Membrane-disruptive peptides/peptidomimetics-based therapeutics: Promising systems to combat bacteria and cancer in the drug-resistant era

Membrane-disruptive peptides/peptidomimetics(MDPs)are antimicrobials or anticarcinogens that present a general killing mechanism through the physical disruption of cell membranes,in contrast to conventional chemotherapeutic drugs,which act on precise targets such as DNA or specific enzymes.Owing to their rapid action,broad-spectrum activity,and mechanisms of action that potentially hinder the development of resistance,MDPs have been increasingly considered as future therapeutics in the drug-resistant era.Recently,growing experimental evidence has demonstrated that MDPs can also be utilized as adjuvants to enhance the therapeutic effects of other agents.In this review,we evaluate the literature around the broad-spectrum antimicrobial properties and anticancer activity of MDPs,and summarize the current development and mechanisms of MDPs alone or in combination with other agents.Notably,this review highlights recent advances in the design of various MDP-based drug delivery systems that can improve the therapeutic effect of MDPs,minimize side effects,and promote the codelivery of multiple chemotherapeutics,for more efficient antimicrobial and anticancer therapy.

Peptidomimetics and metalloprotease inhibitors as anticancer drugs

Peptidomimetics with three types, as the structural or functional mimetics of natural active peptides, can preserve the bioactivity and improve the bioavailability and the specificity towards the targets of the lead peptides. Peptidomimetics of high bioactivity can be designed through various ways including conformation restriction, modification and non-peptide design. Recently the concentration on the de-velopment of cancer chemotherapeutic drugs was transferred from cytotoxic drugs to target-based drugs, and many proteases and peptidases that play key roles in the process of tumor genesis and development was discovered, which means that peptidomimetics as potential cancer chemotherapeu-tic drugs should be paid close attention to. Our laboratory has focused on the development of small-molecule peptidomimetic inhibitors of APN, MMPs and HDACs as target-based anticancer agents. These three zinc-dependent metalloproteinases play very important roles in the process of tumor genesis, invasion, metastasis, angiogenesis and matrix degradation, so small-molecule peptidomimetic inhibitors based on them would be quite potential in the development of chemotherapeutic drugs with high selectivity.

Multivalent Display of Lipophilic DNA Binders for Dual-Selective Anti-Mycobacterium Peptidomimetics with Binary Mechanism of Action

We made oligoamidine-based peptidomimetics highly specific for mycobacteria eradication by introducing and arraying lipophilic DNA binding motifs on macromolecular backbones.The short poly(amidino-phenylindole)(PAPI)structures feature an alternating amphiphilic structure with cationic,lipophilic DNA-binding moieties,enabling fast and selective eradication of mycobacteria through binary,membrane-and DNA-selective mechanisms of action.More importantly,PAPIs address the primary treatment challenge by combating mycobacteria in eukaryotic cells and working as a sensitizer for conventional antibiotics,in bothways promoting more thorough removal of pathogens and reducing the mycobacteria’s resistance generation rate during treatment.Structural optimizationwas achieved to counter specific pathogens,including Mycobacterium tuberculosis,in the Mycobacterium genus.One of the hit peptidomimetics was evaluated in a zebrafish-based aquatic infection model using Mycobacterium fortuitum and a mice tail infection model using Mycobacterium marinum,both revealing excellent in vivo performance.

Design methods for antimicrobial peptides with improved performance

The recalcitrance of pathogens to traditional antibiotics has made treating and eradicating bacterial infections more difficult.In this regard,developing new antimicrobial agents to combat antibiotic-resistant strains has become a top priority.Antimicrobial peptides(AMPs),a ubiquitous class of naturally occurring compounds with broadspectrum antipathogenic activity,hold significant promise as an effective solution to the current antimicrobial resistance(AMR)crisis.Several AMPs have been identified and evaluated for their therapeutic application,with many already in the drug development pipeline.Their distinct properties,such as high target specificity,potency,and ability to bypass microbial resistance mechanisms,make AMPs a promising alternative to traditional antibiotics.Nonetheless,several challenges,such as high toxicity,lability to proteolytic degradation,low stability,poor pharmacokinetics,and high production costs,continue to hamper their clinical applicability.Therefore,recent research has focused on optimizing the properties of AMPs to improve their performance.By understanding the physicochemical properties of AMPs that correspond to their activity,such as amphipathicity,hydrophobicity,structural conformation,amino acid distribution,and composition,researchers can design AMPs with desired and improved performance.In this review,we highlight some of the key strategies used to optimize the performance of AMPs,including rational design and de novo synthesis.We also discuss the growing role of predictive computational tools,utilizing artificial intelligence and machine learning,in the design and synthesis of highly efficacious lead drug candidates.

Synthesis of Hydroxyethylene-based β-Secretase Inhibitors

Aim To discuss in depth the synthesis of hydroxyethylene dipeptide-based β-secretase inhibitors; Methods Organic reactions such as nucleophilic addition and substitution assisted by organometallic agents, catalytic hydrogenation, and classic peptide coupling were used to synthesize peptidomimetic β-secretase inhibitors. Results Ideal reaction conditions and potential problems were investigated, and one of the designed β-secretase inhibitors 13 （as a model） was synthesized successfully; Conclusion This approach might be used to build up the β-secretase inhibitor library and to search for new molecular candidates.

Computer-aided molecular design and optimization of potent inhibitors disrupting APC-Asef interaction

Colorectal cancer(CRC)is the second leading cause of cancer mortality worldwide.At initial diagnosis,approximately 20%of patients are diagnosed with metastatic CRC(mCRC).Although the APC-Asef interaction is a well-established target for mCRC therapy,the discovery and development of effective and safe drugs for mCRC patients remains an urgent and challenging endeavor.In this study,we identified a novel structural scaffold based on MAI inhibitors,the first-in-class APC-Asef inhibitors we reported previously.ONIOM model-driven optimizations of the N-terminal cap and experimental evaluations of inhibitory activity were performed,and 24-fold greater potency was obtained with the best inhibitor compared to the parental compound.In addition,the cocrystal structure validated that the two-layerπ-πstacking interactions were essential for inhibitor stabilization in the bound state.Furthermore,in vitro and in vivo studies have demonstrated that novel inhibitors suppressed lung metastasis in CRC by disrupting the APC-Asef interaction.These results provide an intrinsic structural basis to further explore drug-like molecules for APC-Asef-mediated CRC therapy.

Photochemical Nitration of Protected Anilines by 5-Methyl-1,4-dinitroimidazole

Nitroanilines are important building blocks in pharmaceuticals,materials and dyes.Nitration methods for anilines under mild conditions are highly desired.Herein,we report a photochemical method for the nitration of anilines bearing various protecting groups by 5-methyl-1,4-dinitroimidazole as a new type of nitro source.This method is light-controlled and proceeds under mild reaction conditions with high efficiency.Fmoc-,Ts-and alkyl-protected anilines are all well nitrated with good functional group tolerance.

Peptidomimetic-liganded gold nanoclusters for controlled iron delivery and synergistic suppression of tumor growth

A novel peptidomimetic-liganded gold nanocluster(CDp-AuNC)is proposed for the synergistic suppression of tumor growth.Taking advantages of the multi-capabilities offered by the surface ligands,including iron chelation,glutathione peroxidases-1(GPx-1)binding,and tumor cells recognition,CDp-AuNCs are able to function as the nanocarriers to deliver iron in a controlled manner for the ferroptosis therapy and as the inhibitors for GPx-1 to induce the apoptosis of tumor cells.The Fe2+@CDp-AuNC nanocomplexes are fabricated through a facile self-assembly method.The experimental data verify that the nanocomplexes are internalized specifically by tumor cells with high efficiency.The acidic microenvironment in endosomes triggers the collapse of the nanocomplexes and thereby releases Fe2+to induce ferroptosis and CDp-AuNCs to inhibit the enzyme activity of GPx-1.Benefiting from the H_(2)O_(2)-depleted pathway inhibition and ferroptosis acceleration,the intracellular reactive oxygen species(ROS)level could be enhanced significantly.As a consequence,the apoptosis/ferroptosis of 4T1 cells as well as the tumor elimination in vivo are observed after treatment with the Fe2+@CDp-AuNC nanocomplexes at a relatively low dose.The facile iron loading method,simple construction procedure,and outstanding tumor suppression performance,provide CDp-AuNCs great application promise.More importantly,the strategy of peptidomimetic ligands design provides a transferable approach to building multifunctional nanomaterials.

α/Sulfono-γ-AA peptide hybrids agonist of GLP-1R with prolonged action both in vitro and in vivo

Peptides are increasingly important resources for biological and therapeutic development,however,their intrinsic susceptibility to proteolytic degradation represents a big hurdle.As a natural agonist for GLP-1R,glucagon-like peptide 1(GLP-1)is of significant clinical interest for the treatment of type-2 diabetes mellitus,but its in vivo instability and short half-life have largely prevented its therapeutic application.Here,we describe the rational design of a series of a/sulfono-γ-AA peptide hybrid analogues of GLP-1 as the GLP-1R agonists.Certain GLP-1 hybrid analogues exhibited enhanced stability(t_(1/2)>14 days)compared to t_(1/2)(<1 day)of GLP-1 in the blood plasma and in vivo.These newly developed peptide hybrids may be viable alternative of semaglutide for type-2 diabetes treatment.Additionally,our findings suggest that sulfono-γ-AA residues could be adopted to substitute canonical amino acids residues to improve the pharmacological activity of peptide-based drugs.

The disruption of protein-protein interactions with co-chaperones and client substrates as a strategy towards Hsp90 inhibition

The 90-kilo Dalton(kD) heat shock protein(Hsp90) is a ubiquitous,ATP-dependent molecular chaperone whose primary function is to ensure the proper folding of several hundred client protein substrates.Because many of these clients are overexpressed or become mutated during cancer progression,Hsp90 inhibition has been pursued as a potential strategy for cancer as one can target multiple oncoproteins and signaling pathways simultaneously.The first discovered Hsp90 inhibitors,geldanamycin and radicicol,function by competitively binding to Hsp90’s N-terminal binding site and inhibiting its ATPase activity.However,most of these N-terminal inhibitors exhibited detrimental activities during clinical evaluation due to induction of the pro-survival heat shock response as well as poor selectivity amongst the four isoforms.Consequently,alternative approaches to Hsp90 inhibition have been pursued and include C-terminal inhibition,isoform-selective inhibition,and the disruption of Hsp90 protein-protein interactions.Since the Hsp90 protein folding cycle requires the assembly of Hsp90 into a large heteroprotein complex,along with various co-chaperones and immunophilins,the development of small molecules that prevent assembly of the complex offers an alternative method of Hsp90 inhibition.

Peptidomimetic-based antibody surrogate for HER2

Inhibition of human epidermal growth factor receptor 2 mediated cell signaling pathway is an important therapeutic strategy for HER2-positive cancers.Although monoclonal antibodies are currently used as marketed drugs,their large molecular weight,high cost of production and susceptibility to proteolysis could be a hurdle for long-term application.In this study,we reported a strategy for the development of artificial antibody based on y-AApeptides to target HER2 extracellular domain(ECD).To achieve this,we synthesized a one-bead-two-compound(OBTC)library containing 320,000 cyclic y-AApeptides,from which we identified a y-AApeptide,M-3-6,that tightly binds to HER2 selectively.Subsequently,we designed an antibody-like dimer of M-3-6,named M-3-6-D,which showed excellent binding affinity toward HER2 comparable to monoclonal antibodies.Intriguingly,M-3-6-D was completely resistant toward enzymatic degradation.In addition,it could effectively inhibit the phosphorylation of HER2,as well as the downstream signaling pathways of AKT and ERK.Furthermore,M-3-6-D also efficiently inhibited cell proliferation in vitro,and suppressed tumor growth in SKBR3 xenograft model in vivo,implying its therapeutic potential for the treatment of cancers.Its small molecular weight,antibody-like property,resistance to proteolysis,may enable it a new generation of artificial antibody surrogate.Furthermore,our strategy of artificial antibody surrogate based on dimers of cyclicγ-AApeptides could be applied to a myriad of disease-related receptor targets in future.

Stereodivergent synthesis of C-glycosamino acids via Pd/Cu dual catalysis

Herein,we reported the stereodivergent synthesis of C-glycosamino acids via Pd/Cu dual catalysis and found a suitable system to resolve many challenges,such as the tolerance towards the density of functional groups,the variability of the anomeric position,the compatibility of appropriate catalyst combinations,the regioselectivity of nucleophiles,and the match/mismatch problems between chiral substrates and chiral ligand-metal complexes.The method enables the efficient preparation of a series of unnatural C-glycosamino acid skeletons bearing two contiguous stereogenic centers in good yields with excellent diastereoselectivity.From this crucial precursor,various C-glycosamino acid derivatives have been achieved diversely.The readily prepared C-glycosamino acid hybrids will meet the growing demands for the development of new molecular entities for discovering new drugs and materials.This stereodivergent synthesis of C-glycosamino acids will further accelerate the study of their structural features,mode of action,and potential biological applications in the near future.

Design,synthesis and biological evaluation of pyrrolidinone analogs as potential 20S proteasome inhibitors

A novel series of pyrrolidinone analogs that are designed as Michael addition acceptors to react irreversibly with the proteasome active site Thr1O~γhave been synthesized.Although biological evaluation results show that the compounds display poor inhibitory activity towards the proteasome active sites,pyrrolidinone analogs might still be modified to be potential 20S proteasome inhibitors.

Development of peptidomimetic hydroxamates as PfA-M1 and PfA-M17 dual inhibitors: Biological evaluation and structural characterization by cocrystallization

Plasmodium parasites causing malaria have developed resistance to most of the antimalarials in use,in-cluding the artemisinin-based combinations,which are the last line of defense against malaria.This ne-cessitates the discovery of new targets and the development of novel antimalarials.Plasmodium falciparum alanyl aminopeptidase(PfA-M1)and leucyl aminopeptidase(PfA-M17)belong to the M1 and M17 family of metalloproteases respectively and play critical roles in the asexual erythrocytic stage of development.These enzymes have been suggested as potential antimalarial drug targets.Herein we describe the devel-opment of peptidomimetic hydroxamates as PfA-M1 and PfA-M17 dual inhibitors.Most of the compounds described in this study display inhibition at sub-micromolar range against the recombinant PfA-M1 and PfA-M17.More importantly,compound 26 not only exhibits potent malarial aminopeptidases inhibitory activities(PfA-M1 K i=0.11±0.0002μmol/L,PfA-M17 K_(i)=0.05±0.005μmol/L),but also possesses remarkable selectivity over the mammalian counterpart(pAPN K_(i)=17.24±0.08μmol/L),which endows 26 with strong inhibition of the malarial parasite growth and negligible cytotoxicity on human cell lines.Crystal structures of PfA-M1 at atomic resolution in complex with four different compounds including compound 26 establish the structural basis for their inhibitory activities.Notably,the terminal ureidoben-zyl group of 26 explores the S2' region where differences between the malarial and mammalian enzymes are apparent,which rationalizes the selectivity of 26.Together,our data provide important insights for the rational and structure-based design of selective and dual inhibitors of malarial aminopeptidases that will likely lead to novel chemotherapeutics for the treatment of malaria.

Transformation of peptides to small molecules in medicinal chemistry:Challenges and opportunities

Peptides are native binders involved in numerous physiological life procedures,such as cellular signaling,and serve as ready-made regulators of biochemical processes.Meanwhile,small molecules compose many drugs owing to their outstanding advantages of physiochemical properties and synthetic convenience.A novel field of research is converting peptides into small molecules,providing a convenient portable solution for drug design or peptidomic research.Endowing properties of peptides onto small molecules can evolutionarily combine the advantages of both moieties and improve the biological druggability of molecules.Herein,we present eight representative recent cases in this conversion and elaborate on the transformation process of each case.We discuss the innovative technological methods and research approaches involved,and analyze the applicability conditions of the approaches and methods in each case,guiding further modifications of peptides to small molecules.Finally,based on the aforementioned cases,we summarize a general procedure for peptide-to-small molecule modifications,listing the technological methods available for each transformation step and providing our insights on the applicable scenarios for these methods.This review aims to present the progress of peptide-to-small molecule modifications and propose our thoughts and perspectives for future research in this field.