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The photoredox electron donor–acceptor (EDA) complex‐mediated radical coupling reaction has gained prominence in the field of organic synthesis, finding widespread application in two‐component coupling reactions. However, EDA complex‐promoted multi‐component reactions are not well developed with only a limited number of examples have been reported. Herein, we report a photoinduced and EDA complex‐promoted highly chemoselective three‐component radical arylalkylation of [1.1.1]propellane, which allows the direct functionalization of C(sp3)−H with bicyclo[1.1.1]pentanes (BCP)‐aryl groups under mild conditions. A variety of unnatural α‐amino acids, featuring structurally diversified 1,3‐disubstituted BCP moieties, were synthesized in a single‐step process. Notably, leveraging the high tension release of [1.1.1]propellane, the highly unstable transient aryl radical undergoes rapid conversion into a relatively stable tertiary alkyl transient radical, and consequently, the competing side‐reaction of two‐component coupling was entirely suppressed. The strategic use of this transient radical conversion approach would be useful for the design of diverse EDA complex‐mediated multi‐component reactions. It is noteworthy that the highly chemoselective late‐stage incorporation of the 1,3‐disubstituted BCP pharmacophores into peptides was achieved both in liquid‐phase and solid‐phase reactions. This advancement is anticipated to have significant application potential in the future development of peptide drugs. [ABSTRACT FROM AUTHOR]

Therapeutic peptides are a major class of pharmaceutical drugs owing to their target‐binding specificity as well as their versatility in inhibiting aberrant protein‐protein interactions associated with human pathologies. Within the realm of amyloid diseases, the use of peptides and peptidomimetics tailor‐designed to overcome amyloidogenesis has been an active research endeavor since the late 90s. In more recent years, incorporating nanoparticles for enhancing the biocirculation and delivery of peptide drugs has emerged as a frontier in nanomedicine, and nanoparticles have further demonstrated a potency against amyloid aggregation and cellular inflammation to rival strategies employing small molecules, peptides, and antibodies. Despite these efforts, however, a fundamental understanding of the chemistry, characteristics and function of peptido‐nanocomposites is lacking, and a systematic analysis of such strategy for combating a range of amyloid pathogeneses is missing. Here we review the history, principles and evolving chemistry of constructing peptido‐nanocomposites from bottom up and discuss their future application against amyloid diseases that debilitate a significant portion of the global population. [ABSTRACT FROM AUTHOR]

Cyclic peptides are fascinating molecules abundantly found in nature and exploited as molecular format for drug development as well as other applications, ranging from research tools to food additives. Advances in peptide technologies made over many years through improved methods for synthesis and drug development have resulted in a steady stream of new drugs, with an average of around one cyclic peptide drug approved per year. Powerful technologies for screening random peptide libraries, and de novo generating ligands, have enabled the development of cyclic peptide drugs independent of naturally derived molecules and now offer virtually unlimited development opportunities. In this review, we feature therapeutically relevant cyclic peptides derived from nature and discuss the unique properties of cyclic peptides, the enormous technological advances in peptide ligand development in recent years, and current challenges and opportunities for developing cyclic peptides that address unmet medical needs. [ABSTRACT FROM AUTHOR]

This document is a corrigendum for an article titled "Cyclic Peptides for Drug Development." The authors of the original article provided an incomplete list of cyclic peptide drugs approved in the last 30 years. The corrigendum adds four drugs to the list and makes adjustments to the main text, figure legend, and supplementary information accordingly. Additionally, a mistake in the chemical structure of the isoleucine side chains of sunflower trypsin inhibitor (SFTI) was corrected. [Extracted from the article]

Protein and peptide drugs are predominantly administered by injection to achieve high bioavailability, but this greatly compromises patient compliance. Oral and transdermal drug delivery with minimal invasiveness and high adherence represent attractive alternatives to injection administration. However, oral and transdermal administration of bioactive proteins must overcome biological barriers, namely the gastrointestinal and skin barriers, respectively. The rapid development of new materials and technologies promises to address these physiological obstacles. This review provides an overview of the latest advances in oral and transdermal protein delivery, including chemical strategies, synthetic nanoparticles, medical microdevices, and biomimetic systems for oral administration, as well as chemical enhancers, physical approaches, and microneedles in transdermal delivery. We also discuss challenges and future perspectives of the field with a focus on innovation and translation. [ABSTRACT FROM AUTHOR]

Over recent decades, the pipeline of antibiotics acting against Gram‐negative bacteria is running dry, as most discovered candidate antibiotics suffer from insufficient potency, pharmacokinetic properties, or toxicity. The darobactins, a promising new small peptide class of drug candidates, bind to novel antibiotic target BamA, an outer membrane protein. Previously, we reported that biosynthetic engineering in a heterologous host generated novel darobactins with enhanced antibacterial activity. Here we utilize an optimized purification method and present cryo‐EM structures of the Bam complex with darobactin 9 (D9), which served as a blueprint for the biotechnological generation of twenty new darobactins including halogenated analogs. The newly engineered darobactin 22 binds more tightly to BamA and outperforms the favorable activity profile of D9 against clinically relevant pathogens such as carbapenem‐resistant Acinetobacter baumannii up to 32‐fold, without observing toxic effects. [ABSTRACT FROM AUTHOR]

Radical addition to dehydroalanine (Dha) represents an appealing, modular strategy to access non‐canonical peptide analogues for drug discovery. Prior studies on radical addition to the Dha residue of peptides and proteins have demonstrated outstanding functional group compatibility, but the lack of stereoselectivity has limited the synthetic utility of this approach. Herein, we address this challenge by employing chiral nickel catalysts to control the stereoselectivity of radical addition to Dha on oligopeptides. The conditions accommodate a variety of primary and secondary electrophiles to introduce polyethylene glycol, biotin, halo‐tag, and hydrophobic and hydrophilic side chains to the peptide. The reaction features catalyst control to largely override substrate‐based control of stereochemical outcome for modification of short peptides. We anticipate that the discovery of chiral nickel complexes that confer catalyst control will allow rapid, late‐stage modification of peptides featuring nonnatural sidechains. [ABSTRACT FROM AUTHOR]

The glycosylative modification of peptides could improve the pharmacological properties of peptide drugs and deliver them efficiently to the target sites. Compared with O‐/N‐glycosides, C‐glycosides exhibit more metabolic stability. We here disclose the first example of visible‐light‐promoted and Cu‐catalyzed stereoselective C‐glycosylation. The mild reaction conditions are compatible with various carbohydrate substrates, as demonstrated with a series of monosaccharides and a disaccharide, and are amenable to the synthesis of a wide variety of C‐glycoamino acids and C‐glycopeptidomimetics with good yields and excellent stereoselectivities. The dual‐functional photocatalyst formed in situ via coordination of the glycine derivative and the chiral phosphine Cu complex could not only catalyze the photoredox process but also control the stereoselectivity of the glycosylation reaction. [ABSTRACT FROM AUTHOR]

Therapeutic peptides have been widely concerned, but their efficacy is limited by the inability to penetrate cell membranes, which is a key bottleneck in peptide drugs delivery. Herein, an in vivo self‐assembly strategy is developed to induce phase separation of cell membrane that improves the peptide drugs internalization. A phosphopeptide KYp is synthesized, containing an anticancer peptide [KLAKLAK]2 (K) and a responsive moiety phosphorylated Y (Yp). After interacting with alkaline phosphatase (ALP), KYp can be dephosphorylated and self‐assembles in situ, which induces the aggregation of ALP and the protein‐lipid phase separation on cell membrane. Consequently, KYp internalization is 2‐fold enhanced compared to non‐responsive peptide, and IC50 value of KYp is approximately 5 times lower than that of free peptide. Therefore, the in vivo self‐assembly induced phase separation on cell membrane promises a new strategy to improve the drug delivery efficacy in cancer therapy. [ABSTRACT FROM AUTHOR]

Efficient optimization of a peptide lead into a drug candidate frequently needs further transformation to augment properties such as bioavailability. Among the different options, foldamers, which are sequence‐based oligomers with precise folded conformation, have emerged as a promising technology. We introduce oligourea foldamers to reduce the peptide character of inhibitors of protein–protein interactions (PPI). However, the precise design of such mimics is currently limited by the lack of structural information on how these foldamers adapt to protein surfaces. We report a collection of X‐ray structures of peptide–oligourea hybrids in complex with ubiquitin ligase MDM2 and vitamin D receptor and show how such hybrid oligomers can be designed to bind with high affinity to protein targets. This work should enable the generation of more effective foldamer‐based disruptors of PPIs in the context of peptide lead optimization. [ABSTRACT FROM AUTHOR]

Large macrocyclic peptides can achieve surprisingly high membrane permeability, although the properties that govern permeability in this chemical space are only beginning to come into focus. We generated two libraries of cyclic decapeptides with stable cross‐β conformations, and found that peptoid substitutions within the β‐turns of the macrocycle preserved the rigidity of the parent scaffold, whereas peptoid substitutions in the opposing β‐strands led to "chameleonic" species that were rigid in nonpolar media but highly flexible in water. Both rigid and chameleonic compounds showed high permeability over a wide lipophilicity range, with peak permeabilities differing significantly depending on scaffold rigidity. Our findings indicate that modulating lipophilicity can be used to engineer favorable ADME properties into both rigid and flexible macrocyclic peptides, and that scaffold rigidity can be used to tune optimal lipophilicity. [ABSTRACT FROM AUTHOR]

The late‐stage functionalization (LSF) of peptides represents a valuable strategy for the design of potent peptide pharmaceuticals by enabling rapid exploration of chemical diversity and offering novel opportunities for peptide conjugation. While the C(sp2)−H activation of tryptophan (Trp) is well documented, the resurgence of radical chemistry is opening new avenues for the C−H functionalization of other aromatic side‐chains. Herein, we report the first example of LSF at C2 of histidine (His) utilizing a broad scope of aliphatic sulfinate salts as radical precursors. In this work, the exquisite selectivity for histidine functionalization was demonstrated through the alkylation of complex unprotected peptides in aqueous media. Finally, this methodology was extended for the installation of a ketone handle, providing an unprecedented anchor for selective oxime/hydrazone conjugation at histidine. [ABSTRACT FROM AUTHOR]

Loops at protein–protein interfaces are a rich source of peptide leads that have high specificity and low toxicity. Although such peptides typically need to be constrained to overcome thermodynamic and metabolic limitations, design guidelines to obtain a successfully constrained peptides, and thus facilitate the transition from loop to drug, are relatively poorly formulated. In this work, we surveyed the structures of interface loops and found the position of the terminal residues to be a key determinant of conformation. We used this knowledge to improve the process of molecular grafting, a valuable approach for constraining and stabilising peptides by fusing them to a suitable scaffold. We show that an informed choice of where a loop is "anchored" to a scaffold improves its form and function. This knowledge can help guide the choice of loop and its matching scaffold, and thus increase the success rate for designing stable and potent peptide drug leads. [ABSTRACT FROM AUTHOR]

Antibody-drug conjugates (ADCs) offer increased efficacy and reduced toxicity compared to systemic chemotherapy. Less attention has been paid to peptide-drug delivery, which has the potential for increased tumor penetration and facile synthesis. We report a knottin peptide-drug conjugate (KDC) and demonstrate that it can selectively deliver gemcitabine to malignant cells expressing tumor-associated integrins. This KDC binds to tumor cells with low-nanomolar affinity, is internalized by an integrin-mediated process, releases its payload intracellularly, and is a highly potent inhibitor of brain, breast, ovarian, and pancreatic cancer cell lines. Notably, these features enable this KDC to bypass a gemcitabine-resistance mechanism found in pancreatic cancer cells. This work expands the therapeutic relevance of knottin peptides to include targeted drug delivery, and further motivates efforts to expand the drug-conjugate toolkit to include non-antibody protein scaffolds. [ABSTRACT FROM AUTHOR]

Animal venoms represent a rich source of pharmacologically active peptides that interact with ion channels. However, a challenge to discovering drugs remains because of the slow pace at which venom peptides are discovered and refined. An efficient autocrine-based high-throughput selection system was developed to discover and refine venom peptides that target ion channels. The utility of this system was demonstrated by the discovery of novel Kv1.3 channel blockers from a natural venom peptide library that was formatted for autocrine-based selection. We also engineered a Kv1.3 blocker peptide (ShK) derived from sea anemone to generate a subtype-selective Kv1.3 blocker with a long half-life in vivo. [ABSTRACT FROM AUTHOR]

α-Conotoxins are disulfide-rich peptides that target nicotinic acetylcholine receptors. Recently we identified several α-conotoxins that also modulate voltage-gated calcium channels by acting as G protein-coupled GABAB receptor (GABABR) agonists. These α-conotoxins are promising drug leads for the treatment of chronic pain. To elucidate the diversity of α-conotoxins that act through this mechanism, we synthesized and characterized a set of peptides with homology to α-conotoxins known to inhibit high voltage-activated calcium channels via GABABR activation. Remarkably, all disulfide isomers of the active α-conotoxins Pu1.2 and Pn1.2, and the previously studied Vc1.1 showed similar levels of biological activity. Structure determination by NMR spectroscopy helped us identify a simplified biologically active eight residue peptide motif containing a single disulfide bond that is an excellent lead molecule for developing a new generation of analgesic peptide drugs. [ABSTRACT FROM AUTHOR]

Although peptide-based therapeutics are finding increasing application in the clinic, extensive structural modification is typically required to prevent their rapid degradation by proteases in the blood. We have evaluated the ability of erythrocytes to serve as reservoirs, protective shields (against proteases), and light-triggered launch pads for peptides. We designed lipidated peptides that are anchored to the surface of red blood cells, which furnishes a protease-resistant environment. A photocleavable moiety is inserted between the lipid anchor and the peptide backbone, thereby enabling light-triggered peptide release from erythrocytes. We have shown that a cell-permeable peptide, a hormone (melanocyte stimulating hormone), and a blood-clotting agent can be anchored to erythrocytes, protected from proteases, and photolytically released to create the desired biological effect. [ABSTRACT FROM AUTHOR]

Bioinspired tryptophan-rich peptide dendrimers (TRPDs) are designed as a new type of dendritic peptide drugs for efficient tumor therapy. The TRPDs feature a precise molecular structure and excellent water solubility and are obtained in a facile process. Based on the unique features of peptide dendrimers, including highly branched structures, abundant terminal groups, and globular-protein-like architectures, the therapeutic dendrimers show significant supramolecular interactions with DNA through the tryptophan residues (indole rings and amino groups). Further experimental results indicate that TRPDs are efficient antitumor agents both in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Conjugation to human serum albumin (HSA) has emerged as a powerful approach for extending the in vivo half-life of many small molecule and peptide/protein drugs. Current HSA conjugation strategies, however, can often yield heterogeneous mixtures with inadequate pharmacokinetics, low efficacies, and variable safety profiles. Here, we designed and synthesized analogues of TAK-242, a small molecule inhibitor of Toll-like receptor 4, that primarily reacted with a single lysine residue of HSA. These TAK-242-based cyclohexene compounds demonstrated robust reactivity, and Lys64 was identified as the primary conjugation site. A bivalent HSA conjugate was also prepared in a site-specific manner. Additionally, HSA-cyclohexene conjugates maintained higher levels of stability both in human plasma and in mice than the corresponding maleimide conjugates. This new conjugation strategy promises to broadly enhance the performance of HSA conjugates for numerous applications. [ABSTRACT FROM AUTHOR]

Cyclic disulfide-rich peptides have exceptional stability and are promising frameworks for drug design. We were interested in obtaining X-ray structures of these peptides to assist in drug design applications, but disulfide-rich peptides can be notoriously difficult to crystallize. To overcome this limitation, we chemically synthesized the L- and D-forms of three prototypic cyclic disulfide-rich peptides: SFTI-1 (14-mer with one disulfide bond), cVc1.1 (22-mer with two disulfide bonds), and kB1 (29-mer with three disulfide bonds) for racemic crystallization studies. Facile crystal formation occurred from a racemic mixture of each peptide, giving structures solved at resolutions from 1.25 Å to 1.9 Å. Additionally, we obtained the quasi-racemic structures of two mutants of kB1, [G6A]kB1, and [V25A]kB1, which were solved at a resolution of 1.25 Å and 2.3 Å, respectively. The racemic crystallography approach appears to have broad utility in the structural biology of cyclic peptides. [ABSTRACT FROM AUTHOR]

The cover page of the journal "Angewandte Chemie," is presented.

The inside back cover of the volume 54, number 14 issue of the journal "Angewandte Chemie International Edition" is presented.