A Clinical Study to Test How Effective and Safe GLPG1690 is for Participants With Idiopathic Pulmonary Fibrosis (IPF) When Used Together With Standard of Care

Inclusion Criteria:

• Male or female subject aged ≥40 years on the day of signing the Informed Consent Form (ICF).
• A diagnosis of IPF within 5 years prior to the screening visit, as per applicableAmerican Thoracic Society (ATS)/European Respiratory Society (ERS)/JapaneseRespiratory Society (JRS)/Latin American Thoracic Association (ALAT) guidelines at thetime of diagnosis.
• Chest high-resolution computed tomography (HRCT) historically performed within 12months prior to the screening visit and according to the minimum requirements for IPFdiagnosis by central review based on subject's HRCT only (if no lung biopsy (LB)available), or based on both HRCT and LB (with application of the different criteriain either situation). If an evaluable HRCT <12 months prior to screening is notavailable, an HRCT can be performed at screening to determine eligibility, accordingto the same requirements as the historical HRCT.
• Subjects receiving local standard of care for the treatment of IPF, defined as eitherpirfenidone or nintedanib, at a stable dose for at least two months before screening,and during screening; or neither pirfenidone or nintedanib (for any reason). A stabledose is defined as the highest dose tolerated by the subject during those two months.
• The extent of fibrotic changes is greater than the extent of emphysema on the mostrecent HRCT scan (investigator-determined).
• Meeting all of the following criteria during the screening period: FVC ≥45% predictedof normal, Forced expiratory volume in 1 second (FEV1)/FVC ≥0.7, diffusing capacity ofthe lung for carbon monoxide (DLCO) corrected for Hb ≥30% predicted of normal.
• Estimated minimum life expectancy of at least 30 months for non IPF related disease inthe opinion of the investigator.
• Male subjects and female subjects of childbearing potential agree to use highlyeffective contraception/preventive exposure measures from the time of first dose ofinvestigational medicinal product (IMP) (for the male subject) or the signing of theICF (for the female subject), during the study, and until 90 days (male) or 30 days (female) after the last dose of IMP.
• Able to walk at least 150 meters during the 6-Minute Walk Test (6MWT) at screeningVisit 1; without having a contraindication to perform the 6MWT or without a conditionputting the subject at risk of falling during the test (investigator's discretion).The use of a cane is allowed, the use of a stroller is not allowed at all for anycondition. At Visit 2, for the oxygen titration test, resting oxygen saturation (SpO2)should be ≥88% with maximum 6 L O2/minute; during the walk, SpO2 should be ≥83% with 6L O2/minute or ≥88% with 0, 2 or 4 L O2/minute.

Exclusion Criteria:

• History of malignancy within the past 5 years (except for carcinoma in situ of theuterine cervix, basal cell carcinoma of the skin that has been treated with noevidence of recurrence, prostate cancer that has been medically managed through activesurveillance or watchful waiting, squamous cell carcinoma of the skin if fullyresected, and Ductal Carcinoma In Situ).
• Clinically significant abnormalities detected on ECG of either rhythm or conduction, aQT interval corrected for heart rate using Fridericia's formula (QTcF) >450 ms, or aknown long QT syndrome. Patients with implantable cardiovascular devices (e.g.pacemaker) affecting the QT interval time may be enrolled in the study based uponinvestigator judgment following cardiologist consultation if deemed necessary, andonly after discussion with the medical monitor.
• Acute IPF exacerbation within 6 months prior to screening and/or during the screeningperiod. The definition of an acute IPF exacerbation is as follows: Previous orconcurrent diagnosis of IPF; Acute worsening or development of dyspnea typically < 1month duration; Computed tomography with new bilateral ground-glass opacity and/orconsolidation superimposed on a background pattern consistent with usual interstitialpneumonia pattern and deterioration not fully explained by cardiac failure or fluidoverload.
• Lower respiratory tract infection requiring treatment within 4 weeks prior toscreening and/or during the screening period.
• Interstitial lung disease associated with known primary diseases (e.g. sarcoidosis andamyloidosis), exposures (e.g. radiation, silica, asbestos, and coal dust), or drugs (e.g. amiodarone).
• Diagnosis of severe pulmonary hypertension (investigator determined).
• Unstable cardiovascular, pulmonary (other than IPF), or other disease within 6 monthsprior to screening or during the screening period (e.g. acute coronary disease, heartfailure, and stroke).
• Had gastric perforation within 3 months prior to screening or during screening, and/orunderwent major surgery within 3 months prior to screening, during screening or havemajor surgery planned during the study period.
• History of nintedanib-related increase in ALT and/or AST of >5 x upper limit of thenormal range (ULN) and increased susceptibility to elevated LFT; moderate to severehepatic impairment (Child-Pugh B or C) and/or abnormal liver function test (LFT) atscreening, defined as aspartate aminotransferase (AST), and/or alanineaminotransferase (ALT), and/or total bilirubin ≥1.5 x upper limit of the normal range (ULN), and/or gamma glutamyl transferase (GGT) ≥3 x ULN. Retesting is allowed once forabnormal LFT.
• Abnormal renal function defined as estimated creatinine clearance, calculatedaccording to Cockcroft-Gault calculation (CCr) <30 mL/min. Retesting is allowed once.
• Use of any of the following therapies within 4 weeks prior to screening and during thescreening period, or planned during the study: warfarin, imatinib, ambrisentan,azathioprine, cyclophosphamide, cyclosporine A, bosentan, methotrexate, sildenafil (except for occasional use), prednisone at steady dose >10 mg/day or equivalent.