Gaucher disease is a rare lysosomal storage disorder caused by the deficiency of the enzyme glucocerebrosidase (GCB). Due to the deficiency of functional GCB, glucocerebroside accumulates within macrophages leading to cellular engorgement, organomegaly, and organ system dysfunction. The purpose of this treatment protocol is to observe the safety of velaglucerase alfa in patients with type 1 Gaucher disease who are either treatment naive (newly diagnosed) or who are currently being treated with the Enzyme Replacement Therapy (ERT) imiglucerase.

Type 1 Gaucher disease, the most common form, accounts for more than 90% of all cases of Gaucher disease and does not involve the CNS. Typical manifestations of type 1 Gaucher disease include hepatomegaly, splenomegaly, thrombocytopenia, bleeding tendencies, anemia, hypermetabolism, skeletal pathology, growth retardation, pulmonary disease, and decreased quality of life. Velaglucerase alfa (Gene-Activated™ human glucocerebrosidase;GA-GCB) is produced in a continuous human cell line using proprietary gene-activation technology and has an identical amino acid sequence to the naturally occurring human enzyme. Velaglucerase alfa contains terminal mannose residues that target the enzyme to the macrophages-the primary target cells in Gaucher disease. This treatment protocol will observe the safety of velaglucerase alfa in patients with type 1 Gaucher disease who are either treatment naive (newly diagnosed) or who are currently being treated with the Enzyme Replacement Therapy (ERT) imiglucerase. Patients currently being treated with ERT for their Gaucher disease will receive the same number of units of velaglucerase alfa per month as their imiglucerase dose for doses between 30-120 U/kg/month. For patients who experienced dose reductions in their imiglucerase treatment due to supply constraints the pre-reduction monthly dose may be used to determine the monthly dose of velaglucerase alfa.

Inclusion Criteria:

1. The patient has a documented diagnosis of type 1 Gaucher disease
2. The patient is > 2 years of age
3. The patient has NOT previously experienced an anaphylactic or anaphylactoid reaction to another ERT including imiglucerase
4. Women of child-bearing potential must agree to use a medically acceptable method of contraception at all times during the study; and must have a negative result to a pregnancy test as required throughout their participation in the study. Male patients must use a medically acceptable method of birth control throughout their participation in the study and must report their partner's pregnancy.
5. The patient is sufficiently cooperative to participate in this treatment plan as judged by the Investigator

6. If the patient is naïve or new to treatment, the patient has one or more of the following (in absence of the following criteria, please call the sponsor for treatment justification):

   • Gaucher disease-related anemia
   • Moderate splenomegaly (2 to 3 cm below the left costal margin), by palpation
   • Gaucher disease-related thrombocytopenia
   • Gaucher disease-related palpable enlarged liver

Exclusion Criteria: None