The INBUILD trial investigated nintedanib versus placebo in patients with progressive fibrosing interstitial lung diseases (ILDs). We investigated decline in forced vital capacity (FVC) in subgroups based on the inclusion criteria for ILD progression.Subjects had a fibrosing ILD other than idiopathic pulmonary fibrosis and met these criteria for ILD progression within the 24 months before screening despite management deemed appropriate in clinical practice: Group A, relative decline in FVC ≥10% predicted; Group B, relative decline in FVC ≥5-<10% predicted with worsened respiratory symptoms and/or increased extent of fibrosis on HRCT; Group C, worsened respiratory symptoms and increased extent of fibrosis on HRCT only.In the placebo group, the rates of FVC decline over 52 weeks in Groups A, B and C, respectively, were -241.9, -133.1 and -115.3 mL·year-1 in the overall population (p=0.0002 for subgroup-by-time interaction) and -288.9, -156.2 and -100.1 mL·year-1 among subjects with a usual interstitial pneumonia [UIP]-like fibrotic pattern on HRCT (p=0.0005 for subgroup-by-time interaction). Nintedanib had a greater absolute effect on reducing the rate of FVC decline in Group A than Group B or C. However, the relative effect of nintedanib versus placebo was consistent across the subgroups (p>0.05 for heterogeneity).In conclusion, the inclusion criteria used in the INBUILD trial, based on FVC decline or worsening of symptoms and extent of fibrosis on HRCT, were effective at identifying patients with progressive fibrosing ILDs. Nintedanib reduced the rate of decline in FVC across the subgroups based on the inclusion criteria related to ILD progression.