Development of an in vitro potency bioassay for therapeutic IL-13 antagonists: the A-549 cell bioassay

RPC4046, A Novel Anti-interleukin-13 Antibody, Blocks IL-13 Binding to IL-13 α1 and α2 Receptors: A Randomized, Double-Blind, Placebo-Controlled, Dose-Escalation First-in-Human Study

Introduction

A unique anti-interleukin (IL)-13 monoclonal antibody, RPC4046, was generated on the basis of differential IL-13 receptor (R) blockade as assessed in a murine asthma model; the safety, tolerability, pharmacokinetics, and pharmacodynamics of RPC4046 were evaluated in a first-in-human study.

Methods

Anti-IL-13 antibodies with varying receptor blocking specificity were evaluated in the ovalbumin-induced murine asthma model. A randomized, double-blind, placebo-controlled, dose-escalation first-in-human study (NCT00986037) was conducted with RPC4046 in healthy adults and patients with mild to moderate controlled asthma.

Results

In the ovalbumin model, blocking IL-13 binding to both IL-13Rs (IL-13Rα1 and IL-13Rα2) inhibited more asthma phenotypic features and more fully normalized the distinct IL-13 gene transcription associated with asthma compared with blocking IL-13Rα1 alone. In humans, RPC4046 exposure increased dose-dependently; pharmacokinetics were similar in healthy and asthmatic subjects, and blockade of both IL-13Rs uniquely affected IL-13 gene transcription. A minority of participants (28%) had antidrug antibodies, which were transient and appeared not to affect pharmacokinetics. Adverse event profiles were similar in healthy and asthmatic subjects, without dose-related or administration route differences, systemic infusion-related reactions, or asthma symptom worsening. Adverse events were mild to moderate, with none reported as probably related to RPC4046 or leading to discontinuations. Non-serious upper respiratory tract infections were more frequent with RPC4046 versus placebo.

Conclusion

RPC4046 is a novel anti-IL-13 antibody that blocks IL-13 binding to both receptors and more fully blocks the asthma phenotype. These results support further investigation of RPC4046 for IL-13-related allergic/inflammatory diseases (e.g., asthma and eosinophilic esophagitis).

Funding

AbbVie Inc. sponsored the studies and contributed to the design and conduct of the studies, data management, data analysis, interpretation of the data, and in the preparation and approval of the manuscript.

Electronic supplementary material

The online version of this article (doi:10.1007/s12325-017-0525-8) contains supplementary material, which is available to authorized users.

Identification of potent antagonist antibodies against mouse IL-13Rα1 using novel bioassays

Interleukin-13 (IL-13) is a cytokine implicated in airway diseases such as asthma and idiopathic pulmonary fibrosis. IL-13 signals through a heterodimeric receptor complex consisting of IL-13Rα1 and IL-4Rα, known as the type II IL-4R. IL-4 also signals through this receptor and as such many of the biological effects of IL-13 and IL-4 are similar. Here we describe the development of two sensitive bioassays to determine the potency of antagonists of the mouse type II IL-4R. Both IL-13 and IL-4 dose-dependently induce CCL17 production from J774 mouse monocytic cells and CCL11 production from NIH3T3 mouse fibroblasts in the presence of TNFα. The assays were optimized to minimize TNFα concentration, cell number and incubation time whilst retaining a suitable signal-to-background ratio. Anti-cytokine antibodies or recombinant soluble receptors completely neutralized IL-13 or IL-4 activity in these bioassays. The J774 assay was used to screen a panel of anti-mIL-13Rα1 antibodies for neutralizing activity against this receptor. We report the identification of the first monoclonal antibodies that bind mouse IL-13Rα1 and neutralize both IL-13-induced and IL-4-induced cellular function. These antibodies should prove useful for determining the effects of neutralizing IL-13Rα1 in mouse models of disease. In addition, these bioassays may be used for measuring the bioactivity of mouse IL-13 and IL-4 and for the discovery of additional antagonists of the mouse IL-13Rα1/IL-4Rα complex.

IL-13 induces connective tissue growth factor in rat hepatic stellate cells via TGF-β-independent Smad signaling

Connective tissue growth factor (CTGF) plays a central role in stimulating extracellular matrix deposition in the liver, and hence is considered a critical mediator of TGF-β-dependent fibrogenesis. Hepatic stellate cells (HSCs) are known as the major source of CTGF in damaged liver. However, previous studies revealed that IL-13, rather than TGF-β, represents the predominant inducer of CTGF expression in HSCs. We now dissected IL-13 downstream signaling that modulates CTGF expression in HSCs. IL-13 induces a time- and dosage-dependent increase of CTGF in a TGF-β-independent manner. This process requires participation of different Smad proteins and their upstream receptor kinases (activin receptor-like kinases). Smad1 and Smad2 were identified as the key mediators of IL-13-dependent CTGF expression. Furthermore, IL-13 induces Stat6 phosphorylation in HSCs, but Stat6 was not involved in CTGF induction. Instead, the Erk1/2-MAPK pathway was found to be responsible for IL-13-induced early Smad phosphorylation and CTGF synthesis. We demonstrate that IL-13 induces CTGF expression in HSCs by activating TGF-β-independent activin receptor-like kinase/Smad signaling via the Erk-MAPK pathway rather than via its canonical JAK/Stat6 pathway. These results provide an improved new insight into the molecular mechanisms of profibrotic IL-13 activities in the liver.

Analytical validation of a highly sensitive microparticle-based immunoassay for the quantitation of IL-13 in human serum using the Erenna immunoassay system

IL-13 is a Th2 cytokine that has been shown to be an important mediator of airway inflammation contributing to asthma lesions. Given its proposed role in asthma, measurements of this cytokine in serum may provide insights into disease mechanisms, progression and pharmacodynamic effects of IL-13 targeted therapeutics. However, current commercially available ELISA immunoassays are frequently unable to detect baseline concentrations of IL-13 in serum from healthy individuals, which are below the limit of detection. Here we describe the use of the novel microparticle-based Erenna IL-13 human immunoassay (Singulex, Inc.), which utilizes proprietary antibodies and single molecule counting technology, to quantify IL-13 from 100 microL of serum from apparently healthy subjects and clinically defined symptomatic and asymptomatic asthma subjects. The lower limit of quantification of the Erenna assay was validated at 0.07 pg/mL and the assay detected baseline concentrations of IL-13 in 98% of serum samples tested. The calibration curve showed good precision over the entire linear range of 0.07-50 pg/mL, with inter-assay imprecision <10% CV except at the lowest concentration tested (<15%). The intra- and inter-assay imprecision of spiked serum samples containing three different IL-13 concentrations (2, 8, and 25 pg/mL) ranged from 2.2-2.4% and 6.1-6.8%, respectively. Using the Erenna IL-13 assay, we observe that serum IL-13 concentrations range from <0.07-1.02 pg/mL in apparently healthy subjects (N=60) with similar ranges in asymptomatic (0.07-0.66 pg/mL, N=26) and symptomatic (<0.07-1.26 pg/mL, N=96) asthma subjects. The Erenna immunoassay improved sensitivity by over two full logs compared to previous ELISA methods, while using smaller sample volumes. In addition, the Erenna assay reliably measured IL-13 in endogenous and spiked human serum samples that were not quantifiable using other methods. Taken together, these results show that this novel assay offers a significant improvement over previous methods for high-sensitive quantitative measurement of IL-13 in human serum samples obtained from both apparently healthy and asthmatic subjects, and can be used in future clinical studies to accurately measure concentrations of this cytokine prior to and following drug therapy in human serum.