A patent review of peptidylarginine deiminase 4 (PAD4) inhibitors (2014-present).

INTRODUCTION: PAD4 mediates the post-translational modification of arginine residues into citrulline which can have profound effects on protein structure, function and interactions. Protein citrullination and neutrophil extracellular trap (NET) formation associated with increased PAD4 activity have been implicated in the development of autoimmune conditions, cardiovascular diseases, neurodegenerative disorders, and cancer. PAD4 inhibitors have been shown to suppress citrullination and NETs formation. AREAS COVERED: This review covers 10 years of industrial drug discovery campaigns reported in 28 patent applications from 10 companies. Cortellis, the World Intellectual Property Organization website, Scopus and SciFinder were used to search the patent literature using the keywords 'PAD4' and 'PAD4 inhibitor.' Most of the reported inhibitors share the same core scaffold with varied decoration of different complexity, including highly functionalized macrocycles, with some in vivo and pharmacokinetic (PK) data reported for selected examples. EXPERT OPINION: Despite PAD4's clear involvement in multiple disease pathways, its detailed mechanism remains insufficiently understood. Selective and potent compounds with improved PK properties have been provided but most research on PAD4 is still at the experimental stage or preclinical development; the most promising is JBI-1044, at the IND stage, while some companies have turned to antibodies despite considerable previous investment in small molecules.