A new disulfide click stapling method converts inactive linear peptides into ring-shaped forms with anti-cancer activity that can reverse inside cells to release the native peptide.
IC50 = 6.81 μMLinear peptides had zero anticancer activity, but after disulfide click stapling into a helical macrocyclic form, the same peptides killed HCT-116 colorectal cancer cells — demonstrating that the staple transforms inactive sequences into active drugs.
What the researchers found
Researchers developed a "disulfide click" stapling method that converts linear peptides into stable macrocyclic (ring-shaped) forms with improved metabolic stability and ability to enter cells. Using a library of 17 stapling reagents with adjustable lengths and angles, they could bridge peptides from 3 to 18 amino acids long, creating ring structures of 18 to 48 atoms under gentle, biocompatible conditions. The stapled peptides gained anti-cancer activity against HCT-116 colorectal cancer cells (IC50 = 6.81 μM) while the unstapled linear versions had no biological activity. A unique feature: the disulfide staple can be chemically reversed inside cells, releasing the native peptide for intracellular delivery.
Why it matters
Most therapeutic peptides fail because they are quickly degraded by enzymes and cannot cross cell membranes. Stapling — chemically locking peptides into a ring shape — addresses both problems, but existing methods often use harsh chemistry or irreversible crosslinks. This disulfide click approach is notable because it works under mild conditions, offers a large toolbox of linker geometries, and is reversible — the staple breaks down inside cells to release the active peptide. This "staple, enter, release" strategy is a clever solution to the peptide drug delivery problem.
The numbers in context
17 stapling reagents · Peptides 3-18 amino acids · 18-48 membered macrocycles · IC50 = 6.81 μM (HCT-116 cells) · Biocompatible conditions
How the study worked
The researchers designed and synthesized 17 disulfide-based stapling reagents with varying lengths and angles. These were reacted with sulfur-containing (S-terminal) peptides via double or triple click reactions to produce macrocyclic peptides under biocompatible conditions. The stapled peptides were characterized for helical conformation, metabolic stability, and cellular permeability. Anticancer activity was tested against HCT-116 colorectal cancer cells. Reversibility was demonstrated using the reducing agent TCEP to release native peptides from the stapled forms.
Who was studied
Not applicable — in vitro peptide chemistry and cell-based anticancer assays
What this study cannot tell us
This is primarily a chemistry methodology paper with limited biological validation — only one cancer cell line was tested. The IC50 of 6.81 μM, while demonstrating activity, is relatively modest for a drug candidate. No in vivo studies, pharmacokinetic data, or selectivity against normal cells were reported. The requirement for sulfur-containing terminal residues may limit which peptides can be stapled with this method. The intracellular release mechanism (disulfide reduction) assumes a reducing intracellular environment, which may vary across cell types and disease states.
How to read the evidence
This is a chemistry methodology paper with in vitro proof-of-concept against one cancer cell line. While the chemistry is well-characterized, the biological validation is minimal — no in vivo studies, selectivity data, or pharmacokinetic assessment were performed.
When this study was published
Published in 2023 in Angewandte Chemie (a top chemistry journal), this is a recent contribution to the rapidly evolving field of peptide macrocyclization. The reversible stapling concept is relatively novel and could influence future peptide drug design.
The bigger picture
The pharmaceutical industry is increasingly interested in peptide drugs because they can target protein-protein interactions that small molecules cannot reach. However, the fundamental challenges of peptide drug delivery — poor stability and cell permeability — have limited their clinical potential. Macrocyclization (making ring-shaped peptides) is one of the most promising solutions, and this disulfide click approach adds a new tool with unique advantages: mild chemistry, adjustable linker geometry, and the ability to "unstaple" inside cells. This reversibility feature effectively turns the staple into a prodrug delivery system.
Questions still open
- How does the rate of intracellular disulfide reduction (and peptide release) vary across different cell types and disease states?
- Can this method be applied to clinically relevant therapeutic peptides beyond the cancer peptide demonstrated here?
- What is the in vivo metabolic stability of disulfide-stapled peptides compared to other stapling approaches (e.g., hydrocarbon or lactam staples)?
Common questions
What does 'stapling' a peptide mean?
Why is reversible stapling useful?
Read the original research
Disulfide Click Reaction for Stapling of S-terminal Peptides.
Angewandte Chemie (International ed. in English), 62(52), e202314379
Citation
Yu, Qing; Bai, Leiyang; Jiang, Xuefeng. (2023). Disulfide Click Reaction for Stapling of S-terminal Peptides.. Angewandte Chemie (International ed. in English), 62(52), e202314379. https://doi.org/10.1002/anie.202314379