Enhancing the Cell Permeability of Stapled Peptides with a Cyclic Cell-Penetrating Peptide

Abstract

Stapled peptides recapitulate the binding affinity and specificity of α-helices in proteins, resist proteolytic degradation, and may provide a novel modality against challenging drug targets such as protein–protein interactions. However, most of the stapled peptides have limited cell permeability or are impermeable to the cell membrane. We show herein that stapled peptides can be rendered highly cell-permeable by conjugating a cyclic cell-penetrating peptide to their N-terminus, C-terminus, or stapling unit. Application of this strategy to two previously reported membrane-impermeable peptidyl inhibitors against the MDM2/p53 and β-catenin/TCF interactions resulted in the generation of potent proof-of-concept antiproliferative agents against key therapeutic targets.

Stapled Peptides Based on Human Angiotensin-Converting Enzyme 2 (ACE2) Potently Inhibit SARS-CoV-2 Infection In Vitro

“…A novel and highly pathogenic coronavirus named SARS-CoV-2 was first identified in Wuhan, China, in 2019. It causes coronavirus disease 2019 (COVID- 19), and the resultant rapid global spread is a substantial threat to public health and the world economy. On 11 March 2020, the World Health Organization (WHO) declared the COVID-19 outbreak to be a global pandemic.…”

“…Stapled peptides are typically derived from the a-helix from the binding interface, and they are locked into bioactive conformations through the use of chemical linkers. Stapling enhances a-helicity of unstructured short peptides in solution, improves resistance against proteolytic digestion, as well as potency, and often improves cell penetration (15)(16)(17)(18)(19)(20)(21). One of these stapled peptides, ALRN-6924, is in various clinical trials for the treatment of lymphomas (phase 1b/2), peripheral T-cell lymphoma (phase 2a), acute myeloid lymphoma (AML, phase 1), and advanced myelodysplastic syndrome (MDS, phase 1) (22).…”

Unprotected Peptide Macrocyclization and Stapling via A Fluorine-Thiol Displacement Reaction

“…Cellular uptake of peptides has been revealed to be a complicated process driven by hydrophobicity, positive charge, and alpha-helicity, etc. 28 The RCM-based stapling was previously reported to endow enhanced cellular permeability to HIV C-CA binding peptide 46 due to the stabilized secondary structure and the increased hydrophobicity. 47 Particularly for stapled peptides, the staple type also serves as one of the deciding factors for cell penetration.…”

“…[20][21][22]25 More importantly, the vast majority of stapled peptides still had limited cell permeability. 28 As a result, the development of stapled peptides with designable cell permeability remains challenging and requires a delicate balance between positive charges, hydrophobicity, alpha-helicity, and staple position. [28][29][30] Thus, novel strategies capable of stapling unprotected peptides in a straightforward, chemoselective, and clean manner, as well as promoting cellular uptake are highly sought.…”

“…28 As a result, the development of stapled peptides with designable cell permeability remains challenging and requires a delicate balance between positive charges, hydrophobicity, alpha-helicity, and staple position. [28][29][30] Thus, novel strategies capable of stapling unprotected peptides in a straightforward, chemoselective, and clean manner, as well as promoting cellular uptake are highly sought. 11 Unlike other readily reacting α-haloacetamides, a fluoroacetamide functional group has been considered biologically inert due to the poor leaving capability of fluorine.…”