Shin Shimaoka

Antibody recycling by engineered pH-dependent antigen binding improves the duration of antigen neutralization

For many antibodies, each antigen-binding site binds to only one antigen molecule during the antibodys lifetime in plasma. To increase the number of cycles of antigen binding and lysosomal degradation, we engineered tocilizumab (Actemra), an antibody against the IL-6 receptor (IL-6R), to rapidly dissociate from IL-6R within the acidic environment of the endosome (pH 6.0) while maintaining its binding affinity to IL-6R in plasma (pH 7.4). Studies using normal mice and mice expressing human IL-6R suggested that this pH-dependent IL-6R dissociation within the acidic environment of the endosome resulted in lysosomal degradation of the previously bound IL-6R while releasing the free antibody back to the plasma to bind another IL-6R molecule. In cynomolgus monkeys, an antibody with pH-dependent antigen binding, but not an affinity-matured variant, significantly improved the pharmacokinetics and duration of C-reactive protein inhibition. Engineering pH dependency into the interactions of therapeutic antibodies with their targets may enable them to be delivered less frequently or at lower doses.

Cytokine-dependent but acquired immunity-independent arthritis caused by DNA escaped from degradation

DNase II digests the chromosomal DNA in macrophages after apoptotic cells and nuclei from erythroid precursors are engulfed. The DNase II-null mice develop a polyarthritis that resembles rheumatoid arthritis. Here, we showed that when bone marrow cells from the DNase II-deficient mice were transferred to the wild-type mice, they developed arthritis. A deficiency of Rag2 or a lack of lymphocytes accelerated arthritis of the DNase II-null mice, suggesting that the DNase II−/− macrophages were responsible for triggering arthritis, and their lymphocytes worked protectively. A high level of TNFα, IL-1β, and IL-6 was found in the affected joints of the DNase II-null mice, suggesting an inflammatory-skewed cytokine storm was established in the joints. A lack of TNFα, IL-1β, or IL-6 gene blocked the expression of the other cytokine genes as well and inhibited the development of arthritis. Neutralization of TNFα, IL-1β, or IL-6 had a therapeutic effect on the developed arthritis of the DNase II-null mice, indicating that the cytokine storm was essential for the maintenance of arthritis in the DNase II-deficient mice. Methotrexate, an antimetabolite that is often used to treat patients with rheumatoid arthritis, had a therapeutic effect with the DNase II-null mice. These properties of arthritis in the DNase II-null mice were similar to those found in human systemic-onset juvenile idiopathic arthritis or Stills disease, indicating that the DNase II-null mice are a good animal model of this type of arthritis.

Novel genetically-humanized mouse model established to evaluate efficacy of therapeutic agents to human interleukin-6 receptor

For clinical trials of therapeutic monoclonal antibodies (mAbs) to be successful, their efficacy needs to be adequately evaluated in preclinical experiments. However, in many cases it is difficult to evaluate the candidate mAbs using animal disease models because of lower cross-reactivity to the orthologous target molecules. In this study we have established a novel humanized Castlemans disease mouse model, in which the endogenous interleukin-6 receptor gene is successfully replaced by human IL6R, and human IL6 is overexpressed. We have also demonstrated the therapeutic effects of an antibody that neutralizes human IL6R, tocilizumab, on the symptoms in this mouse model. Plasma levels of human soluble IL6R and human IL6 were elevated after 4-week treatment of tocilizumab in this mouse model similarly to the result previously reported in patients treated with tocilizumab. Our mouse model provides us with a novel means of evaluating the in vivo efficacy of human IL6R-specific therapeutic agents.

Cynomolgus monkey model of interleukin-31-induced scratching depicts blockade of human interleukin-31 receptor A by a humanized monoclonal antibody

Scratching is an important factor exacerbating skin lesions through the so‐called itch‐scratch cycle in atopic dermatitis (AD). In mice, interleukin (IL)‐31 and its receptor IL‐31 receptor A (IL‐31RA) are known to play a critical role in pruritus and the pathogenesis of AD; however, study of their precise roles in primates is hindered by the low sequence homologies between primates and mice and the lack of direct evidence of itch sensation by IL‐31 in primates. We showed that administration of cynomolgus IL‐31 induces transient scratching behaviour in cynomolgus monkeys and by that were able to establish a monkey model of scratching. We then showed that a single subcutaneous injection of 1 mg/kg nemolizumab, a humanized anti‐human IL‐31RA monoclonal antibody that also neutralizes cynomolgus IL‐31 signalling and shows a good pharmacokinetic profile in cynomolgus monkeys, suppressed the IL‐31‐induced scratching for about 2 months. These results suggest that the IL‐31 axis and IL‐31RA axis play as critical a role in the induction of scratching in primates as in mice and that the blockade of IL‐31 signalling by an anti‐human IL‐31RA antibody is a promising therapeutic approach for treatment of AD. Nemolizumab is currently under investigation in clinical trials.