Peptide-Drug Conjugates and Their Targets in Advanced Cancer Therapies

Metabolite characterisation of the peptide-drug conjugate LN005 in liver S9s by UHPLC-Orbitrap-HRMS

LN005 is a peptide-drug conjugate (PDC) targeting glucose-regulated protein 78 (GRP78) to treat several types of cancer, such as breast, colon, and prostate cancer.As a new drug modality, understanding its metabolism and elimination pathways will help us to have a whole picture of it. Currently, there are no metabolic studies on LN005; therefore, this study aimed to investigate the metabolism of LN005, clarify its metabolic profile in the liver S9s of different species, and identify the major metabolic pathways and differences between species.The incubation samples were measured by ultra-high performance liquid chromatography combined with orbitrap tandem mass spectrometry (UHPLC-Orbitrap-HRMS).The results showed that LN005 was metabolised by liver S9s, and four metabolites were identified. The main metabolic pathway of LN005 in liver S9s was oxidative deamination to ketone or hydrolysis. Similar metabolic profiles were observed in mouse, rat, dog, monkey, and human liver S9s, indicating no differences between these four animal species and humans.This study provides information for the structural modification and optimisation of LN005 and affords a reference for subsequent animal experiments and human metabolism of other PDCs.

Material and Design Toolkit for Drug Delivery: State of the Art, Trends, and Challenges

The nanomaterial and related toolkit have promising applications for improving human health and well-being. Nanobased drug delivery systems use nanoscale materials as carriers to deliver therapeutic agents in a targeted and controlled manner, and they have shown potential to address issues associated with conventional drug delivery systems. They offer benefits for treating various illnesses by encapsulating or conjugating biological agents, chemotherapeutic drugs, and immunotherapeutic agents. The potential applications of this technology are vast; however, significant challenges exist to overcome such as safety issues, toxicity, efficacy, and insufficient capacity. This article discusses the latest developments in drug delivery systems, including drug release mechanisms, material toolkits, related design molecules, and parameters. The concluding section examines the limitations and provides insights into future possibilities.

Nectin-4 has emerged as a compelling target for breast cancer

The incidence of breast cancer in women has increased year by year, becoming one of the most common malignant tumors in females worldwide. Most patients can be treated with surgery and endocrine drugs, but there are still some patients who lack effective treatment, such as triple-negative breast cancer (TNBC). Nectin-4, a protein encoded by poliovirus receptor-associated protein 4, is a Ca2+-independent immunoglobulin-like protein. It is mainly involved in the adhesion between cells. In recent years, studies have found that Nectin-4 is overexpressed in breast cancer and several other malignancies. Otherwise, several monoclonal antibodies and inhibitors targeting Nectin-4 have shown prosperous outcomes, so Nectin-4 has great potential to be a therapeutic target for breast cancer. The present review systematically describes the significance of Nectin-4 in each aspect of breast cancer, as well as the molecular mechanisms of these aspects mediated by Nectin-4. We further highlight ongoing or proposed therapeutic strategies for breast cancer specific to Nectin-4.

Podophyllotoxin-loaded PEGylated E-selectin peptide conjugate targeted cancer site to enhance tumor inhibition and reduce side effect

E-selectin, which is highly expressed in vascular endothelial cells near tumor and get involved in the all tumor growth steps: occurrence, proliferation and metastasis, is considered as a promise targeted protein for antitumor drug discovery. Herein, we would like to report the design, preparation and the anticancer evaluation of the peptide-PEG-podophyllotoxin conjugate(PEG-Pep-PODO), in which the short peptide (CIELLQAR) was used as the E-selectin ligand for the targeting purpose and the PEG portion the molecule got the conjugate self-assembled to form a water soluble nanoparticle. In vitro release study showed that the conjugated and entrapped PODO could be released simultaneously in the presence of GSH (highly expressed in tumor environmental conditions) and the GSH would catalyze the break of the disufur bond which linked of the PODO and the peptide-PEG portion of the conjugate. Cell adhesion test of the PEG-Pep-PODO indicated that E-selectin ligand peptide CIELLQAR could get specifically and efficiently binding to the E-selectin expressing human umbilical vein endothelial cells (HUVEC). In vitro cytotoxicity assay further revealed that PEG-Pep-PODO significantly improved the selectivity of PEG-Pep-PODO for killing the tumor cells and normal cells compared with PODO solution formulation. More importantly, the in vivo experiment demonstrated that the conjugate would accumulate of the PODO payload in tumor through targeting endothelial cells in the tumor microenvironment, which resulted in the much improved in vivo inhibition of tumor growth, intratumoral microvessel density, and decreased systemic toxicity of this nanoparticle over the free PODO. Furthermore, this water soluble conjugate greatly improved the pharmacokinetic properties of the mother molecule.

Colorectal cancer cell exosome and cytoplasmic membrane for homotypic delivery of therapeutic molecules

Colorectal cancer (CRC) is one of the most common causes of death in the world. The multi-drug resistance, especially in metastatic colorectal cancer, drives the development of new strategies that secure a positive outcome and reduce undesirable side effects. Nanotechnology has made an impact in addressing some pharmacokinetic and safety issues related to administration of free therapeutic agents. However, demands of managing complex biointerfacing require equally complex methods for introducing stimuli-responsive or targeting elements. In order to procure a more efficient solution to the overcoming of biological barriers, the physiological functions of cancer cell plasma and exosomal membranes provided the source of highly functionalized coatings. Biomimetic nanovehicles based on colorectal cancer (CRC) membranes imparted enhanced biological compatibility, immune escape and protection to diverse classes of therapeutic molecules. When loaded with therapeutic load or used as a coating for other therapeutic nanovehicles, they provide highly efficient and selective cell targeting and uptake. This review presents a detailed overview of the recent application of homotypic biomimetic nanovehicles in the management of CRC. We also address some of the current possibilities and challenges associated with the CRC membrane biomimetics.

A shift in focus towards precision oncology, driven by revolutionary nanodiagnostics; revealing mysterious pathways in colorectal carcinogenesis

Multiple molecular mechanisms contribute to the development of colorectal cancer (CRC), with chromosomal instability (CIN) playing a significant role. CRC is influenced by mutations in several important genes, including APC, TP53, KRAS, PIK3CA, BRAF, and SMYD4. The three molecular subtypes of this disease are CIN, MSI-H, and CIMP (CpG-island phenotype). p53 dysfunction and aberrant Wnt signalling are common characteristics of CRC carcinogenesis. Despite advances in conventional therapy, metastatic CRC remains difficult to treat due to toxicity and resistance. Theranostics for cancer could significantly benefit from nanotechnology, as it would enable more targeted, individualised care with fewer side effects. Utilising functionalized nanoparticles has enabled MRI-guided gene therapy, magnetic hyperthermia, chemotherapy, immunotherapy, and photothermal/photodynamic therapy, thereby radically modifying the way cancer is treated. Active targeting using ligands or peptides on nanoparticles improves the delivery of drugs to cancer cells. Nanostructures such as drug peptide conjugates, chitosan nanoparticles, gold nanoparticles, carbon nanotubes, mesoporous silica-based nanoparticles, silver nanoparticles, hybrid lipid-polymer nanoparticles, iron oxide nanoparticles, and quantum dots may enable targeted drug delivery and enhanced therapeutic efficacy against CRC. Nanomedicines are presently being evaluated in clinical trials for the treatment of colorectal cancer, with the promise of more effective and individualised therapies. This article examines current nanomedicine patents for CRC, including the work of Delta-Fly, Merrimack, and Pfenning, Meaning & Partner, among others. In terms of future nanomedicine research and development, ligand production, particle size, and clearance are crucial factors. Lastly, the numerous nanostructures utilized in nanomedicine for targeted drug administration and diagnostics indicate optimistic prospects for enhancing CRC treatment. The successes of nanomedicine research and development for existing colon cancer treatments are also highlighted in this review.

Molecular View on the iRGD Peptide Binding Mechanism: Implications for Integrin Activity and Selectivity Profiles

Receptor-selective peptides are widely used as smart carriers for specific tumor-targeted delivery. A remarkable example is the cyclic nonapeptide iRGD (CRGDKPGDC, 1) that couples intrinsic cytotoxic effects with striking tumor-homing properties. These peculiar features are based on a rather complex multistep mechanism of action, where the primary event is the recognition of RGD integrins. Despite the high number of preclinical studies and the recent success of a phase I trial for the treatment of pancreatic ductal adenocarcinoma (PDAC), there is little information available about the iRGD three-dimensional (3D) structure and integrin binding properties. Here, we re-evaluate the peptide's affinity for cancer-related integrins including not only the previously known targets αvβ3 and αvβ5 but also the αvβ6 isoform, which is known to drive cell growth, migration, and invasion in many malignancies including PDAC. Furthermore, we use parallel tempering in the well-tempered ensemble (PT-WTE) metadynamics simulations to characterize the in-solution conformation of iRGD and extensive molecular dynamics calculations to fully investigate its binding mechanism to integrin partners. Finally, we provide clues for fine-tuning the peptide's potency and selectivity profile, which, in turn, may further improve its tumor-homing properties.

Peptidergic Systems as Antitumor Targets: A Right Direction to Fight Cancer?

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Improving the stability of thiol-maleimide bioconjugates via the formation of a thiazine structure

Linker stability is critically important for the efficacy and safety of peptide and protein conjugates used for biological applications. One common conjugation strategy, thiol-maleimide coupling, generates a succinimidyl thioether linker with limited stability under physiological conditions. We have shown in previous work that when a peptide with an N-terminal cysteine is conjugated to a maleimide reagent, a thiazine structure is formed via a chemical rearrangement. Our preliminary work indicated that the thiazine linker has favorable stability. Here, we report the evaluation of a thiazine linker as an alternative to the widely used succinimidyl thioether linker for thiol-maleimide bioconjugation. The stability of the thiazine conjugate in comparison to the thioether conjugate was assessed across a broad pH range. Additionally, the propensity for retro-Michael reaction and cross-reactivity with other thiols was evaluated by treating conjugates in the presence of glutathione. The studies indicated that the thiazine linker degrades markedly slower than the thioether conjugate. In addition, the thiazine linker is over 20 times less susceptible to glutathione adduct formation. The NMR study of the thiazine structure confirmed that the formation of the thiazine linker is a stereoselective process that yields a single diastereomer. In summary, we propose the use of the thiazine linker obtained by conjugation of maleimide-containing reagents with peptides or proteins presenting an N-terminal cysteine as a novel approach for bioconjugation. The advantages of this approach are the formation of a linker with a well-defined stereochemical configuration, increased stability at physiological pH, and a strongly reduced propensity for thiol exchange.

Targeted drug conjugate systems for ovarian cancer chemotherapy

Ovarian cancer is a highly lethal disease that affects women. Early diagnosis and treatment of women with early-stage disease improve the probability of survival. Unfortunately, the majority of women with ovarian cancer are diagnosed at advanced stages 3 and 4 which makes treatment challenging. While the majority of the patients respond to first-line treatment, i.e. cytoreductive surgery integrated with platinum-based chemotherapy, the rate of disease recurrence is very high and the available treatment options for recurrent disease are not curative. Thus, there is a need for more effective treatment options for ovarian cancer. Targeted drug conjugate systems have emerged as a promising therapeutic strategy for the treatment of ovarian cancer. These systems provide the opportunity to selectively deliver highly potent chemotherapeutic drugs to ovarian cancer, sparing healthy normal cells. Thus, the effectiveness of the drugs is improved and systemic toxicity is greatly reduced. In this review, different targeted drug conjugate systems that have been or are being developed for the treatment of ovarian cancer will be discussed.

Neuropeptide Y and its receptors in prostate cancer: associations with cancer invasiveness and perineural spread

PURPOSE

Neuropeptide Y (NPY) is a pleiotropic peptide, which is involved in many biological mechanisms important in regulation of cell growth and survival. The aim of this study was a comprehensive analysis of the NPY system in prostate pathology.

METHODS

The study was based on immunohistochemical analysis of NPY and its receptors, Y1R, Y2R and Y5R, in tissue samples from benign prostate (BP), primary prostate cancer (PCa) and PCa bone metastases. Tissue microarray (TMA) technique was employed, with analysis of multiple cores from each specimen. Intensity of the immunoreactivity and expression index (EI), as well as distribution of the immunostaining in neoplastic cells and stromal elements were evaluated. Perineural invasion (PNI) and extraprostatic extension (EPE) were areas of special interests. Moreover, a transwell migration assay on the LNCaP PCa cell line was used to assess the chemotactic properties of NPY.

RESULTS

Morphological analysis revealed homogeneous membrane and cytoplasmic pattern of NPY staining in cancer cells and its membrane localization with apical accentuation in BP glands. All elements of the NPY system were upregulated in pre-invasive prostate intraepithelial neoplasia, PCa and metastases. EI and staining intensity of NPY receptors were significantly higher in PCa then in BP with correlation between Y2R and Y5R. The strength of expression of the NPY system was further increased in the PNI and EPE areas. In bone metastases, Y1R and Y5R presented high expression scores.

CONCLUSION

The results of our study suggest that the NPY system is involved in PCa, starting from early stages of its development to disseminated states of the disease, and participates in the invasion of PCa into the auto and paracrine matter.

Synthesis and Evaluation of a Monomethyl Auristatin E─Integrin αvβ6 Binding Peptide-Drug Conjugate for Tumor Targeted Drug Delivery

Many anticancer drugs exhibit high systemic off-target toxicities causing severe side effects. Peptide-drug conjugates (PDCs) that target tumor-specific receptors such as integrin αvβ6 are emerging as powerful tools to overcome these challenges. The development of an integrin αvβ6-selective PDC was achieved by combining the therapeutic efficacy of the cytotoxic drug monomethyl auristatin E with the selectivity of the αvβ6-binding peptide (αvβ6-BP) and with the ability of positron emission tomography (PET) imaging by copper-64. The [64Cu]PDC-1 was produced efficiently and in high purity. The PDC exhibited high human serum stability, integrin αvβ6-selective internalization, cell binding, and cytotoxicity. Integrin αvβ6-selective tumor accumulation of the [64Cu]PDC-1 was visualized with PET-imaging and corroborated by biodistribution, and [64Cu]PDC-1 showed promising in vivo pharmacokinetics. The [natCu]PDC-1 treatment resulted in prolonged survival of mice bearing αvβ6 (+) tumors (median survival: 77 days, vs αvβ6 (-) tumor group 49 days, and all other control groups 37 days).

Stereochemistry-Driven Interactions of α,γ-Peptide Ligands with the Neuropeptide Y Y4-Receptor

The G-protein-coupled Y₄-receptor (Y₄R) and its endogenous ligand, pancreatic polypeptide (PP), suppress appetite in response to food intake and, thus, are attractive drug targets for body-weight control. The C-terminus of human PP (hPP), T³²-R³³-P³⁴-R³⁵-Y³⁶-NH₂, penetrates deep into the binding pocket with its tyrosine-amide and di-arginine motif. Here, we present two C-terminally amidated α,γ-hexapeptides (1a/b) with sequence Ac-R³¹-γ-CBAA³²-R³³-L³⁴-R³⁵-Y³⁶-NH₂, where γ-CBAA is the (1R,2S,3R)-configured 2-(aminomethyl)-3-phenylcyclobutanecarboxyl moiety (1a) or its mirror image (1b). Both peptides bind the Y₄R (K_i of 1a/b: 0.66/12 nM) and act as partial agonists (intrinsic activity of 1a/b: 50/39%). Their induced-fit binding poses in the Y₄R pocket are unique and build ligand-receptor contacts distinct from those of the C-terminus of the endogenous ligand hPP. We conclude that energetically favorable interactions, although they do not match those of the native ligand hPP, still guarantee high binding affinity (with 1a rivaling hPP) but not the maximum receptor activation.

Peptide-Drug Conjugate Targeting Keratin 1 Inhibits Triple-Negative Breast Cancer in Mice

Selective delivery of chemotherapy to the tumor site while sparing healthy cells and tissues is an attractive approach for cancer treatment. Carriers such as peptides can facilitate selective tumor targeting and payload delivery. Peptides with specific affinity for the overexpressed cell-surface receptors in cancer cells are conjugated to chemotherapy to afford peptide-drug conjugates (PDCs) that show selective uptake by cancer cells. Using a 10-mer linear peptide (WxEAAYQrFL) called 18-4 that targets and binds breast cancer cells, we designed a peptide 18-4-doxorubicin (Dox) conjugate with high specific toxicity toward triple-negative breast cancer (TNBC) MDA-MB-231 cells and 30-fold lower toxicity to normal breast MCF10A epithelial cells. Here, we elucidate the in vivo activity of this potent and tumor-selective peptide 18-4-Dox conjugate in mice bearing orthotopic MDA-MB-231 tumors. Mice treated with four weekly injections of the conjugate showed significantly lower tumor volumes compared to mice treated with free Dox at an equivalent Dox dose. Immunohistochemical (IHC) analysis of mice tissues revealed that treatment with a low dose of PDC (2.5 mg/kg of Dox equiv) reduced the expression of proliferation markers (PCNA and Ki-67) and increased apoptosis (evidenced by increased caspase-3 expression). At the same dose of free Dox (2.5 mg/kg), the expression of these markers was similar to that of saline treatment. Accordingly, significantly more Dox accumulated in tumors of conjugate-treated mice (7-fold) compared to the Dox-treated mice, while lower levels of Dox were observed in the liver, heart, and lungs of peptide-Dox conjugate-treated mice (up to 3-fold less) than Dox-treated mice. The IHC analysis of keratin 1 (K1), the receptor for peptide 18-4, revealed K1 upregulation in tumors and low levels in normal mammary fat pad and liver tissues from mice, suggesting preferential uptake of PDCs by TNBC to be K1 receptor-mediated. Taken together, our data support the use of a PDC approach to deliver chemotherapy selectively to the TNBC to inhibit tumor growth.

Recent Advances in Zein-Based Nanocarriers for Precise Cancer Therapy

Cancer has emerged as a leading cause of death worldwide. However, the pursuit of precise cancer therapy and high-efficiency delivery of antitumor drugs remains an enormous obstacle. The major challenge is the lack of a smart drug delivery system with the advantages of biodegradability, biocompatibility, stability, targeting and response release. Zein, a plant-based protein, possesses a unique self-assembly ability to encapsulate anticancer drugs directly or indirectly. Using zein as a nanotherapeutic pharmaceutic preparation can protect anticancer drugs from harsh environments, such as sunlight, stomach acid and pepsin. Moreover, the surface functionalization of zein is easily realized, which can endow it with targeting and stimulus-responsive release capacity. Hence, zein is an ideal nanocarrier for the precise delivery of anticancer drugs. Combined with our previous research experiences, we attempt to review the current state of the preparation of zein-based nanocarriers for anticancer drug delivery. The challenges, solutions and development trends of zein-based nanocarriers for precise cancer therapy are discussed. This review will provide a guideline for precise cancer therapy in the future.

Multi-Functional Boron-Delivery Agents for Boron Neutron Capture Therapy of Cancers

Boron neutron capture therapy (BNCT) is a binary cancer treatment that involves the irradiation of ¹⁰B-containing tumors with low-energy neutrons (thermal or epithermal). The alpha particles and recoiling Li nuclei that are produced in the ¹⁰B-capture nuclear reaction are high-linear-energy transfer particles that destroy boron-loaded tumor cells; therefore, BNCT has the potential to be a localized therapeutic modality. Two boron-delivery agents have been used in clinical trials of BNCT in patients with malignant brain tumors, cutaneous melanoma, or recurrent tumors of the head and neck region, demonstrating the potential of BNCT in the treatment of difficult cancers. A variety of potentially highly effective boron-delivery agents have been synthesized in the past four decades and tested in cells and animal models. These include boron-containing nucleosides, peptides, proteins, polyamines, porphyrins, liposomes, monoclonal antibodies, and nanoparticles of various types. The most promising agents are multi-functional boronated molecules and nanoparticles functionalized with tumor cell-targeting moieties that increase their tumor selectivity and contain a radiolabel or fluorophore to allow quantification of ¹⁰B-biodistribution and treatment planning. This review discusses multi-functional boron agents reported in the last decade, but their full potential can only be ascertained after their evaluation in BNCT clinical trials.

Neuropeptide Y Peptide Family and Cancer: Antitumor Therapeutic Strategies

Currently available data on the involvement of neuropeptide Y (NPY), peptide YY (PYY), and pancreatic polypeptide (PP) and their receptors (YRs) in cancer are updated. The structure and dynamics of YRs and their intracellular signaling pathways are also studied. The roles played by these peptides in 22 different cancer types are reviewed (e.g., breast cancer, colorectal cancer, Ewing sarcoma, liver cancer, melanoma, neuroblastoma, pancreatic cancer, pheochromocytoma, and prostate cancer). YRs could be used as cancer diagnostic markers and therapeutic targets. A high Y1R expression has been correlated with lymph node metastasis, advanced stages, and perineural invasion; an increased Y5R expression with survival and tumor growth; and a high serum NPY level with relapse, metastasis, and poor survival. YRs mediate tumor cell proliferation, migration, invasion, metastasis, and angiogenesis; YR antagonists block the previous actions and promote the death of cancer cells. NPY favors tumor cell growth, migration, and metastasis and promotes angiogenesis in some tumors (e.g., breast cancer, colorectal cancer, neuroblastoma, pancreatic cancer), whereas in others it exerts an antitumor effect (e.g., cholangiocarcinoma, Ewing sarcoma, liver cancer). PYY or its fragments block tumor cell growth, migration, and invasion in breast, colorectal, esophageal, liver, pancreatic, and prostate cancer. Current data show the peptidergic system's high potential for cancer diagnosis, treatment, and support using Y2R/Y5R antagonists and NPY or PYY agonists as promising antitumor therapeutic strategies. Some important research lines to be developed in the future will also be suggested.

Structure-Based Design of Peptides Targeting VEGF/VEGFRs

Vascular endothelial growth factor (VEGF) and its receptors (VEGFRs) play a main role in the regulation of angiogenesis and lymphangiogenesis. Furthermore, they are implicated in the onset of several diseases such as rheumatoid arthritis, degenerative eye conditions, tumor growth, ulcers and ischemia. Therefore, molecules able to target the VEGF and its receptors are of great pharmaceutical interest. Several types of molecules have been reported so far. In this review, we focus on the structure-based design of peptides mimicking VEGF/VEGFR binding epitopes. The binding interface of the complex has been dissected and the different regions challenged for peptide design. All these trials furnished a better understanding of the molecular recognition process and provide us with a wealth of molecules that could be optimized to be exploited for pharmaceutical applications.

Targeting Peptides: The New Generation of Targeted Drug Delivery Systems

Peptides can act as targeting molecules, analogously to oligonucleotide aptamers and antibodies. They are particularly efficient in terms of production and stability in physiological environments; in recent years, they have been increasingly studied as targeting agents for several diseases, from tumors to central nervous system disorders, also thanks to the ability of some of them to cross the blood-brain barrier. In this review, we will describe the techniques employed for their experimental and in silico design, as well as their possible applications. We will also discuss advancements in their formulation and chemical modifications that make them even more stable and effective. Finally, we will discuss how their use could effectively help to overcome various physiological problems and improve existing treatments.

Molecular Complementarity of Proteomimetic Materials for Target-Specific Recognition and Recognition-Mediated Complex Functions

As biomolecules essential for sustaining life, proteins are generated from long chains of 20 different α-amino acids that are folded into unique 3D structures. In particular, many proteins have molecular recognition functions owing to their binding pockets, which have complementary shapes, charges, and polarities for specific targets, making these biopolymers unique and highly valuable for biomedical and biocatalytic applications. Based on the understanding of protein structures and microenvironments, molecular complementarity can be exhibited by synthesizable and modifiable materials. This has prompted researchers to explore the proteomimetic potentials of a diverse range of materials, including biologically available peptides and oligonucleotides, synthetic supramolecules, inorganic molecules, and related coordination networks. To fully resemble a protein, proteomimetic materials perform the molecular recognition to mediate complex molecular functions, such as allosteric regulation, signal transduction, enzymatic reactions, and stimuli-responsive motions; this can also expand the landscape of their potential bio-applications. This review focuses on the recognitive aspects of proteomimetic designs derived for individual materials and their conformations. Recent progress provides insights to help guide the development of advanced protein mimicry with material heterogeneity, design modularity, and tailored functionality. The perspectives and challenges of current proteomimetic designs and tools are also discussed in relation to future applications.

Polymer-Based mRNA Delivery Strategies for Advanced Therapies

Messenger RNA (mRNA)-based therapies offer great promise for the treatment of a variety of diseases. In 2020, two FDA approvals of mRNA-based vaccines have elevated mRNA vaccines to global recognition. However, the therapeutic capabilities of mRNA extend far beyond vaccines against infectious diseases. They hold potential for cancer vaccines, protein replacement therapies, gene editing therapies, and immunotherapies. For realizing such advanced therapies, it is crucial to develop effective carrier systems. Recent advances in materials science have led to the development of promising nonviral mRNA delivery systems. In comparison to other carriers like lipid nanoparticles, polymer-based delivery systems often receive less attention, despite their unique ability to carefully tune their chemical features to promote mRNA protection, their favorable pharmacokinetics, and their potential for targeting delivery. In this review, the central features of polymer-based systems for mRNA delivery highlighting the molecular design criteria, stability, and biodistribution are discussed. Finally, the role of targeting ligands for the future of RNA therapies is analyzed.

Peptides as multifunctional players in cancer therapy

Peptides exhibit lower affinity and a shorter half-life in the body than antibodies. Conversely, peptides demonstrate higher efficiency in tissue penetration and cell internalization than antibodies. Regardless of the pros and cons of peptides, they have been used as tumor-homing ligands for delivering carriers (such as nanoparticles, extracellular vesicles, and cells) and cargoes (such as cytotoxic peptides and radioisotopes) to tumors. Additionally, tumor-homing peptides have been conjugated with cargoes such as small-molecule or chemotherapeutic drugs via linkers to synthesize peptide-drug conjugates. In addition, peptides selectively bind to cell surface receptors and proteins, such as immune checkpoints, receptor kinases, and hormone receptors, subsequently blocking their biological activity or serving as hormone analogs. Furthermore, peptides internalized into cells bind to intracellular proteins and interfere with protein-protein interactions. Thus, peptides demonstrate great application potential as multifunctional players in cancer therapy.

Late-stage peptide labeling with near-infrared fluorogenic nitrobenzodiazoles by manganese-catalyzed C-H activation

Late-stage diversification of structurally complex amino acids and peptides provides tremendous potential for drug discovery and molecular imaging. Specifically, labeling peptides with fluorescent tags is one of the most important methods for visualizing their mode of operation. Despite major recent advances in the field, direct molecular peptide labeling by C-H activation is largely limited to dyes with relatively short emission wavelengths, leading to high background signals and poor signal-to-noise ratios. In sharp contrast, here we report on the fluorescent labeling of peptides catalyzed by non-toxic manganese(i) via C(sp²)-H alkenylation in chemo- and site-selective manners, providing modular access to novel near-infrared (NIR) nitrobenzodiazole-based peptide fluorogenic probes.

Overcoming Non-Specific Interactions for Efficient Encapsulation of Doxorubicin in Ferritin Nanocages for Targeted Drug Delivery

Due to its beneficial pharmacological properties, ferritin (Ftn) is considered as an interesting drug delivery vehicle to alleviate the cardiotoxicity of doxorubicin (DOX) in chemotherapy. However, the encapsulation of DOX in Ftn suffers from heavy precipitation and low protein recovery yield which limits its full potential. Here, a new DOX encapsulation strategy by cysteine-maleimide conjugation is proposed. In order to demonstrate that this strategy is more efficient compared to the other approaches, DOX is encapsulated in Ftn variants carrying different surface charges. Furthermore, in contrast to the common belief, this data show that DOX molecules are also found to bind non-specifically to the surface of Ftn. This can be circumvented by the use of Tris(2-carboxyethyl)phosphine (TCEP) during encapsulation or by washing with acidic buffer. The biocompatibility studies of the resulting DOX Ftn variants in MCF-7 and MHS cancer cells shows a complex relationship between the cytotoxicity, the DOX loading and the different surface charges of Ftn. Further investigation on the cell uptake mechanism provides reasonable explanations for the cytotoxicity results and reveals that surface charging of Ftn hinders its transferrin receptor 1 (TfR-1) mediated cellular uptake in MCF-7 cells.

Antibody drug conjugates as targeted cancer therapy: past development, present challenges and future opportunities

Antibody drug conjugates (ADCs) are promising cancer therapeutics with minimal toxicity as compared to small cytotoxic molecules alone and have shown the evidence to overcome resistance against tumor and prevent relapse of cancer. The ADC has a potential to change the paradigm of cancer chemotherapeutic treatment. At present, 13 ADCs have been approved by USFDA for the treatment of various types of solid tumor and haematological malignancies. This review covers the three structural components of an ADC-antibody, linker, and cytotoxic payload-along with their respective structure, chemistry, mechanism of action, and influence on the activity of ADCs. It covers comprehensive insight on structural role of linker towards efficacy, stability & toxicity of ADCs, different types of linkers & various conjugation techniques. A brief overview of various analytical techniques used for the qualitative and quantitative analysis of ADC is summarized. The current challenges of ADCs, such as heterogeneity, bystander effect, protein aggregation, inefficient internalization or poor penetration into tumor cells, narrow therapeutic index, emergence of resistance, etc., are outlined along with recent advances and future opportunities for the development of more promising next-generation ADCs.

Construction of Peptide-Isoquinolone Conjugates via Rh(III)-Catalyzed C-H Activation/Annulation

Herein, we disclose a Rh(III)-catalyzed C-H activation/annulation reaction for the derivatization of Lys-based peptides, in situ affording diverse peptide-isoquinolone conjugates. This approach features racemization-free conditions, high atom- and step-economy, excellent chemo- and site-selectivity, and broad scope including substrates bearing unprotected Trp and Tyr, free Ser and Gln, and Met residues. The peptide-isoquinolone conjugates also display good fluorescent properties with maximum emission wavelengths up to 460 nm. Importantly, preliminary antifungal activity studies indicate that peptide-isoquinolone conjugates show potential activities toward crop and forest pathogenic fungi, in which the peptide-isoquinolone conjugate bearing unprotected Tyr residue exhibits much better antifungal activities toward B. cinerea Pers. and C. chrysosperma than the positive control.

Drug Delivery Strategies for the Treatment of Pancreatic Cancer

Pancreatic cancer is fast becoming a global menace and it is projected to be the second leading cause of cancer-related death by 2030. Pancreatic adenocarcinomas, which develop in the pancreas' exocrine region, are the predominant type of pancreatic cancer, representing about 95% of total pancreatic tumors. The malignancy progresses asymptomatically, making early diagnosis difficult. It is characterized by excessive production of fibrotic stroma known as desmoplasia, which aids tumor growth and metastatic spread by remodeling the extracellular matrix and releasing tumor growth factors. For decades, immense efforts have been harnessed toward developing more effective drug delivery systems for pancreatic cancer treatment leveraging nanotechnology, immunotherapy, drug conjugates, and combinations of these approaches. However, despite the reported preclinical success of these approaches, no substantial progress has been made clinically and the prognosis for pancreatic cancer is worsening. This review provides insights into challenges associated with the delivery of therapeutics for pancreatic cancer treatment and discusses drug delivery strategies to minimize adverse effects associated with current chemotherapy options and to improve the efficiency of drug treatment.

Peptide cargo administration: current state and applications

Effective delivery of drug molecules to the target site is a challenging task. In the last decade, several innovations in the drug delivery system (DDS) have tremendously improved the therapeutic efficacy of drug molecules. Among various DDS, cell-penetrating peptides (CPPs) based DDS have gathered notable attention owing to their safety, efficacy, selectivity, specificity, and ease of synthesis. CPPs are emerging as an efficient and effective pharmaceutical nanocarriers-based platforms for successful management of various important human health disorders. Failure of several current chemotherapeutic strategies is attributed to low solubility, reduced bioavailability, and off-target delivery of several anti-cancer drugs. Similarly, development of therapeutics for vision-threatening disorders is challenged by the anatomical as well as physiological complexity of the eye. Such therapeutic challenges in cancer and ocular disease management can be overcome by developing cell-penetrating peptide (CPP) based peptide drug conjugates (PDCs). CPPs can be used to deliver various types of cargo molecules including nucleic acids, small molecules, and peptides/proteinaceous agents. In this review, we have briefly introduced CPPs and the linker strategies employed for the development of PDCs. Furthermore, recent studies employing CPP-based PDCs for cancer and ocular disease management have been discussed in detail highlighting their significance over conventional DDS. Later sections of the review are focused on the current status of clinical trials and future implications of CPP-based PDCs in vaccine development. KEY POINTS: • Cell-penetrating peptides (CPPs) can deliver a variety of cargo macromolecules via covalent and non-covalent conjugation. • CPP-based peptide drug conjugates (PDCs) can overcome drawbacks of conventional drug delivery methods such as biocompatibility, solubility, stability, and specificity. • Various PDCs are in clinical trial phase for cancer and ocular therapeutics.

Carborane-Containing Hydroxamate MMP Ligands for the Treatment of Tumors Using Boron Neutron Capture Therapy (BNCT): Efficacy without Tumor Cell Entry

New carborane-bearing hydroxamate matrix metalloproteinase (MMP) ligands have been synthesized for boron neutron capture therapy (BNCT) with nanomolar potency against MMP-2, -9 and -13. New analogs are based on MMP inhibitor CGS-23023A, and two previously reported MMP ligands 1 (B1) and 2 (B2) were studied in vitro for BNCT activity. The boronated MMP ligands 1 and 2 showed high in vitro tumoricidal effects in an in vitro BNCT assay, exhibiting IC50 values for 1 and 2 of 2.04 × 10-2 mg/mL and 2.67 × 10-2 mg/mL, respectively. The relative killing effect of 1 to L-boronophenylalanine (BPA) is 0.82/0.27 = 3.0, and that of 2 is 0.82/0.32 = 2.6, whereas the relative killing effect of 4 is comparable to boronophenylalanine (BPA). The survival fraction of 1 and 2 in a pre-incubation boron concentration at 0.143 ppm 10B and 0.101 ppm 10B, respectively, were similar, and these results suggest that 1 and 2 are actively accumulated through attachment to the Squamous cell carcinoma (SCC)VII cells. Compounds 1 and 2 very effectively killed glioma U87 delta EGFR cells after BNCT. This study is noteworthy in demonstrating BNCT efficacy through binding to MMP enzymes overexpressed at the surface of the tumor cell without tumor cell penetration.

New Boron Delivery Agents

This proceeding article compiles current research on the development of boron delivery drugs for boron neutron capture therapy that was presented and discussed at the National Cancer Institute (NCI) Workshop on Neutron Capture Therapy that took place on April 20-22, 2022. The most used boron sources are icosahedral boron clusters attached to peptides, proteins (such as albumin), porphyrin derivatives, dendrimers, polymers, and nanoparticles, or encapsulated into liposomes. These boron clusters and/or carriers can be labeled with contrast agents allowing for the use of imaging techniques, such as PET, SPECT, and fluorescence, that enable quantification of tumor-localized boron and their use as theranostic agents.

Mitochondrial quality control proteases and their modulation for cancer therapy

Mitochondria, the main provider of energy in eukaryotic cells, contains more than 1000 different proteins and is closely related to the development of cells. However, damaged proteins impair mitochondrial function, further contributing to several human diseases. Evidence shows mitochondrial proteases are critically important for protein maintenance. Most importantly, quality control enzymes exert a crucial role in the modulation of mitochondrial functions by degrading misfolded, aged, or superfluous proteins. Interestingly, cancer cells thrive under stress conditions that damage proteins, so targeting mitochondrial quality control proteases serves as a novel regulator for cancer cells. Not only that, mitochondrial quality control proteases have been shown to affect mitochondrial dynamics by regulating the morphology of optic atrophy 1 (OPA1), which is closely related to the occurrence and progression of cancer. In this review, we introduce mitochondrial quality control proteases as promising targets and related modulators in cancer therapy with a focus on caseinolytic protease P (ClpP), Lon protease (LonP1), high-temperature requirement protein A2 (HrtA2), and OMA-1. Further, we summarize our current knowledge of the advances in clinical trials for modulators of mitochondrial quality control proteases. Overall, the content proposed above serves to suggest directions for the development of novel antitumor drugs.

A peptide binding to the tetraspanin CD9 reduces cancer metastasis

As an organizer of multi-molecular membrane complexes, the tetraspanin CD9 has been implicated in a number of biological processes, including cancer metastasis, and is a candidate therapeutic target. Here, we evaluated the suppressive effects of an eight-mer CD9-binding peptide (CD9-BP) on cancer cell metastasis and its mechanisms of action. CD9-BP impaired CD9-related functions by adversely affecting the formation of tetraspanin webs-networks composed of CD9 and its partner proteins. The anti-cancer metastasis effect of CD9-BP was evidenced by the in vitro inhibition of cancer cell migration and invasion as well as exosome secretion and uptake, which are essential processes during metastasis. Finally, using a mouse model, we showed that CD9-BP reduced lung metastasis in vivo. These findings provide insight into the mechanism by which CD9-BP inhibits CD9-dependent functions and highlight its potential application as an alternative therapeutic nano-biomaterial for metastatic cancers.

Transcytosable Peptide-Paclitaxel Prodrug Nanoparticle for Targeted Treatment of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an extremely aggressive subtype associated with a poor prognosis. At present, the treatment for TNBC mainly relies on surgery and traditional chemotherapy. As a key component in the standard treatment of TNBC, paclitaxel (PTX) effectively inhibits the growth and proliferation of tumor cells. However, the application of PTX in clinical treatment is limited due to its inherent hydrophobicity, weak penetrability, nonspecific accumulation, and side effects. To counter these problems, we constructed a novel PTX conjugate based on the peptide-drug conjugates (PDCs) strategy. In this PTX conjugate, a novel fused peptide TAR consisting of a tumor-targeting peptide, A7R, and a cell-penetrating peptide, TAT, is used to modify PTX. After modification, this conjugate is named PTX-SM-TAR, which is expected to improve the specificity and penetrability of PTX at the tumor site. Depending on hydrophilic TAR peptide and hydrophobic PTX, PTX-SM-TAR can self-assemble into nanoparticles and improve the water solubility of PTX. In terms of linkage, the acid- and esterase-sensitive ester bond was used as the linking bond, with which PTX-SM-TAR NPs could remain stable in the physiological environment, whereas PTX-SM-TAR NPs could be broken and PTX be released at the tumor site. A cell uptake assay showed that PTX-SM-TAR NPs were receptor-targeting and could mediate endocytosis by binding to NRP-1. The vascular barrier, transcellular migration, and tumor spheroids experiments showed that PTX-SM-TAR NPs exhibit great transvascular transport and tumor penetration ability. In vivo experiments, PTX-SM-TAR NPs showed higher antitumor effects than PTX. As a result, PTX-SM-TAR NPs may overcome the shortcomings of PTX and present a new transcytosable and targeted delivery system for PTX in TNBC treatment.

A Novel Homodimer Peptide-Drug Conjugate Improves the Efficacy of HER2-Positive Breast Cancer Therapy

Tumor-targeting peptide-drug conjugates (PDCs) have become a focus of research in recent years. However, due to the instability of peptides and their short in vivo effective half-life, they have limited clinical application. Herein, we propose a new DOX PDC based on a homodimer HER-2-targeting peptide and acid-sensitive hydrazone bond, which could enhance the anti-tumor effect of DOX and reduce systemic toxicities. The PDC could accurately deliver DOX into HER2-positive SKBR-3 cells, with it showing 2.9 times higher cellular uptake than free DOX and enhanced cytotoxicity with respect to IC₅₀ of 140 nM (vs. 410 nM for free DOX). In vitro assays showed that the PDC had high cellular internalization efficiency and cytotoxicity. In vivo anti-tumor experiments indicated that the PDC could significantly inhibit the growth of HER2-positive breast cancer xenografts in mice and reduce the side effects of DOX. In summary, we constructed a novel PDC molecule targeting HER2-positive tumors, which may overcome some deficiencies of DOX in breast cancer therapy.

Targeting the Gastrin-Releasing Peptide Receptor (GRP-R) in Cancer Therapy: Development of Bombesin-Based Peptide-Drug Conjugates

Targeted tumour therapy has proved to be an efficient alternative to overcome the limitations of conventional chemotherapy. Among several receptors upregulated in cancer cells, the gastrin-releasing peptide receptor (GRP-R) has recently emerged as a promising target for cancer imaging, diagnosing and treatment due to its overexpression on cancerous tissues such as breast, prostate, pancreatic and small-cell lung cancer. Herein, we report on the in vitro and in vivo selective delivery of the cytotoxic drug daunorubicin to prostate and breast cancer, by targeting GRP-R. Exploiting many bombesin analogues as homing peptides, including a newly developed peptide, we produced eleven daunorubicin-containing peptide-drug conjugates (PDCs), acting as drug delivery systems to safely reach the tumour environment. Two of our bioconjugates revealed remarkable anti-proliferative activity, an efficient uptake by all three tested human breast and prostate cancer cell lines, high stability in plasma and a prompt release of the drug-containing metabolite by lysosomal enzymes. Moreover, they revealed a safe profile and a consistent reduction of the tumour volume in vivo. In conclusion, we highlight the importance of GRP-R binding PDCs in targeted cancer therapy, with the possibility of further tailoring and optimisation.

Advancements, challenges and future perspectives on peptide-based drugs: Focus on antimicrobial peptides

Among other health related issues, the rising concerns on drug resistance led to look for alternative pharmaceutical drugs that are effective both against infectious and noninfectious diseases. Antimicrobial peptides (AMPs) emerged as potential therapeutic molecule with wide range of applications. With their limitations, AMPs have gained reputable attentions in research as well as in the pharmaceutical industry. This review highlighted the historical background, research trends, technological advancements, challenges, and future perspectives in the development and applications of peptide drugs. Some vital questions related with the need for pharmaceutical production, factors for the slow and steady journey, the importance of oral bioavailability, and the drug resistance possibilities of AMPs were raised and addressed accordingly. Therefore, the current study is believed to provide a profound understanding in the past and current scenarios and future directions on the therapeutic impacts of peptide drugs.

Antiviral Peptide-Based Conjugates: State of the Art and Future Perspectives

Infectious diseases caused by microbial pathogens (bacteria, virus, fungi, parasites) claim millions of deaths per year worldwide and have become a serious challenge to global human health in our century. Viral infections are particularly notable in this regard, not only because humankind is facing some of the deadliest viral pandemics in recent history, but also because the arsenal of drugs to combat the high levels of mutation, and hence the antigenic variability of (mostly RNA) viruses, is disturbingly scarce. Therefore, the search for new antivirals able to successfully fight infection with minimal or no adverse effects on the host is a pressing task. Traditionally, antiviral therapies have relied on relatively small-sized drugs acting as proteases, polymerases, integrase inhibitors, etc. In recent decades, novel approaches involving targeted delivery such as that achieved by peptide-drug conjugates (PDCs) have gained attention as alternative (pro)drugs for tackling viral diseases. Antiviral PDC therapeutics typically involve one or more small drug molecules conjugated to a cell-penetrating peptide (CPP) carrier either directly or through a linker. Such integration of two bioactive elements into a single molecular entity is primarily aimed at achieving improved bioavailability in conditions where conventional drugs are challenged, but may also turn up novel unexpected functionalities and applications. Advances in peptide medicinal chemistry have eased the way to antiviral PDCs, but challenges remain on the way to therapeutic success. In this paper, we review current antiviral CPP-drug conjugates (antiviral PDCs), with emphasis on the types of CPP and antiviral cargo. We integrate the conjugate and the chemical approaches most often applied to combine both entities. Additionally, we comment on various obstacles faced in the design of antiviral PDCs and on the future outlooks for this class of antiviral therapeutics.

Peptide Drug Conjugates and Their Role in Cancer Therapy

Drug conjugates have become a significant focus of research in the field of targeted medicine for cancer treatments. Peptide-drug conjugates (PDCs), a subset of drug conjugates, are composed of carrier peptides ranging from 5 to 30 amino acid residues, toxic payloads, and linkers that connect the payload to the peptide. PDCs are further broken down into cell-penetrating peptides (CPPs) and cell-targeting peptides (CTPs), each having their own differences in the delivery of cytotoxic payloads. Generally, PDCs as compared to other drug conjugates-like antibody-drug conjugates (ADCs)-have advantages in tumor penetration, ease of synthesis and cost, and reduced off-target effects. Further, as compared to traditional cancer treatments (e.g., chemotherapy and radiation), PDCs have higher specificity for the target cancer with generally less toxic side effects in smaller doses. However, PDCs can have disadvantages such as poor stability and rapid renal clearance due to their smaller size and limited oral bioavailability due to digestion of its peptide structure. Some of these challenges can be overcome with modifications, and despite drawbacks, the intrinsic small size of PDCs with high target specificity still makes them an attractive area of research for cancer treatments.

LWJ-M30, a conjugate of DM1 and B6, for the targeted therapy of colorectal cancer with improved therapeutic effects†

Colorectal cancer (CRC) is one of the most prevalent cancers worldwide as well as a significant cause of mortality. The conventional treatment could cause serious side effects and induce drug resistance, recurrence and metastasis of cancers. Hence, specific targeting of cancer cells without affecting the normal tissues is currently an urgent necessity in cancer therapy. The emerging of peptide–drug conjugates (PDC) is regarded as a promising approach to address malignant tumors. LWJ-M30, a conjugate of DM1 and B6 peptide, targeted transferrin receptors (TfRs) on the surface of the CRC cells, showing a powerful anti-cancer effect. LWJ-M30 significantly inhibited the HCT116 cells proliferation and migration in vitro. LWJ-M30 also dramatically decreased the level of polymeric tubulin, while the disruption of microtubules caused the cell cycle to be arrested in the G2/M phase. LWJ-M30 induced the HCT116 cells apoptosis both in vivo and in vitro. The results in vivo demonstrated that LWJ-M30 could inhibit the HCT116 growth without affecting the mouse body weight. Taking these results together, our data indicated that LWJ-M30 could improve the therapeutic effects of DM1 while reducing the systemic toxicity in normal tissues.

LWJ-M30 targeted TfR, dramatically decreased the level of polymeric tubulin, while the disruption of microtubules meant the cell cycle was arrested in the G2/M phase and thus caused cells apoptosis.

Melittin derived peptide-drug conjugate, M-DM1, inhibits tumor progression and induces effector cell infiltration in melanoma by targeting M2 tumor-associated macrophages

Background

Melanoma has the highest mortality rate among all the types of skin cancer. In melanoma, M2-like tumor-associated macrophages (TAMs) are associated with the invasiveness of tumor cells and a poor prognosis. Hence, the depletion or reduction of M2-TAMs is a therapeutic strategy for the inhibition of tumor progression. The aim of this study was to evaluate the therapeutic effects of M-DM1, which is a conjugation of melittin (M), as a carrier for M2-like TAMs, and mertansine (DM1), as a payload to induce apoptosis of TAMs, in a mouse model of melanoma.

Methods

Melittin and DM1 were conjugated and examined for the characterization of M-DM1 by high-performance liquid chromatography and electrospray ionization mass spectrometry. Synthesized M-DM1 were examined for in vitro cytotoxic effects. For the in vivo study, we engrafted murine B16-F10 into right flank of C57BL/6 female mice and administered an array of treatments (PBS, M, DM1, or M-DM1 (20 nmol/kg)). Subsequently, the tumor growth and survival rates were analyzed, as well as examining the phenotypes of tumor-infiltrating leukocytes and expression profiles.

Results

M-DM1 was found to specifically reduce M2-like TAMs in melanoma, which potentially leads to the suppression of tumor growth, migration, and invasion. In addition, we also found that M-DM1 improved the survival rates in a mouse model of melanoma compared to M or DM1 treatment alone. Flow cytometric analysis revealed that M-DM1 enhanced the infiltration of CD8+ cytotoxic T cells and natural killer cells (NK cells) in the tumor microenvironment.

Conclusion

Taken together, our findings highlight that M-DM1 is a prospective agent with enhanced anti-tumor effects.

Drug conjugate-based anticancer therapy - Current status and perspectives

Drug conjugates are conjugates comprising a tumor-homing carrier tethered to a cytotoxic agent via a linker that are designed to deliver an ultra-toxic payload directly to the target cancer cells. This strategy has been successfully used to increase the therapeutic efficacy of cytotoxic agents and reduce their toxic side effects. Drug conjugates are being developed worldwide, with the potential to revolutionize current cancer treatment strategies. Antibody-drug conjugates (ADCs) have developed rapidly, and 14 of them have received market approval since the first approval event by the Food and Drug Administration in 2000. However, there are some limitations in the use of antibodies as carriers. Other classes of drug conjugates are emerging, such as targeted drugs conjugated with peptides (peptide-drug conjugates, PDCs) and polymers (polymer-drug conjugates, PolyDCs) with the remaining constructs similar to those of ADCs. These novel drug conjugates are gaining attention because they overcome the limitations of ADCs. This review summarizes the current state and advancements in knowledge regarding the design, constructs, and clinical efficacy of different drug conjugates.

Future in precise surgery: Fluorescence-guided surgery using EVs derived fluorescence contrast agent

Surgery is the only cure for many solid tumors, but positive resection margins, damage to vital nerves, vessels and organs during surgery, and the range and extent of lymph node dissection are significant concerns which hinder the development of surgery. The emergence of fluorescence-guided surgery (FGS) means a farewell to the era when surgeons relied only on visual and tactile feedback, and it gives surgeons another eye to distinguish tumors from normal tissues for precise resection and helps to find a balance between complete tumor lesions removal and maximal organ function conservation. However, the existing synthetic fluorescence contrast agent has flaws in safety, specificity and biocompatibility to various extents. Extracellular vesicles (EVs) are a group of heterogeneous types of cell-derived membranous structures present in all biological fluids. EVs, especially engineered targeting EVs, play an increasingly important role in drug delivery because of their good biocompatibility, validated safety and targeting ability. Nevertheless, few studies have employed EVs loaded with fluorophores to construct fluorescence contrast agents and used them in FGS. Here, we systematically reviewed the current state of knowledge regarding FGS, fundamental characteristics of EVs, and the development of engineered targeting EVs, and put forward a novel strategy and procedures to produce EVs-based fluorescence contrast agent used in fluorescence-guided surgery.

Development of radiopharmaceuticals for targeted alpha therapy: Where do we stand?

Targeted alpha therapy is an oncological treatment, where cytotoxic doses of alpha radiation are locally delivered to tumor cells, while the surrounding healthy tissue is minimally affected. This therapeutic strategy relies on radiopharmaceuticals made of medically relevant radionuclides chelated by ligands, and conjugated to targeting vectors, which promote the drug accumulation in tumor sites. This review discusses the state-of-the-art in the development of radiopharmaceuticals for targeted alpha therapy, breaking down their key structural components, such as radioisotope, targeting vector, and delivery formulation, and analyzing their pros and cons. Moreover, we discuss current drawbacks that are holding back targeted alpha therapy in the clinic, and identify ongoing strategies in field to overcome those issues, including radioisotope encapsulation in nanoformulations to prevent the release of the daughters. Lastly, we critically discuss potential opportunities the field holds, which may contribute to targeted alpha therapy becoming a gold standard treatment in oncology in the future.

Synthesis of Functionalized Isoquinolone Derivatives via Rh(III)-Catalyzed [4+2]-Annulation of Benzamides with Internal Acetylene-Containing α-CF3-α-Amino Carboxylates

A convenient pathway to a new series of α-CF3-substituted α-amino acid derivatives bearing pharmacophore isoquinolone core in their backbone has been developed. The method is based on [4+2]-annulation of N-(pivaloyloxy) aryl amides with orthogonally protected internal acetylene-containing α-amino carboxylates under Rh(III)-catalysis. The target annulation products can be easily transformed into valuable isoquinoline derivatives via a successive aromatization/cross-coupling operation.

Targeting FGFRs for tumor therapy: current status and novel strategies

The FGF receptors (FGFRs) belong to a family of receptor tyrosine kinases. Abundant evidence shows that FGFRs are closely related to tumor cell invasion and angiogenesis. Hence, targeted modulation of FGFRs has become an effective strategy for cancer treatment. Recently, the development of small-molecule inhibitors targeting FGFRs has been extensively studied, and three inhibitors have been approved for marketing. Based on the clinical problems with the current inhibitors, there is a need to develop novel inhibitors and technologies to address the pitfalls. This review summarizes recent advances in small-molecule inhibitors targeting FGFRs, focusing on structure-activity relationships. Moreover, recent progress of novel technologies are summarized to provide a reference for promoting the application of drugs targeting FGFRs in tumor therapy.

Functional ligands for improving anticancer drug therapy: current status and applications to drug delivery systems

Conventional chemotherapy lacking target selectivity often leads to severe side effects, limiting the effectiveness of chemotherapy. Therefore, drug delivery systems ensuring both selective drug release and efficient intracellular uptake at the target sites are highly demanded in chemotherapy to improve the quality of life of patients with low toxicity. One of the effective approaches for tumor-selective drug delivery is the adoption of functional ligands that can interact with specific receptors overexpressed in malignant cancer cells. Various functional ligands including folic acid, hyaluronic acid, transferrin, peptides, and antibodies, have been extensively explored to develop tumor-selective drug delivery systems. Furthermore, cell-penetrating peptides or ligands for tight junction opening are also actively pursued to improve the intracellular trafficking of anticancer drugs. Sometimes, multiple ligands with different roles are used in combination to enhance the cellular uptake as well as target selectivity of anticancer drugs. In this review, the current status of various functional ligands applicable to improve the effectiveness of cancer chemotherapy is overviewed with a focus on their roles, characteristics, and preclinical/clinical applications.

Learn from antibody–drug conjugates: consideration in the future construction of peptide-drug conjugates for cancer therapy

Cancer is one of the leading causes of death worldwide due to high heterogeneity. Although chemotherapy remains the mainstay of cancer therapy, non-selective toxicity and drug resistance of mono-chemotherapy incur broad criticisms. Subsequently, various combination strategies have been developed to improve clinical efficacy, also known as cocktail therapy. However, conventional “cocktail administration” is just passable, due to the potential toxicities to normal tissues and unsatisfactory synergistic effects, especially for the combined drugs with different pharmacokinetic properties. The drug conjugates through coupling the conventional chemotherapeutics to a carrier (such as antibody and peptide) provide an alternative strategy to improve therapeutic efficacy and simultaneously reduce the unspecific toxicities, by virtue of the advantages of highly specific targeting ability and potent killing effect. Although 14 antibody–drug conjugates (ADCs) have been approved worldwide and more are being investigated in clinical trials so far, several limitations have been disclosed during clinical application. Compared with ADCs, peptide-drug conjugates (PDCs) possess several advantages, including easy industrial synthesis, low cost, high tissue penetration and fast clearance. So far, only a handful of PDCs have been approved, highlighting tremendous development potential. Herein, we discuss the progress and pitfalls in the development of ADCs and underline what can learn from ADCs for the better construction of PDCs in the future.

Programmable self-regulated molecular buffers for precise sustained drug delivery

Unlike artificial nanosystems, biological systems are ideally engineered to respond to their environment. As such, natural molecular buffers ensure precise and quantitative delivery of specific molecules through self-regulated mechanisms based on Le Chatelier's principle. Here, we apply this principle to design self-regulated nucleic acid molecular buffers for the chemotherapeutic drug doxorubicin and the antimalarial agent quinine. We show that these aptamer-based buffers can be programmed to maintain any specific desired concentration of free drug both in vitro and in vivo and enable the optimization of the chemical stability, partition coefficient, pharmacokinetics and biodistribution of the drug. These programmable buffers can be built from any polymer and should improve patient therapeutic outcome by enhancing drug activity and minimizing adverse effects and dosage frequency.

Advancement of cell-penetrating peptides in combating triple-negative breast cancer

Extensive research efforts have been made and are still ongoing in the search for an ideal anti-cancer therapy. Almost all chemotherapeutics require a carrier or vehicle, a drug delivery system that can transport the drug specifically to the targeted cancer cells, sparing normal cells. Cell-penetrating peptides (CPPs) provide an effective and efficient pathway for the intra-cellular transportation of various bioactive molecules in several biomedical therapies. They are now well-recognized as facilitators of intracellular cargo delivery and have excellent potential for targeted anti-cancer therapy. In this review, we explain CPPs, recent progress in the development of new CPPs, and their utilization to transport cargoes such as imaging agents, chemotherapeutics, and short-interfering RNAs (siRNA) into tumor cells, contributing to the advancement of novel tumor-specific delivery systems.