Antibody-mediated depletion of CCR10+EphA3+ cells ameliorates fibrosis in IPF.

Idiopathic pulmonary fibrosis (IPF) is characterized by aberrant repair that diminishes lung function via mechanisms that remain poorly understood. CC chemokine receptor (CCR10) and its ligand CCL28 were both elevated in IPF compared with normal donors. CCR10 was highly expressed by various cells from IPF lungs, most notably stage-specific embryonic antigen-4-positive mesenchymal progenitor cells (MPCs). In vitro, CCL28 promoted the proliferation of CCR10+ MPCs while CRISPR/Cas9-mediated targeting of CCR10 resulted in the death of MPCs. Following the intravenous injection of various cells from IPF lungs into immunodeficient (NOD/SCID-γ, NSG) mice, human CCR10+ cells initiated and maintained fibrosis in NSG mice. Eph receptor A3 (EphA3) was among the highest expressed receptor tyrosine kinases detected on IPF CCR10+ cells. Ifabotuzumab-targeted killing of EphA3+ cells significantly reduced the numbers of CCR10+ cells and ameliorated pulmonary fibrosis in humanized NSG mice. Thus, human CCR10+ cells promote pulmonary fibrosis, and EphA3 mAb-directed elimination of these cells inhibits lung fibrosis.

Phase 2, randomised placebo-controlled trial to evaluate the efficacy and safety of an anti-GM-CSF antibody (KB003) in patients with inadequately controlled asthma.

OBJECTIVES: We wished to evaluate the effects of an antigranulocyte-macrophage colony-stimulating factor monoclonal antibody (KB003) on forced expiratory volume in 1 s (FEV1), asthma control and asthma exacerbations in adult asthmatics inadequately controlled by long-acting bronchodilators and inhaled/oral corticosteroids. SETTINGS: 47 ambulatory asthma care centres globally. PRIMARY OUTCOME MEASURES: Change in FEV1 at week 24. PARTICIPANTS: 311 were screened, 160 were randomised and 129 completed the study. INTERVENTIONS: 7 intravenous infusions of either 400 mg KB003 or placebo at baseline and weeks 2, 4, 8, 12, 16 and 20. PRIMARY AND SECONDARY OUTCOME MEASURES: FEV1 at week 24, asthma control, exacerbation rates and safety in all participants as well as prespecified subgroups. MAIN RESULTS: In the KB003 treated group, FEV1 at week 24 improved to 118 mL compared with 54 mL in the placebo group (p=0.224). However, FEV1 improved to 253 vs 26 mL at week 24 (p=0.02) in eosinophilic asthmatics (defined as >300 peripheral blood eosinophils/mL at baseline) and comparable improvements were seen at weeks 20 (p=0.034) and 24 (p=0.077) in patients with FEV1 reversibility ≥ 20% at baseline and at weeks 4 (p=0.029), 16 (p=0.018) and 20 (p=0.006) in patients with prebronchodilator FEV1 ≤ 50% predicted at baseline. There were no effects on asthma control or exacerbation rates. The most frequent adverse events in the KB003 group were rhinosinusitis and headache. There was no significant difference in antidrug antibody response between placebo and treated groups. There were no excess infections or changes in biomarkers known to be associated with the development of pulmonary alveolar proteinosis. CONCLUSIONS: Higher doses and/or further asthma phenotyping may be required in future studies with KB003. TRIAL REGISTRATION NUMBER: NCT01603277; Results.

A high affinity recombinant antibody to the human EphA3 receptor with enhanced ADCC activity.

EphA3 is expressed in solid tumors and leukemias and is an attractive target for the therapy. We have generated a panel of Humaneered® antibodies to the ligand-binding domain using a Fab epitope-focused library that has the same specificity as monoclonal antibody mIIIA4. A high-affinity antibody was selected that competes with the mIIIA4 antibody for binding to EphA3 and has an improved affinity of ∼1 nM. In order to generate an antibody with potent cell-killing activity the variable regions were assembled with human IgG1k constant regions and expressed in a Chinese hamster ovary (CHO) cell line deficient in fucosyl transferase. Non-fucosylated antibodies have been reported to have enhanced binding affinity for the IgG receptor CD16a (FcγRIIIa). The affinity of the antibody for recombinant CD16a was enhanced approximately 10-fold. This resulted in enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) activity against EphA3-expressing leukemic cells, providing a potent antibody for the evaluation as a therapeutic agent.

Targeting EphA3 inhibits cancer growth by disrupting the tumor stromal microenvironment.

Eph receptor tyrosine kinases are critical for cell-cell communication during normal and oncogenic tissue patterning and tumor growth. Somatic mutation profiles of several cancer genomes suggest EphA3 as a tumor suppressor, but its oncogenic expression pattern and role in tumorigenesis remain largely undefined. Here, we report unexpected EphA3 overexpression within the microenvironment of a range of human cancers and mouse tumor xenografts where its activation inhibits tumor growth. EphA3 is found on mouse bone marrow-derived cells with mesenchymal and myeloid phenotypes, and activation of EphA3(+)/CD90(+)/Sca1(+) mesenchymal/stromal cells with an EphA3 agonist leads to cell contraction, cell-cell segregation, and apoptosis. Treatment of mice with an agonistic α-EphA3 antibody inhibits tumor growth by severely disrupting the integrity and function of newly formed tumor stroma and microvasculature. Our data define EphA3 as a novel target for selective ablation of the tumor microenvironment and demonstrate the potential of EphA3 agonists for anticancer therapy.

The eosinophil surface receptor epidermal growth factor-like module containing mucin-like hormone receptor 1 (EMR1): a novel therapeutic target for eosinophilic disorders.

BACKGROUND: Although several novel agents are currently in clinical trials for eosinophilic disorders, none has demonstrated efficacy in reducing blood and tissue eosinophilia in all subjects. Additional approaches are clearly needed. OBJECTIVE: We sought to explore the potential of the human eosinophil surface receptor epidermal growth factor-like module containing mucin-like hormone receptor 1 (EMR1) as a therapeutic target for eosinophilic disorders. METHODS: EMR1 expression was assessed in blood and bone marrow specimens from eosinophilic and healthy subjects, cell lines, CD34(+) cells differentiated in vitro, and tissue biopsy specimens by using flow cytometry, quantitative PCR, and immunostaining. Eosinophil targeting by a novel, humanized, afucosylated anti-EMR1 IgG1 was evaluated in vitro by using a natural killer cell-mediated killing assay and in vivo in cynomolgus monkeys. RESULTS: Analysis of blood and bone marrow cells from healthy and eosinophilic donors and in vitro-differentiated CD34(+) cells confirmed restriction of human EMR1 surface and mRNA expression to mature eosinophils. Tissue eosinophils also expressed EMR1. Although EMR1 was highly expressed on eosinophils from all subjects, surface expression was negatively correlated with absolute eosinophil counts (r = -0.46, P < .001), and soluble plasma levels correlated positively with absolute eosinophil counts (r = 0.69, P < .001), suggesting modulation of EMR1 in vivo. Nevertheless, afucosylated anti-EMR1 mAb dramatically enhanced natural killer cell-mediated killing of eosinophils from healthy and eosinophilic donors and induced a rapid and sustained depletion of eosinophils in monkeys. CONCLUSION: EMR1 expression is restricted to mature blood and tissue eosinophils. Targeting of eosinophils with afucosylated anti-EMR1 antibody shows promise as a treatment for eosinophilic disorders.

Anti-PcrV antibody in cystic fibrosis: a novel approach targeting Pseudomonas aeruginosa airway infection.

Pseudomonas aeruginosa (Pa) airway infection is associated with increased morbidity and mortality in cystic fibrosis (CF). The type III secretion system is one of the factors responsible for the increased virulence and pro-inflammatory effects of Pa. KB001 is a PEGylated, recombinant, anti-Pseudomonas-PcrV antibody Fab' fragment that blocks the function of Pa TTSS. We studied the safety, pharmacokinetic (PK), and pharmacodynamic properties of KB001 in CF subjects with chronic Pa infection. Twenty-seven eligible CF subjects (≥12 years of age, FEV1 ≥40% of predicted, and sputum Pa density >10(5) CFU/g) received a single intravenous dose of KB001 (3 mg/kg or 10 mg/kg) or placebo. Safety, PK, Pa density, clinical outcomes, and inflammatory markers were assessed. KB001 had an acceptable safety profile and a mean serum half-life of 11.9 days. All subjects had Pa TTSS expression in sputum. There were no significant differences between KB001 and placebo for changes in Pa density, symptoms, or spirometry after a single dose. However, compared to baseline, at Day 28 there was a trend towards a dose-dependent reduction in sputum myeloperoxidase, IL-1, and IL-8, and there were significant overall differences in change in sputum neutrophil elastase and neutrophil counts favoring the KB001 10 mg/kg group versus placebo (-0.61 log(10) and -0.63 log(10) , respectively; P < 0.05). These results support targeting Pa TTSS with KB001 as a nonantibiotic strategy to reduce airway inflammation and damage in CF patients with chronic Pa infection. Repeat-dosing studies are necessary to evaluate the durability of the anti-inflammatory effects and how that may translate into clinical benefit. (NCT00638365).

GM-CSF-dependent pSTAT5 sensitivity is a feature with therapeutic potential in chronic myelomonocytic leukemia.

Granulocyte-macrophage-colony-stimulating factor (GM-CSF) hypersensitivity is a hallmark of juvenile myelomonocytic leukemia (JMML) but has not been systematically shown in the related human disease chronic myelomonocytic leukemia (CMML). We find that primary CMML samples demonstrate GM-CSF-dependent hypersensitivity by hematopoietic colony formation assays and phospho-STAT5 (pSTAT5) flow cytometry compared with healthy donors. Among CMML patients, the pSTAT5 hypersensitive response positively correlated with high-risk disease, peripheral leukocytes, monocytes, and signaling-associated mutations. When compared with IL-3 and G-CSF, GM-CSF hypersensitivity was cytokine specific and thus a possible target for intervention in CMML. To explore this possibility, we treated primary CMML cells with KB003, a novel monoclonal anti-GM-CSF antibody, and JAK2 inhibitors. We found that an elevated proportion of immature GM-CSF receptor-α(R) subunit-expressing cells were present in the bone marrow myeloid compartment of CMML. In survival assays, we found that myeloid and monocytic progenitors were sensitive to GM-CSF signal inhibition. Our data indicate that a committed myeloid precursor expressing CD38 may represent the progenitor population with enhanced GM-CSF dependence in CMML, consistent with results in JMML. These preclinical data indicate that GM-CSF signaling inhibitors merit further investigation in CMML and that GM-CSFR expression on myeloid progenitors may be a biomarker for this therapy.

Safety and pharmacokinetics of an anti-PcrV PEGylated monoclonal antibody fragment in mechanically ventilated patients colonized with Pseudomonas aeruginosa: a randomized,double-blind, placebo-controlled trial.

OBJECTIVE: The type III secretion system is an important Pseudomonas aeruginosa-virulence determinant in animal models of infection and in humans. Antibody-mediated inhibition of the PcrV protein, an essential component of this system, might abrogate the Pseudomonas aeruginosa ability to damage epithelial cells, neutrophils, and macrophages, thereby limiting its pathogenicity. The objective of the trial was to determine the safety, pharmacokinetics, and ability to prevent Pseudomonas aeruginosa ventilator-associated pneumonia of KB001, a recombinant, PEGylated, engineered, human Fab' fragment that specifically binds to a Pseudomonas aeruginosa PcrV epitope and blocks its function. DESIGN: Multicenter, randomized, placebo-controlled, double-blind, phase-2a trial. SETTING: Ten intensive care units across France. PATIENTS: Thirty-nine Pseudomonas aeruginosa-colonized, but not infected, mechanically ventilated patients. INTERVENTIONS: Patients were randomized 1:1:1 to receive a single intravenous infusion of KB001, 3 mg/kg (n=13) or 10 mg/kg (n=14), or placebo (n=12). MEASUREMENTS AND MAIN RESULTS: The primary end points were KB001 safety and tolerability, assessed as treatment-related adverse-event frequency and severity. Secondary end points included serum and lung KB001 pharmacokinetics, and Pseudomonas aeruginosa pneumonia rate within 28 days of its infusion. KB001 was well tolerated and not immunogenic. The 3- and 10-mg/kg groups had respective maximum serum concentrations of 52,811-88,660 and 121,857-285,454 ng/mL, with mean elimination half-lives of 8.1 and 9.3 days. KB001 was detected in endotracheal aspirates from all patients receiving it, as early as day 1 and up to 28 days. Respective mean endotracheal aspirate/serum concentration ratios were 0.092 and 0.085 for the 3- and 10-mg/kg groups, who developed Pseudomonas aeruginosa pneumonia less frequently (33% and 31%, respectively) than placebo recipients (60%). CONCLUSIONS: KB001 was safe and well tolerated in this study, with a favorable pharmacokinetic profile and promising potential for reducing Pseudomonas aeruginosa pneumonia incidence in intensive care unit mechanically ventilated patients colonized with this bacterium.

Antibody to granulocyte macrophage colony-stimulating factor reduces the number of activated tissue macrophages and improves left ventricular function after myocardial infarction in a rat coronary artery ligation model.

Granulocyte macrophage colony-stimulating factor (GM-CSF) promotes infarct expansion and inappropriate collagen synthesis in a myocardial infarction (MI). This study was designed to determine if treatment with anti-GM-CSF will inhibit macrophage migration, preserve function, and limit left ventricular (LV) remodeling in the rat coronary artery ligation model. Treatment with a monoclonal antibody to GM-CSF (5 mg/kg) was initiated 24 hours before coronary artery ligation and continued every 3 days for 3 weeks. Left coronary arteries of rats were ligated, animals were recovered, and cardiac function was evaluated 3 weeks postligation. Tissue samples were processed for histochemistry. Anti-GM-CSF treatment increased LV ejection fraction (37 ± 3% vs 47 ± 5%) and decreased LV end systolic diameter (0.75 ± 0.12 vs 0.59 ± 0.05 cm) with no changes in LV systolic pressure (109 ± 4 vs 104 ± 5 mm Hg), LV end diastolic pressure (22 ± 4 vs 21 ± 2 mm Hg), LV end diastolic diameter (0.96 ± 0.04 vs 0.92 ± 0.05 cm), or the time constant of LV relaxation tau (25.4 ± +2.4 vs 22.7 ± 1.4 milliseconds) (P < 0.05). Significantly lower numbers of tissue macrophages and significant reductions in infarct size were found in the myocardium of antibody-treated animals (81 ± 21.24 vs 195 ± 31.7 positive cells per 0.105 mm, compared with controls. These findings suggest that inhibition of macrophage migration may be beneficial in the treatment of heart failure after MI.

Granulocyte-macrophage colony-stimulating factor antibody suppresses microglial activity: implications for anti-inflammatory effects in Alzheimer's disease and multiple sclerosis.

The objective of our study was to determine granulocyte-macrophage colony-stimulating factor (GM-CSF) activity in the brain following GM-CSF induction. We injected recombinant mouse GM-CSF into the brains of 8-month-old C57BL6 mice via intracerebroventricular injections and studied the activities of microglia, astrocytes, and neurons. We also sought to determine whether an anti-GM-CSF antibody could suppress endogenous microglial activity in the C57BL6 mice and could also suppress microglial activity induced by the recombinant mouse GM-CSF in another group of C57BL6 mice. Using quantitative real-time RT-PCR, we assessed microglial, astrocytic, and neuronal activity by measuring mRNA expression of pro-inflammatory cytokines, GFAP, and the neuronal marker NeuN in the cerebral cortex tissues from C57BL6 mice. We performed immunoblotting and immunohistochemistry of activated microglia in different regions of the brains from control (phosphate-buffered saline-injected C57BL6 mice) and experimental mice (recombinant GM-CSF-injected C57BL6 mice, GM-CSF antibody-injected C57BL6 mice, and recombinant mouse GM-CSF plus anti-GM-CSF antibody-injected C57BL6 mice). We found increased mRNA expression of CD40 (9.75-fold), tumor necrosis factor-alpha (2.1-fold), CD45 (1.73-fold), and CD11c (1.70-fold) in the cerebral cortex of C57BL6 mice that were induced with recombinant GM-CSF, compared with control mice. Further, the anti-GM-CSF antibody suppressed microglia in mice that were induced with recombinant GM-CSF. Our immunoblotting and immunohistochemistry findings of GM-CSF-associated cytokines in C57BL6 mice induced with recombinant GM-CSF, in C57BL6 mice injected with the anti-GM-CSF antibody, and in C57BL6 mice injected with recombinant mouse GM-CSF plus anti-GM-CSF antibody concurred with our real-time RT-PCR findings. These findings suggest that GM-CSF is critical for microglial activation and that anti-GM-CSF antibody suppresses microglial activity in the CNS. The findings from this study may have implications for anti-inflammatory effects of Alzheimer's disease and experimental autoimmune encephalomyelitis mice (a multiple sclerosis mouse model).

An engineered human antibody fab fragment specific for Pseudomonas aeruginosa PcrV antigen has potent antibacterial activity.

Pseudomonas aeruginosa is an opportunistic pathogen that can cause acute lung injury and mortality through the delivery of exotoxins by the type III secretion system (TTSS). PcrV is an important structural protein of the TTSS. An engineered human antibody Fab fragment that binds to the P. aeruginosa PcrV protein with high affinity has been identified and has potent in vitro neutralization activity against the TTSS. The instillation of a single dose of Fab into the lungs of mice provided protection against lethal pulmonary challenge of P. aeruginosa and led to a substantial reduction of viable bacterial counts in the lungs. These results demonstrate that blocking of the TTSS by a Fab lacking antibody Fc-mediated effector functions can be sufficient for the effective clearance of pulmonary P. aeruginosa infection.

Antibodies for the treatment of bacterial infections: current experience and future prospects.

Antibodies can be used for the prevention and treatment of bacterial infections in animal models of disease. Current antibody technology allows the generation of high affinity human/humanized antibodies that can be optimized for antibacterial activity and in vivo biodistribution and pharmacokinetics. Such antibodies have exquisite selectivity for their bacterial target antigen and promise efficacy and safety. Why are there no monoclonal antibody products approved for the treatment or prevention of bacterial infections? Can antibodies succeed where antibiotics are failing? Some antibody therapies are currently being evaluated in clinical trials but several have failed despite positive data in animal disease models. This review will discuss the pros and cons of antibody therapeutics targeted at bacterial infections.

CD10 is a key enzyme involved in the activation of tumor-activated peptide prodrug CPI-0004Na and novel analogues: implications for the design of novel peptide prodrugs for the therapy of CD10+ tumors.

Traditional chemotherapeutic drugs are often restricted by severe side effects and lack of tumor specificity. Peptide prodrugs cleavable by peptidases present in the tumor environment have been explored to improve the therapeutic index of cytotoxic drugs. One such prodrug of doxorubicin (Dox), CPI-0004Na [N-succinyl-beta-alanyl-L-leucyl-L-alanyl-L-leucyl-Dox (sALAL-Dox)] has been shown to have an improved antitumor efficacy profile with reduced toxicity compared with Dox in tumor xenograft models (V. Dubois et al., Cancer Res., 62: 2327-2331, 2002). In this study, we demonstrate that CD10, a cell surface metalloprotease expressed on a variety of tumor cell types, is capable of cleaving CPI-0004Na and related peptide prodrugs such as N-succinyl-beta-alanyl-L-isoleucyl-L-alanyl-L-leucyl-Dox (sAIAL-Dox). This proteolytic cleavage generates leucyl-Dox, which is capable of entering cells and generating intracellular Dox. In a [(3)H]thymidine proliferation assay, analogues of CPI-0004Na showed a 100-300-fold increase in potency on CD10(+) cells compared with CD10(-) cells. Cytotoxicity of CPI-0004Na was inhibited by phosphoramidon, a known inhibitor of CD10 enzymatic activity. Furthermore, Chinese hamster ovary CHO-S cells, which are resistant to CPI-0004Na, could be sensitized to the cytotoxic effect of the prodrug by transfection of a CD10 cDNA. Tumor xenograft studies using LNCaP prostate tumor cells support the important role of CD10 in the antitumor efficacy of these prodrugs against tumors expressing CD10. CPI-0004Na and sAIAL-Dox achieved statistically significant 70% tumor growth inhibition at day 22. CD10 is expressed on many types of human tumors including B-cell lymphoma, leukemia, and prostate, breast, colorectal, and lung carcinomas; therefore, CD10-cleavable prodrugs may be effective in a range of different tumor types.

CPI-0004Na, a new extracellularly tumor-activated prodrug of doxorubicin: in vivo toxicity, activity, and tissue distribution confirm tumor cell selectivity.

The search for cancer therapies that are more selective for tumor cells and spare normal sensitive cells has been very active for at least 20 years. The extracellularly tumor-activated peptidic prodrug of doxorubicin (Dox) CPI-0004Na (N-succinyl-beta-alanyl-L-leucyl-L-alanyl-L-leucyl-Dox) is potentially such a treatment. Here, we report the results of lethality studies performed with this compound in the mouse, showing that it is up to 4.6 times less toxic than Dox.HCl by the i.v. route and up to 16.2 times after i.p. administration. Pharmacokinetics and tissue distribution data indicate that this reduced toxicity is attributable to a lower uptake of Dox in normal tissues after treatment with CPI-0004Na than after the administration of an equimolar dose of Dox.HCl. For example, heart exposure to Dox is reduced >10-fold. Because of this reduced toxicity, higher doses of CPI-0004Na than of the parent drug could be used to treat nude mice bearing s.c. human breast (MCF-7/6) and colon (LS-174-T and CXF-280/10) tumors. In all three models, the prodrug showed a much improved efficacy as compared with Dox.HCl. Particularly, LS-174-T tumors that do not respond to Dox were inhibited by 68% after treatment with CPI-0004Na. Tissue distribution studies performed with MCF-7/6 tumor-bearing nude mice and comparing CPI-0004Na and Dox.HCl confirmed that the improved activity of the prodrug is actually the result of selective generation and uptake of Dox at the tumor site. Dox levels in tumor tissue were 2-fold higher after treatment with CPI-0004Na than after treatment with an equimolar dose of Dox.HCl, whereas normal tissue levels were reduced 1.4-29-fold.

Binding to CD20 by anti-B1 antibody or F(ab')(2) is sufficient for induction of apoptosis in B-cell lines.

CD20 is a B-cell-specific cell surface protein expressed on mature B lymphocytes and is a target for monoclonal antibody therapy for non-Hodgkin's lymphoma (NHL). Though clear clinical efficacy has been demonstrated with several anti-CD20 antibodies, the mechanisms by which the antibodies activate CD20 and kill cells remain unclear. Proposed mechanisms of action include complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), and induction of apoptosis. In this report we compared the activity of two anti-CD20 antibodies, Anti-B1 Antibody (tositumomab) and rituximab (C2B8), in a variety of cellular assays using a panel of B-cell lines. Anti-B1 Antibody showed a low level of activity in a CDC assay against complement-sensitive B-cell lines, Ramos and Daudi. We found that there is an inverse correlation between the expression of CD55 and CD59 and CDC mediated by either Anti-B1 Antibody or rituximab. Rituximab was more potent at inducing CDC when compared to Anti-B1 Antibody. Using Raji cells as target cells and human peripheral blood leukocytes as effector cells, Anti-B1 Antibody was a potent inducer of ADCC. The activities of Anti-B1 Antibody and rituximab were nearly identical in the ADCC assay. In addition, Anti-B1 Antibody showed direct induction of apoptosis in all B-cell lines tested. In general, crosslinking Anti-B1 Antibody with a goat anti-mouse Ig did not further enhance the percentage of cells undergoing apoptosis. Importantly, a F(ab')(2) fragment of Anti-B1 Antibody induced apoptosis, while the Fab fragment did not, indicating that the Fc region was not required and dimerization of CD20 may be sufficient for induction of apoptosis. In contrast, rituximab, which binds to an overlapping epitope on CD20 with a three-fold lower affinity than Anti-B1 Antibody, did not efficiently induce apoptosis in the cell lines tested in the absence of crosslinking. In conclusion, these two anti-CD20 antibodies have overlapping, but distinct mechanisms of action on B-cell lines.