressing cancers. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4494. doi:10.1158/1538-7445.AM2014-4494

Abstract 4502: Nonclinical characterization and tolerability of a surrogate anti-mesothelin-MMAE antibody-drug conjugate

Mesothelin (MSLN) is a cell surface glycoprotein widely expressed in several cancers with normal expression limited to the serosal mesothelia, features of an ideal target for antibody-based therapy. SS1P, a (dsFv)-PE38 immunotoxin to MSLN that kills cells by inhibition of protein synthesis, exhibits minor clinical responses as monotherapy, but was dose-limited by pleuritis, likely an antigen-dependent toxicity (Hassan et al., (2007) Clin Cancer Res 13 p3144). As mesothelial cells divide infrequently, we evaluated whether an anti-mitotic antibody-drug conjugate (ADC) directed to MSLN would be better tolerated. Our humanized lead anti-MSLN-MMAE (mc-vc-PAB-monomethylauristatin E) conjugate shows excellent preclinical activity (see accompanying abstract by Scales et al), but is specific to human MSLN, so a surrogate ADC that cross-reacts with cynomolgus monkey and rat MSLN was generated for non-clinical toxicity studies.

While both the lead and the surrogate antibodies recognize human MSLN, they bound to different epitopes and the surrogate binding was sensitive to glycosylation, only recognizing a subset of cell lines expressing human MSLN with high affinity. The affinity of the surrogate antibody for cynomolgus monkey MSLN is 5 to 22-fold lower than that of the lead antibody for human MSLN, depending on its glycosylation pattern in the human parental cell line to which it was compared. Nonetheless, the surrogate antibody detects endogenous MSLN in monkey pleura and the surrogate ADC exhibits robust cytotoxic activity against monkey MSLN-expressing cells in vitro. Importantly, the surrogate ADC demonstrated comparable in vivo efficacy to the lead ADC against BJAB xenografts expressing monkey or human MSLN respectively, thus validating its use in safety studies. We thus conducted a repeat-dose monkey toxicity study with a clinically relevant (q3w x5) dosing schedule, which yielded similar results for both surrogate and lead ADCs (the primary finding being reversible myelotoxicity, an antigen-independent toxicity similar to those of other IgG1-MMAE ADCs (Li et al., (2013), Mol Can Thera 12 p1255)). Unlike SS1P, there was no evidence of target-dependent pleuritis, nor any other serositis. Our data suggest that anti-MSLN-MMAE ADCs may be safer than SS1P and helped define the Phase I starting dose.

Citation Format: Nidhi Gupta, Willy A. Solis, Reina N. Fuji, Amy Oldendorp, Glenn Pacheco, Elizabeth Luis, Josefa Chuh, Dorothy M. French, Elizabeth Drake, Mark S. Dennis, Katherine R. Kozak, Sarajane Ross, Jay Tibbitts, Susan D. Spencer, Suzie J. Scales. Nonclinical characterization and tolerability of a surrogate anti-mesothelin-MMAE antibody-drug conjugate. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4502. doi:10.1158/1538-7445.AM2014-4502

An antimesothelin-monomethyl auristatin e conjugate with potent antitumor activity in ovarian, pancreatic, and mesothelioma models

Mesothelin (MSLN) is an attractive target for antibody-drug conjugate therapy because it is highly expressed in various epithelial cancers, with normal expression limited to nondividing mesothelia. We generated novel antimesothelin antibodies and conjugated an internalizing one (7D9) to the microtubule-disrupting drugs monomethyl auristatin E (MMAE) and MMAF, finding the most effective to be MMAE with a lysosomal protease-cleavable valine-citrulline linker. The humanized (h7D9.v3) version, αMSLN-MMAE, specifically targeted mesothelin-expressing cells and inhibited their proliferation with an IC50 of 0.3 nmol/L. Because the antitumor activity of an antimesothelin immunotoxin (SS1P) in transfected mesothelin models did not translate to the clinic, we carefully selected in vivo efficacy models endogenously expressing clinically relevant levels of mesothelin, after scoring mesothelin levels in ovarian, pancreatic, and mesothelioma tumors by immunohistochemistry. We found that endogenous mesothelin in cancer cells is upregulated in vivo and identified two suitable xenograft models for each of these three indications. A single dose of αMSLN-MMAE profoundly inhibited or regressed tumor growth in a dose-dependent manner in all six models, including two patient-derived tumor xenografts. The robust and durable efficacy of αMSLN-MMAE in preclinical models of ovarian, mesothelioma, and pancreatic cancers justifies the ongoing phase I clinical trial.

E-cadherin couples death receptors to the cytoskeleton to regulate apoptosis

Epithelial-to-mesenchymal transition (EMT) is a cellular process essential to the development and maintenance of solid tissues. In cancer, EMT suppresses apoptosis, but the mechanisms remain unclear. EMT selectively attenuated apoptosis signaling via the death receptors DR4 and DR5. Loss of the epithelial cell adhesion protein E-cadherin recapitulated this outcome, whereas homotypic E-cadherin engagement promoted apoptotic signaling via DR4/DR5, but not Fas. Depletion of α-catenin, which couples E-cadherin to the actin cytoskeleton, or actin polymerization inhibitors similarly attenuated DR4/DR5-induced apoptosis. E-cadherin bound specifically to ligated DR4/DR5, requiring extracellular cadherin domain 1 and calcium. E-cadherin augmented DR4/DR5 clustering and assembly of the death-inducing signaling complex (DISC), increasing caspase-8 activation in high molecular weight cell fractions. Conversely, EMT attenuated DR4/DR5-mediated DISC formation and caspase-8 stimulation. Consistent with these findings, epithelial cancer cell lines expressing higher E-cadherin levels displayed greater sensitivity to DR4/DR5-mediated apoptosis. These results have potential implications for tissue homeostasis as well as cancer therapy.

Defining the ligand specificity of the deleted in colorectal cancer (DCC) receptor

The growth and guidance of many axons in the developing nervous system require Netrin-mediated activation of Deleted in Colorectal Cancer (DCC) and other still unknown signaling cues. Commissural axon guidance defects are more severe in DCC mutant mice than Netrin-1 mutant mice, suggesting additional DCC activating signals besides Netrin-1 are involved in proper axon growth. Here we report that interaction screens on extracellular protein microarrays representing over 1,000 proteins uniquely identified Cerebellin 4 (CBLN4), a member of the C1q-tumor necrosis factor (TNF) family, and Netrin-1 as extracellular DCC-binding partners. Immunofluorescence and radio-ligand binding studies demonstrate that Netrin-1 competes with CBLN4 binding at an overlapping site within the membrane-proximal fibronectin domains (FN) 4–6 of DCC and binds with ∼5-fold higher affinity. CBLN4 also binds to the DCC homolog, Neogenin-1 (NEO1), but with a lower affinity compared to DCC. CBLN4-null mice did not show a defect in commissural axons of the developing spinal cord but did display a transient increase in the number of wandering axons in the brachial plexus, consistent with a role in axon guidance. Overall, the data solidifies CBLN4 as a bona fide DCC ligand and strengthens its implication in axon guidance.

Functional consequences of the macrophage stimulating protein 689C inflammatory bowel disease risk allele

Background

Macrophage stimulating protein (MSP) is a serum growth factor that binds to and activates the receptor tyrosine kinase, Recepteur d'Origine Nantais (RON). A non-synonymous coding variant in MSP (689C) has been associated with genetic susceptibility to both Crohn's disease and ulcerative colitis, two major types of inflammatory bowel disease (IBD) characterized by chronic inflammation of the digestive tract. We investigated the consequences of this polymorphism for MSP-RON pathway activity and IBD pathogenesis.

Methods

RON expression patterns were examined on mouse and human cells and tissues under normal and disease conditions to identify cell types regulated by MSP-RON. Recombinant MSP variants were tested for their ability to bind and stimulate RON and undergo proteolytic activation. MSP concentrations were quantified in the serum of individuals carrying the MSP 689R and 689C alleles.

Results

In intestinal tissue, RON was primarily expressed by epithelial cells under normal and disease conditions. The 689C polymorphism had no impact on the ability of MSP to bind to or signal through RON. In a cohort of normal individuals and IBD patients, carriers of the 689C polymorphism had lower concentrations of MSP in their serum.

Conclusions

By reducing the quantities of circulating MSP, the 689C polymorphism, or a variant in linkage disequilibrium with this polymorphism, may impact RON ligand availability and thus receptor activity. Given the known functions of RON in regulating wound healing and our analysis of RON expression patterns in human intestinal tissue, these data suggest that decreased RON activity may impact the efficiency of epithelial repair and thus underlie the increased IBD susceptibility associated with the MSP 689C allele.

Inhibitory mechanism of an allosteric antibody targeting the glucagon receptor

Elevated glucagon levels and increased hepatic glucagon receptor (GCGR) signaling contribute to hyperglycemia in type 2 diabetes. We have identified a monoclonal antibody that inhibits GCGR, a class B G-protein coupled receptor (GPCR), through a unique allosteric mechanism. Receptor inhibition is mediated by the binding of this antibody to two distinct sites that lie outside of the glucagon binding cleft. One site consists of a patch of residues that are surface-exposed on the face of the extracellular domain (ECD) opposite the ligand-binding cleft, whereas the second binding site consists of residues in the αA helix of the ECD. A docking model suggests that the antibody does not occlude the ligand-binding cleft. We solved the crystal structure of GCGR ECD containing a naturally occurring G40S mutation and found a shift in the register of the αA helix that prevents antibody binding. We also found that alterations in the αA helix impact the normal function of GCGR. We present a model for the allosteric inhibition of GCGR by a monoclonal antibody that may form the basis for the development of allosteric modulators for the treatment of diabetes and other class B GPCR-related diseases.

Sialylated ligands interact in cis to modulate PILRα inhibitory receptor in myeloid cells (P1358)

Paired Ig-like type 2 receptor alpha (PILRα) is an inhibitory receptor expressed in myeloid cells. We show that an evolutionary conserved arginine-containing domain is critical for PILRα interaction with its sialylated ligands. In addition, PILRα is pre-engaged with its ligands in cis on the surface of primary cells and dissociation of PILRa-ligand interactions by sialidase-A treatment unmasks PILRα to bind soluble ligands. At the cellular level, the engagement of PILRα with monoclonal antibody suppresses the production of proinflammatory cytokines. Our data provides novel insights into nature of PILRα interactions and means to modulate the immune response by agonizing this inhibitory pathway.

Reorienting the Fab domains of trastuzumab results in potent HER2 activators

The structure of the Fab region of antibodies is critical to their function. By introducing single cysteine substitutions into various positions of the heavy and light chains of the Fab region of trastuzumab, a potent antagonist of HER2, and using thiol chemistry to link the different Fabs together, we produced a variety of monospecific F(ab′)₂-like molecules with activities spanning from activation to inhibition of breast tumor cell growth. These isomers (or bis-Fabs) of trastuzumab, with varying relative spatial arrangements between the Fv-regions, were able to either promote or inhibit cell-signaling activities through the PI3K/AKT and MAPK pathways. A quantitative phosphorylation mapping of HER2 indicated that the agonistic isomers produced a distinct phosphorylation pattern associated with activation. This study suggests that antibody geometric isomers, found both in nature and during synthetic antibody development, can have profoundly different biological activities independent of their affinities for their target molecules.

Evolutionarily conserved paired immunoglobulin-like receptor α (PILRα) domain mediates its interaction with diverse sialylated ligands

Paired immunoglobulin-like receptor (PILR) α is an inhibitory receptor that recognizes several ligands, including mouse CD99, PILR-associating neural protein, and Herpes simplex virus-1 glycoprotein B. The physiological function(s) of interactions between PILRα and its cellular ligands are not well understood, as are the molecular determinants of PILRα/ligand interactions. To address these uncertainties, we sought to identify additional PILRα ligands and further define the molecular basis for PILRα/ligand interactions. Here, we identify two novel PILRα binding partners, neuronal differentiation and proliferation factor-1 (NPDC1), and collectin-12 (COLEC12). We find that sialylated O-glycans on these novel PILRα ligands, and on known PILRα ligands, are compulsory for PILRα binding. Sialylation-dependent ligand recognition is also a property of SIGLEC1, a member of the sialic acid-binding Ig-like lectins. SIGLEC1 Ig domain shares ∼22% sequence identity with PILRα, an identity that includes a conserved arginine localized to position 97 in mouse and human SIGLEC1, position 133 in mouse PILRα and position 126 in human PILRα. We observe that PILRα/ligand interactions require conserved PILRα Arg-133 (mouse) and Arg-126 (human), in correspondence with a previously reported requirement for SIGLEC1 Arg-197 in SIGLEC1/ligand interactions. Homology modeling identifies striking similarities between PILRα and SIGLEC1 ligand binding pockets as well as at least one set of distinctive interactions in the galactoxyl-binding site. Binding studies suggest that PILRα recognizes a complex ligand domain involving both sialic acid and protein motif(s). Thus, PILRα is evolved to engage multiple ligands with common molecular determinants to modulate myeloid cell functions in anatomical settings where PILRα ligands are expressed.

Murine insulin growth factor-like (IGFL) and human IGFL1 proteins are induced in inflammatory skin conditions and bind to a novel tumor necrosis factor receptor family member, IGFLR1

Psoriasis is a human skin condition characterized by epidermal hyperproliferation and infiltration of multiple leukocyte populations. In characterizing a novel insulin growth factor (IGF)-like (IGFL) gene in mice (mIGFL), we found transcripts of this gene to be most highly expressed in skin with enhanced expression in models of skin wounding and psoriatic-like inflammation. A possible functional ortholog in humans, IGFL1, was uniquely and significantly induced in psoriatic skin samples. In vitro IGFL1 expression was up-regulated in cultured primary keratinocytes stimulated with tumor necrosis factor α but not by other psoriasis-associated cytokines. Finally, using a secreted and transmembrane protein library, we discovered high affinity interactions between human IGFL1 and mIGFL and the TMEM149 ectodomain. TMEM149 (renamed here as IGFLR1) is an uncharacterized gene with structural similarity to the tumor necrosis factor receptor family. Our studies demonstrate that IGFLR1 is expressed primarily on the surface of mouse T cells. The connection between mIGFL and IGFLR1 receptor suggests mIGFL may influence T cell biology within inflammatory skin conditions.

Antibodies specific for a segment of human membrane IgE deplete IgE-producing B cells in humanized mice

IgE-mediated hypersensitivity is central to the pathogenesis of asthma and other allergic diseases. Although neutralization of serum IgE with IgE-specific antibodies is in general an efficacious treatment for allergic asthma, one limitation of this approach is its lack of effect on IgE production. Here, we have developed a strategy to disrupt IgE production by generating monoclonal antibodies that target a segment of membrane IgE on human IgE-switched B cells that is not present in serum IgE. This segment is known as the M1' domain, and using genetically modified mice that contain the human M1' domain inserted into the mouse IgE locus, we demonstrated that M1'-specific antibodies reduced serum IgE and IgE-producing plasma cells in vivo, without affecting other immunoglobulin isotypes. M1'-specific antibodies were effective when delivered prophylactically and therapeutically in mouse models of immunization, allergic asthma, and Nippostrongylus brasiliensis infection, likely by inducing apoptosis of IgE-producing B cells. In addition, we generated a humanized M1'-specific antibody that was active on primary human cells in vivo, as determined by its reduction of serum IgE levels and IgE plasma cell numbers in a human PBMC-SCID mouse model. Thus, targeting of human IgE-producing B cells with apoptosis-inducing M1'-specific antibodies may be a novel treatment for asthma and allergy.

Site-specifically 89Zr-labeled monoclonal antibodies for ImmunoPET

Three thiol reactive reagents were developed for the chemoselective conjugation of desferrioxamine (Df) to a monoclonal antibody via engineered cysteine residues (thio-trastuzumab). The in vitro stability and in vivo imaging properties of site-specifically radiolabeled (89)Zr-Df-thio-trastuzumab conjugates were investigated.

METHODS

The amino group of desferrioxamine B was acylated by bromoacetyl bromide, N-hydroxysuccinimidyl iodoacetate, or N-hydroxysuccinimidyl 4-[N-maleimidomethyl]cyclohexane-1-carboxylate to obtain thiol reactive reagents bromoacetyl-desferrioxamine (Df-Bac), iodoacetyl-desferrioxamine (Df-Iac) and maleimidocyclohexyl-desferrioxamine (Df-Chx-Mal), respectively. Df-Bac and Df-Iac alkylated the free thiol groups of thio-trastuzumab by nucleophilic substitution forming Df-Ac-thio-trastuzumab, while the maleimide reagent Df-Chx-Mal reacted via Michael addition to provide Df-Chx-Mal-thio-trastuzumab. The conjugates were radiolabeled with (89)Zr and evaluated for serum stability, and their positron emission tomography (PET) imaging properties were investigated in a BT474M1 (HER2-positive) breast tumor mouse model.

RESULTS

The chemoselective reagents were obtained in 14% (Df-Bac), 53% (Df-Iac) and 45% (Df-Chx-Mal) yields. Site-specific conjugation of Df-Chx-Mal to thio-trastuzumab was complete within 1 h at pH 7.5, while Df-Iac and Df-Bac respectively required 2 and 5 h at pH 9. Each Df modified thio-trastuzumab was chelated with (89)Zr in yields exceeding 75%. (89)Zr-Df-Ac-thio-trastuzumab and (89)Zr-Df-Chx-Mal-thio-trastuzumab were stable in mouse serum and exhibited comparable PET imaging capabilities in a BT474M1 (HER2-positive) breast cancer model reaching 20-25 %ID/g of tumor uptake and a tumor to blood ratio of 6.1-7.1.

CONCLUSIONS

The new reagents demonstrated good reactivity with engineered thiol groups of trastuzumab and very good chelation properties with (89)Zr. The site-specifically (89)Zr-labeled thio-antibodies were stable in serum and showed PET imaging properties comparable to lysine conjugates.

Molecular predictors of response to a humanized anti-insulin-like growth factor-I receptor monoclonal antibody in breast and colorectal cancer

The insulin-like growth factor-I receptor (IGF-IR) pathway is required for the maintenance of the transformed phenotype in neoplastic cells and hence has been the subject of intensive drug discovery efforts. A key aspect of successful clinical development of targeted therapies directed against IGF-IR will be identification of responsive patient populations. Toward that end, we have endeavored to identify predictive biomarkers of response to an anti-IGF-IR-targeting monoclonal antibody in preclinical models of breast and colorectal cancer. We find that levels of the IGF-IR itself may have predictive value in these tumor types and identify other gene expression predictors of in vitro response. Studies in breast cancer models suggest that IGF-IR expression is both correlated and functionally linked with estrogen receptor signaling and provide a basis for both patient stratification and rational combination therapy with antiestrogen-targeting agents. In addition, we find that levels of other components of the signaling pathway such as the adaptor proteins IRS1 and IRS2, as well as the ligand IGF-II, have predictive value and report on the development of a pathway-focused panel of diagnostic biomarkers that could be used to test these hypotheses during clinical development of IGF-IR-targeting therapies.

Armed antibodies targeting the mucin repeats of the ovarian cancer antigen, MUC16, are highly efficacious in animal tumor models

MUC16 is a well-validated cell surface marker for serous adenocarcinomas of the ovary and other gynecologic malignancies that is distinguished by highly repetitive sequences ("mucin repeats") in the extracellular domain (ECD). We produced and compared two monoclonal antibodies: one (11D10) recognizing a unique, nonrepeating epitope in the ECD and another (3A5) that recognizes the repeats and binds multiple sites on each MUC16 protein. 3A5 conjugated to cytotoxic drugs exhibited superior toxicity against tumor cells in vitro and in tumor xenograft models compared with antibody-drug conjugates of 11D10. Importantly, drug conjugates of 3A5 were well tolerated in primates at levels in excess of therapeutic doses. Additionally, the presence of circulating CA125 in a rat model did not exacerbate the toxicity of 3A5 drug conjugates. We conclude that targeting the repeat MUC16 domains, thereby increasing cell-associated levels of drug-conjugated antibody, provides superior efficacy in vitro and in vivo without compromising safety.

EphB2 as a Therapeutic Antibody Drug Target for the Treatment of Colorectal Cancer

Analysis of human colorectal cancer specimens revealed overexpression of the EphB2 receptor tyrosine kinase. Monoclonal antibodies (MAbs) to extracellular sequence of EphB2 were raised and tested for activity against colorectal cancer cells. One of the MAbs, 2H9, effectively blocked the interaction of ephB2 with ephrin ligands and inhibited the resulting autophosphorylation of the receptor. However, this antibody did not affect the proliferation of cancer cells expressing ephB2. Immunocytochemical analysis revealed rapid internalization of the MAb 2H9 on binding ephB2, suggesting that target-dependent cell killing could be achieved with an antibody-drug conjugate. When MAb 2H9 was conjugated to monomethylauristatin E through a cathepsin B-cleavable linker, it specifically killed ephB2-expressing cancer cells in vitro and in vivo. Our results suggest that ephB2 is an attractive target for immunoconjugate cancer therapy.

Experimental results on constructed wetland pilot system

Research into a constructed wetland for wastewater treatment using M.H.E.A. (Hierarchical Mosaic of Artificial Ecosystems) pilot system was carried out over a vegetative period in 8 different flow and vegetable composition series. The system consisted of a free water pond as a first step working as primary treatment followed by a zone with Typha sp. and surface flow and finally a woody zone with a subsurface flow and planted with ligneous species (Salixsp., Populus sp., Fraxinus sp. and Alnus sp.). Removal efficiency in the study reflects an optimal result: 80-99% total suspended matter removal, 82-98% organic matter removal, 70-98% nutrients removal and up to 99.9% faecal bacterial disinfecting. Effluent characteristics were in accordance with European Union legislation criteria for wastewater treatment systems.

Cardiac fibroblasts produce leukemia inhibitory factor and endothelin, which combine to induce cardiac myocyte hypertrophy in vitro

Cardiac fibroblasts in culture produce factor(s) that induce hypertrophy of neonatal rat ventricular myocytes in vitro. As in vivo, the myocyte hypertrophy response in culture is characterized by an increase in cell size and contractile protein content, and by the activation of embryonic genes, including the gene for atrial natriuretic peptide. The purpose of this study was to identify the factor(s) produced by fibroblasts that induce myocyte hypertrophy. The fibroblast hypertrophy activity was inhibited using a combination of the endothelin A receptor blocker BQ-123 and an antibody to leukemia inhibitory factor. The individual antagonists each caused a partial inhibition. The mRNAs for both leukemia inhibitory factor and endothelin were detected by RT-PCR analysis and the concentration of both proteins was determined to be approximately 200 pmol/L in the conditioned medium using immunoassays. Purified leukemia inhibitory factor and endothelin each induced distinctive morphological changes in the myocytes. Their combination generated a different morphology similar to that induced by fibroblast conditioned medium. Each factor also induced atrial natriuretic peptide production, but both were required for the myocytes to produce the levels measured after exposure to fibroblast conditioned medium. These results show that hypertrophy activity produced by cardiac fibroblasts in culture is a result of leukemia inhibitory factor and endothelin.

Expression cloning of cardiotrophin 1, a cytokine that induces cardiac myocyte hypertrophy

Heart failure continues to be a leading cause of mortality worldwide. A hallmark of this disease is dilated cardiac hypertrophy, which is accompanied by a reactivation of genes expressed in fetal heart development. Reasoning that fetal or embryonic growth factors may mediate the onset of cardiac hypertrophy, we have coupled expression cloning with an embryonic stem cell-based model of cardiogenesis to isolate a 21.5-kDa protein, cardiotrophin 1, that potently induces cardiac myocyte hypertrophy in vitro. Amino acid similarity data indicate that cardiotrophin 1 is a member of the leukemia inhibitory factor/ciliary neurotrophic factor/oncostatin M/interleukin 6/interleukin 11 family of cytokines. Several members of this family that are known to signal through the transmembrane protein gp130 stimulate cardiac myocyte hypertrophy, like cardiotrophin 1, suggesting that the gp130 signaling pathway may play a role in cardiac hypertrophy. A 1.4-kb cardiotrophin 1 mRNA is expressed in the heart and several other mouse tissues.