Introduction. The study aimed to assess the safety, immunogenicity, and efficacy of long-term therapy with biosimilar of eculizumab (Elizaria®) in PNH patients. Methods. The study included 30 patients with PNH who had completed previous clinical trials. Of these, 25 patients continued receiving the biosimilar product, and 5 patients switched from the originator product Soliris. The maximum duration of follow-up was 104 weeks, during which the investigational product was administered 52 times at a standard dose. Results. Throughout the study, the levels of LDH, hemoglobin, reticulocytes, and PNH clone remained stable compared to baseline, regardless of the previous therapy (p > 0.05). There were no significant differences in the number of patients with chronic kidney disease at different visits, as well as in the number of patients who received donor red blood cell and platelet transfusions during the study (p > 0.05). There were two cases of adverse reactions reported in two patients (6.6%): elevated aspartate aminotransferase (3.3%) and alopecia (3.3%). Immunogenicity analysis showed no significant differences in the frequency of anti-drug antibody detection compared to baseline (p > 0.05). Conclusion. The study findings confirm the long-term efficacy and safety of biosimilar in patients with PNH.