Safety and Efficacy Study of Inhaled PUR003 on a Controlled Influenza Virus Challenge in Healthy Adult Subjects

Inclusion Criteria: * Male and female subjects aged 18 to 45 years. * In general good health determined by a screening evaluation ≤120 days prior to double-blind IMP administration and on the day of admittance to quarantine. * Seronegative (NDA) for challenge virus. * Have not been vaccinated for influenza virus since 2006 (as determined in the medical history) or had a known influenza infection in the current season, defined as in the last 12 months. Exclusion Criteria: * Presence or evidence of significant acute or chronic, uncontrolled medical or psychiatric illness. * Abnormal pulmonary function as evidenced by clinically significant abnormality in spirometry. * Health care workers (including doctors, nurses, medical students and allied healthcare professionals) anticipated to have patient contact within two weeks of discharge from quarantine. * Intending to travel (to countries for which vaccinations are recommended or where high risk of infections exists). * Presence of household member or close contact (until 14 days after discharge from quarantine) who is: less than 3 years of age; has any known immunodeficiency; is receiving immunosuppressant medications; is undergoing or soon to undergo cancer chemotherapy within 28 days of challenge. * Subjects with diagnosed emphysema or chronic obstructive pulmonary disease (COPD); elderly residing in a nursing home, affected by severe lung disease or medical condition; or a transplant (bone marrow or solid organ) organ recipient * Subjects with any history of asthma, COPD, pulmonary hypertension, reactive airway disease, or any chronic lung condition of any aetiology. * Regular daily smokers during the 6 months prior to study entry or those who have a significant history of any tobacco use at any time (≥ total 10 pack year history = one pack a day for 10 years). * Presence of any febrile illness or symptoms of upper or lower tract respiratory infection in the 28 days prior to viral inoculation (such subjects may be re-evaluated for enrolment after resolution of the illness). * Receipt of any investigational drug within 3 months, or prior participation in a clinical trial of any influenza vaccine or medication within 1 year of participation.