Abstract
Idursulfase and idursulfase beta currently used for enzyme replacement therapy of mucopolysaccharidosis type II (MPS II) do not cross the blood-brain barrier (BBB), which significantly limits the treatment of neurocognitive impairment in patients. Verenafusp alfa (Clotilia®, GENERIUM JSC) contains a recombinant modified iduronate-2-sulfatase enzyme covalently linked to the Fab fragment of a monoclonal antibody against the human insulin receptor, which crosses the BBB. Objective: The aim of this multicenter, open-label, multicohort phase II–III study was to evaluate the safety, pharmacokinetics, pharmacodynamics (PD), efficacy, and optimal dose selection of verenafusp alfa in different age groups of patients. Materials and methods: The interim analysis included data from 18 patients under 18 years of age in 6 age cohorts. Cohort enrollment was performed sequentially with decreasing patient age, first for the 2 mg/kg dose (Group 1) in cohorts 2, 3, 5, and then for the 3 mg/kg dose (Group 2) in cohorts 4, 6, 7. The study included 52 weekly infusions of verenafusp alfa. The PD criterion was the level of glycosaminoglycans (GAGs) in urine, blood, and cerebrospinal fluid (CSF). Efficacy parameters included assessment of somatic manifestations and neurocognitive functions; safety parameters included assessment of adverse events (AEs) and the dynamics of anti-drug antibody (ADA) formation. Results: The increase in verenafusp alfa concentration in CSF was more pronounced in Group 2 (3 mg/kg) – 252.5 [221.4; 351.54] pg/mL, as well as in the group of children under 6 years of age – 302.02 [244.72; 388.83] pg/mL. The decrease in heparan sulfate (HS) levels in CSF at week 52 was more pronounced in Group 2 (3 mg/kg) – 49% (p=0.084), and also in the group of patients under 6 years of age – 53% (p=0.027). Urinary and blood GAG levels remained stable, taking into account prior idursulfase therapy in 94% of patients. An 18% increase in the 6-minute walk test distance was observed in the overall group of patients under 18 years of age (p=0.020), accompanied by a statistically significant increase in range of motion in the shoulder, knee, and left hip joints. Liver and spleen volumes remained stable. Stabilization and/or improvement of neurocognitive function parameters were observed in patients with MPS II. The AEs observed in 50% of patients were non-serious, classified as infusion reactions of mild or moderate severity, with a predictable and manageable spectrum and frequency. ADA formation against the drug was observed in 40% of patients. Conclusion: Weekly intravenous administration of verenafusp alfa for one year achieved control of urinary GAG levels, stabilization and/or improvement of neurocognitive functions, and reduction of somatic manifestations of MPS II in previously treated patients with idursulfase drugs aged 2 to 16 years. After one year of therapy, an increase in verenafusp alfa concentration and a decrease in HS levels in CSF were observed, confirming its ability to cross the BBB and prevent neurodegenerative changes in the CNS.