This will be a multi-center, double-blind, parallel group, extension trial to assess the safety and efficacy of prGCD in patients completing NCT00376168. Patients will receive IV infusion of prGCD every two weeks at the selected medical center. The duration of the extension study will be fifteen months. There will be two treatment groups: 30 units/kg every 2 weeks or 60 units/kg every 2 weeks.
