Safety, Tolerability, and Pharmacodynamic Effect Study of PUR118

Main Inclusion Criteria Parts I \& II * Healthy males or non pregnant, non lactating healthy females; * Age 18-65 years of age; * Must be willing and able to communicate in English and participate in the whole study; * Must provide written informed consent. Main Exclusion Criteria Parts I \& II * Current smokers and those who have smoked within the last 12 months; * Females of child bearing age not willing to use an acceptable form of contraception; * Presence or history of allergy requiring treatment; * Serious adverse reaction or hypersensitivity to any drug; Main Inclusion Criteria: Parts III and IV * Males or non pregnant, non lactating females; * Age 45-70 years; * Current (Part III only) or ex-smokers who at least a 15 pack-year smoking history. For Part IV, subjects must be non-smokers for at least 3 months; * Medically stable, with no evidence of uncontrolled co-existing conditions at screening; * Must not be taking any inhaled or oral corticosteroids; * FEV1/FVC ratio \<70% and FEV1 60 - 80% (or \>/= 60% for Part IV only) of predicted following administration of a bronchodilator; * Patients must have a medical history of COPD confirmed by their General Practitioner (GP) or treating hospital physician or must have a chest x-ray (CXR) which is normal or consistent with mild COPD and excludes other clinically significant respiratory abnormalities; * Must be willing and able to communicate in English and participate in the whole study; * Must provide written informed consent. Main Exclusion Criteria: Parts III and IV * Must agree to use an adequate method of contraception; * Upper respiratory tract infection within 30 days of the first study day, or lower respiratory tract infection within the last 60 days; * Patients taking medication that may affect the respiratory tract within 14 days of the first study day other than their usual COPD medication; * No active exacerbations requiring antibiotics or steroids within 60 days of dosing.