Broad Immunomodulatory Effects of the Dipeptidyl Peptidase-1 Inhibitor Brensocatib in Bronchiectasis: Data from the Phase 2, Double-Blind, Placebo-controlled WILLOW Trial

Rationale: In the WILLOW trial, the Dipeptidyl peptidase-1 inhibitor brensocatib reduced neutrophil serine protease (NSP) activity and prolonged time to first exacerbation in patients with bronchiectasis. Objectives: We hypothesized that, by reducing NSPs, brensocatib would affect antimicrobial peptides, mucins, and cytokines throughout the inflammatory cascade. Methods: The WILLOW trial was a phase 2 randomized trial of brensocatib (10mg and 25mg) versus placebo. Sputum was collected at baseline, week 4, week 24 (end of treatment) and week 28 (4 weeks post-treatment). The antimicrobial peptides secretory leukoproteinase inhibitor (SLPI) and α-defensin-3 were measured by ELISA, mucin-5AC (MUC5AC) by liquid chromatography mass spectrometry, myeloperoxidase by immunoassay and 45 inflammatory cytokines by Olink® Target 48 assay. The relationship between these markers and sputum neutrophil elastase was validated using the EMBARC-BRIDGE bronchiectasis cohort. Measurements and main results: Of 82 patients randomized to 10mg brensocatib, 87 to 25mg brensocatib, and 87 to placebo, 71, 71 and 73 with sputum available for at least two time points were included. SLPI and α-defensin-3 increased significantly with brensocatib compared to placebo at both week 4 and week 24. MUC5AC reduced in response to treatment. Sub-analysis showed this was primarily among patients with high baseline neutrophil elastase. Myeloperoxidase did not change. 15 cytokines and chemokines increased significantly compared to placebo at week 4 or 28. CXCL10, CCL8, CCL7, CCL3 and IL-6 increased at both doses at both timepoints. In the EMBARC-BRIDGE cohort neutrophil elastase correlated inversely with SLPI, CCL13, IL7, CCL11, CXCL10, CCL8, CCL7, all markers increased by brensocatib. Conclusions: Brensocatib exerts broad anti-inflammatory effects beyond its known effects on serine proteases. Clinical trial registration available at www. Clinicaltrials: gov, ID: NCT03218917.