A 2-Part, Phase 2 Open-label and Crossover Study of Belumosudil for Treatment of Idiopathic Pulmonary Fibrosis

1. Adult male and postmenopausal/surgically sterilized female subjects at least 18 years of age (if female, was surgically sterilized [i.e., total hysterectomy, or bilateral salpingo-oophorectomy]).

2. Able to provide written informed consent before the performance of any study specific procedures.

3. IPF diagnosis within 5 years before study entry, proven according to the American Thoracic Society/European Respiratory Society consensus conference criteria, with surgical lung biopsy. In the absence of a surgical lung biopsy, high-resolution computerized tomography (HRCT) consistent with usual interstitial pneumonitis.

4. Resting state pulse oximeter oxygen saturation (SpO2) ≥ 88% with or without supplemental oxygen, Forced Vital Capacity % (FVC%) ≥ 50% normal predicted value, and diffusing capcity (in the lung) of carbon monoxide (DLCO) ≥ 30% normal predicted value at baseline.

5. Men with partners of childbearing potential willing to use 2 medically acceptable methods of contraception during the trial and for 3 months after the last dose of study drug. Effective birth control includes:

6. Have adequate bone marrow function:

7. Willing to complete all study measurements and assessments in compliance with protocol

8. Had either received pirfenidone and/or nintedanib or offered both treatments (with last dose administered at least 1 month before the expected start of study drug dosing). If either or both pirfenidone and nintedanib treatment had not been given, then documentation that the subject was offered both treatments must have been documented.

1. Interstitial lung disease caused by conditions other than IPF

2. Severe concomitant illness limiting life expectancy (< 1 year)

3. DLCO < 30% predicted

4. Residual volume (RV) ≥ 120% predicted

5. Obstructive lung disease: Forced Expiratory Volume in 1 Second (FEV1/FVC ratio < 0.70)

6. Documented sustained improvement of the subject's IPF condition up to 12 months before study entry with or without IPF-specific therapy

7. Pulmonary infection or upper respiratory tract infection (URTI) within 4 weeks before study entry

8. Acute or chronic impairment (other than dyspnea) limiting the ability to comply with study requirements (e.g., pulmonary function tests [PFTs])

9. Chronic heart failure with New York Heart Association Class III/IV or known left ventricular ejection fraction < 25%

10. Moderate to severe hepatic impairment (i.e., Child-Pugh Class B or C)

11. Estimated creatinine clearance < 30 mL/min

12. Aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) > 2.0 * upper limit of normal (ULN)

13. Hb < 75% of the lower limit of normal

14. Systolic blood pressure < 100 mmHg

15. Pregnant or breastfeeding female subject

16. Men whose partner is pregnant or breastfeeding

17. Current drug or alcohol dependence

18. Chronic treatment with the following drugs within 4 weeks of study entry and during the study:

19. Treatment with endothelin receptor antagonists within 4 weeks before study entry

20. Systemic treatment within 4 weeks before study entry with cyclosporine A or tacrolimus, everolimus, or sirolimus (calcineurin or mammalian target of rapamycin inhibitors)

21. Previous exposure to belumosudil or known allergy/sensitivity to belumosudil or any other Rho-associated protein kinase 2 (ROCK2) inhibitor

22. Planned treatment or treatment with another investigational drug within 4 weeks before study entry

23. Taking a medication with the potential for QTc prolongation

24. Taking a drug sensitive substrate of CYP enzymes

25. Taking a strong inducer of CYP3A4

26. Had consumed an herbal medication (e.g., St. John's Wort) or grapefruit/grapefruit juice within 14 days prior to the Week 1 Day 1 visit