Gaucher disease and the clinical experience with substrate reduction therapy.

Gaucher disease is caused by an enzymatic defect with consequent accumulation of glucocerebroside. Type I, the non-neuronopathic form, is rather common and panethnic. Patients may present with hepatosplenomegaly, anaemia, thrombocytopenia and skeletal or lung involvement. Enzyme replacement therapy ameliorates disease symptoms and signs; however, it involves lifelong intravenous therapy, is costly and is incapable of crossing the blood-brain barrier. Substrate reduction with N-butyldeoxynojirimycin (OGT 918) is a harbinger of oral iminosugars for glycolipid storage disorders. Long-term data in the seminal trial (100 mg three times per day), demonstrate safety and efficacy in adult type I patients naive to enzyme therapy, and suggest its application in patients unwilling or unable to receive enzyme replacement and tolerating side effects, including diarrhoea, weight loss, tremor and peripheral neuropathy (mostly reversible with dose reduction or withdrawal). Dose dependency was demonstrated with 50 mg three times per day. In patients stabilized on enzyme therapy switched from or in combination with enzyme, no deterioration in disease parameters was seen but side effects were as above. Although efficacy is less dramatic than enzyme treatment, it may be that plateaux are achieved asymptotically so therapeutic outcomes with OGT 918 may ultimately be comparable. Yet, given the above side effects and the lack of long-term experience, patients with very mild manifestations would probably not be appropriate candidates.