The proposed initial trial in healthy subjects and subjects with mild COPD will establish the tolerability of PUR118 in these subjects over single and short multi-day dosing periods. The study will also provide preliminary data regarding PUR118's potential impact on biomarkers in COPD. Finally, this trial will assess PUR118's effect on mucociliary clearance. This is a four part study enrolling healthy volunteers in a single ascending dose design (SAD; Part I), followed by multiple ascending dose design (MAD; Part II). Contingent on demonstration of safety in a healthy subject population, the study will enroll mild COPD subjects for a short multi-dose design (Part III) incorporating safety and pharmacodynamic endpoints. Lastly Part IV of the trial will assess the effect of PUR118 on mucociliary clearance in mild COPD subjects.