CHIT1 is a novel therapeutic target in idiopathic pulmonary fibrosis (IPF): anti-fibrotic efficacy of OATD-01, a potent and selective chitinase inhibitor in the mouse model of pulmonary fibrosis

Abstract

Rationale: Chitotriosidase (CHIT1) and acidic mammalian chitinase (AMCase) are the enzymatically active chitinases in humans. CHIT1 has been implicated in the pathogenesis of interstitial lung diseases (ILDs) including IPF.

Methods: Chitinolytic activity was assessed in induced sputum (IS) and serum from IPF patients and controls (n=20-28) and CHIT1 expression was evaluated in bronchoalveolar lavage (BAL) cells from IPF patients. The therapeutic efficacy of OATD-01 – a selective chitinase inhibitor was evaluated in the mouse model of bleomycin-induced pulmonary fibrosis. Mice were dosed with OATD-01 or nintedanib (100 mg/kg, po, qd) in a therapeutic scheme.

Results: The chitinolytic activity in serum and IS from IPF patients was significantly elevated when compared to controls. Additionally, CHIT1 was shown to be highly expressed in BAL macrophages from IPF patients. OATD-01 - a potent chitinase inhibitor (hAMCase IC₅₀=9nM, hCHIT1 IC₅₀=26nM) significantly reduced lung fibrosis in the bleomycin-induced fibrosis model, comparably to nintedanib, as assessed by modified Ashcroft scoring. The anti-fibrotic activity of OATD-01 was associated with pharmacodynamic effect: plasma chitinolytic activity was significantly reduced in mice dosed with OATD-01 as compared to control group.

Conclusion: We have demonstrated that expression of CHIT1 is increased in IPF and that inhibition of chitinases with OATD-01 provided significant therapeutic efficacy, comparable to nintedanib, in the bleomycin-induced pulmonary fibrosis model. These data support further development of OATD-01 as a first-in-class therapy for IPF.