3-Aminoxypropionate-based linker system for cyclization activation in prodrug design

A novel linker system based on 3-aminoxypropionate was designed and evaluated for drug release using proteolysis as an activation trigger followed by intramolecular cyclization. The hydroxylamine moiety present in the linker system enabled faster release of the parent drug from the linker-drug conjugate at lower pH as compared to an aliphatic amine moiety. Introduction of two methyl groups strategically at the alpha position to the carboxylate in the linker further improved the rate of cyclization by nearly 2-fold. The 3-aminoxypropionate linker was successfully applied to a model prodrug for protease activation using alpha-chymotrypsin as the activating enzyme; the activation of the model prodrug bearing the 3-aminoxypropionate linker was 136 times faster than the corresponding model prodrug bearing an amine linker.