Enhancement of the Uptake and Cytotoxic Activity of Doxorubicin in Cancer Cells by Novel cRGD-Semipeptide-Anchoring Liposomes

Peptides as Therapeutic Agents: Challenges and Opportunities in the Green Transition Era

Peptides are at the cutting edge of contemporary research for new potent, selective, and safe therapeutical agents. Their rise has reshaped the pharmaceutical landscape, providing solutions to challenges that traditional small molecules often cannot address. A wide variety of natural and modified peptides have been obtained and studied, and many others are advancing in clinical trials, covering multiple therapeutic areas. As the demand for peptide-based therapies grows, so does the need for sustainable and environmentally friendly synthesis methods. Traditional peptide synthesis, while effective, often involves environmentally draining processes, generating significant waste and consuming vast resources. The integration of green chemistry offers sustainable alternatives, prioritizing eco-friendly processes, waste reduction, and energy conservation. This review delves into the transformative potential of applying green chemistry principles to peptide synthesis by discussing relevant examples of the application of such approaches to the production of active pharmaceutical ingredients (APIs) with a peptide structure and how these efforts are critical for an effective green transition era in the pharmaceutical field.

Small Molecules against Metastatic Tumors: Concrete Perspectives and Shattered Dreams

Metastasis is the main cause of anti-cancer therapy failure, leading to unfavorable prognosis for patients. The true challenge to increase cancer patient life expectancy by making cancer a chronic disease with periodic but manageable relapses relies on the development of efficient therapeutic strategies specifically directed against key targets in the metastatic process. Traditional chemotherapy with classical alkylating agents, microtubule inhibitors, and antimetabolites has demonstrated its limited efficacy against metastatic cells due to their capacity to select chemo-resistant cell populations that undergo epithelial-to-mesenchymal transition (EMT), thus promoting the colonization of distant sites that, in turn, sustain the initial metastatic process. This scenario has prompted efforts aimed at discovering a wide variety of small molecules and biologics as potential anti-metastatic drugs directed against more specific targets known to be involved in the various stages of metastasis. In this short review, we give an overview of the most recent advances related to important families of antimetastatic small molecules: intracellular tyrosine kinase inhibitors, cyclin-dependent kinase inhibitors, KRAS inhibitors, and integrin antagonists. Although the majority of these small molecules are not yet approved and not available in the drug market, any information related to their stage of development could represent a precious and valuable tool to identify new targets in the endless fight against metastasis.

Peptide Self-Assembled Nanocarriers for Cancer Drug Delivery

The design of novel cancer drug nanocarriers is critical in the framework of cancer therapeutics. Nanomaterials are gaining increased interest as cancer drug delivery systems. Self-assembling peptides constitute an emerging novel class of highly attractive nanomaterials with highly promising applications in drug delivery, as they can be used to facilitate drug release and/or stability while reducing side effects. Here, we provide a perspective on peptide self-assembled nanocarriers for cancer drug delivery and highlight the aspects of metal coordination, structure stabilization, and cyclization, as well as minimalism. We review particular challenges in nanomedicine design criteria and, finally, provide future perspectives on addressing a portion of the challenges via self-assembling peptide systems. We consider that the intrinsic advantages of such systems, along with the increasing progress in computational and experimental approaches for their study and design, could possibly lead to novel classes of single or multicomponent systems incorporating such materials for cancer drug delivery.

Functional drug carriers formed by RGD-modified β-CD-HPG for the delivery of docetaxel for targeted inhibition of nasopharyngeal carcinoma cells

In this study, a drug delivery system was prepared by grafting the targeting molecule arginine-glycine-aspartic acid (RGD) onto hyperbranched polyglycerol (HPG)-modified β-cyclodextrin (β-CD-HPG) for the targeted inhibition of nasopharyngeal carcinoma (NPC) cells. The obtained β-CD-HPG-RGD with a relatively small size and low surface charge delivered docetaxel (Doc) effectively and displayed a targeting effect to human NPC HNE-1 cells, as confirmed by confocal laser scanning microscopy and flow cytometry. The in vitro drug release analysis exhibited the controlled drug release kinetics of the β-CD-HPG-RGD/Doc nanomedicine. β-CD-HPG-RGD/Doc effectively inhibited the proliferation of HNE-1 cells and promoted apoptosis. Moreover, its biocompatibility in vitro and in vivo was assessed. The results indicate that the β-CD-HPG-RGD/Doc nanomedicine has potential application in NPC targeting therapy.

New 4-Aminoproline-Based Small Molecule Cyclopeptidomimetics as Potential Modulators of α4β1 Integrin

Integrin α₄β₁ belongs to the leukocyte integrin family and represents a therapeutic target of relevant interest given its primary role in mediating inflammation, autoimmune pathologies and cancer-related diseases. The focus of the present work is the design, synthesis and characterization of new peptidomimetic compounds that are potentially able to recognize α₄β₁ integrin and interfere with its function. To this aim, a collection of seven new cyclic peptidomimetics possessing both a 4-aminoproline (Amp) core scaffold grafted onto key α₄β₁-recognizing sequences and the (2-methylphenyl)ureido-phenylacetyl (MPUPA) appendage, was designed, with the support of molecular modeling studies. The new compounds were synthesized through SPPS procedures followed by in-solution cyclization maneuvers. The biological evaluation of the new cyclic ligands in cell adhesion assays on Jurkat cells revealed promising submicromolar agonist activity in one compound, namely, the c[Amp(MPUPA)Val-Asp-Leu] cyclopeptide. Further investigations will be necessary to complete the characterization of this class of compounds.

Peptide-functionalized liposomes as therapeutic and diagnostic tools for cancer treatment

Clinically efficacious medication in anticancer therapy has been successfully designed with liposome-based nanomedicine. The liposomal formulation in cancer drug delivery can be facilitated with a functionalized peptide that mediates the specific drug delivery opportunities with increased drug penetrability, specific accumulation in the targeted site, and enhanced therapeutic efficacy. This review aims to focus on recent advances in peptide-functionalized liposomal formulation techniques in cancer diagnosis and treatment regarding recently published literature. It also will highlight different aspects of novel liposomal formulation techniques that incorporate surface functionalization with peptides for better anticancer effect and current challenges in peptide-functionalized liposomal drug formulation.

Endothelial capture using antibodies and nanoparticles in human tissues: Antigen identification and liver segment imaging

BACKGROUND

The unique phenomenon of endothelial antibody capture (endocapt) leads to site-specific accumulation of antibodies on the endothelium after its locoregional injection. The potential of this phenomenon has already been demonstrated in animal models. In the present study, the translational potential of several human endothelium-specific antibodies for their use in the endocapt-based approach was analysed.

METHODS

The binding of different endothelium-surface specific monoclonal antibody clones was analysed in human tissue and in endothelial cells using image-based immunofluorescence and the determination of half-maximal effective concentration (EC₅₀). The potential of endocapt-based locoregional application of antibodies or antibody-coated liposomes was analysed ex vivo using isolated mouse liver perfusion and in vivo using superselective injection in tumour models.

RESULTS

Eight out of ten antibody clones were assigned to the group of "fast binding antibodies". Different antibody clones showed various binding kinetics to the same endothelial marker whereas the binding kinetics of single antibody clones was independent from the tissue type. Anti-CD49e, anti-CD31, anti-CD34 and anti-CD102 antibodies showed the lowest EC₅₀ of antibody binding concentration and constant results in EC₅₀ determination of antibody binding to cells and human tissue. Experimental studies using anti-mouse CD49e antibody and coated immunoliposomes confirmed their effective capture by endothelial cells in vitro and in vivo by which fluorescent liver segment labelling was achieved.

CONCLUSIONS

Our findings identify the high potential of several human antibody clones, especially anti-CD49e, -CD31, -CD34 and -CD102, for endocapt technology. We also propose important translational implications of these antibodies for image-guided liver surgery and for use of nanoparticles/immunoliposomes. Toxicological studies are indispensable for further translational development of new antibodies for endocapt.

STATEMENT OF SIGNIFICANCE

The phenomenon of endothelial antibody capture (endocapt) leads to site-specific accumulation of antibodies on the endothelium after its locoregional injection. This phenomenon broadly prevents systemic circulation of the antibody or antibody-drug conjugates. In the present study, our findings identify several human antibody clones promising for endothelial capture technology. This study provided the experimental demonstration of liver segment labelling ex vivo using isolated mouse liver perfusion and in vivo using superselective injection in tumor models. In addition, this study proposed the important translational implications of selected antibodies for image-guided liver surgery and for use of nanoparticles/immunoliposomes.

Targeting integrins for cancer management using nanotherapeutic approaches: Recent advances and challenges

Integrins are the main cell surface receptors and execute multifaceted functions such as the bidirectional transmission of signals (i.e., inside-out and outside-in) and provide communication between cells and their microenvironments. Integrins are the key regulators of critical biological functions and contribute significantly to the promotion of cancer at almost every stage of disease progression from initial tumor formation to metastasis. Integrin expressions are frequently altered in different cancers, and consequently, several therapeutic strategies targeting integrins have been developed. Furthermore, nanotechnology-based approaches have been devised to overcome the intrinsic limitations of conventional therapies for cancer management, and have been shown to more precise, safer, and highly effective therapeutic tools. Although nanotechnology-based approaches have achieved substantial success for the management of cancer, certain obstacles remain such as inadequate knowledge of nano-bio interactions and the challenges associated with the three stages of clinical trials. This review highlights the different roles of integrins and of integrin-dependent signaling in various cancers and describes the applications of nanotherapeutics targeting integrins. In addition, we discuss RGD-based approaches and challenges posed to cancer management.

Integrin-targeted AmpRGD sunitinib liposomes as integrated antiangiogenic tools

We report here the preparation, physico-chemical characterization, and biological evaluation of a new liposome formulation as a tool for tumor angiogenesis inhibition. Liposomes are loaded with sunitinib, a tyrosine kinase inhibitor, and decorated with cyclo-aminoprolineRGD units (cAmpRGD), efficient and selective ligands for integrin α_Vβ₃. The RGD units play multiple roles since they target the nanovehicles at the integrin α_Vβ₃-overexpressing cells (e.g. activated endothelial cells), favor their active cell internalization, providing drug accumulation in the cytoplasm, and likely take part in the angiogenesis inhibition by interfering in the α_Vβ₃-VEGFR2 cross-talk. Both in vitro and in vivo studies show a better efficacy of this integrated antiangiogenic tool with respect to the free sunitinib and untargeted sunitinib-loaded liposomes. This system could allow a lower administration of the drug and, by increasing the vector specificity, reduce side-effects in a prolonged antiangiogenic therapy.

Peptide-Based Drug-Delivery Systems in Biotechnological Applications: Recent Advances and Perspectives

Peptides of natural and synthetic sources are compounds operating in a wide range of biological interactions. They play a key role in biotechnological applications as both therapeutic and diagnostic tools. They are easily synthesized thanks to solid-phase peptide devices where the amino acid sequence can be exactly selected at molecular levels, by tuning the basic units. Recently, peptides achieved resounding success in drug delivery and in nanomedicine smart applications. These applications are the most significant challenge of recent decades: they can selectively deliver drugs to only pathological tissues whilst saving the other districts of the body. This specific feature allows a reduction in the drug side effects and increases the drug efficacy. In this context, peptide-based aggregates present many advantages, including biocompatibility, high drug loading capacities, chemical diversity, specific targeting, and stimuli responsive drug delivery. A dual behavior is observed: on the one hand they can fulfill a structural and bioactive role. In this review, we focus on the design and the characterization of drug delivery systems using peptide-based carriers; moreover, we will also highlight the peptide ability to self-assemble and to actively address nanosystems toward specific targets.

Arginylglycylaspartic Acid-Surface-Functionalized Doxorubicin-Loaded Lipid-Core Nanocapsules as a Strategy to Target Alpha(V) Beta(3) Integrin Expressed on Tumor Cells

Doxorubicin (Dox) clinical use is limited by dose-related cardiomyopathy, becoming more prevalent with increasing cumulative doses. Previously, we developed Dox-loaded lipid-core nanocapsules (Dox-LNC) and, in this study, we hypothesized that self-assembling and interfacial reactions could be used to obtain arginylglycylaspartic acid (RGD)-surface-functionalized-Dox-LNC, which could target tumoral cells overexpressing αvβ3 integrin. Human breast adenocarcinoma cell line (MCF-7) and human glioblastoma astrocytoma (U87MG) expressing different levels of αvβ3 integrin were studied. RGD-functionalized Dox-LNC were prepared with Dox at 100 and 500 mg·mL-1 (RGD-MCMN (Dox100) and RGD-MCMN (Dox500)). Blank formulation (RGD-MCMN) had z-average diameter of 162 ± 6 nm, polydispersity index of 0.11 ± 0.04, zeta potential of +13.2 ± 1.9 mV and (6.2 ± 1.1) × 1011 particles mL-1, while RGD-MCMN (Dox100) and RGD-MCMN (Dox500) showed respectively 146 ± 20 and 215 ± 25 nm, 0.10 ± 0.01 and 0.09 ± 0.03, +13.8 ± 2.3 and +16.4 ± 1.5 mV and (6.9 ± 0.6) × 1011 and (6.1 ± 1.0) × 1011 particles mL-1. RGD complexation was 7.73 × 10⁴ molecules per nanocapsule and Dox loading were 1.51 × 10⁴ and 7.64 × 10⁴ molecules per nanocapsule, respectively. RGD-functionalized nanocapsules had an improved uptake capacity by U87MG cells. Pareto chart showed that the cell viability was mainly affected by the Dox concentration and the period of treatment in both MCF-7 and U87MG. The influence of RGD-functionalization on cell viability was a determinant factor exclusively to U87MG.

RGD Peptide-Based Target Drug Delivery of Doxorubicin Nanomedicine

Preclinical Research Doxorubicin (DOX) is commonly used for the treatment of breast cancer and lymphoma. However, its clinical use has been severely limited due to cardiotoxicity, requiring the development of safer and more efficient pharmaceutical formulations of DOX. Advances in nanotechnology have provided new ways to administer chemotherapeutic drugs like DOX are conveyed into the body and to tumor sites. These Nanotechnology approaches have aided in the selective accumulation of DOX into tumor sites via the enhanced permeability and retention. However, the absence of active targeting ligands still hinders the effective delivery of DOX. Among all active targeting ligands developed to date, RGD peptide (Arginylglycylaspartic acid) occupies a unique position owing to its inherent safety, biocompatibility, and targeting ability. Accordingly, modification of DOX with RGD ligand is anticipated to improve transport of DOX into tumor cells. In this review, we discuss using RGD peptide for improving the therapeutic efficacy of DOX nanomedicine. Drug Dev Res 78 : 283-291, 2017. © 2017 Wiley Periodicals, Inc.

The design of peptide-amphiphiles as functional ligands for liposomal anticancer drug and gene delivery

Liposomal nanomedicine has led to clinically useful cancer therapeutics like Doxil and DaunoXome. In addition, peptide-functionalized liposomes represent an effective drug and gene delivery vehicle with increased cancer cell specificity, enhanced tumor-penetrating ability and high tumor growth inhibition. The goal of this article is to review the recently published literature of the peptide-amphiphiles that were used to functionalize liposomes, to highlight successful designs that improved drug and gene delivery to cancer cells in vitro, and cancer tumors in vivo, and to discuss the current challenges of designing these peptide-decorated liposomes for effective cancer treatment.

Synthesis of Novel c(AmpRGD)-Sunitinib Dual Conjugates as Molecular Tools Targeting the αvβ3 Integrin/VEGFR2 Couple and Impairing Tumor-Associated Angiogenesis

On the basis of a previously discovered anti-α_Vβ₃ integrin peptidomimetic (c(AmpRGD)) and the clinically approved antiangiogenic kinase inhibitor sunitinib, three novel dual conjugates were synthesized (compounds 1-3), featuring the covalent and robust linkage between these two active modules. In all conjugates, the ligand binding competence toward α_Vβ₃ (using both isolated receptors and α_Vβ₃-overexpressing endothelial progenitor EP cells) and the kinase inhibitory activity (toward both isolated kinases and EPCs) remained almost untouched and comparable to the activity of the single active units. Compounds 1-3 showed interesting antiangiogenesis properties in an in vitro tubulogenic assay; furthermore, dimeric-RGD conjugate 3 strongly inhibited in vivo angiogenesis in Matrigel plug assays in FVB mice. These results offer proof-of-concept of how the covalent conjugation of two angiogenesis-related small modules may result in novel and stable molecules, which impair tumor-related angiogenesis with equal or even superior ability as compared to the single modules or their simple combinations.

Design, synthesis and biological evaluation of novel dimeric and tetrameric cRGD-paclitaxel conjugates for integrin-assisted drug delivery

Integrins are associated with tumour cell survival and progression, and their expression has been shown to be increased in tumours. Thus, four novel conjugates of the tripeptide integrin ligand Arg-Gly-Asp (RGD) and the cytotoxic agent paclitaxel (cRGD-PTX) were prepared to investigate the potential of the multivalent presentation of the RGD moiety in improving the antitumor efficacy of PTX by tumour targeting. PTX was conjugated to two or four integrin recognizing ligands. The influence of multivalent presentation on in vitro αvβ3-receptor affinity was confirmed. For all the conjugates compared to the previously synthesized monovalent counterparts, an enhancement of the binding strength was observed; this behaviour was more pronounced when considering the tetravalent presented RGD-conjugate. Cell growth inhibition assays on a panel of human tumour cell lines showed remarkable cytotoxic activity for all conjugates with IC50 values in a nanomolar range. Among the four conjugates, the bivalent derivative 3b was selected for in vivo studies in an ovarian carcinoma cell model xenografted in immunodeficient mice. A marked antitumor activity was observed, similar to that of PTX, but with a much more favourable toxicity profile. Overall, the novel cRGD-PTX conjugates disclosed here represent promising candidates for further advancement in the domain of targeted anti-tumour therapy.

Advancement in integrin facilitated drug delivery

The research of integrin-targeted anticancer agents has recorded important advancements in ingenious design of delivery systems, based either on the prodrug approach, or on nanoparticle carriers, but for now, none of these has reached a clinical stage of development. Past work in this area has been extensively reviewed by us and others. Thus, the purpose and scope of the present review is to survey the advancement reported in the last 3years, with focus on innovative delivery systems that appear to afford openings for future developments. These systems exploit the labelling with conventional and novel integrin ligands for targeting the interface of cancer cells and of endothelial cells involved in cancer angiogenesis, with the proteins of the extracellular matrix, in the circulation, in tissues, and in tumour stroma, as the site of progression and metastatic evolution of the disease. Furthermore, these systems implement the expertise in the development of nanomedicines to the purpose of achieving preferential biodistribution and uptake in cancer tissues, internalisation in cancer cells, and release of the transported drugs at intracellular sites. The assessment of the value of controlling these factors, and their combination, for future developments requires support of biological testing in appropriate mechanistic models, but also imperatively demand confirmation in therapeutically relevant in vivo models for biodistribution, efficacy, and lack of off-target effects. Thus, among many studies, we have tried to point out the results supported by relevant in vivo studies, and we have emphasised in specific sections those addressing the medical needs of drug delivery to brain tumours, as well as the delivery of oligonucleotides modulating gene-dependent pathological mechanism. The latter could constitute the basis of a promising third branch in the therapeutic armamentarium against cancer, in addition to antibody-based agents and to cytotoxic agents.

Synthesis and preclinical evaluation of a novel, selective 111In-labelled aminoproline-RGD-peptide for non-invasive melanoma tumor imaging

An ¹¹¹In-labelled Amp-based RGD-DOTA conjugate was synthesized and evaluated in preclinical models of human melanoma as a novel integrin-targeted SPECT imaging tracer.