The article discusses results of a prospective observational study of long-term use of the biosimilar dornase alfa (Tigerase) (Generium, Russia) as part of complex therapy in patients with cystic fibrosis in real clinical practice.The aim was to analyze the outcomes of long-term use of the dornase alfa dornase alfa as part of complex therapy in patients with CF (protocol #DRN-CFR-N01).Methods. The study included patients (n = 165) aged 5 years and older from 11 centers for treatment of cystic fibrosis in the Russian Federation with a confirmed diagnosis of cystic fibrosis who were prescribed dornase alfa by their attending physician.Results. The analysis revealed that exacerbations of chronic pulmonary disease during the treatment with dornase alfa were observed in 29 (17.58%) patients included in the study. At the same time, there were no statistically significant changes in FEV1 and FVC (%) against baseline during the treatment in the study population. Adverse events related to the study drug were recorded in 9 (5.45%) patients.Conclusion. Biosimilar dornase alfa demonstrated a favorable efficacy and safety profile in routine clinical practice, which confirms the results of previously published studies.