Abstract Rationale Idiopathic Pulmonary Fibrosis (IPF) results from an aberrant and excessive deposition of extracellular matrix, including overexpression of fibronectin (Fn) in regions of active fibrogenesis. We previously identified a novel Fn integrin-binding mechanoswitch that is exposed due to force-induced conformational change that was successfully targeted with a single chain antibody fragment (scFv, VSR-H5; Cao et al, 2017:). We subsequently converted the scFv into an IgG1 mAb (VSR-1045) for development in IPF. Methods Target expression was characterized by staining healthy and IPF patients’ lung biopsies for Fn and VSR-H5/VSR-1045 binding. We tested the activity of VSR-H5 in our scar-in-a-jar system with normal and IPF patient-derived lung fibroblasts. Two bleomycin (BLM)-induced lung fibrosis mouse models were performed with H5: wild-type (self-resolving) and Thy-1 -/- (non-resolving) with twice weekly (BIW) treatment initiated on Day 7 and Day 14, respectively. The standard model compared VSR-H5 at 0.1, 1, and 10 mg/kg IP BIW with nintedanib (100mg/kg po QD), while the Thy-1 model tested VSR-H5 at 1 and 5 mg/kg IP BIW, without a nintedanib arm. Lung fibrosis by Ashcroft score was the primary endpoint. Studies comparing VSR-H5, VSR-1045, and nintedanib are ongoing in the standard BLM model and in precision cut lung slices (PCLS) from IPF patients using histopathology and biomarkers e.g., pro-C3,-C4,-C6, TGFβ, CTGF. Single-nuclear RNAseq will be performed on PCLS samples to characterize the anti-fibrotic and regenerative gene signatures. Results Based on bilayer interferometry VSR-H5 and VSR-1045 show apparent Kd’s of 16nM and 277 pM, respectively. VSR-H5 and VSR-1045 show 3-5 times higher normalized binding in fibrotic regions of IPF lung tissue, as compared to healthy lung tissue. In the scar-in-a-jar system VSR-H5 completely inhibited TGFβ-induced cell spreading in IPF primary human lung fibroblasts (p = 0.023), and significantly reduced TGFβ-induced nuclear translocation of SMAD2 by 50% (p 0.0001) and fully inhibited YAP1 (p 0.0001). VSR-H5 at 1 and 10 mg/kg resulted in a 50% reduction of Ashcroft score (p 0.05) in the standard BLM model, which were numerically superior to nintedanib, and VSR-H5 at 5mg/kg caused a 25% reduction of the Ashcroft score (p 0.01) in the Thy-1 model that was accompanied by an increase in normal alveolar structures on histopathologic examination. Comparative results in the BLM model and PCLS will also be presented. Conclusion These results suggest that this therapeutic approach has the potential to reduce profibrotic signaling and restore the normal, homeostatic role of Fn to halt fibrosis and restore lung function. This abstract is funded by: Federal grant
Hu et al. (Fri,) studied this question.