Exendin-4, a glucagon-like peptide-1 agonist, is a relatively short-lived species in the circulatory system in vivo. We have linked three moieties of 2-sulfo-9-fluorenylmethoxycarbonyl (FMS) to the three amino functions of exendin-4. FMS(3)-exendin-4 thus obtained has about 0.1% the glucose-lowering potency of the native peptide. Upon in vitro incubation at physiological conditions, the FMS moieties undergo hydrolysis generating the parent fully active, exendin-4. A single subcutaneous administration of FMS(3)-exendin-4 to healthy and type II diabetic mice has induced a glucose-lowering profile that exceeds in length several times that obtained by the native peptide. The reduction of blood glucose level began 1h after administration and was maximal 3-4h later. The blood glucose level returned to pre-administered values with t(1/2) of 12+/-0.7, 26+/-2, and 44+/-3h with doses of 1, 10, and 100 micro g/mouse, respectively. In sum, we have synthesized and characterized FMS(3)-exendin-4, a prodrug derivative of the native insulinotropic peptide, and found it to facilitate a prolonged and stable, glucose-lowering action in healthy and diabetic mice.