Miglustat (OGT 918, N-butyl-deoxynojirimycin) is a drug developed by Oxford GlycoSciences and marketed by Actelion and is used primarily to treat type I Gaucher disease (GD1). It is marketed under the trade name Zavesca. Miglustat is used to treat adults with mild-to-moderate type I Gaucher disease for whom enzyme replacement therapy is unsuitable.[1] It was approved in Europe in 2002[2] and by the US FDA in 2003.[3] Miglustat is the first treatment to be approved for treating progressive neurological complications in people with Niemann–Pick disease, type C (NPC); it has been approved in Europe in 2009, Canada in 2010, and Japan in 2012, but not in the US where the FDA declined to approve it in 2010 and called for more data.[4][5][6][7] Miglustat is contraindicated for people with neurological conditions, kidney problems, women who are pregnant, and men and women planning to conceive a child.[8] Serious side effects include pain, burning, numbness or tingling in the hands, arms, legs, or feet; shaking hands that cannot be controlled; changes in vision; and easy bruising or bleeding. Common side effects include gastrointestinal effects (including diarrhea, stomach pain or bloating, gas, loss of appetite, weight loss, upset stomach, vomiting, constipation), dry mouth, muscular effects (including weakness, muscle cramps, especially in the legs, feeling of heaviness in the arms or legs, unsteadiness when walking), back pain, dizziness, nervousness, headache, memory problems, and difficult or irregular menstruation (period).[8] Type I Gaucher's disease is an autosomal recessive disorder; parents are generally healthy carriers with one functional and one mutated (nonfunctioning) copy of the Gaucher disease gene, GBA. People with type I Gaucher have a defect in the enzyme called glucocerebrosidase (also known as acid β-glucosidase). Glucocerebrosidase is an enzyme, and its function is to convert glucocerebroside (also known as glucosylceramide) into ceramide and glucose. When this enzyme doesn't work, glucocerebroside accumulates, which in turn causes liver and spleen enlargement, changes in the bone marrow and blood, and bone disease.[9] Other treatments on the market (imiglucerase (approved in 1995)[10], velaglucerase (approved in 2010)[11], taliglucerase alfa (Elelyso) (approved in 2012)[12]) are enzyme replacement therapy - they are functioning versions of the enzyme that doesn't work. Miglustat works differently - it prevents the formation of the substance that builds up when the enzyme doesn't work; this is called substrate reduction therapy.[13] Miglustat is an iminosugar, a synthetic analogue of D-glucose[14] and a white to off-white crystalline solid that has a bitter taste.[15] In July 2004 Actelion started a clinical trial of miglustat to treat Tay–Sachs disease, particularly late-onset Tay–Sachs with an estimated enrollment of 10 subjects; the trial ended August 2007.[16] In November 2007, Actelion initiated a clinical trial with miglustat in people with cystic fibrosis (CF) who have the ΔF508 in both copies of the cystic fibrosis transmembrane conductance regulator (CFTR) gene; the study ended in March 2008.[17] The cystic fibrosis trial showed no effect.[18]