Clinical Study to Evaluate the Long Term Efficacy, Safety and Tolerability of Miglustat in Patients With Stable Type 1 Gaucher Disease

Inclusion Criteria:

1. Males or females aged 18 years or older

2. Type 1 Gaucher disease, diagnosed by glucocerebrosidase assay or molecular analysis of
the glucocerebrosidase gene.

3. Treatment with ERT for at least 3 years, with a stable dose regimen for at least the
last 6 months.

4. Clinically and biologically stable disease for the previous 2 years, with at least 2
time points assessments (including baseline as one potential time point), defined as:

- Stable organomegaly (assessed by magnetic resonance imaging (MRI) or computed
tomography (CT)):

- Liver volume within 10% of the mean.

- Spleen volume within 10% of the mean.

- Free of progressive symptomatic documented bone disease.

- Hemoglobin levels > 11g/dl

- Mean platelet count > 100x10^9 /l.

- Chitotriosidase activity within 20% of the mean.

- If chitotriosidase is not available (in the case of chitotriosidase
deficiency, or if it was not determined), other relevant biomarkers (e.g.,
angiotensin converting enzyme (ACE), tartrate resistant acid phosphatase
(TRAP) and ferritin) could be considered.

5. Written informed consent.

Exclusion Criteria:

1. History or evidence of oculomotor gaze palsy, ataxia or other clinical manifestations
typically associated with neuronopathic type 3 Gaucher disease.

2. Not ambulant patients, or with progressive symptomatic documented bone disease.

3. Splenectomy before 18 years of age for splenomegaly and/or thrombocytopenia.

4. Peripheral polyneuropathy (not mononeuropathy) documented with both clinical signs and
symptoms, and electrodiagnostic (EDX).

5. Patients (males and females) who do not agree to use reliable contraception throughout
the study and for 3 months after cessation of miglustat treatment.

6. Female patients who are pregnant or breast feeding, or without pregnancy test prior to
Day 1.

7. History of significant lactose intolerance.

8. Clinically significant diarrhea (>3 liquid stools per day for >7 days) without
definable cause within 6 months prior to Day 1, or a history of clinically relevant
gastrointestinal disorders.

9. History of cataracts or known increased risk of cataract formation.

10. Severe renal impairment i.e., with a creatinine clearance <30 ml/min/1.73m^2

11. Concomitant active medical condition such as human immunodeficiency virus (HIV) or
hepatitis B/C that would render patients unsuitable for study.

12. Previous treatment with miglustat.