A Comparative Assessment of the Antifibrotic Effect of Nintedanib Administered via a Medicated Diet or Oral Gavage in a Rat Model of Bleomycin-Induced Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) remains a progressive and fatal disease despite major advances in antifibrotic therapy. Pirfenidone and nintedanib slow lung function decline, and the PDE4B inhibitor nerandomilast and treprostinil have recently shown promise as next-generation treatments. However, current therapies neither halt nor reverse disease progression, and tolerability issues often limit adherence. We compared the antifibrotic activity and plasma levels of nintedanib administered by either oral gavage or dietary supplementation in a rat model of pulmonary fibrosis. Male Sprague-Dawley rats received intratracheal bleomycin (1 U/kg) on days 0 and 4. From day 7 to day 28, animals were treated with nintedanib (100 mg/kg/day) by either oral gavage or medicated chow. Lung weight, fibrosis biomarkers (procollagen-I, metalloproteinase-7 or MMP7, WNT1-inducible signaling pathway protein or WISP-1), epithelial injury marker KL-6, target engagement biomarkers (Fibroblast Growth Factor 2 or FGF-2, Vascular Endothelial Growth Factor or VEGF), plasma drug levels, and histological fibrosis scores were evaluated. Both administration regimens significantly reduced procollagen-I, WISP-1 and KL-6, and histological fibrosis scores. Oral gavage produced approximately fourfold-higher peak plasma concentrations of nintedanib 30 min after dosing, whereas dietary administration resulted in lower, more stable plasma levels with reduced variability while resulting in comparable antifibrotic efficacy. In conclusion, nintedanib retained robust antifibrotic activity when administered via dietary supplementation despite lower, but continuous, active plasma concentrations. Collectively, these findings indicate that optimizing drug delivery and absorption kinetics may achieve sustained therapeutic efficacy while reducing unnecessary exposure to supratherapeutic concentrations, thereby potentially improving tolerability.