This Phase 3 study was designed to confirm the efficacy and safety of Genz-112638 in patients with Gaucher disease type 1 who have been stabilized on Cerezyme

Gaucher disease is characterized by lysosomal accumulation of glucosylceramide due to impaired glucosylceramide hydrolysis. Gaucher disease type 1, which is the most common form, accounts for >90% of cases and does not involve the CNS. Typical manifestations of Gaucher disease type 1 include splenomegaly, hepatomegaly, thrombocytopenia, anemia, bone disease, and decreased quality of life. The disease manifestations are caused by the accumulation of glucosylceramide (storage material) in macrophages (called Gaucher cells) which have infiltrated the spleen and liver as well as other tissues.

Genz-112638 is a small molecule drug developed as an oral therapy which acts to specifically inhibit production of this storage material in Gaucher cells.

This study is designed to determine the efficacy, safety, and pharmacokinetics (PK) of Genz-112638 in adult patients with Gaucher disease type 1 who have been stabilized on Cerezyme.

• Drug: Genz-112638
  Capsules: 50, 100, or 150 mg BID
• Biological: Cerezyme
  IV Infusion, Varied Dose, Q2

• Investigational: Experimental
  Genz-112638
  Intervention: Drug: Genz-112638
• Active: Active Comparator
  Cerezyme
  Intervention: Biological: Cerezyme

Inclusion Criteria:

• The patient (and/or their parent/legal guardian) is willing and able to provide signed informed consent prior to any study-related procedures to be performed.
• The patient is 18 to 65 years old at the time of randomization.
• The patient has a confirmed diagnosis of Gaucher disease type 1.
• The patient has received treatment with Cerezyme for at least 3 years at a prescribed dose of ≥ 20 U/kg to ≤ 60 U/kg (± 5 U/kg) q2w during the last year of treatment and has not had a dose reduction, regimen change, or treatment interruption for greater than 6 consecutive months prior to randomization.
• The patient has clinically stable Gaucher disease prior to randomization.
• Female patients of childbearing potential must have a documented negative pregnancy test prior to dosing. In addition, all female patients of childbearing potential must use a medically accepted form of contraception throughout the study.

Exclusion Criteria:

• The patient has had a partial or total splenectomy within 3 years prior to randomization.
• The patient has received pharmacological chaperones or miglustat within 6 months prior to randomization.
• The patient has Gaucher disease type 2 or 3 or is suspected of having Gaucher disease type 3.
• The patient has any clinically significant disease, other than Gaucher disease,including cardiovascular, renal, hepatic, gastrointestinal (GI), pulmonary,neurologic, endocrine, metabolic (e.g. hypokalemia, hypomagnesemia), or psychiatric disease, other medical conditions, or serious intercurrent illnesses that may confound the study results or, in the opinion of the Investigator, may preclude participation in the study.
• The patient has tested positive for the human immunodeficiency virus (HIV) antibody, Hepatitis C antibody, or Hepatitis B surface antigen.
• The patient has received an investigational product within 30 days prior to randomization.
• The patient is pregnant or lactating.