Duazomycin (N-acetyl-DON) is one of the few naturally occurring compounds containing an aliphatic alpha diazoketo group, and is produced by Streptomyces ambofaciens. It is a derivative of 6-diazo-5-oxo-L-norleucine (DON) which was initially isolated from an unidentified Streptomyces species and which is produced together with N-acetyl-DON and duazomycin B (azotomycin) by S. ambofaciens. Duazomycin inhibited purine biosynthesis and caused accumulation of phosphoribosyl-N-formylglycineamide (FGAR) at low levels of inhibitor; higher levels blocked the synthesis of FGAR, indicating that the antibiotic behaved essentially like DON. Duazomycin is readily deacetylated by mammalian acylase to DON. As a glutamine antagonist, duazomycin was used in combination with azathioprine for the treatment of patients with advanced Wegener’s granulomatosis with renal involvement. Prolonged survival, remission of systemic signs and symptoms, roentogenologic improvement of pulmonary lesions, reduction in proteinuria and arrest of progression of renal insufficiency were observed.