Verona Pharma plc is a United Kingdom-based clinical-stage biopharmaceutical company. The principal activity of the Company is the development of drugs for the treatment of chronic respiratory diseases, such as chronic obstructive pulmonary disease (COPD), asthma and cystic fibrosis. The Company's product candidate, RPL554, is a dual inhibitor of the enzymes phosphodiesterase 3 and 4 (PDE3 and PDE4) that acts as both a bronchodilator and an anti-inflammatory agent in a single compound. The Company is developing RPL554 in a nebulized formulation for the maintenance treatment of COPD patients and for the treatment of cystic fibrosis. It also is developing RPL554 as an add-on therapy to commonly used therapies for the treatment of acute exacerbations of COPD in the hospital setting. In addition to its nebulized formulation of RPL554, the Company is developing RPL554 in both dry powder inhaler (DPI) and metered dose inhaler (MDI) formulations for the maintenance treatment of COPD.