eNAMPT Is a Novel DAMP and Therapeutic Target in Human and Murine Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal disorder without curative therapies, underscoring the critical unmet need for identification of novel therapeutic strategies. eNAMPT (extracellular nicotinamide phosphoribosyltransferase) is a damage-associated molecular pattern protein (DAMP) and TLR4 (Toll-like receptor 4) ligand that contributes to the severity of radiation-induced lung fibrosis and nonalcoholic steatohepatitis-associated hepatic fibrosis. This study investigates eNAMPT as a druggable target in human and preclinical IPF using the eNAMPT-neutralizing ALT-100 monoclonal antibody (mAb). Blood, peripheral blood mononuclear cells (PBMCs), and lung tissues from patients with IPF and from an experimental bleomycin-induced lung fibrosis model in C57Bl6 mice were analyzed. Biochemical and histologic measurements, as well as gene expression through bulk and single-cell RNA sequencing of human PBMCs and murine lung tissues, were performed. Human studies revealed NAMPT expression to be significantly increased in plasma, lung tissues, and PBMCs from subjects with IPF, correlating with disease severity and inversely associated with IPF survival. Bleomycin-exposed mice exhibited increased inflammatory indices associated with lung fibrosis development (including NAMPT levels), as well as physiologic lung stiffening and TGF-β pathway-related protein and gene expression, with each index significantly mitigated in mice receiving ALT-100 mAb. Single-cell RNA sequencing studies demonstrated the ALT-100 mAb to reverse the bleomycin-induced dramatic expansion of alveolar type 2 epithelium and induction of endothelial cell- and epithelial cell-to-mesenchymal/myofibroblast transitions. These finding support the fundamental involvement of eNAMPT/TLR4 signaling pathway in lung fibrosis pathobiology, with eNAMPT neutralization a viable therapeutic strategy to directly address the unmet need for novel IPF treatments.