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Cellular signaling via binding of the cytokines IL‐36α, β, and γ along with binding of the accessory protein IL‐36RAcP, to their cognate receptor IL‐36R is believed to play a major role in epithelial and immune cell‐mediated inflammation responses. Antagonizing the signaling cascade that results from these binding events via a directed monoclonal antibody provides an opportunity to suppress such immune responses. We report here the molecular structure of a complex between an extracellular portion of human IL‐36R and a Fab derived from a high affinity anti‐IL‐36R neutralizing monoclonal antibody at 2.3 Å resolution. This structure, the first of IL‐36R, reveals similarities with other structurally characterized IL‐1R family members and elucidates the molecular determinants leading to the high affinity binding of the monoclonal antibody. The structure of the complex reveals that the epitope recognized by the Fab is remote from both the putative ligand and accessory protein binding interfaces on IL‐36R, suggesting that the functional activity of the antibody is noncompetitive for these binding events.

Ang1 is a soluble ligand to receptor Tie2, and increasing the circulating Ang1 level may improve vascular stabilization under certain disease conditions. Here, we found that the circulating Ang1 level was significantly increased in cynomolgus monkeys treated with non-neutralizing anti-Ang1 antibodies. Improving the antibodies’ pharmacokinetic properties by IgG Fc mutations further increased the circulating Ang1 level. However, the mutations decreased the thermal stability of the molecules, which may limit their use as therapeutic antibodies. Nevertheless, we showed that non-neutralizing antibodies may have therapeutic potential by increasing the level of a target molecule in the circulation.

Patients with severe Th2 type asthma often have a steroid resistant phenotype and are prone to acute exacerbations. Current novel therapies have only marginal therapeutic effects. One of the hypotheses for lack of major efficacy in most patients is targeting only one redundant pathway leaving others active. Hence, we have designed and developed novel highly potent bispecific anti-TSLP/IL13 antibodies called Zweimabs (monovalent bispecific) and Doppelmabs (bivalent bispecific) that concurrently inhibits the signaling by these two cytokines.

Weak protein–protein interactions may be important to binding cooperativity. A panel of seven fluorescently labeled tracer monoclonal IgG antibodies, differing in variable (V) and constant (C) region sequences, were sedimented in increasing concentrations of unlabeled IgGs of identical, similar, and different backgrounds. Weak IgG::IgG attractive interactions were detected and characterized by global analysis of the hydrodynamic nonideality coefficient, k s. The effects of salt concentration and temperature on k s suggest the interactions are predominantly enthalpic in origin. The interactions were found to be variable in strength, affected by both the variable and constant regions, but indiscriminate with respect to IgG subclass. Furthermore, weak attractive interactions were observed for all the mAbs with freshly purified human poly‐IgG. The universality of the weak interactions suggest that they may contribute to effector function cooperativity in the normal immune response, and we postulate that the generality of the interactions allows for a broader range of epitope spacing for complement activation. These studies demonstrate the utility of analytical ultracentrifuge fluorescence detection in measuring weak protein–protein interactions. It also shows the strength of global analysis of sedimentation velocity data by SEDANAL to extract hydrodynamic nonideality k s to characterize weak macromolecular interactions.

Antibodies targeting the CD40-CD40L pathway have great potential for treating autoimmune diseases like rheumatoid arthritis, systemic lupus erythematosus (SLE), lupus nephritis (LN), and inflammatory bowel diseases (IBD). However, in addition to the known difficulty in generating a purely antagonistic CD40 antibody, the presence of CD40 and CD40L on platelets creates additional unique challenges for the safety, target coverage, and clearance of antibodies targeting this pathway. Previously described therapeutic antibodies targeting this pathway have various shortcomings, and the full therapeutic potential of this axis has yet to be realized. Herein, we describe the generation and characterization of BI 655064, a novel, purely antagonistic anti-CD40 antibody that potently neutralizes CD40-CD40L-dependent B-cell stimulation without evidence of impacting platelet functions. This uniquely optimized antibody targeting a highly challenging pathway was obtained by applying stringent functional and biophysical criteria during the lead selection process. BI 655064 has favorable target-mediated drug disposition (TMDD)-saturation pharmacokinetics, consistent with that of a high-quality therapeutic monoclonal antibody.

A central dogma in immunology is that an antibody's in vivo functionality is mediated by 2 independent events: antigen binding by the variable (V) region, followed by effector activation by the constant (C) region. However, this view has recently been challenged by reports suggesting allostery exists between the 2 regions, triggered by conformational changes or configurational differences. The possibility of allosteric signals propagating through the IgG domains complicates our understanding of the antibody structure-function relationship, and challenges the current subclass selection process in therapeutic antibody design. Here we review the types of cooperativity in IgG molecules by examining evidence for and against allosteric cooperativity in both Fab and Fc domains and the characteristics of associative cooperativity in effector system activation. We investigate the origin and the mechanism of allostery with an emphasis on the C-region-mediated effects on both V and C region interactions, and discuss its implications in biological functions. While available research does not support the existence of antigen-induced conformational allosteric cooperativity in IgGs, there is substantial evidence for configurational allostery due to glycosylation and sequence variations.

Antibodies with pH-dependent binding to both target antigens and neonatal Fc receptor (FcRn) provide an alternative tool to conventional neutralizing antibodies, particularly for therapies where reduction in antigen level is challenging due to high target burden. However, the requirements for optimal binding kinetic framework and extent of pH dependence for these antibodies to maximize target clearance from circulation are not well understood. We have identified a series of naturally-occurring high affinity antibodies with pH-dependent target binding properties. By in vivo studies in cynomolgus monkeys, we show that pH-dependent binding to the target alone is not sufficient for effective target removal from circulation, but requires Fc mutations that increase antibody binding to FcRn. Affinity-enhanced pH-dependent FcRn binding that is double-digit nM at pH 7.4 and single-digit nM at pH 6 achieved maximal target reduction when combined with similar target binding affinities in reverse pH directions. Sustained target clearance below the baseline level was achieved 3 weeks after single-dose administration at 1.5 mg/kg. Using the experimentally derived mechanistic model, we demonstrate the essential kinetic interplay between target turnover and antibody pH-dependent binding during the FcRn recycling, and identify the key components for achieving maximal target clearance. These results bridge the demand for improved patient dosing convenience with the “know-how” of therapeutic modality by design.

Deficiency of interleukin (IL)-36 receptor antagonist (DITRA) syndrome is a rare autosomal recessive disease caused by mutations in IL36RN. IL-36R is a cell surface receptor and a member of the IL1R family that is involved in inflammatory responses triggered in skin and other epithelial tissues. Accumulating evidence suggests that IL-36R signaling may play a role in the pathogenesis of psoriasis. Therapeutic intervention of IL-36R signaling offers an innovative treatment paradigm for targeting epithelial cell-mediated inflammatory diseases such as the life-threatening psoriasis variant called generalized pustular psoriasis (GPP). We report the discovery and characterization of MAB92, a potent, high affinity anti-human IL-36 receptor antagonistic antibody that blocks human IL-36 ligand (α, β and γ)-mediated signaling. In vitro treatment with MAB92 directly inhibits human IL-36R-mediated signaling and inflammatory cytokine production in primary human keratinocytes and dermal fibroblasts. MAB92 shows exquisite species specificity toward human IL-36R and does not cross react to murine IL-36R. To enable in vivo pharmacology studies, we developed a mouse cross-reactive antibody, MAB04, which exhibits overlapping binding and pharmacological activity as MAB92. Epitope mapping indicates that MAB92 and MAB04 bind primarily to domain-2 of the human and mouse IL-36R proteins, respectively. Treatment with MAB04 abrogates imiquimod and IL-36-mediated skin inflammation in the mouse, further supporting an important role for IL-36R signaling in epithelial cell-mediated inflammation.

To determine the effectiveness of immunization strategies used in therapeutic antibody or vaccine development, it is critical to assess the quality of immunization-induced polyclonal antibody responses. Here, we developed a workflow that uses sensitive methods to quantitatively and qualitatively assess immune responses against foreign antigens with regard to antibody binding affinity and epitope diversity. The application of such detailed assessments throughout an immunization campaign can significantly reduce the resources required to generate highly specific antibodies. Our workflow consists of the following two steps: 1) the use of surface plasmon resonance to quantify antigen-specific antibodies and evaluate their apparent binding affinities, and 2) the recovery of serum IgGs using an automated small scale purification system, followed by the determination of their epitope diversity using hydrogen deuterium exchange coupled with mass spectrometry. We showed that these methods were sensitive enough to detect antigen-specific IgGs in the nanogram/μl range and that they provided information for differentiating the antibody responses of the various immunized animals that could not be obtained by conventional methods. We also showed that this workflow can guide the selection of an animal that produces high affinity antibodies with a desired epitope coverage profile, resulting in the generation of potential therapeutic monoclonal antibody clones with desirable functional profiles. We postulate that this workflow will be an important tool in the development of effective vaccines to combat the highly sophisticated evasion mechanisms of pathogens.

Herein, we describe the generation and characterization of BI 655066, a novel, highly potent neutralizing anti-interleukin-23 (IL23) monoclonal antibody in clinical development for autoimmune conditions, including psoriasis and Crohn's disease. IL23 is a key driver of the differentiation, maintenance, and activity of a number of immune cell subsets, including T helper 17 (Th17) cells, which are believed to mediate the pathogenesis of several immune-mediated disorders. Thus, IL23 neutralization is an attractive therapeutic approach. Designing an antibody for clinical activity and convenience for the patient requires certain properties, such as high affinity, specificity, and solubility. These properties were achieved by directed design of the immunization, lead identification, and humanization procedures. Favorable substance and pharmacokinetic properties were established by biophysical assessments and studies in cynomolgus monkeys.

Background Costimulatory molecule pair CD40-CD40L plays a central role not only in immune cell interactions but also in immune-non immune cell activation. Targeting this pathway has generated great interest but early attempts to target CD40L failed mainly due to thrombotic complications observed in the clinic. In addition, developing a potent truly antagonistic CD40 antibody has proven to be challenging. Objectives Here we describe the preclinical characterization of BI 655064, an anti-human CD40 mAb that is being developed for the treatment of autoimmune disorders. BI 655064 is engineered as a human IgG1 molecule with a mutated Fc region to abrogate effector function. Methods Binding of BI 655064 to CD40 expressed on primary B cells was measured by flow cytometry. The ability of BI 655064 to block CD40L-induced B cell proliferation in vitro was measured by tritium uptake, while blockade of endothelial and DC activation was measured by inhibition of cytokine release. A subcutaneous PK/PD study in the cynomolgus monkey was performed to establish correlations between BI 655064 exposure, target coverage using a receptor occupancy assay and pharmacodynamic effects using an ex vivo CD54-induction assay. In vivo blockade of B cell function was also tested in a human-peripheral blood lymphocyte (huPBL) induced SCID mouse model of graft-versus-host disease (GvHD) and in cynomolgus monkeys immunized with keyhole limpet hemocyanin (KLH). Results In human whole blood, BI 655064 binds to CD40 on B cells (EC 90 of 6.85 nM ±0.74). Blockade of CD40L-induced B cell proliferation was observed at an average IC 50 of 0.4 nM. Inhibition of CD40L mediated cytokine release was observed in DCs (IC 50 =0.25 nM and 0.59 nM for TNFα and IL12/23p40, respectively) and to verify effects beyond immune cells, BI655064 was tested in CD40L stimulated endothelial cell cultures. Binding of BI 655064 to human platelets did not induce or augment platelet activation as determined by in vitro induction of CD62P. In the PK/PD study, cynomolgus monkeys dosed with greater than 1 mg/kg of BI 655064 exhibited complete blockade of ex vivo CD54 upregulation corresponding to full CD40 target coverage on B cells. In vivo , BI 655064 demonstrated clear effects on B cell function in the GvHD model where both human IgM and IgG responses were completely abrogated. As part of a repeat dose tolerability study, BI 655064 given to cynomolgus monkeys prior to immunization with KLH resulted in inhibition of KLH-specific IgM and IgG antibody responses. At doses of 5 mg/kg and above, germinal center size was decreased microscopically in Peyer9s patches, lymph nodes, spleens and tonsils in treated monkeys. Evaluation of platelet function in cynomolgus monkeys dosed with BI 655064 did not reveal any effects on ex vivo platelet activation or aggregation. Conclusions BI 655064 is a humanized antagonistic anti-CD40 mAb which is to be tested in human clinical trials for autoimmune disorders to establish safety and efficacy. BI 655064 demonstrated relevant pharmacologic in vitro and in vivo activity, blocking CD40-related functions at clinical dosing levels of >1 mg/kg in animal models. Disclosure of Interest K. Ralph Employee of: Boehringer Ingelheim Pharmaceuticals, A. Nicoletti Employee of: Boehringer Ingelheim Pharmaceuticals, E. Musvasva Employee of: Boehringer Ingelheim Pharmaceuticals, S. Cannan Employee of: Boehringer Ingelheim Pharmaceuticals, S. VanTongeren Employee of: Boehringer Ingelheim Pharmaceuticals, D. Blanset Employee of: Boehringer Ingelheim Pharmaceuticals, S. Brodeur Employee of: Boehringer Ingelheim Pharmaceuticals, J. Ahlberg Employee of: Boehringer Ingelheim Pharmaceuticals, H. Li Employee of: Boehringer Ingelheim Pharmaceuticals, S. Fogal Employee of: Boehringer Ingelheim Pharmaceuticals, S. Desai Employee of: Boehringer Ingelheim Pharmaceuticals, K. O9Shea Employee of: Boehringer Ingelheim Pharmaceuticals, R. Kroe-Barrett Employee of: Boehringer Ingelheim Pharmaceuticals, E. Mainolfi Employee of: Boehringer Ingelheim Pharmaceuticals, G. Nabozny: None declared, H. Wu Employee of: Boehringer Ingelheim Pharmaceuticals, G. Hansen Employee of: Boehringer Ingelheim Pharmaceuticals, K. Canada Employee of: Boehringer Ingelheim Pharmaceuticals, S. Singh Employee of: Boehringer Ingelheim Pharmaceuticals, X. Zhu Employee of: Boehringer Ingelheim Pharmaceuticals, M. Ramanujam Employee of: Boehringer Ingelheim Pharmaceuticals, C. Grimaldi Employee of: Boehringer Ingelheim Pharmaceuticals