A Study to Test the Efficacy and Safety of Inhaled GB0139 in Subjects With Idiopathic Pulmonary Fibrosis (IPF)

Inclusion Criteria: 1. Male and female subjects aged ≥ 40 years of age with a diagnosis of IPF established during the previous five years according to ATS/ERS/Fleischner criteria. 2. Lung function parameters as follows: 1. Forced Vital Capacity (FVC) \> 45% of the predicted value at screening 2. Diffusion lung capacity for carbon monoxide (DLCO) (corrected for Hb) of 30% to 79% of the predicted value at screening 3. Subjects who currently are not being treated with nintedanib or pirfenidone; or cannot tolerate nintedanib or pirfenidone 4. Subjects must sign and date a written, IRB/EC approved informed consent form and any required authorization prior to initiation of any study procedures. Exclusion Criteria: 1. Currently has significant airways obstruction: Forced Expiratory Volume in 1 s (FEV1)/Forced Vital Capacity (FVC) ratio of \< 0.7 at screening. 2. Has clinical evidence of active infection, including, but not limited to, bronchitis, pneumonia, sinusitis, urinary tract infection, and cellulitis. 3. Has a history of malignancy within the last 2 years with the exception of basal cell carcinoma, chronic lymphocytic leukaemia (under observation) and prostate cancer requiring anti-androgens, localised treatment (minor surgery, radiotherapy) and/or managed by observation. 4. Has any condition other than IPF that, in the opinion of the investigator, is likely to result in the death of the subject within the next 2 years. 5. Presence of other disease that may interfere with testing procedures or in the judgement of the Investigator may interfere with trial participation or may put the patient at risk when participating in this trial. 6. Is likely to receive lung transplantation within the next 12 months. 7. Currently receiving nintedanib, pirfenidone, high dose corticosteroid, cytotoxic (e.g., chlorambucil, azathioprine, cyclophosphamide, methotrexate), vasodilator therapy for pulmonary hypertension (e.g., bosentan). A current dose of less than or equal to 15 mg/day of prednisone or its equivalent is acceptable if the dose is anticipated to remain stable during the study. 8. Prior use of GB0139 (also called TD139) or previously randomized in GALACTIC-1. 9. Prior use of nintedanib or pirfenidone within 7 days of initiation of screening. 10. Prior use of investigational drugs within 30 days (or 5 half-lives, whichever is longer) of initiation of screening. 11. Participating in another clinical trial, either interventional or observational. 12. Has a history of unstable or deteriorating cardiac or pulmonary disease (other than IPF) within the previous six months, including, but not limited to, the following: 1. Unstable angina pectoris or myocardial infarction, or percutaneous coronary intervention within the last 6 months 2. Congestive heart failure requiring hospitalization 3. Uncontrolled clinically significant arrhythmias 13. If female, the subject is pregnant or lactating or intending to become pregnant before participating in this study during the study and within (5 half- lives plus 30 days) after last dose of the study drug; or intending to donate ova during such time period. 14. Woman considered to be of childbearing potential who do not use highly effective birth control methods during the study. 15. Hypersensitivity to the active substance (TD139/GB0139) or the excipient (lactose).