Dataset from An Open-Label Extension of Study TKT024 Evaluating Long-Term Safety and Clinical Outcomes in MPS II Patients Receiving Iduronate-2-Sulfatase Enzyme Replacement Therapy

Study TKT024EXT was a long-term, single-arm, open-label extension of Study TKT024, a one year
Phase 2/Phase 3 registration study. The primary objective of this extension study was to
collect long-term safety and clinical outcome data in Mucopolysaccharidosis II (MPS II), also
known as Hunter Syndrome, from the Phase 2/Phase 3 Study TKT024. All patients enrolling into
this study received weekly active treatment with idursulfase, the primary dosing regimen
investigated in Study TKT024.

Hunter Syndrome is an X-linked recessive lysosomal storage disease caused by a deficiency of
iduronate-2-sulfatase, an enzyme required to catabolize glycosaminoglycans (GAGS) in cells.
As a result, GAGs accumulate in the lysosomes leading to cellular engorgement, organomegaly,
tissue destruction, and organ system dysfunction. Hunter Syndrome is a rare disease with an
estimated incidence of 1 in 162,000 live births.