Chemical protein synthesis-assisted high-throughput screening strategies for D-peptides in drug discovery

D-peptides are recognized as a new class of synthetic chemical drugs and they possess many interesting advantages such as high enzymatic stability,improved oral bioavailability,as well as high binding affinity and specificity.Recently,D-peptide drugs have been attracting increasing attention in both academic and industrial researches over recent years.One D-peptide etelcalcetide has even entered the market that targets the calcium(Ca2+)-sensing receptor(CaSR) to fight secondary hyperparathyroidism.Effective discovery and optimization of D-peptide ligands that can bind to various disease-related targets with high specificity and potency is of great importance for the development of D-peptide drugs.This review surveys the recent method development in this area especially the chemical protein synthesis-assisted high-throughput screening strategies for D-peptide ligands and their application in drug discovery.

finDr:A web server for in silico D-peptide ligand identification

In the rapidly expanding field of peptide therapeutics,the short in vivo half-life of peptides represents a considerable limitation for drug action.D-peptides,consisting entirely of the dextrorotatory enantiomers of naturally occurring levorotatory amino acids(AAs),do not suffer from these shortcomings as they are intrinsically resistant to proteolytic degradation,resulting in a favourable pharmacokinetic profile.To experimentally identify D-peptide binders to interesting therapeutic targets,so-called mirror-image phage display is typically performed,whereby the target is synthesized in D-form and L-peptide binders are screened as in conventional phage display.This technique is extremely powerful,but it requires the synthesis of the target in D-form,which is challenging for large proteins.Here we present finDr,a novel web server for the computational identification and optimization of D-peptide ligands to any protein structure(https://findr.biologie.uni-freiburg.de/).finDr performs molecular docking to virtually screen a library of helical 12-mer peptides extracted from the RCSB Protein Data Bank(PDB)for their ability to bind to the target.In a separate,heuristic approach to search the chemical space of 12-mer peptides,finDr executes a customizable evolutionary algorithm(EA)for the de novo identification or optimization of D-peptide ligands.As a proof of principle,we demonstrate the validity of our approach to predict optimal binders to the pharmacologically relevant target phenol soluble modulin alpha 3(PSMα3),a toxin of methicillin-resistant Staphylococcus aureus(MRSA).We validate the predictions using in vitro binding assays,supporting the success of this approach.Compared to conventional methods,finDr provides a low cost and easy-to-use alternative for the identification of D-peptide ligands against protein targets of choice without size limitation.We believe finDr will facilitate D-peptide discovery with implications in biotechnology and biomedicine.

Whole-body PET tracking of a D-dodecapeptide and its radiotheranostic potential for PD-L1 overexpressing tumors

Peptides that are composed of dextrorotary(D)-amino acids have gained increasing attention as a potential therapeutic class.However,our understanding of the in vivo fate of D-peptides is limited.This highlights the need for whole-body,quantitative tracking of D-peptides to better understand how they interact with the living body.Here,we used mouse models to track the movement of a programmed death-ligand 1(PD-L1)-targeting D-dodecapeptide antagonist(DPA)using positron emission tomography(PET).More specifically,we profiled the metabolic routes of[^(64)Cu]DPA and investigated the tumor engagement of[^(64)Cu/^(68)Ga]DPA in mouse models.Our results revealed that intact[^(64)Cu/^(68)Ga]DPA was primarily eliminated by the kidneys and had a notable accumulation in tumors.Moreover,a single dose of[^(64)Cu]DPA effectively delayed tumor growth and improved the survival of mice.Collectively,these results not only deepen our knowledge of the in vivo fate of D-peptides,but also underscore the utility of D-peptides as radiopharmaceuticals.