Aerosol administration of a protein capable of degrading DNA fibers in the bronchial secretion (DNase) improves lung function in patients with cystic fibrosis. The efficacy of this therapy is however limited by the low permanence of the active enzyme in the bronchial site. In addition to the DNase used by aerosol in CF (DNase I: commercial product Pulmozyme), the human genome encodes for other DNases, whose therapeutic potential in the treatment of CF is so far unexplored. The addition of polyethylene glycol (PEG) chains to DNases, improves effectiveness and duration of treatment. The project aims to explore the therapeutic potential of human DNases and in particular of a form expressed specifically in the lung. The perspective is the development of a drug based on a new DNase (DNase2b) modified in order to guarantee a more effective and lasting action. The new DNase will be produced in a purified form and characterized by its properties and then subjected to an innovative PEGhilation system and tested in the laboratory for the mucolytic action on sputum of FC patients. The results could provide important information on the functional role of pulmonary DNases and produce a drug with improved pharmacological properties for the treatment of CF lung symptoms.