ABSTRACT
Background and aims: Transforming growth factor beta (TGF-beta) signalling is a key driver of liver fibrosis. In primary sclerosing cholangitis (PSC), integrins over-expressed on injured cholangiocytes (alpha-v/beta-6) and myofibroblasts (alpha-v/beta-1) regulate TGFbeta activity. PLN-74809 is an oral, once-daily, dual-selective inhibitor of integrins alpha-v/beta-6 and alpha-v/beta-1 in development for the treatment of PSC and idiopathic pulmonary fibrosis. It has shown favourable tolerability in over 280 healthy participants, reduced TGF-beta signalling and achieved high target engagement in human lungs. Pre-clinical evaluation of antifibrotic activity resulting from dual integrin inhibition was performed to support clinical evaluation. Method: PLN-74809 was administered orally for 6 weeks in BALBc. Mdr2-/- mice with established fibrosis. A tool alpha-v/beta-6 and alpha-v/beta-1 inhibitor compound, PLN-75068, was tested therapeutically in a diet-induced mouse model of biliary fibrosis using 3, 5-diethoxycarbonyl-1, 4-dihydrocollidine (DDC). Hepatic collagen was quantified by hydroxyproline (OHP) and collagen proportionate area (CPA) and TGF-beta signalling by phosphorylated SMAD3 (pSMAD3) levels. An ex vivo study evaluated the effects of 2-day treatment with PLN-74809 on the expression of profibrotic genes, COL1A1 and COL1A2, in precision-cut liver slices (PCLivS) from tissue explants of participants with biliary fibrosis (n = 2 PSC;n = 2 primary biliary cholangitis [PBC]). A review of available blinded safety data from the enrolling Phase 2a study in participants with PSC was performed (NCT04480840). Results: PLN-74809 dose-dependently reduced OHP (up to ∼30%, p < 0.05), CPA (up to ∼50%, p < 0.05) and pSMAD3 (up to ∼40%, p < 0.001) in the BALBc.Mdr2-/- mouse model, as well as COL1A1 and COL1A2 gene expression (up to ∼30%, p = 0.0789) in PCLivS from tissue explants of participants with PSC and PBC. PLN-75068 reduced OHP (up to ∼20%, p < 0.05) in DDC-injured mice in a dose-dependent manner. PLN-74809waswell tolerated in participants with PSC. Most adverse events (AEs)were mild;nonewere severe. The most common AE was mild headache. One participant experienced serious AEs at least 20 days after the last dose of study drug, deemed not related by the investigator. One participant prematurely discontinued due to COVID-19. PLN-74809 pharmacokinetics in participants with PSC were consistent with those of healthy participants. Conclusion: Pharmacological inhibition of integrins alpha-v/beta-6 and alpha-v/beta-1 demonstrated antifibrotic activity in two models of biliary fibrosis and in PCLivS from participants with PSC or PBC. Available safety findings from participants with PSC enrolled in the ongoing Phase 2a INTEGRIS-PSC study, continue to support the favourable tolerability profile of PLN-74809.