BOS-857

BOS-857 is a first-in-class, highly selective, and potent small molecule inhibitor of furin (proprotein convertase subtilisin/kexin type 3, PCSK3). Developed by Boston Pharmaceuticals as an inhaled formulation, BOS-857 is designed to target respiratory diseases by preventing the proteolytic activation of key precursor proteins. Furin is a calcium-dependent serine protease that activates several substrates involved in airway pathology, including the epithelial sodium channel (ENaC), transforming growth factor-beta (TGF-beta), and various matrix metalloproteinases (MMPs). By selectively inhibiting furin, BOS-857 reduces ENaC-mediated sodium absorption, attenuates TGF-beta-driven fibrotic responses, and decreases the expression of inflammatory cytokines (such as IL-6 and IL-8) and MMPs (such as MMP-1, MMP-9, MMP-10, and MMP-25). It is currently in preclinical development for the treatment of cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD), and has also demonstrated potential in blocking the entry of enveloped viruses like SARS-CoV-2.