Enhancing the Cell Permeability and Metabolic Stability of Peptidyl Drugs by Reversible Bicyclization

Abstract

Therapeutic applications of peptides are currently limited by their proteolytic instability and impermeability to the cell membrane. Here, we report a general, reversible bicyclization strategy to increase both the proteolytic stability and cell permeability of peptidyl drugs. A peptide drug is fused with a short cell-penetrating motif and converted into a conformationally constrained bicyclic structure through the formation of a pair of disulfide bonds. The resulting bicyclic peptide has greatly enhanced proteolytic stability as well as cell-permeability. Once inside the cell, the disulfide bonds are reduced to produce a linear, biologically active peptide. This strategy was applied to generate a cell-permeable bicyclic peptidyl inhibitor against the NEMO-IKK interaction.

Cell-permeable bicyclic peptidyl inhibitors against T-cell protein tyrosine phosphatase from a combinatorial library

“…This inhibitor may serve as a useful tool for investigating the biological function of TCPTP in signalling pathways. Together with our previously reported examples, 6,7 this work demonstrates that bicyclic peptides featuring both cell-penetrating and target-binding units may provide a general strategy for developing cell-permeable ligands against intracellular proteins.…”

“…The bicyclic approach was subsequently shown to be effective for delivering a wide variety of peptide sequences including negatively charged phosphopeptides into the cytosol of mammalian cells. 7 In this study, we set out to test whether the bicyclic peptide approach might be applied to generate isoform-specific inhibitors against other members of the PTP superfamily.…”

“…The lower cellular entry efficiency of peptide 25 than 33 is expected, as the negatively charged F 2 Pmp would partially neutralize the arginine positive charges and reduce the CPP efficiency. 7,10 …”

Targeting intracellular protein–protein interactions with cell-permeable cyclic peptides

“…To render the linear peptide ligands cell-permeable and proteolytically stable, Qian et al devised reversible cyclization strategies, in which the linear peptide ligands were fused with a short CPP motif (e.g., Arg-Arg-Arg-Arg-Nal-Phe) and cyclized into mono- or bicyclic structures by disulphide bond(s) [51,52]. When outside the cell (e.g., in serum), the cyclic peptides have dramatically improved cellular uptake efficiency and metabolic stability relative to their linear precursors.…”

Cell-Permeable Bicyclic Peptidyl Inhibitors against NEMO-IκB Kinase Interaction Directly from a Combinatorial Library

“…However, its low potency and poor pharmacokinetics (e.g., serum half-life of ~15 min) prevented further clinical development. We 38 and others 39 have attempted to improve the potency, proteolytic stability, and/or cell-permeability of Antp-NBD through cyclization, but the potency of the resulting peptides remained rather modest (IC 50 in the low μ M range). In this work, we have discovered a relatively potent bicyclic peptidyl inhibitor against the NEMO-IKK interaction (IC 50 =1.0 μ M), by screening of a combinatorial library followed by limited optimization.…”