Prodrug formulations of bioactive polypeptides are provided wherein the bioactive polypeptide has been modified by the linkage of a dipeptide to the bioactive polypeptide through an ester linkage. The prodrugs disclosed herein in some embodiments have extended half lives of at least 1.5 hours (e.g., at least 10 hours), and more typically greater than 20 hours and less than 70 hours, and are converted to the active form at physiological conditions through a non-enzymatic reaction driven by chemical instability.