Aims and objectives: TGF?-ALK5 signaling is critical in the progression of IPF. The aim of the present study was to characterize the effects of ALK5 inhibition (ALK5i) on pulmonary function in addition to metabolic, biochemical, histological and transcriptomic endpoints using a high fat diet (HFD) + bleomycin (BLEO)-induced and spirometry-confirmed mouse model of IPF.

Methods: 12-week-old male C57BL/6JRj mice were fed HFD (60% kcal fat) for two weeks prior to a single intratracheal instillation of BLEO (1.5 mg/kg, 50 µL) or saline (CTRL) at study day 1. Animals remained on HFD for the entire study period. HFD-BLEO-IPF animals were randomized into study groups on study day 7 post-BLEO, followed by 21 days of vehicle and ALK5i treatment (30 mg/kg, PO, BID). Terminal endpoints included spirometry, hydroxyproline (HP) content and histopathological assessment. Additionally, target-engagement and RNA-sequencing analysis were performed. 

Results: ALK5i treatment decreased lung TGF? signaling (pSMAD3) and pro-fibrogenic genes in HFD-BLEO-IPF mice. Compared to vehicle-dosed HFD-BLEO-IPF mice, ALK5i improved lung function (inspiratory capacity, static compliance, FEV0.1, FVC) accompanied by reduced lung weight and total HP content. Histological markers of lung fibrosis (PSR, ?-SMA, COL1A1, and COL3) and histopathological Ashcroft scoring were consistently decreased by ALK5i treatment.

Conclusions: ALK5i improves pulmonary function and lung fibrosis in the HFD-BLEO-IPF mouse model, highlighting promising antifibrotic action. The HFD-BLEO-IPF mouse model demonstrates clinical translatability for exploring novel therapeutic agents for treatment of IPF.