Miglustat / OGT 918 in the Treatment of Cystic Fibrosis

Inclusion Criteria: * Aged 12 years and older * Male or female * Non-pregnant women who are to remain non-pregnant for 3 months after the end of the study: only women who are surgically sterile, who are in the menopause (no menstruation for at least one year) or those of childbearing potential who are using a reliable method of contraception. Reliable methods of contraception for female patients include the following: * Barrier type devices (e.g., female condom, diaphragm and contraceptive sponge) used ONLY in combination with a spermicide * Intrauterine devices * Oral contraceptive agent * Depo-Provera™ (medroxyprogesterone acetate) * Levonorgestrel implants Abstention, the rhythm method or contraception by the partner alone are NOT reliable methods of contraception. For children, a reliable method of contraception must be considered, if appropriate. * Accepting for the duration of the study and for 3 months thereafter to use a condom and not to procreate a child (males only) * Cystic fibrosis patients homozygous for the ΔF508 mutation as confirmed by genetic test * Signed informed consent prior to any study-mandated procedure Exclusion Criteria: * Any condition prohibiting the correct measurement of the NPD such as upper respiratory tract infection * Acute upper respiratory tract or pulmonary exacerbation requiring antibiotic intervention within 2 weeks of screening * Severe renal impairment (creatinine clearance \< 30 ml/min as per Cockroft and Gault) * Female patients who will not undergo a pregnancy test prior to enrollment in the study * History of significant lactose intolerance * History of neuropathy * History of cataracts or known increased risk of cataract formation * Presence of clinically significant diarrhea (\>3 liquid stolls per days for \>7 days) without definable cause within 1 month prior to screening * Any known factor of disease that might interfere with treatment compliance, study conduct or interruption of the results such as drug or alcohol dependence or psychiatric disease * FEVI \<25% of predicted normal * Oxygen saturation at rest \<88% * Active or passive smoking as measured using the Smokelyzer® * Hypersensitivity to miglustat or any excipients * Planned treatment or treatment with another investigational drug or therapy (e.g., gene therapy) within 1 month prior to randomization