Tailored Cross-β Assemblies Establish Peptide "Dominos" Structures for Anchoring Undruggable Pharmacophores

β-sheets have the ability to hierarchically stack into assemblies, and much effort has been spent on designing different peptides to regulate their assembly behaviors. Although the progress is remarkable, it remains challenging to manipulate them in a controllable way for achieving both tailored structures and specific functions. In this study, we obtained bola-like peptides using de novo design and combinatorial chemical screening. By regulating the solvent-accessible surface area of the peptide chain, a series of assemblies with different tilt angles and active sites of the β-sheet were obtained, resembling collapsed dominos. The structure-activity relationship of the optimized peptide NQ40 system was established and its ability to target the PD-L1 was demonstrated. This study successfully established the structure-function relationship of β-sheets assemblies and has positive implications on the rational design of peptide assemblies that possess recognition abilities.

Evaluation of a Radiolabelled Macrocyclic Peptide as Potential PET Imaging Probe for PD-L1

The interaction between the immune checkpoint PD‐1 and PD−L1 promotes T‐cell deactivation and cancer proliferation. Therefore, immune checkpoint inhibition therapy, which relies on prior assessment of the target, has been widely used for many cancers. As a non‐invasive molecular imaging tool, radiotracers bring novel information on the in vivo expression of biomarkers (e. g., PD−L1), enabling a personalized treatment of patients. Our work aimed at the development of a PD−L1‐specific, peptide‐based PET radiotracer. We synthesized and evaluated a radiolabeled macrocyclic peptide adapted from a patent by Bristol Myers Squibb. Synthesis of [⁶⁸Ga]Ga‐NJMP1 yielded a product with a radiochemical purity>95 % that was evaluated in vitro. However, experiments on CHO−K1 hPD−L1 cells showed very low cell binding and internalization rates of [⁶⁸Ga]Ga‐NJMP1 in comparison to a control radiopeptide (WL12). Non‐radioactive cellular assays using time‐resolved fluorescence energy transfer confirmed the low affinity of the reported parent peptide and the DOTA‐derivatives towards PD−L1. The results of our studies indicate that the macrocyclic peptide scaffold reported in the patent literature is not suitable for radiotracer development due to insufficient affinity towards PD−L1 and that C‐terminal modifications of the macrocyclic peptide interfere with important ligand/receptor interactions.

Proteomic tools for the quantitative analysis of artificial peptide libraries: detection and characterization of target-amplified PD-1 inhibitors

We report a quantitative proteomics data analysis pipeline which, coupled to protein-directed dynamic combinatorial chemistry (DDC) experiments, enables the rapid discovery and direct characterization of protein-protein interaction (PPI) modulators. A low-affinity PD-1 binder was incubated with a library of >100 D-peptides under thiol-exchange favoring conditions, in the presence of the target protein PD-1, and we determined the S-linked dimeric species that resulted amplified in the protein samples versus the controls. We chemically synthesized the target dimer candidates and validated them by thermophoresis binding and protein-protein interaction assays. The results provide a proof-of-concept for using this strategy in the high-throughput search of improved drug-like peptide binders that block therapeutically relevant protein-protein interactions.