The Effects of RPL554 on Top of Standard COPD Reliever Medications

Inclusion Criteria: * Provide informed consent * Males not donating sperm and using adequate contraception or females who are surgically sterile or postmenopausal * 12-lead ECG showing:Heart rate 45 to 90 bpm, QTcF≤450 msec, QRS ≤120 msec, PR interval ≤220 msec, no clinically significant abnormality * Capable of complying with all study restrictions and procedures including ability to use the study nebuliser correctly. * BMI 18 to 33 kg/m2 with a minimum weight of 45 kg. * COPD diagnosis for at least 1 year and clinically stable COPD in previous 4 weeks * Demonstrates reversibility to bronchodilator (two puffs of salbutamol followed by two puffs of ipratropium) via spirometry: * Post-bronchodilator FEV1/forced vital capacity (FVC) ratio of ≤0.70 * Post-bronchodilator FEV1 ≥40 % and ≤80% of predicted normal * ≥150 mL increase from pre-bronchodilator FEV1 * Chest X-ray showing no abnormalities * Meet the concomitant medication restrictions and be expected to do so for the rest of the study. * Smoking history of ≥10 pack years. * Capable of withdrawing from long acting bronchodilators throughout the study and short acting bronchodilators for 8 hours prior to study treatment. Exclusion Criteria: * History of life-threatening COPD including Intensive Care Unit admission and/or requiring intubation. * COPD exacerbation requiring oral steroids in the previous 3 months * History of one or more hospitalisations for COPD in the previous 12 months * Respiratory tract infection (both upper and lower) treated with antibiotics in previous 12 weeks * Evidence of cor pulmonale or clinically significant pulmonary hypertension. * Other respiratory disorders * Previous lung resection or lung reduction surgery. * Oral therapies for COPD in the previous 3 months and throughout the study. * Drug or alcohol abuse in the past 3 years * Received an experimental drug within 3 months or five half lives, whichever is longer. * Prior exposure to RPL554 * Patients with a history of chronic uncontrolled disease that the Investigator believes are clinically significant. * Documented cardiovascular disease in last 3 months * Major surgery, (requiring general anaesthesia) in the previous 6 weeks, or will not have fully recovered from surgery, or planned surgery through the end of the study. * History of malignancy of any organ system within 5 years with the exception of localised skin cancers (basal or squamous cell) * Clinically significant abnormal values for safety laboratory tests * A disclosed history, or one known to the Investigator, of significant non compliance in previous investigational studies or with prescribed medications. * Requires oxygen therapy, even on an occasional basis. * Inability to adequately perform whole body plethysmography. * Any other reason that the Investigator considers makes the subject unsuitable to participate. * Patients with known hypersensitivity to atropine or its derivatives, or to ipratropium bromide, salbutamol or RPL554 or their excipients/components.