Treatment outcomes maintained in Hunter syndrome patients: a case series on switching from idursulfase to idursulfase beta in Belarus.

Hunter syndrome (Mucopolysaccharidosis type II, MPS II) is a rare X-linked lysosomal storage disorder caused by iduronate-2-sulfatase deficiency, leading to glycosaminoglycan accumulation. Enzyme replacement therapy (ERT) with idursulfase is a standard treatment, although supply shortages may disrupt continuity of care. This retrospective case series describes clinical and biochemical outcomes in seven patients with Hunter syndrome in Belarus who were switched from idursulfase (Elaprase®) to idursulfase beta (Hunterase®). Patients were evaluated before and after the switch using urinary GAG levels, 6-minute walking test (6MWT), liver and spleen size, and safety parameters. Following the transition, patients maintained or improved clinical outcomes, with continued reductions in urinary GAG levels, stable or improved 6MWT performance, and further decreases in organ enlargement. No new safety concerns were identified. These findings suggest that switching to idursulfase beta may preserve therapeutic benefits and support treatment continuity in real-world settings.