Bicyclic cell-penetrating peptide chimeras (CPPTACs) selectively degrade extracellular and cell membrane proteins via endocytosis and lysosomal delivery.
Extracellular protein degradationCPPTACs extend targeted protein degradation beyond intracellular targets to cell surface and secreted proteins
What the researchers found
Bicyclic CPPTACs selectively degrade extracellular and cell surface proteins through CPP-induced endocytosis and lysosomal delivery.
Why it matters
Targeted protein degradation is revolutionizing drug development, but most technologies only work on intracellular proteins. CPPTACs extend this approach to the much larger pool of extracellular targets.
How the study worked
Peptide chemistry: conjugation of bicyclic CPP (KRK motif) with target-binding elements; demonstration of endocytosis-mediated protein degradation.
What this study cannot tell us
Early-stage proof-of-concept; in vivo stability, selectivity, and safety need extensive testing; manufacturing of bicyclic peptide conjugates may be complex.
How to read the evidence
Proof-of-concept chemistry/biology study — demonstrates a novel technology platform but is very early stage.
When this study was published
Published 2026 in Bioorganic & Medicinal Chemistry Letters.
The bigger picture
Expanding targeted protein degradation to extracellular targets could enable treatment of diseases driven by surface receptors, secreted growth factors, and circulating proteins.
Questions still open
- Which extracellular disease targets are most amenable to CPPTAC degradation?
- How does CPPTAC selectivity compare to antibody-based approaches?
Common questions
What is targeted protein degradation?
Why is degrading extracellular proteins difficult?
Read the original research
Bicyclic peptide-based CPPTACs for extracellular and cell membrane protein degradation.
Bioorganic & medicinal chemistry letters, 132, 130496
Citation
Bai, Jinyu; Shi, Huaihuai; Chen, Jitun; Tian, Hui; Liang, Jiaxin; Chen, Bichun; Li, Jiazhong; Fang, Lijing. (2026). Bicyclic peptide-based CPPTACs for extracellular and cell membrane protein degradation.. Bioorganic & medicinal chemistry letters, 132, 130496. https://doi.org/10.1016/j.bmcl.2025.130496