Chemically stabilized peptides modeled after the ACE2 receptor helix potently blocked SARS-CoV-2 from entering human cells with no toxicity and strong resistance to degradation.
IC50: 1.9 μMmost potent stapled peptide inhibited SARS-CoV-2 pseudovirus infection with no cytotoxicity and >289 min plasma stability
What the researchers found
Researchers designed four double-stapled peptides based on the ACE2 receptor helix that SARS-CoV-2 uses to enter human cells. Three of four showed potent antiviral activity with IC50 values of 1.9–4.1 μM in ACE2-overexpressing cells. The most effective peptide, NYBSP-1, completely prevented viral damage at 17.2 μM against authentic SARS-CoV-2. The stapled peptides achieved 50–94% helicity versus only 19% for the linear control, and showed no cytotoxicity. Lead peptide NYBSP-4 demonstrated a plasma half-life exceeding 289 minutes.
Why it matters
This work demonstrates a peptide-based strategy for blocking viral entry by mimicking the host receptor. The stapling technique stabilized the peptide structure, dramatically improving both antiviral activity and resistance to degradation — showcasing a generalizable approach for designing therapeutic peptides against emerging viruses.
The numbers in context
IC50: 1.9–4.1 μM · IC100: 17.2 μM (NYBSP-1) · 50–94% helicity · 19% helicity (linear control) · T1/2 >289 min plasma stability · no cytotoxicity
How the study worked
Four double-stapled peptides were designed based on the ~30 amino acid ACE2 binding helix. Helicity was measured by circular dichroism. Antiviral activity was tested using pseudovirus assays in HT1080/ACE2 and A549/ACE2 cells, then validated against authentic SARS-CoV-2 (US_WA-1/2020) in Vero E6 cells. Cytotoxicity and proteolytic stability in human plasma were also assessed.
Who was studied
In vitro cell culture study (HT1080/ACE2, A549/ACE2, and Vero E6 cell lines)
What this study cannot tell us
All testing was in vitro (cell cultures); no animal or human studies were conducted. The IC50 values are in the micromolar range, which may present challenges for achieving therapeutic concentrations in vivo. The study was conducted early in the pandemic with the original SARS-CoV-2 strain; effectiveness against later variants is unknown.
How to read the evidence
This is an in vitro study demonstrating proof of concept for stapled peptide antivirals. While it shows potent activity against both pseudovirus and authentic SARS-CoV-2, it remains preclinical laboratory evidence without animal model or human validation.
When this study was published
Published in December 2020 during the early pandemic. While SARS-CoV-2 has since evolved significantly, the stapled peptide design principles demonstrated here remain broadly applicable to peptide-based antiviral development.
The bigger picture
Stapled peptides represent an innovative class of therapeutics that bridge the gap between small molecule drugs and large biologics. This work demonstrated that peptide stapling can create stable, potent viral entry inhibitors — a strategy that could be rapidly adapted for future pandemic threats. The approach is particularly valuable because it targets the highly conserved virus-receptor interaction rather than viral proteins that mutate frequently.
Questions still open
- Would these stapled peptides retain activity against SARS-CoV-2 variants with mutations in the receptor-binding domain?
- Can the peptides be formulated for inhaled delivery to target the respiratory tract directly?
- Could this ACE2-mimicking stapled peptide platform be pre-adapted for other coronaviruses as pandemic preparedness?
Common questions
What are stapled peptides and why are they useful?
How do these peptides block SARS-CoV-2 infection?
Read the original research
Stapled Peptides Based on Human Angiotensin-Converting Enzyme 2 (ACE2) Potently Inhibit SARS-CoV-2 Infection In Vitro.
mBio, 11(6)
Citation
Curreli, Francesca; Victor, Sofia M B; Ahmed, Shahad; Drelich, Aleksandra; Tong, Xiaohe; Tseng, Chien-Te K; Hillyer, Christopher D; Debnath, Asim K. (2020). Stapled Peptides Based on Human Angiotensin-Converting Enzyme 2 (ACE2) Potently Inhibit SARS-CoV-2 Infection In Vitro.. mBio, 11(6). https://doi.org/10.1128/mBio.02451-20