Inclusion Criteria:

1. Male and female subjects with a diagnosis of IPF established during the previous seven years according to ATS/ERS/Fleischner criteria. 2. Score ≥ 40 mm on the Cough Severity VAS at Screening. 3. 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. 4. Any existing Standard of Care (SoC) treatment (e.g. pirfenidone or nintedanib) must be deemed as stable (minimum three months) before enrollment. 5. Subjects must sign and date a written, 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, and squamous cell carcinoma if diagnosed and successfully treated more than 6 months prior to the study. SCC diagnosed with the past 6 months will be exclusionary. 4. Patients experiencing cerebral hemorrhage or cerebral infarction at screening/baseline. 5. 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. 6. 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. 7. Is likely to receive lung transplantation within the next 12 months. 8. Currently receiving high dose corticosteroid, cytotoxic (e.g., chlorambucil, azathioprine, cyclophosphamide, methotrexate), vasodilator therapy for pulmonary hypertension (e.g., bosentan), and or investigational therapy for idiopathic pulmonary fibrosis (IPF) or administration of such therapeutics within 4 weeks of initial screening (or 5 half-lives, whichever is longer). 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. 9. 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. 10. 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. 11. Women considered to be of childbearing potential who do not use highly effective birth control methods during the study. 12. Known or suspected allergy to the trial drug or the relevant drugs given in the trial. 13. Involvement in a clinical research study within 4 weeks prior to screening and/or prior enrollment in the study. Participation in registry studies is permitted.

Arms

Other: Single Arm Active

Ifenprodil

Interventions

Drug: - Ifenprodil

Ifenprodil 20 mg TID