A Study Evaluating the Safety, Pharmacokinetics, Pharmacodynamics, and Efficacy of SM04646 Inhalation Solution in Subjects With Idiopathic Pulmonary Fibrosis (IPF)

Inclusion Criteria: * IPF diagnosis within 5 years of study start based upon thoracic society guidelines and confirmed by Investigator at study start * Able to walk \> 150 m in 6 Minute Walk Test without the use of supplemental oxygen at study start * Has a life expectancy of at least 12 months in the opinion of the Investigator * Full understanding of the requirements of the study and willingness and ability to comply with all study visits and procedures * Able to comprehend and willing to sign an informed consent form (ICF) prior to any study-related procedure being performed * Able to tolerate and complete placebo (vehicle) inhalation for 10 minutes without experiencing a significant cough, in the opinion of the Investigator * Subjects currently treated with pirfenidone or nintedanib must be willing to remain on their current treatment for the duration of the protocol, unless they experience rapid progression, or if, in the opinion of the Investigator, treatment adjustments are necessary Exclusion Criteria: * Women who are pregnant or lactating * Women of childbearing potential who are sexually active and are not willing to use an appropriate method of birth control during the study treatment period until 90 days post study medication administration * Males who are sexually active and not willing to use a condom, and have a partner who is capable of becoming pregnant, if neither has had surgery to become sterilized, and/or who are not willing to use an appropriate method of birth control during the study treatment period until 90 days post study medication administration * Males unwilling to refrain from sperm donation during the study treatment period until 90 days post study medication administration * Subjects unwilling to refrain from blood and plasma donation during the study treatment period until 90 days post study medication administration * A history of abuse of prescription or illicit drugs within 6 months prior to study start * Positive urine drug and alcohol screen with the exception of positive findings related to current prescription therapy at study start * Occurrence of serious illness requiring hospitalization within 90 days prior to study start * Presence of active infections at study start * Current smoker or past history of smoking (e.g., cigarettes, e-cigarettes, pipes, cigars) within 6 months of study start or \>50 pack years * Use of non-inhaled tobacco- or nicotine-containing products (e.g., chewing tobacco, nicotine gum, lozenges, or patches) within 30 days prior to study start until completion of the study * Regular alcohol consumption exceeding 7 drinks/week for females or 14 drinks/week for males (1 drink = 5 ounces \[150 mL\] of wine or 12 ounces \[360 mL\] of beer or 1.5 ounces \[45 mL\] of hard liquor) within 30 days prior to study start until completion of the study * Lung transplantation anticipated during the duration of the trial * Subjects receiving treatment with pirfenidone or nintedanib that: 1. Have been on treatment for less than 12 weeks prior to study start 2. Have not been on a stable dose for at least 30 days prior to study start * Subjects who are not currently on but have previously received pirfenidone or nintedanib that have not been off of pirfenidone or nintedanib for at least 30 days prior to study start * Receipt of any of the following medication or treatment prior to study start: 1. N-acetylcysteine prescribed for the treatment of IPF within 30 days prior to study start 2. Previous therapeutic radiation treatment of the lungs, mediastinum, or chest wall 3. Participation in a clinical research trial that included the receipt of an investigational product or any experimental therapeutic procedure within 30 days or 5 half-lives of the investigational product (if known), whichever is longer, prior to study start 4. Immunosuppressive medications \[e.g., methotrexate, cyclosporine, azathioprine, systemic or inhaled glucocorticosteroids with the exception of short term use of systemic glucocorticosteroids less than or equal to 10 mg of prednisone daily (or equivalent) for a non-IPF condition such as an allergic reaction or rash\] within 8 weeks prior to study start 5. Use of any therapy targeted to treat IPF (including but not limited to d-penicillamine, endothelium receptor antagonist \[e.g., bosentan, ambrisentan\], and interferon gamma-1B) within 30 days prior to study start 6. Use of any cytokine modulator (etanercept, adalimumab, efalizumab, infliximab, golimumab, certolizumab, rituximab) within 90 days or 5 half-lives, whichever is longer, prior to study start 7. A bronchodilator used within 1 week of study start 8. SM04646 * A "bronchodilator response" at study start, defined by an absolute increase of ≥ 12% and an increase of 0.2 L in FEV1 or FVC, or both, after bronchodilator use compared with the values before bronchodilator use * History of any of the following conditions: 1. Pulmonary embolism or pulmonary hypertension 2. Creatinine clearance of less than 50mL per minute 3. Active tuberculosis (TB) infection or history of incompletely treated latent TB infection 4. History of malignancy within the last 5 years; however, the following subjects are eligible: 1. Subjects with prior history of in situ cancer or basal or squamous cell skin cancer that has been completely excised 2. Subjects with other malignancies if they have been continuously disease free for at least 5 years prior to any study drug administration 3. Subjects with prostate cancer followed by surveillance. 5. Any connective tissue disease, including but not limited to scleroderma, systemic lupus erythematosus, rheumatoid arthritis, and polymyositis/dermatomyositis 6. Congenital respiratory conditions (e.g., cystic fibrosis) 7. Chronic obstructive pulmonary disease (COPD) or asthma 8. Current or recent respiratory tract infection (e.g., pneumonia, purulent bronchitis, or viral upper respiratory tract infection) within 30 days prior to study start 9. Acute exacerbation of IPF, in the opinion of the Investigator, within 30 days prior to study start 10. Human immunodeficiency virus (HIV), hepatitis C, or active hepatitis B infection 11. Clinically significant hepatic impairment (e.g., Child-Pugh A or greater severity) 12. Symptomatic coronary artery disease, congestive heart failure (CHF) New York Heart Association (NYHA) Class II-IV, myocardial infarction (MI), or unstable angina within 6 months prior to study start 13. Hypertension (systolic blood pressure (SBP) \>160 millimeters of mercury (mmHg) or diastolic blood pressure (DBP) \>100 mmHg) 14. Hypotension (blood pressure (BP) less than 90/60 mmHg) or mean arterial blood pressure (MAP) \< 65 mmHg 15. Current use of supplemental oxygen therapy for any condition * Subjects who are immediate family members (spouse, parent, child, or sibling; biological or legally adopted) of personnel directly affiliated with the study at the investigative site, or are directly affiliated with the study at the investigative site * Subjects employed by Samumed Pacific Pty Ltd, or any of its affiliates or development partners (that is, an employee, temporary contract worker, or designee) responsible for the conduct of the study