#$%^&*AU2016202591A120160519.pdf#####H:Vc Intrwovn NRPortbl DCC REC l0029214_I.docx-21/04/2016 ABSTRACT The hemitartrate salt of a compound represented by the following structural formula: N O H 0 N H (Formula I Hemitartrate), which may be used in pharmaceutical applications, are disclosed. Particular single crystalline forms of the Formula (I) Hemitartrate are characterized by a variety of properties and physical measurements. As well, methods of producing crystalline Formula (I) Hemitartrate, and using it to inhibit glucosylceramide synthase or lowering glycosphingolipid concentrations in subjects to treat a number of diseases, are also discussed. Pharmaceutical compositions are also described.