Background/Purpose:

Aberrant Neutrophil Extracellular Trap (NET) formation contributes to the induction and propagation of inflammation and plays a key role in causing tissue damage in conditions like sepsis, SLE, RA and vasculitis. Citrullination of proteins is involved in the formation of NETs, autoimmunity, and the breaking of tolerance in NET-driven autoimmune diseases. In SLE and RA, neutrophils undergo enhanced NETosis, and NET components are observed in blood, inflamed tissues and joints.

Therapeutic ACPA (tACPA) are first in class NETosis-inhibiting antibodies targeting citrullinated histones 2A and 4, which are being developed for the treatment of human diseases in which aberrant NET formation adds to the severity of the pathology with an initial focus on autoimmune diseases.

Here, we demonstrate the utility of tACPA as a NETosis-inhibiting therapy for different NET-based diseases beyond RA, including SLE and Idiopathic pulmonary fibrosis (IPF).

Methods:

Previously, using two RA animal models, the therapeutic properties of tACPA have been demonstrated (Chirivi et al., 2013). In the current studies, neutrophils from RA and SLE donors, as well as biological NET-inducing stimuli, such as RA synovial fluid (SF), gout SF and activated platelets, have been used to demonstrate the NETosis-inhibiting properties of tACPA in different human disease contexts. We have further expanded tACPA’s therapeutic utility by testing it in a surrogate model for NET-mediated organ damage (sepsis) and idiopathic pulmonary fibrosis (IPF).

Results:

NETosis in human RA and SLE neutrophils have been induced with a calcium ionophore and could be inhibited by tACPA treatment (40-100% reduction). Similar results were obtained using RA and gout SF or activated platelets as NETosis inducers in combination with neutrophils from healthy donors. These observations have been confirmed with multiple NET readouts such as MPO activity, MPO/DNA ELISA, DNA quantification as well as imaging readouts. In addition, we demonstrated that in an LPS-induced sepsis model 30% of tACPA-treated mice survived (compared to 0 % in placebo controls), showing protection against organ failure. In a bleomycin-induced IPF mouse model, tACPA protected mice from the development of lung fibrosis (compared to placebo controls). When determining neutrophil counts in bronchoalveolar lavage samples, we found that in tACPA-treated mice, neutrophil levels were normal, while levels in placebo-treated mice were elevated.

Conclusion:

In a sepsis and IPF mouse model, tACPA prevented NET-mediated organ damage, providing evidence that tACPA could be a promising therapeutic strategy for diseases where NET-mediated endothelial toxicity causes organ damage like SLE, vasculitis and IPF. Central to our strategy for generating a preclinical data package supporting clinical testing, is to demonstrate that patient NETosis can be significantly inhibited ex vivo. We will present data that confirm that tACPA can block human SLE NETosis as well as human NETosis induced by activated platelets or gout SF.

« Back to 2017 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/expanded-therapeutic-acpa-utility-for-different-net-driven-human-autoimmune-diseases/