Search Results (744)

Peptide therapeutics have emerged as a versatile class of biomolecules bridging the gap between small-molecule drugs and large biologics. Advantages of such molecules include high target specificity, potent bioactivity and reduced off-target toxicity. Despite these, broader clinical translation remains constrained by inherent limitations like poor metabolic stability, rapid renal clearance, limited membrane permeability and scalable synthesis. This review aims to systematically integrate advances in peptide science across natural discovery, synthetic methodologies, structural engineering, and translational delivery systems, while identifying critical research gaps hindering clinical adoption. We highlight diverse natural sources of bioactive peptides, including plant- (lunasin), animal- (Val-Pro-Pro (VPP) and Ile-Pro-Pro (IPP)), microbial- (nisin and cyclosporine), marine- (dolastatins) and venom-derived (chlorotoxin and ω-conotoxin MVIIA (ziconotide)) agents. Advances in solid-phase peptide synthesis (SPPS), green chemistry, and catalytic strategies are discussed alongside emerging in silico approaches, including artificial intelligence-driven sequence design and molecular modeling. Structural modifications such as cyclization, hydrocarbon stapling, PEGylation, and lipidation are critically evaluated for their role in enhancing pharmacokinetic and pharmacodynamic properties. Furthermore, nanoformulation strategies, including self-assembling peptides and cell-penetrating systems, are examined for their potential to overcome biological barriers. Importantly, this review identifies key unresolved challenges, including the lack of predictive models for peptide delivery systems, safety concerns associated with long-term modifications, and limited in vivo validation of naturally derived peptides. Addressing these gaps through integrated computational and experimental approaches will be essential for advancing next-generation peptide therapeutics. Collectively, this work provides a comprehensive framework for the rational design and translation of peptide-based precision medicines. Full article

Traumatic brain injury (TBI) is a prevalent neurological disorder that induces severe neurological dysfunction and markedly reduces quality of life owing to its complex pathophysiology and limited therapeutic options. Conventional pharmacological and surgical interventions show restricted efficacy because of poor blood–brain barrier penetration and inability to address secondary injury cascades. In recent years, hydrogels have shown significant potential for TBI repair due to their superior biocompatibility, high water content, and ability to mimic the native extracellular matrix (ECM). This review systematically examines recent advances in hydrogel applications for TBI therapy, focusing on their roles as drug delivery platforms, stem cell scaffolds, neuroregeneration promoters, inflammation modulators, and angiogenesis facilitators. Particular emphasis is placed on the therapeutic benefits and underlying mechanisms of ECM-derived hydrogels, self-assembling peptide (SAP) hydrogels, stimuli-responsive smart hydrogels, and functionalized multicomponent systems. Current challenges and limitations in hydrogel applications are also discussed, along with future research directions, to provide scientific rationale and practical guidance for precision TBI therapy. Full article

Dpep is a cell-penetrating peptide that targets transcription factors ATF5, CEBPB and CEBPD to selectively suppress growth and survival of diverse tumor cell types in vitro and in vivo. Due to these actions and its apparent safety, the peptide has potential as a cancer therapeutic. How Dpep might be combined with other anti-cancer agents to achieve synergistic efficacy and to overcome possible peptide resistance has not been assessed in depth. Based on prior work indicating that Dpep promotes apoptotic cancer cell death and up-regulates multiple pro-apoptotic and tumor suppressor genes, we studied combinations of Dpep with ABT-263, a pro-apoptotic BCL2 family inhibitor, and decitabine, a hypomethylating drug. Combining Dpep with each agent alone or together synergistically suppressed the growth of a range of solid and liquid tumor cell types. Moreover, the combinations synergistically inhibited the growth of cells lines that were selected either in vivo or in vitro for Dpep resistance. Finally, we tested the combination of Dpep with ABT-263 in a mouse melanoma xenograft model. The combination more effectively inhibited tumor growth than either agent alone and, in contrast to vehicle or ABT-263, produced a 40% durable survival rate. Taken together, these observations highlight potential drug partners for the therapeutic development of Dpep. Full article

Background/Objectives: Longer oligoarginines are very effective cell-penetrating peptides. It has been shown that a minimal number of positively charged side chains is necessary for efficient cellular uptake. But a highly positively charged peptide may interact with its cargo molecule, thereby reducing its efficiency. Several chemical modifications were tested to improve the internalization of short tetraarginine derivatives. Aromatic groups, such as Dabcyl at the N-terminus, Trp in the sequence, and AMBA or PABA in the backbone, were used to improve internalization. The other useful modification was the aza-glycine substitution in the case of penetratin. Methods: In this study, the effect of aza-glycine insertion into the peptide Dabcyl-RRRRK(Cf) on internalization was studied and compared with that of the Trp-modified peptide Dabcyl-RRWRRK(Cf). To explain the noticed difference in the biological activity of peptides, DFT calculations and the prediction of membrane-binding free energy (ΔΔF) from a peptide sequence were performed. Results: It turned out that the position of the aza-glycine moiety does not have an influence on the cellular uptake. The aza-glycine-containing peptide showed higher internalization than the Dabcyl-RRRRK(Cf) peptide. Besides this, these peptides have similar or higher cellular uptake than that of octaarginine at lower concentrations (c < 2 µM). The aza-glycine affected not only cellular uptake but also the entry mechanism. The structure of peptides depended on the amino acids (Trp, Gly, or azaGly) in their sequences and their positions. Conclusions: These may result in the different amphiphilicity of peptides, and thus changes in the hydrophobic moment and in the binding affinity of peptides to the negatively charged membrane surface. Full article

Background/Objectives: Investigating the modified derivatives of known cell-penetrating peptides can highlight the important residues in the peptide sequence and help understand the cellular uptake mechanism better. Moreover, comparing peptides with different fluorescent-dye positions can highlight the importance of the conjugation site. Earlier, it was demonstrated that the fluorescence quencher 4-((4-(dimethylamino)phenyl)azo)benzoyl (Dabcyl) group can enhance the internalization efficiency of highly cationic oligoarginine peptides. However, its effect in the case of arginine-rich penetratin, a secondary amphipathic cationic CPP, remains undiscovered. Methods: Here, several penetratin derivatives were studied in which the aromatic residues were substituted and the effect of Dabcyl modification was also studied on the cellular uptake of peptides by flow cytometry. Results: The triple Nal-substituted penetratin and dodeca-penetratin with N-terminally positioned carboxyfluoresein (Cf) dye demonstrated remarkable internalization efficiency compared to penetratin. Moreover, almost all the Dabcyl-modified peptides were superior to penetratin except two peptides with C-terminal Cf-labelling. This result highlights the importance of the structure of the conjugate. The position of the cargo molecule may have a high impact on internalization ability. The relatively low cellular uptake of the Trp48 residue-substituted Dabcyl-Pen12 points to the importance of this residue in the cellular uptake of dodeca-penetratin. The confocal microscopic studies revealed that, besides the greater penetration efficiency of Dabcyl penetratin derivatives, these peptides enter the cytoplasm of cells in an increased manner. Conclusions: We identified several intriguing derivatives and expanded the applicability of Dabcyl, while also highlighting its limitations. Additionally, the critical role of Trp48 in the penetratin sequence was reaffirmed, along with the importance of the fluorescent molecule’s position. Full article

Peptide therapeutics occupy a unique chemical space between small molecules and biologics, combining high target specificity with structural programmability and favorable safety profiles. Recent regulatory approvals and expanding clinical pipelines underscore the growing therapeutic and commercial relevance of peptide-based drugs. This review outlines chemical modification approaches and contemporary design strategies, and evaluates their impact on proteolytic stability, pharmacokinetics, membrane permeability, and target engagement. We then highlight recent advances in artificial intelligence (AI)-guided peptide drug design, including machine learning models, protein language models, and generative architectures that enable high-throughput activity prediction, property optimization, and de novo sequence generation. These approaches collectively accelerate the traditional discovery–design–validation cycle while reducing experimental attrition through data-driven, structure-informed modeling frameworks. Among these applications, AI also enables the rational design of cell-penetrating peptides (CPPs) to enhance intracellular delivery and biological activity. Building on these methodological advances, we further examine their application to peptide therapeutics, with particular emphasis on AI-based predictive models for CPPs as well as on therapeutic applications within the central nervous and pulmonary systems. We conclude by outlining future perspectives and emphasize that the systematic integration of AI-enabled sequence design with rational chemical engineering and advanced delivery technologies, supported by rigorous experimental validation, will be critical for developing robust and clinically durable peptide-based medicines. Full article

Cell-penetrating peptide (CPP) conjugation represents a promising strategy for enhancing the biological activity of therapeutic peptides. In this study, three analogues were designed by conjugating the trypsin inhibitory loop (TIL) derived from a Bowman–Birk-type inhibitor with the transactivator of transcription (TAT) peptide to improve their bioactivity. All TAT-TIL conjugates exhibited significantly enhanced antimicrobial activity compared with the parent peptide. Notably, the analogue containing a glycine linker (-GG-) showed further improvement in antiproliferative activity against cancer cells, indicating the potential role of linker design in optimizing peptide function. All analogues exhibited low hemolytic activity at the highest tested concentrations, although increased cytotoxicity toward normal HaCaT cells was observed, suggesting the need for further optimization of selectivity. Interestingly, comparable antimicrobial activities were observed regardless of protease inhibitory capacity, indicating that protease inhibition is not essential for the enhanced biological effects. Overall, TAT conjugation significantly improves the biological activity of Bowman–Birk-type inhibitor-derived peptides, and the incorporation of a glycine linker further enhances their functional properties. These findings support CPP-mediated peptide modification as an effective strategy for developing potential antimicrobial and anticancer peptide candidates. Full article

Anticancer peptides (ACPs) offer a promising alternative to conventional chemotherapy but face challenges, including poor selectivity, limited tumor penetration, low cellular uptake, and rapid degradation in serum. To address these barriers, we developed synthetic mRNAs encoding chimeric ACPs designed for enhanced intracellular delivery and activity. mRNAs for constructs SAK6L9AS(1X), SAK6L9AS(4X), and WTAS-K6L9(4X) were transcribed in vitro and tested against 4T1 breast cancer cells. Cytotoxicity was assessed by cell confluence and MTT assays, while apoptosis was evaluated using caspase 3/7 activation, PI staining, and Annexin V flow cytometry. Our results demonstrate that all SAK6L9AS variants induced robust apoptosis and cellular toxicity in 4T1 cells. Importantly, this work provides the first demonstration of intracellular expression of an mRNA-encoded ACP fused to a cell-penetrating peptide, thereby validating a modular platform for RNA-based delivery of anticancer agents. This study highlights the feasibility of mRNA-encoded peptide therapeutics as a scalable and customizable strategy for cancer treatment. By combining the advantages of mRNA delivery with rational peptide design, ACP chimeras can be expressed directly inside tumor cells, overcoming the limitations of exogenous peptide administration. Our findings support further development of synthetic mRNA therapeutics to generate potent, selective anticancer peptides with reduced systemic toxicity and improved translational potential. Full article

Adeno-associated viruses (AAVs) are a promising gene therapy technology, but major technical challenges remain. One problem is that commonly used AAVs have a low efficiency in penetrating the blood–brain barrier (BBB) and the blood–retina barrier (BRB). Consequently, gene delivery to the nervous system has limitations. Another problem is that AAVs induce immune reactions that cause serious side effects. To avoid immune reactions, the AAV dose must be reduced to lower levels that may result in insufficient gene delivery. Researchers have been modifying viral capsid protein sequences and searching for effective peptide sequences to solve these problems. As a result, Cell-Penetrating Penta-Peptides (CPP5s) have been shown to be effective in improving the BBB/BRB penetration of AAVs and suppressing immune reactions against AAVs. CPP5s were originally developed from peptide sequences of the Bax (a pro-apoptotic protein) binding domain of Ku70 (a DNA repair protein) and from negative control cell-penetrating peptides without Bax-binding activity. This article will discuss the background science of CPP5s and future directions of CPP5s for AAV-mediated gene delivery to the nervous system as well as other organs. Full article

The appearance of antibiotic-resistant strains of Helicobacter pylori (H. pylori) is leading to a decreased eradication rate of H. pylori infection. There is an urgent need to find new agents with antimicrobial mechanisms different from those of antibiotics, with therapeutic potential to clear colonization of H. pylori in the stomach. Some antimicrobial peptides (AMPs) possess bactericidal activity by enhancing the permeability of the outer membrane and damaging the integrity of the cell membrane. Bacteria are not susceptible to drug resistance through this antimicrobial mechanism. In this study, 28 short peptides containing 12 amino acid residues were designed based on nine amino acid fragments (KRIVQRIKD) from human cathelicidin LL-37, which is stable in gastric juice, and 3 amino acids were added at the C-terminus of the peptide. These designed peptides were not digested and degraded by pepsin at low pH values. The peptides were predicted using the online tool platform. Then, the strongest antimicrobial peptide, named SAMP-12aa (KRIVQRIKDVIR), was screened from 28 short peptides. Further studies found that SAMP-12aa retained anti-H. pylori activity after incubation in simulated gastric juice. The MIC and MBC of SAMP-12aa were 8 μg/mL and 32 μg/mL, respectively. SAMP-12aa showed good bactericidal kinetics. SAMP-12aa was found to have cell selectivity, penetrating and damaging bacterial cell membranes and exhibiting almost no toxicity to human cells at a relatively high concentration (128 μg/mL). Regulatory T (Treg) cells express CD25^High with immunosuppressive activity that induces immune tolerance in response to H. pylori. Molecular docking prediction revealed that SAMP-12aa could target the active center of Foxp3. Flow cytometry analysis revealed that SAMP-12aa can inhibit Foxp3 activity and downregulate CD25 protein expression on CD4⁺ T cells, thereby reducing the development and differentiation of CD4⁺Foxp3⁺CD25^High Treg cells with immunosuppressive effects. Further research revealed that the levels of the cytokine interferon-γ (IFN-γ), which activates CD8⁺ T-cell activity, were significantly elevated, and the levels of transforming growth factor-β (TGF-β), which inhibits CD8⁺ T-cell activity, were significantly reduced. The results of this study reveal that SAMP-12aa not only possesses antibacterial activity but also has immunomodulatory effects. Full article

Drug repurposing in oncology is often framed as a drug–target matching exercise, yet many candidates with plausible biological rationales fail in the clinic. In solid tumors, therapeutic outcomes are constrained not only by pharmacological target relevance but also by limited tumor accessibility, heterogeneous intratumoral exposure, loss of context-dependent activity, and dose-limiting systemic toxicity. This perspective argues that repurposing strategies should treat exposure engineering as a design principle alongside molecular selectivity. Peptides that bind cell- or matrix-associated molecules at the tumor site have the potential to implement spatial, temporal, and subcellular control over where and when a drug engages its pharmacological target, thereby enabling confinement of polypharmacology to tumor contexts. Mechanistic modes of peptide-enabled exposure selectivity (homing, anchoring/retention, conditional activation, penetration enhancement, and subcellular biasing), key failure modes, and translational constraints are discussed, together with an exposure-centric screening workflow to prioritize repurposed agents most amenable to peptide-guided rescue. Emphasizing the combination of exposure control and the addressing-element layer clarifies when and how pharmacologically promiscuous drugs may be repurposed safely and effectively. Full article

Skeletal muscle is the largest metabolic demanding organ in human body. Alterations of skeletal muscle in shape and size significantly affect its biological functions. Botulinum neurotoxin type A1 (BoNT/A1) has been successfully used in clinics to treat masseter, trapezius and gastrocnemius hypertrophy. Here, we used a healthy rat-based skeletal muscle hypertrophy model to evaluate the muscle-reducing activity of recombinant BoNT/A1 (rBoNT/A1) with genetically fused cell-penetrating peptides (CPPs), which was previously reported to increase the cellular uptake of BoNT/A1. Analyses of treated muscle sections using hematoxylin–eosin and immunofluorescence staining showed that both wild-type rBoNT/A1 without modification (WT-rBoNT/A1) and rBoNT/A1 with CPP fusion (CPP-rBoNT/A1) could induce myocomma atrophy and altered gastrocnemius muscle fiber proportions as a result of denervation and reinnervation. Importantly, rBoNT/A1 with the fusion of a specific CPP, zinc finger protein (ZFP), resulted in the highest degree of muscle atrophy and greatest increase in the ratio of type I muscle fibers over type II fibers. An examination of gastrocnemius muscle cells at the subcellular levels using TEM staining revealed swelled mitochondria and diminished mitochondrial crista upon rBoNT/A1 administration. Transcriptomic RNA sequencing (RNA-Seq) analysis followed by RT-qPCR validation showed that rBoNT/A1 treatment also caused changes in mitochondrial biogenesis and mitophagy. Collectively, our results demonstrated that rBoNT/A1 proteins could alleviate skeletal muscle hypertrophy, with associated alterations of mitochondrial homeostasis. Full article

BNCT (Boron Neutron Capture Therapy) is a binary radiotherapeutic modality in which high LET (Linear Energy Transfer) particles are generated from ¹⁰B(n,α)⁷Li reaction, ideally within boron-loaded tumour cells, so the therapeutic outcome depends critically on the pharmacokinetics and biodistribution of boron carriers. In this review, boron-containing agents for BNCT, with a focus on ADMET (absorption, distribution, metabolism, excretion and toxicity) and model-informed design, were examined. Low-MW (low-molecular-weight) compounds, peptide conjugates, polymeric and nanostructured platforms and cell-based vectors were surveyed and how physicochemical properties, transporter engagement and nano–bio interactions govern tumour uptake, subcellular localisation and normal tissue exposure were discussed. A shift from maximising boron content towards optimising exposure profiles using PET (Positron Emission Tomography), PBK (physiologically based pharmacokinetic) modelling and in silico ADMET tools to define irradiation windows was also discussed. Classical agents such as BPA (Boronophenylalanine) and BSH (Sodium Borocaptate) are contrasted with newer polymeric and metallacarborane-based carriers, with attention to brain penetration, endosomal escape, linker stability, biodegradation and elimination routes, as well as platform-specific toxicities. Incontestably, further progress in BNCT will highly depend on integrating imaging-derived kinetics with PBPK-informed dose planning and engineering subcellularly precise yet degradable carriers, and that ADMET-guided design and spatiotemporal coordination are central to achieving reproducible clinical benefit from BNCT’s spatial selectivity. Full article

Glioblastoma, with a 5-year survival rate of just under 7.0%, is the most common form of brain cancer in adults. In this study, we evaluated the antiproliferative activity of the biopolymer p21-ELP1-Bac, a p21-derived peptide delivered via an elastin-like polypeptide (ELP1) carrier and a cell-penetrating peptide (CPP), across three glioblastoma cell lines: U87, GBM43, and GBM6. We assessed proliferation, cell cycle progression, and apoptosis to determine whether ELP-mediated intracellular delivery of p21-ELP1-Bac suppresses glioblastoma growth through cytostatic mechanisms rather than inducing apoptosis. Treatment with the modified protein effectively inhibited proliferation across all three lines, with U87 cells showing the greatest sensitivity and GBM6 cells demonstrating the greatest drug tolerance. Although apoptotic responses were generally low, they appeared more pronounced in GBM6 cells. Confocal microscopy revealed sustained cellular uptake and signal observed in both the cytoplasm and in proximity to the nucleus in all cell lines. Collectively, these findings indicate that p21-ELP1-Bac is efficiently internalized and capable of modulating proliferation across all three glioblastoma cell lines, supporting its further evaluation as a cytostatic delivery platform. Full article

The global rise in antimicrobial resistance (AMR) demands innovative strategies beyond traditional antibiotics. Peptide Nucleic Acids (PNAs), synthetic DNA analogues with peptide-like backbones, act as thermically, chemically, and enzymatically stable sequence-specific agents capable of silencing essential bacterial genes. Through antisense mechanisms, PNAs bind bacterial mRNA or rRNA, blocking translation or ribosome assembly and thereby inducing species-specific growth inhibition. Their programmable design enables precise targeting of multidrug-resistant pathogens while sparing commensal microbiota. Recent advances, including γ-modified backbones, cationic substitutions, and delivery platforms such as cell-penetrating peptides (CPPs), dendron conjugates, and nanoparticles, have improved solubility, stability, and cellular uptake. Studies show promising in vitro and, albeit less frequently, in vivo efficacy against both Gram-positive and Gram-negative bacteria, often with synergistic activity when combined with conventional antibiotics. Although challenges remain in delivery and large-scale production, PNAs represent a promising class of antimicrobials to combat AMR through targeted gene inhibition. Full article