A Flexible Strategy for Stapling and De-Stapling of Unprotected Peptides

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Cyclic (stapled) peptides often possess superior biological activity compared to their linear counterparts and are more attractive leads in drug development. This is for several reasons: conformational rigidity (enhanced binding to target molecules and receptor selectivity), resistance to degradation by peptidases (increased stability and potency), and greater cell permeability. Reliable strategies for peptide stapling are therefore in high demand, especially if cyclizations are reversible under certain controllable conditions. The reason is that a linear peptide can be biologically more active. If de-stapling can be triggered by an intracellular signal, then once the cyclic peptide has entered the cytosol, it can be converted to its more active acyclic form. We propose to develop a robust, practical, and broadly applicable catalytic method for stabling of peptides. Cyclizations, which will be promoted by inexpensive and easily available Cu(I) catalysts, are inspired by recent findings by the host group in Strasbourg. The Hoveyda group has shown that a highly functional group tolerant catalytic click reaction can be used to link a drug-bound allene to a ketone that is bound to unprotected penetratin, a cell-penetrating peptide (CPP). The process was completed in just 3-5 hours in aqueous media and at ambient temperature. Also inspired by the recent discoveries in the host group, de-stapling will be triggered by a reactive oxygen species (ROS) and specifically H2O2, higher concentration of which have been shown to signal the onset of diseases such as cancer and diabetes. The results of these studies are expected to have an immediate impact on catalytic chemical synthesis, aiding in the elucidation of biological mechanisms and accelerating drug development and discovery. Additionally, the proposed work will significantly contribute to environmentally responsible and green chemistry, aligning with the EU sustainable development strategy.