A Trial to Evaluate the Efficacy of PRM-151 in Subjects With Idiopathic Pulmonary Fibrosis (IPF)

Inclusion Criteria 1. Is aged 40-80 years. 2. Has IPF satisfying the American Thoracic Society/European Respiratory Society /Japanese Respiratory Society/Latin American Thoracic Association (ATS/ERS/JRS/ALAT) diagnostic criteria (Raghu, Collard et al. 2011). In the absence of a surgical lung biopsy, high-resolution computed tomography (HRCT) must be "consistent with "usual interstitial pneumonia" (UIP) defined as meeting either criteria A, B, and C, or criteria A and C, or criteria B and C below: * Definite honeycomb lung destruction with basal and peripheral predominance. * Presence of reticular abnormality AND traction bronchiectasis consistent with fibrosis, with basal and peripheral predominance. * Atypical features are absent, specifically nodules and consolidation. Ground glass opacity, if present, is less extensive than reticular opacity pattern. 3. If on pirfenidone or nintedanib, subject must have been on a stable dose of pirfenidone or nintedanib for at least 3 months without increase in forced vital capacity (FVC)% predicted on two consecutive pulmonary function tests (PFTs), including screening PFTs. Subjects may not be on both pirfenidone and nintedanib. 4. If not currently receiving pirfenidone or nintedanib, subject must have been off pirfenidone or nintedanib for ≥ 4 weeks before baseline. 5. Has a FVC ≥ 50% and ≤ 90% of predicted. 6. Has a DLCO ≥ 25% and ≤ 90% of predicted. 7. Minimum distance on 6-Minute Walk Test (6MWT) of 150 meters. 8. Has a forced expiratory volume in 1 second (FEV1)/FVC ratio \> 0.70. 9. Women of child bearing potential (WCBP), defined as a sexually mature woman not surgically sterilized or not post-menopausal for at least 24 consecutive months if ≤ 55 years or 12 months if \> 55 years, must have a negative serum pregnancy test within four weeks prior to the first dose of study drug and must agree to use adequate methods of birth control throughout the study. Adequate methods of contraception are defined in the protocol. 10. Has a life expectancy of at least 9 months 11. According to the investigator's best judgment, can comply with the requirements of the protocol. 12. Has provided written informed consent to participate in the study. Exclusion Criteria: 1. Has emphysema ≥ 50% on HRCT or the extent of emphysema is greater than the extent of fibrosis according to reported results from the most recent HRCT. 2. Has a history of cigarette smoking within the previous 3 months. 3. Has received investigational therapy for IPF within 4 weeks before baseline. 4. Is receiving systemic corticosteroids equivalent to prednisone \> 10 mg/day or equivalent within 2 weeks of baseline. 5. Received azathioprine, cyclophosphamide, or cyclosporine A within 4 weeks of baseline. 6. Has a history of a malignancy within the previous 5 years, with the exception of basal cell skin neoplasms. In addition, a malignant diagnosis or condition first occurring prior to 5 years must be considered cured, inactive, and not under current treatment. 7. Has any concurrent condition other than IPF that, in the Investigator's opinion, is unstable and/or would impact the likelihood of survival for the study duration or the subject's ability to complete the study as designed, or may influence any of the safety or efficacy assessments included in the study. 8. Has baseline resting oxygen saturation of \< 89% on room air or supplemental oxygen. 9. Is unable to refrain from use of the following: * Short acting bronchodilators on the day of and within 12 hours of pulmonary function, DLCO, and 6 minute walk assessments. * Long acting bronchodilators on the day of and within 24 hours of these assessments. 10. Has a known post bronchodilator (short acting beta agonist \[SABA\] - albuterol or salbutamol) increase in FEV1 of \>10% and in FVC of \>7.5%.