Rationale: The high prevalence of hepatitis D virus (HDV) infection in the Republic of Dagestan, significantly exceeding that in the European part of the Russian Federation, as well as the limited choice of therapeutic options, have led to the need to analyze the accumulated experience of interferon therapy in the real clinical practice to further select possible treatment regimens.
 Aim: To evaluate the efficacy of pegylated interferon alpha (Peg-IFN-) in patients with chronic hepatitis D (CHD) in real world clinical practice.
 Materials and methods: In a retrospective study, the efficacy, safety and tolerability of Peg-IFN- were analyzed in 34 patients with CHD living in the Republic of Dagestan. Main virological parameters (anti-HDV antibodies (anti-HDV), HDV RNA and HBV DNA), alanine aminotransferase levels, changes over time in liver density by elastometry, and clinical parameters (hematology and urine tests, clinical chemistry, thyroid function tests) were assessed at 24 and 48 weeks of therapy, as well as at 48 weeks after its completion.
 Results: The treatment with Peg-IFN- for 48 weeks resulted in a virological response, defined as a HDV RNA decrease by more than 2 lg copies/mL, in 32% (11/34) of the patients. A sustained virological response, defined as undetectable HDV RNA at 48 weeks after the end of therapy, was not observed in any case. Treatment with interferon was associated with a decrease in liver density by average 4.1 kPa by week 48 on therapy. Normalization of alanine aminotransferase levels after 48 weeks of treatment was observed in 59% (20/34) of the patients; however, sustained biochemical response was achieved in none of them. Serious adverse events of high or moderate severity that resulted in the discontinuation of therapy were observed in 12% (4/34) of the cases.
 Conclusion: The results obtained indicate low efficacy of Peg-IFN- in the treatment of CHD in the Dagestan patients. Further research is needed to refine optimal interferon therapy regimens, to search for predictors of treatment response, and to evaluate the impact of interferon treatment regimens on the risk of hepatic complications, clinical outcomes, and patient survival. However, the most obvious solution to the problem of CHD therapy is the development and implementation of interferon-free treatment regimens.