A Study to Evaluate the Efficacy and Safety of GSK3915393 in Participants With Idiopathic Pulmonary Fibrosis (IPF)

Inclusion Criteria:

• Participants with IPF diagnosed within 5 years prior to screening based on theapplicable American Thoracic Society (ATS)/ European Respiratory Society (ERS)/Japanese Respiratory Society (JRS)/ Latin American Thoracic Society (ALAT) Guidelineat the time of diagnosis.

• Centrally read chest High Resolution Computed Tomography (HRCT) obtained atscreening or historical HRCT obtained within 12 months of screening that isconsistent with Usual interstitial pneumonia (UIP) or probable UIP (if indeterminateHRCT finding, IPF may be confirmed locally by historical biopsy).

• FVC greater than or equal to (>=) 45 percent (%) of predicted normal.

• Diffusing Capacity (of Lung) for Carbon Monoxide (DLCO) >=25% of predicted normalcorrected for hemoglobin (Hb).

• Prebronchodilator Forced Expiratory Volume in 1 second (FEV1)/FVC ≥ 0.7.

• If receiving antifibrotics must be on stable dose of nintedanib or pirfenidone forat least 12 weeks prior to screening.

• If not currently receiving pirfenidone or nintedanib, participant must have stoppedpirfenidone or nintedanib for at least 4 weeks prior to screening.

• Body weight ≥40 kilogram (kg) and body mass index within the range 18.5-35 kilogramper meter square (kg/m2) (inclusive).

• A female participant is eligible to participate if a woman of nonchildbearingpotential (WONCBP)

• Capable of giving signed informed consent

Exclusion Criteria:

• Participants with Interstitial Lung Disease (ILD) associated with other knowncauses.

• Diagnosis of sarcoidosis or any systemic autoimmune disease (including but notlimited to scleroderma, polymyositis/dermatomyositis, systemic lupus erythematosusand rheumatoid arthritis).

• Acute IPF exacerbation within 6 months prior to screening and/or during thescreening period (investigator-determined).

• Clinically significant non-parenchymal lung disease (e.g., asthma, chronicobstructive pulmonary disease, cavitary or pleural diseases) at screening.

• Diagnosis of severe pulmonary hypertension (investigator-determined)

• Extent of emphysema is greater than the extent of fibrosis according to reportedresults from the most recent HRCT.

• History of previous lung transplant or recent major surgery (investigator-determined) within 12 weeks prior to screening or planned during thetrial period. Registration on a transplant waiting list is allowed.

• Clinically significant respiratory tract infection (e.g., active tuberculosis,infectious pneumonia, Corona virus disease 2019 [COVID-19]) requiring treatmentwithin 4 weeks prior to and/or during the screening period.

• Cigarette smoking (including e-cigarettes) either current or within 3 months beforescreening.

• Current or chronic liver disease or known hepatic or biliary abnormalities (with theexception of Gilbert's syndrome or asymptomatic gallstones).

• Alanine transaminase (ALT), Aspartate transaminase (AST), Alkaline phosphatase (ALP) >2x Upper Limit of Normal (ULN) and bilirubin >1.5x ULN (isolated bilirubin >1.5xULNis acceptable if bilirubin is fractionated and direct bilirubin less than (<) 35% atscreening).

• Clinically significant abnormalities detected on ECG of either rhythm or conduction,a Corrected QT interval (QTc) >450 millisecond (msec) or QTc > 480msec forparticipants with a bundle branch block and/or a pacemaker who are activelyventricularly pacing during the screening ECG.

• Participants with pacemakers who are not pacing at the time of the screening ECGshould have a non-paced QTc <450 msec.

Prior/Concomitant Therapy-

• Simultaneous use of pirfenidone and nintedanib at screening.

• Received systemic corticosteroids equivalent to prednisone >10 mg/day or equivalentwithin 2 weeks of screening period.

• Use of any of the following therapies within 4 weeks prior to screening and duringthe screening period or planned during the study:

• Immunomodulatory therapies, including but not limited to azathioprine, mycophenolatemofetil, methotrexate, tacrolimus, cyclophosphamide, imatinib, Tumour NecrosisFactor -Alpha (TNF- α) inhibitors.

• Medications that are under investigation for the treatment of IPF including inhaledtreprostinil and Phosphodiesterase-4 (PDE-4) inhibitors. Symptomatic cough therapiesare allowed.

• Current use of systemic strong and moderate inducers or inhibitors of CytochromeP450 3A4 (CYP3A4) (see prohibited medication section for further information) thatcannot be safely discontinued or switched to an alternative agent at least 14 daysbefore randomization.

• Current use of systemic CYP3A4 substrates that have a narrow therapeutic index thatcannot be safely discontinued or switched to an alternative agent at least 14 daysbefore randomization.