Safety profile, pharmacokinetics, and biologic activity of MEDI-563, an anti-IL-5 receptor alpha antibody, in a phase I study of subjects with mild asthma.

BACKGROUND: Increased eosinophil levels have been linked to airway inflammation and asthma exacerbations. IL-5 is responsible for eosinophil differentiation, proliferation, and activation; IL-5 receptors are expressed on eosinophils and their progenitors, and targeting such receptors induces eosinophil apoptosis. OBJECTIVE: To evaluate the safety profile, pharmacokinetics, and pharmacodynamics of MEDI-563, a humanized mAb targeting the IL-5 receptor alpha chain. METHODS: Single, escalating, intravenous doses (0.0003-3 mg/kg) of MEDI-563 were administered to subjects with mild atopic asthma (n = 44) over approximately 3 to 30 minutes in this open-label study. Pulmonary function, symptom scores, adverse events, MEDI-563 pharmacokinetics, and levels of C-reactive protein (CRP), IL-6, eosinophil cationic protein (ECP), and eosinophils were evaluated. RESULTS: Mean peripheral blood (PB) eosinophil levels decreased in a dose-dependent fashion (baseline +/- SD, 0.27 +/- 0.2 x 10(3)/microL; 24 hours postdose, 0.01 +/- 0.0 x 10(3)/microL); 94.0% of subjects receiving >or=0.03 mg/kg exhibited levels between 0.00 x 10(3)/microL and 0.01 x 10(3)/microL. Eosinopenia lasted at least 8 or 12 weeks with doses of 0.03 to 0.1 and 0.3 to 3 mg/kg, respectively. ECP levels were reduced from 21.4 +/- 17.2 microg/L (baseline) to 10.3 +/- 7.0 microg/L (24 hours postdose). The most frequently reported adverse events were reduced white blood cell counts (34.1%), nasopharyngitis (27.3%), and increased blood creatine phosphokinase (25.0%). Mean C-reactive protein levels increased approximately 5.5-fold at 24 hours postdose but returned to baseline by study end; mean IL-6 levels increased approximately 3.9-fold to 4.7-fold at 6 to 12 hours postdose, respectively. Pharmacokinetic activity was dose proportional at doses of 0.03 to 3 mg/kg. CONCLUSION: Single escalating doses of MEDI-563 had an acceptable safety profile and resulted in marked reduction of PB eosinophil counts within 24 hours after dosing.

MEDI-563, a humanized anti-IL-5 receptor alpha mAb with enhanced antibody-dependent cell-mediated cytotoxicity function.

BACKGROUND: Peripheral blood eosinophilia and lung mucosal eosinophil infiltration are hallmarks of bronchial asthma. IL-5 is a critical cytokine for eosinophil maturation, survival, and mobilization. Attempts to target eosinophils for the treatment of asthma by means of IL-5 neutralization have only resulted in partial removal of airway eosinophils, and this warrants the development of more effective interventions to further explore the role of eosinophils in the clinical expression of asthma. OBJECTIVE: We sought to develop a novel humanized anti-IL-5 receptor alpha (IL-5Ralpha) mAb with enhanced effector function (MEDI-563) that potently depletes circulating and tissue-resident eosinophils and basophils for the treatment of asthma. METHODS: We used surface plasmon resonance to determine the binding affinity of MEDI-563 to FcgammaRIIIa. Primary human eosinophils and basophils were used to demonstrate antibody-dependent cell-mediated cytotoxicity. The binding epitope of MEDI-563 on IL-5Ralpha was determined by using site-directed mutagenesis. The consequences of MEDI-563 administration on peripheral blood and bone marrow eosinophil depletion was investigated in nonhuman primates. RESULTS: MEDI-563 binds to an epitope on IL-5Ralpha that is in close proximity to the IL-5 binding site, and it inhibits IL-5-mediated cell proliferation. MEDI-563 potently induces antibody-dependent cell-mediated cytotoxicity of both eosinophils (half-maximal effective concentration = 0.9 pmol/L) and basophils (half-maximal effective concentration = 0.5 pmol/L) in vitro. In nonhuman primates MEDI-563 depletes blood eosinophils and eosinophil precursors in the bone marrow. CONCLUSIONS: MEDI-563 might provide a novel approach for the treatment of asthma through active antibody-dependent cell-mediated depletion of eosinophils and basophils rather than through passive removal of IL-5.

A DeImmunized chimeric anti-C3b/iC3b monoclonal antibody enhances rituximab-mediated killing in NHL and CLL cells via complement activation.

Complement-dependent cytotoxicity (CDC) is a key mechanism of Rituximab (RTX) action in killing non-Hodgkin's lymphoma (NHL) cells both in vitro and probably in vivo. A DeImmunized, mouse/human chimeric monoclonal antibody (Mab), H17, specific for cell-associated complement C3 cleavage products, C3b and iC3b, was generated to enhance RTX-mediated killing of target cells by CDC. When NHL cell lines were treated with RTX and H17 in the presence of complement for 1 h, there was 40-70% more cell death than that observed with RTX alone. The enhancing effect of H17 was also seen over longer treatment periods. H17 was tested ex vivo against primary cells from NHL and chronic lymphocytic leukemia (CLL) patients. In RTX-resistant NHL samples, H17 enhanced RTX-mediated killing; in the remaining samples RTX + complement alone promoted more than 80% killing, and no significant enhancement was observed. The H17 antibody also increased RTX-mediated killing in four out of nine CLL samples. H17 may have therapeutic applications in NHL and CLL treatment as an adjunctive therapy to RTX. It might also enhance the activity of other therapeutic antibodies that work through CDC.

Heteropolymers: a novel technology against blood-borne infections.

Heteropolymer (HP) technology is a novel cassette technology which is being developed for the treatment of infectious and autoimmune diseases. HPs are dual antibody conjugates, composed of a monoclonal antibody (mAb) directed against the complement receptor type 1 (CR1) on primate red blood cells (RBCs) chemically cross-linked to mAbs that recognize blood-borne antigens. Upon administration of an HP, the target is bound to its counterpart mAb in the HP and immobilized on an RBC by binding of the anti-CR1 mAb to CR1 in a complement-independent manner, forming an immune complex. When the RBC traverses the liver during circulation, the immune complex is recognized by fixed tissue macrophages, the CR1 molecule is cleaved and the HP-pathogen complex is phagocytosed and destroyed. Due to rapid binding and immobilization of the target by HPs, the anti-target mAb used in the HP need not be directed to a neutralizing epitope on the target organism. Studies in animal models have shown that HPs are effective in treating infectious diseases and autoimmune diseases such as systemic lupus erythematosus. HPs are advantageous over natural immune adherence or conventional mAb therapies due to their complement-independent mechanism, low therapeutic dose and lack of the need for neutralizing mAbs against the target.

Enhancement of anthrax lethal toxin cytotoxicity: a subset of monoclonal antibodies against protective antigen increases lethal toxin-mediated killing of murine macrophages.

We investigated the ability of using monoclonal antibodies (MAbs) against anthrax protective antigen (PA), an anthrax exotoxin component, to modulate exotoxin cytotoxic activity on target macrophage cell lines. Anthrax PA plays a critical role in the pathogenesis of Bacillus anthracis infection. PA is the cell-binding component of the two anthrax exotoxins: lethal toxin (LeTx) and edema toxin. Several MAbs that bind the PA component of LeTx are known to neutralize LeTx-mediated killing of target macrophages. Here we describe for the first time an overlooked population of anti-PA MAbs that, in contrast, function to increase the potency of LeTx against murine macrophage cell lines. The results support a possible mechanism of enhancement: binding of MAb to PA on the macrophage cell surface stabilizes the PA by interaction of MAb with macrophage Fcgamma receptors. This results in an increase in the amount of PA bound to the cell surface, which in turn leads to an enhancement in cell killing, most likely due to increased internalization of LF. Blocking of PA-receptor binding eliminates enhancement by MAb, demonstrating the importance of this step for the observed enhancement. The additional significance of these results is that, at least in mice, immunization with PA appears to elicit a poly-clonal response that has a significant prevalence of MAbs that enhance LeTx-mediated killing in macrophages.