ABSTRACT
Spencer’s group first investigated the radiolabeled enzyme inhibitor approach in 1968. Substitution of the amino group in the 4 position of the pteridine ring apparently makes possible the formation of a new hydrogen bond or ionic bond between the inhibitor and the enzyme. In pursuit of drugs that would modulate steroid hormone production, they developed a large array of inhibitors of steroid enzymes. The tissue distributions of the radiolabeled enzyme inhibitors were determined in dogs at various time intervals. A potential criticism of the enzyme inhibitor approach is that success to date has been limited mainly to the adrenal gland — an organ with unique biochemistry concentrated in a very small region of tissue. In designing irreversible-binding radiopharmaceuticals, enzymes as target receptors have a major advantage over drug receptors. Suicide inhibitors possess latent reactive groups that are selectively activated by the target enzyme.
