Maarten van der Linden1, Sangeeta Kumari1, Daphne Montizaan1, Stephanie van Dalen1, Annemarie Kip1, Martyn FOSTER2, Inge Reinieren1, Elsa Neubert3, Luise Erpenbeck4, Tirza Bruurmijn1, Peter van Zandvoort1, Paul Vink1, Eric Meldrum5, Helmuth van Es1 and Renato Chirivi1, 1Citryll BV, Oss, Netherlands, 2Experimental Pathology Consultancy, Benfleet, United Kingdom, 3Leiden Academic Centre for Drug Research, Leiden, Netherlands, 4University Medical Center Münster, General Dermatology and Venereology, Münster, Germany, 5Citryll BV, Basel, Switzerland
Background/Purpose: Neutrophil extracellular traps (NETs) contribute to the pathophysiology of multiple inflammatory and autoimmune diseases (Chirivi et al., 2021; DOI: 10.1038/s41423-020-0381-3). Targeting the NETosis pathway has demonstrated significant therapeutic potency in various disease models. Here we describe a first in class monoclonal antibody (CIT-013) with high affinity for citrullinated histones H2A and H4 which inhibits NET formation and reduces tissue NET burden in vivo with significant anti-inflammatory consequences. CIT-013 is currently in phase 1 clinical trials with phase 2a studies in RA due to commence in 2024.
The objective of the current study was to further unravel CIT-013's mode of action. Questions which we wanted to answer are: 1) How and when does CIT-013 interfere with the NETosis pathway?; and 2) what is the faith of CIT-013 opsonized NETs and NETting neutrophils? Furthermore, we investigated whether CIT-013's epitope is expressed in rheumatoid arthritis (RA) synovial tissue.
Methods: In vitro life imaging studies using neutrophils and macrophages in combination with monovalent as well as bivalent CIT-013 have been performed to investigate CIT-013's mode of action. An in vivo lung inflammation mouse model was used to investigate CIT-013's effect on NET burden as well as phagocytic macrophages. Finally, the presence of CIT-013's epitope in human RA synovial tissues have been investigated using immunohistochemistry techniques.
Results: Detection of CIT-013 epitopes in RA synovium provides evidence that RA is an autoimmune disease with excessive citrullinated-NETs that can be targeted by CIT-013. We show that CIT-013 acts upon the final stage of NET formation, binding to its chromatin epitopes when plasma membrane integrity is compromised to prevent NET release. Bivalency of CIT-013 is necessary for NETosis inhibition. In addition, we show that CIT-013 binding to NETs and netting neutrophils enhances their phagocytosis by macrophages. Furthermore, we demonstrate that a mouse variant of CIT-013 reduces tissue NET burden in vivo at least in part through enhanced macrophage phagocytosis.
Conclusion: Since NETs contribute to the pathophysiology of many immune mediated inflammatory diseases, including autoimmune diseases such as RA, CIT-013's unique ability to both inhibit NET release and enhance NET clearance indicates the importance of this first in class therapeutic antibody as a new emerging therapy.
M. van der Linden: Citryll BV, 3, 12, STOCK APPRECIATION RIGHTS; S. Kumari: Citryll BV, 3, 12, STOCK APPRECIATION RIGHTS; D. Montizaan: Citryll BV, 3, 12, STOCK APPRECIATION RIGHTS; S. van Dalen: Citryll BV, 3, 12, STOCK APPRECIATION RIGHTS; A. Kip: Citryll BV, 3, 12, STOCK APPRECIATION RIGHTS; M. FOSTER: Citryll BV, 2, Ermium Therapeutics, 2; I. Reinieren: None; E. Neubert: None; L. Erpenbeck: None; T. Bruurmijn: Citryll BV, 3, 12, STOCK APPRECIATION RIGHTS; P. van Zandvoort: Citryll BV, 3, 12, STOCK APPRECIATION RIGHTS; P. Vink: None; E. Meldrum: Citryll BV, 3, 12, STOCK APPRECIATION RIGHTS; H. van Es: Citryll BV, 1, 4, 12, STOCK APPRECIATION RIGHTS; R. Chirivi: Citryll BV, 3, 12, STOCK APPRECIATION RIGHTS.
