This is an open label switch over study to assess the safety and efficacy of PRX-102
(pegunigalsidase alfa). Patients treated with agalsidase alfa for at least 2 years and on a
stable dose (>80% labelled dose/kg) for at least 6 months. Patients will be screened and
evaluated over 3 months while continuing on agalsidase alfa. Following the screening period,
the patient will be enrolled and switched from their agalsidase alfa treatment to receive
intravenous (IV) infusions of PRX-102 1 mg/kg every two weeks for 12 months. No more than 25%
of treated patients will be female.