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Proteins involved in immune checkpoint pathways, such as CTLA4, PD1, and PD-L1, have become important targets for cancer immunotherapy; however, development of small molecule drugs targeting these pathways has proven difficult due to the nature of their protein–protein interfaces. Here, using a hierarchy of computational techniques, we design a cyclic peptide that binds CTLA4 and follow this with experimental verification of binding and biological activity, using bio-layer interferometry, cell culture, and a mouse tumor model. Beginning from a template excised from the X-ray structure of the CTLA4:B7-2 complex, we generate several peptide sequences using flexible docking and modeling steps. These peptides are cyclized head-to-tail to improve structural and proteolytic stability and screened using molecular dynamics simulation and MM-GBSA calculation. The standard binding free energies for shortlisted peptides are then calculated in explicit-solvent simulation using a rigorous multistep technique. The most promising peptide, cyc(EIDTVLTPTGWVAKRYS), yields the standard free energy −6.6 ± 3.5 kcal mol^−1, which corresponds to a dissociation constant of ∼15 μmol L^−1. The binding affinity of this peptide for CTLA4 is measured experimentally (31 ± 4 μmol L^−1) using bio-layer interferometry. Treatment with this peptide inhibited tumor growth in a co-culture of Lewis lung carcinoma (LLC) cells and antigen primed T cells, as well as in mice with an orthotropic Lewis lung carcinoma allograft model.
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Dendrimer Conjugates with PD‐L1‐Binding Peptides Enhance In Vivo Antitumor Immune Response
Abstract Peptides are an emerging class of biologics for cancer immunotherapy; however, their clinical translation is hindered by poor binding kinetics, bioavailability, and short plasma half‐life compared to their corresponding antibodies. Nanoparticles present potential solutions but face scale‐up difficulties due to complexity. Here, a translatable, modular nanoparticle scaffold is presented for peptide‐based immune checkpoint inhibitors (ICIs). This platform is based on a simple structure of generation 7 (G7) poly(amidoamine) (PAMAM) dendrimers conjugated with engineered peptides (dendrimer‐peptide conjugates, DPCs). DPCs functionalized with multiple copies of a programmed death‐ligand 1 (PD‐L1)‐binding peptide exhibited significantly enhanced avidity‐based binding kinetics and in vitro specificity, in addition to the substantially prolonged plasma half‐life in vivo. Notably, a series of in vivo experiments revealed that DPCs displayed selective tumor accumulation and high efficacy, without apparent toxicity, when applied to a syngeneic mouse model bearing mouse oral carcinoma (MOC1) tumors. The results indicate that the DPC platform significantly improves the antagonistic effect and in vivo behaviors of the PD‐L1‐binding peptides, which can be potentially applied to virtually any peptide‐based ICIs. The DPC platform's simplicity and modular nature will likely increase the potential of its clinical translation and ultimately enable precision/personalized cancer immunotherapy.
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- Award ID(s):
- 2211932
- PAR ID:
- 10641129
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Healthcare Materials
- Volume:
- 14
- Issue:
- 20
- ISSN:
- 2192-2640
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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