Background/Purpose: The IL-1 receptor accessory protein (IL1RAP) is a co-receptor required for signaling through the IL-1, IL-33, and IL-36 receptors. IL1RAP-dependent signaling has been implicated in several autoimmune/inflammatory diseases such as atherosclerosis, allergy, psoriasis, gout, myocarditis and systemic sclerosis (SSc). IL1RAP-mediated signaling results in increased production and release of chemokines and cytokines, upregulation of adhesion molecules and influx of inflammatory cells, which can result in organ inflammation and fibrosis.

CAN10 is a fully humanized IgG1-LALA antibody that binds IL1RAP with high affinity and disrupts IL-1α/β, IL-33 and IL-36α/β/γ signaling. CAN10 has shown potent anti-inflammatory and anti-fibrotic properties in several preclinical models and is currently under development for treatment of SSc and myocarditis. The aim of this study was to further investigate the potential of IL1RAP blockade in preclinical models of SSc to provide a scientific background for clinical trials in SSc.

Methods: To study if the IL1RAP pathway was upregulated in SSc patients we analyzed RNAseq data from SSc skin samples from the Prospective Registry for Early SSc (GSE130955) cohort. For efficacy studies, we used two well established mouse models of SSc, sclerodermatous graft vs host disease (sclGvHD) and the skin bleomycin model. In both studies, mice were treated with an anti-mouse IL1RAP antibody (mCAN10) or controls in a therapeutic fashion, i.e., starting treatment when fibrosis was established. Fibrosis was analyzed by immunohistochemistry, hydroxyproline content and by quantification of myofibroblast. Skin biopsies from sclGvHD mice were also analyzed by RNAseq.

Results: Skin samples from SSc patients showed upregulation of the IL1RAP pathway compared to healthy controls. Human dermal fibroblasts responded to IL1RAP-mediated stimuli in vitro with production of e.g., IL-6 and IL-8, and CAN10 treatment could potently block these responses.

In the sclGvHD model, mCAN10 treatment reduced dermal thickening, hydroxyproline content and skin myofibroblast counts compared to controls. In addition, mCAN10-treated mice had decreased Ashcroft score and hydroxyproline content in the lungs suggesting that mCAN10 reduced disease severity both in the skin and in the lung of sclGvHD mice. The effects of mCAN10 on dermal fibrosis were confirmed in the skin bleomycin mouse model where mCAN10 treatment potently reduced skin thickness and myofibroblast counts.

RNAseq analyses of skin from sclGvHD mice revealed several inflammatory pathways that were affected by mCAN10 treatment including decreased expression of IL-1β, IL1RAP and IL-36 as well as several other chemokines and receptors. Interestingly, a machine learning approach revealed potential target gene regulation in macrophages/fibroblasts that indicates a modular transcriptional regulatory network of global gene-sets related to inflammatory and fibrotic signaling pathways.

Conclusion: This study suggests that IL1RAP targeting by CAN10 may be a promising approach in treating several of the pathophysiological changes in inflammatory and fibrotic diseases such as SSc.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/blocking-il-1-il-33-and-il-36-signaling-with-the-anti-il1rap-antibody-mcan10-ameliorates-inflammation-and-fibrosis-in-preclinical-models-of-systemic-sclerosis/