Aim: to conduct a comparative assessment of the efficacy and safety of ERT drugs in MPS II type patients and analyze drug provision organization for pa- tients with this nosology. Methods: to conduct a comparative assessment of the efficacy and safety of ERT drugs, clinical trials data and real clinical practice data, including data from the Hunter outcomes survey register, were used. To assess the drug pro- vision organization were analyzed the current legal framework of the Russian Federation and public procurement data. Results and discussions: provision of pathogenetic therapy to the patients with orphan diseases is attributed to a number of administrative, clinical and eco- nomic constraints. The best example of the management of provision of this patients in Russia is a so-called Federal Program of High-cost nosologies (HCN) that has clear and transparent state regulation and the patient register that is essential for budget planning. The example of mucopolysaccharidosis type II (MPS II) that was included in HCN in 2019 shows noticeable increase in pa- tients’ access to therapy when transferring from regional budgets. Two medical products – idursulfase and idursulfase beta – are available in Russia for life-time pathogenetic treatment of this nosology. These products are produced using different cell lines; they have different INNs and are not interchangeable. Both drugs have registration clinical research, however, unique real world evidence is available for idursulfase only and show the survival rate of the patients with MPS II collected during 15 years of maintaining the international patient register cov- ering more than 1,000 patients from 129 countries, including Russia. According to the analysis, mortality risk in the patients treated with idursulfase is lower by 54% than in those who received no treatment (HR 0.46, 95% CI: 0.29; 0.72). This evidence can be used by health care decision makers to prioritize value of this medicinal product from both clinical and pharmacoeconomic perspectives. Predictability of therapy outcomes and higher prescription frequency according to current standards of care justifies idursulfase as a first choice treatment.