Tumor-targeted Nanobullets: Anti-EGFR nanobody-liposomes loaded with anti-IGF-1R kinase inhibitor for cancer treatment

Nanobody-liposomes as novel cancer vaccine platform to efficiently stimulate T cell immunity

Cancer vaccines can be utilized in combination with checkpoint inhibitors to optimally stimulate the anti-tumor immune response. Uptake of vaccine antigen by antigen presenting cells (APCs) is a prerequisite for T cell priming, but often relies on non-specific mechanisms. Here, we have developed a novel vaccination strategy consisting of cancer antigen-containing liposomes conjugated with CD169- or DC-SIGN-specific nanobodies (single domain antibodies) to achieve specific uptake by APCs. Our studies demonstrate efficient nanobody liposome uptake by human and murine CD169+ and DC-SIGN+ APCs in vitro and in vivo when compared to control liposomes or liposomes with natural ligands for CD169 and DC-SIGN. Uptake of CD169 nanobody liposomes resulted in increased T cell activation by human APCs and stimulated naive T cell priming in mouse models. In conclusion, while nanobody liposomes have previously been utilized to direct drugs to tumors, here we show that nanobody liposomes can be applied as vaccination strategy that can be extended to other receptors on APCs in order to elicit a potent immune response against tumor antigens.

Single-domain antibodies as therapeutics for solid tumor treatment

Single-domain antibodies (sdAbs), initially identified in camelids or sharks and commonly referred to as nanobodies or VNARs, have emerged as a promising alternative to conventional therapeutic antibodies. These sdAbs have many superior physicochemical and pharmacological properties, including small size, good solubility and thermostability, easier accessible epitopes, and strong tissue penetration. However, the inherent challenges associated with the animal origin of sdAbs limit their clinical use. In recent years, various innovative humanization technologies, including complementarity-determining region (CDR) grafting or complete engineering of fully human sdAbs, have been developed to mitigate potential immunogenicity issues and enhance their compatibility. This review provides a comprehensive exploration of sdAbs, emphasizing their distinctive features and the progress in humanization methodologies. In addition, we provide an overview of the recent progress in developing drugs and therapeutic strategies based on sdAbs and their potential in solid tumor treatment, such as sdAb-drug conjugates, multispecific sdAbs, sdAb-based delivery systems, and sdAb-based cell therapy.

Chimeric nanobody-decorated liposomes by self-assembly

Liposomes as drug vehicles have advantages, such as payload protection, tunable carrying capacity and improved biodistribution. However, due to the dysfunction of targeting moieties and payload loss during preparation, immunoliposomes have yet to be favoured in commercial manufacturing. Here we report a chemical modification-free biophysical approach for producing immunoliposomes in one step through the self-assembly of a chimeric nanobody (cNB) into liposome bilayers. cNB consists of a nanobody against human epidermal growth factor receptor 2 (HER2), a flexible peptide linker and a hydrophobic single transmembrane domain. We determined that 64% of therapeutic compounds can be encapsulated into 100-nm liposomes, and up to 2,500 cNBs can be anchored on liposomal membranes without steric hindrance under facile conditions. Subsequently, we demonstrate that drug-loaded immunoliposomes increase cytotoxicity on HER2-overexpressing cancer cell lines by 10- to 20-fold, inhibit the growth of xenograft tumours by 3.4-fold and improve survival by more than twofold.

A landscape of recent advances in lipid nanoparticles and their translational potential for the treatment of solid tumors

Lipid nanoparticles (LNPs) are biocompatible drug delivery systems that have found numerous applications in medicine. Their versatile nature enables the encapsulation and targeting of various types of medically relevant molecular cargo, including oligonucleotides, proteins, and small molecules for the treatment of diseases, such as cancer. Cancers that form solid tumors are particularly relevant for LNP-based therapeutics due to the enhanced permeation and retention effect that allows nanoparticles to accumulate within the tumor tissue. Additionally, LNPs can be formulated for both locoregional and systemic delivery depending on the tumor type and stage. To date, LNPs have been used extensively in the clinic to reduce systemic toxicity and improve outcomes in cancer patients by encapsulating chemotherapeutic drugs. Next-generation lipid nanoparticles are currently being developed to expand their use in gene therapy and immunotherapy, as well as to enable the co-encapsulation of multiple drugs in a single system. Other developments include the design of targeted LNPs to specific cells and tissues, and triggerable release systems to control cargo delivery at the tumor site. This review paper highlights recent developments in LNP drug delivery formulations and focuses on the treatment of solid tumors, while also discussing some of their current translational limitations and potential opportunities in the field.

Preparation of Nanosized Pharmaceutical Formulations by Dual Centrifugation

Dual centrifugation (DC) is an innovative in-vial homogenization and in-vial nanomilling technique that has been in use for the preparation of liposomes for more than one decade. Since then, DC has continuously been developed for preparing various liposomes and other lipid nanoparticles including emulsions and solid lipid nanoparticles (SLNs) as well as polymersomes and nanocrystals. Improvements in equipment technology have been achieved over the past decade, so that DC is now on its way to becoming the quasi-standard for the simple, fast, and aseptic production of lipid nanoparticles and nanocrystals in small and medium batch sizes, including the possibility of simple and fast formulation screening or bedside preparations of therapeutic nanoparticles. More than 68 publications in which DC was used to produce nanoparticles have appeared since then, justifying an initial review of the use of DC for pharmaceutical nanotechnology.

Nanobodies: Robust miniprotein binders in biomedicine

Variable domains of heavy chain-only antibodies (VHH), also known as nanobodies (Nbs), are monomeric antigen-binding domains derived from the camelid heavy chain-only antibodies. Nbs are characterized by small size, high target selectivity, and marked solubility and stability, which collectively facilitate high-quality drug development. In addition, Nbs are readily expressed from various expression systems, including E. coli and yeast cells. For these reasons, Nbs have emerged as preferred antibody fragments for protein engineering, disease diagnosis, and treatment. To date, two Nb-based therapies have been approved by the U.S. Food and Drug Administration (FDA). Numerous candidates spanning a wide spectrum of diseases such as cancer, immune disorders, infectious diseases, and neurodegenerative disorders are under preclinical and clinical investigation. Here, we discuss the structural features of Nbs that allow for specific, versatile, and strong target binding. We also summarize emerging technologies for identification, structural analysis, and humanization of Nbs. Our main focus is to review recent advances in using Nbs as a modular scaffold to facilitate the engineering of multivalent polymers for cutting-edge applications. Finally, we discuss remaining challenges for Nb development and envision new opportunities in Nb-based research.

The Impact of Nanobody Density on the Targeting Efficiency of PEGylated Liposomes

Nanoparticles (NPs) are commonly modified with tumor-targeting moieties that recognize proteins overexpressed on the extracellular membrane to increase their specific interaction with target cells. Nanobodies (Nbs), the variable domain of heavy chain-only antibodies, are a robust targeting ligand due to their small size, superior stability, and strong binding affinity. For the clinical translation of targeted Nb-NPs, it is essential to understand how the number of Nbs per NP impacts the receptor recognition on cells. To study this, Nbs targeting the hepatocyte growth factor receptor (MET-Nbs) were conjugated to PEGylated liposomes at a density from 20 to 800 per liposome and their targeting efficiency was evaluated in vitro. MET-targeted liposomes (MET-TLs) associated more profoundly with MET-expressing cells than non-targeted liposomes (NTLs). MET-TLs with approximately 150-300 Nbs per liposome exhibited the highest association and specificity towards MET-expressing cells and retained their targeting capacity when pre-incubated with proteins from different sources. Furthermore, a MET-Nb density above 300 Nbs per liposome increased the interaction of MET-TLs with phagocytic cells by 2-fold in ex vivo human blood compared to NTLs. Overall, this study demonstrates that adjusting the MET-Nb density can increase the specificity of NPs towards their intended cellular target and reduce NP interaction with phagocytic cells.

Therapeutic Potential of Intrabodies for Cancer Immunotherapy: Current Status and Future Directions

Tumor cells are characterized by overexpressed tumor-associated antigens or mutated neoantigens, which are expressed on the cell surface or intracellularly. One strategy of cancer immunotherapy is to target cell-surface-expressed tumor-associated antigens (TAAs) with therapeutic antibodies. For targeting TAAs or neoantigens, adoptive T-cell therapies with activated autologous T cells from cancer patients transduced with novel recombinant TCRs or chimeric antigen receptors have been successfully applied. Many TAAs and most neoantigens are expressed in the cytoplasm or nucleus of tumor cells. As alternative to adoptive T-cell therapy, the mRNA of intracellular tumor antigens can be depleted by RNAi, the corresponding genes or proteins deleted by CRISPR-Cas or inactivated by kinase inhibitors or by intrabodies, respectively. Intrabodies are suitable to knockdown TAAs and neoantigens without off-target effects. RNA sequencing and proteome analysis of single tumor cells combined with computational methods is bringing forward the identification of new neoantigens for the selection of anti-cancer intrabodies, which can be easily performed using phage display antibody repertoires. For specifically delivering intrabodies into tumor cells, the usage of new capsid-modified adeno-associated viruses and lipid nanoparticles coupled with specific ligands to cell surface receptors can be used and might bring cancer intrabodies into the clinic.

Antibody-Incorporated Nanomedicines for Cancer Therapy

Antibody-based cancer therapy, one of the most significant therapeutic strategies, has achieved considerable success and progress over the past decades. Nevertheless, obstacles including limited tumor penetration, short circulation half-lives, undesired immunogenicity, and off-target side effects remain to be overcome for the antibody-based cancer treatment. Owing to the rapid development of nanotechnology, antibody-containing nanomedicines that have been extensively explored to overcome these obstacles have already demonstrated enhanced anticancer efficacy and clinical translation potential. This review intends to offer an overview of the advancements of antibody-incorporated nanoparticulate systems in cancer treatment, together with the nontrivial challenges faced by these next-generation nanomedicines. Diverse strategies of antibody immobilization, formats of antibodies, types of cancer-associated antigens, and anticancer mechanisms of antibody-containing nanomedicines are provided and discussed in this review, with an emphasis on the latest applications. The current limitations and future research directions on antibody-containing nanomedicines are also discussed from different perspectives to provide new insights into the construction of anticancer nanomedicines.

Generation of a High-Affinity Nanobody Against CD147 for Tumor Targeting and Therapeutic Efficacy Through Conjugating Doxorubicin

CD147, a glycosylated transmembrane protein in the immunoglobulin superfamily, is overexpressed on the surfaces of various tumor cells and promotes cancer cell proliferation, invasion, and metastasis. Nanobodies, characterized by small sizes, high affinities and specificities, and low immunogenicities, are promising diagnostic and therapeutic tools. However, there are few reports on nanobodies that specifically target CD147. In this work, a specific anti-CD147 nanobody has been successfully identified using phage display technology. The tumor target and antitumor effects have also been detected in different CD147-positive tumors in in vitro and in vivo assays, respectively. Meanwhile, it has a synergistic effect for inhibiting 4T1-bearing mice through conjugating doxorubicin. It may afford new strategies for cancer therapies.

Emerging applications of nanobodies in cancer therapy

Cancer is a heterogeneous disease, requiring treatment tailored to the unique phenotype of the patient's tumor. Monoclonal antibodies (mAbs) and variants thereof have enabled targeted therapies to selectively target cancer cells. Cancer cell-specific mAbs have been used for image-guided surgery and targeted delivery of radionuclides or toxic agents, improving classical treatment strategies. Cancer cell-specific mAbs can further inhibit tumor cell growth or can stimulate immune-mediated destruction of cancer cells, a feature that has also been achieved through mAb-mediated manipulation of immune cells and pathways. Drawbacks of mAbs and their variants, together with the discovery of camelid heavy chain-only antibodies and the many advantageous features of their variable domains, referred to as V_HHs, single domain antibodies or nanobodies (Nbs), resulted in the exploration of Nbs as an alternative targeting moiety. We therefore review the state-of-the-art as well as novel exploitation strategies of Nbs for targeted cancer therapy.

Structural insights into the non-inhibitory mechanism of the anti-EGFR EgB4 nanobody

Background

The epidermal growth factor receptor (EGFR) is involved in various developmental processes, and alterations of its extracellular segment are associated with several types of cancers, in particular glioblastoma multiforme (GBM). The EGFR extracellular region is therefore a primary target for therapeutic agents, such as monoclonal antibodies and variable domains of heavy chain antibodies (VHH), also called nanobodies. Nanobodies have been previously shown to bind to EGFR, and to inhibit ligand-mediated EGFR activation.

Results

Here we present the X-ray crystal structures of the EgB4 nanobody, alone (to 1.48 Å resolution) and bound to the full extracellular EGFR-EGF complex in its active conformation (to 6.0 Å resolution). We show that EgB4 binds to a new epitope located on EGFR domains I and II, and we describe the molecular mechanism by which EgB4 plays a non-inhibitory role in EGFR signaling.

Conclusion

This work provides the structural basis for the application of EgB4 as a tool for research, for targeted therapy, or as a biomarker to locate EGFR-associated tumors, all without affecting EGFR activation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-022-00412-x.

Smart Lipid-Based Nanosystems for Therapeutic Immune Induction against Cancers: Perspectives and Outlooks

Cancer immunotherapy, a promising and widely applied mode of oncotherapy, makes use of immune stimulants and modulators to overcome the immune dysregulation present in cancer, and leverage the host's immune capacity to eliminate tumors. Although some success has been seen in this field, toxicity and weak immune induction remain challenges. Liposomal nanosystems, previously used as targeting agents, are increasingly functioning as immunotherapeutic vehicles, with potential for delivery of contents, immune induction, and synergistic drug packaging. These systems are tailorable, multifunctional, and smart. Liposomes may deliver various immune reagents including cytokines, specific T-cell receptors, antibody fragments, and immune checkpoint inhibitors, and also present a promising platform upon which personalized medicine approaches can be built, especially with preclinical and clinical potentials of liposomes often being frustrated by inter- and intrapatient variation. In this review, we show the potential of liposomes in cancer immunotherapy, as well as the methods for synthesis and in vivo progression thereof. Both preclinical and clinical studies are included to comprehensively illuminate prospects and challenges for future research and application.

Coupling EGFR-Antagonistic Affibody Enhanced Therapeutic Effects of Cisplatin Liposomes in EGFR-expressing Tumor Models

Epidermal growth factor receptor (EGFR) is an efficient target for cancer therapy. In this study, a high-affinity EGFR-antagonistic affibody (Z_EGFR) molecule coupled with cisplatin-loaded PEGylated liposomes (LS-DDP) was applied to actively target EGFR⁺ A431 tumor cells in vitro and in vivo. The LS-DDP coupled with Z_EGFR (AS-DDP) had an average size of 140.01 ± 0.84 nm, low polydispersity, a zeta potential of -13.40 ± 0.8 mV, an acceptable encapsulation efficiency of 17.30 ± 1.35%, and released cisplatin in a slow-controlled manner. In vitro, AS-DDP demonstrated a higher amount of platinum intracellular uptake by A431 cells than LS-DDP. The IC50 value of AS-DDP (9.02 ± 1.55 μg/ml) was much lower than that of LS-DDP (16.44 ± 0.87 μg/ml), indicating that the anti-tumor effects of AS-DDP were remarkable due to the modification of Z_EGFR. In vivo, the concentration of AS-DDP in the tumor site increased more than 1.76-fold, while an increase in apoptotic cells at 48 h compared to the LS-DDP was also observed, illustrating that AS-DDP possessed excellent tumor-targeting efficiency. As a result, the targeted nano-liposomes achieved greater tumor suppression. Therefore, selective targeting of LS-DDP coupled with Z_EGFR enhanced the anti-tumor effects and appeared to be a promising strategy for the treatment of EGFR⁺ tumors.

Nanobodies Enhancing Cancer Visualization, Diagnosis and Therapeutics

Worldwide, cancer is a serious health concern due to the increasing rates of incidence and mortality. Conventional cancer imaging, diagnosis and treatment practices continue to substantially contribute to the fight against cancer. However, these practices do have some risks, adverse effects and limitations, which can affect patient outcomes. Although antibodies have been developed, successfully used and proven beneficial in various oncology practices, the use of antibodies also comes with certain challenges and limitations (large in size, poor tumor penetration, high immunogenicity and a long half-life). Therefore, it is vital to develop new ways to visualize, diagnose and treat cancer. Nanobodies are novel antigen-binding fragments that possess many advantageous properties (small in size, low immunogenicity and a short half-life). Thus, the use of nanobodies in cancer practices may overcome the challenges experienced with using traditional antibodies. In this review, we discuss (1) the challenges with antibody usage and the superior qualities of nanobodies; (2) the use of antibodies and nanobodies in cancer imaging, diagnosis, drug delivery and therapy (surgery, radiotherapy, chemotherapy and immunotherapy); and (3) the potential improvements in oncology practices due to the use of nanobodies as compared to antibodies.

Nanobodies as efficient drug-carriers: Progress and trends in chemotherapy

Nanobodies (Nb) have a promising future as a part of next generation chemodrug delivery systems. Nb, or VHH, are small (15 kDa) monomeric antibody fragments consisting of the antigen binding region of heavy chain antibodies. Heavy chain antibodies are naturally produced by camelids, however the structure of their VHH regions can be readily reproduced in industrial expression systems, such as bacteria or yeast. Due to their small size, high solubility, remarkable stability, manipulatable characteristics, excellent in vivo tissue penetration, conjugation advantages, and ease of production, Nb have many advantages when compared against their antibody precursors. In this review, we discuss the generation and selection of Nbs via phage display libraries for easy screening, and the conjugation techniques involved in creating target-specific nanocarriers. Furthermore, we provide a comprehensive overview of recent developments and perspectives in the field of Nb drug conjugates (NDCs) and Nb-based drug vehicles (NDv) with respect to antitumor therapeutics.

Nanobody: A Small Antibody with Big Implications for Tumor Therapeutic Strategy

The development of monoclonal antibody treatments for successful tumor-targeted therapies took several decades. However, the efficacy of antibody-based therapy is still confined and desperately needs further improvement. Nanobodies are the recombinant variable domains of heavy-chain-only antibodies, with many unique properties such as small size (~15kDa), excellent solubility, superior stability, ease of manufacture, quick clearance from blood, and deep tissue penetration, which gain increasing acceptance as therapeutical tools and are considered also as building blocks for chimeric antigen receptors as well as for targeted drug delivery. Thus, one of the promising novel developments that may address the deficiency of monoclonal antibody-based therapies is the utilization of nanobodies. This article provides readers the significant factors that the structural and biochemical properties of nanobodies and the research progress on nanobodies in the fields of tumor treatment, as well as their application prospect.

Nanobody-A versatile tool for cancer diagnosis and therapeutics

In spite of the successful use of monoclonal antibodies (mAbs) in clinic for tumor treatment, their applications are still hampered in therapeutic development due to limitations, such as tumor penetration and high cost of manufacture. Nanobody, a single domain antibody that holds the strong antigen targeting and binding capacity, has demonstrated various advantages relative to antibody. Nanobody is considered as a next-generation of antibody-derived tool in the antigen related recognition and modulation. A number of nanobodies have been developed and evaluated in different stages of clinical trials for cancer treatment. Here we summarized the current progress of nanobody in tumor diagnosis and therapeutics, particularly on the conjugation of nanobody with functional moieties. The nanobody conjugation of diagnostic agents, such as radionuclide and optical tracers, can achieve specific tumor imaging. The nanobody-drug conjugates can enhance the therapeutic efficacy of anti-tumor drugs and reduce the adverse effects. The decoration of nanobody on nanodrug delivery systems can further improve the drug targeting to specific tumors. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Nanobody: a promising toolkit for molecular imaging and disease therapy

Nanobodies are the recombinant variable domains of heavy-chain-only antibodies, with many unique properties such as small size, excellent solubility, superior stability, quick clearance from blood, and deep tissue penetration. As a result, nanobodies have become a promising tool for the diagnosis and therapy of diseases. As imaging tracers, nanobodies allow an early acquisition of high-quality images, provide a comprehensive evaluation of the disease, and subsequently enable a personalized precision therapy. As therapeutic agents, nanobodies enable a targeted therapy by lesion-specific delivery of drugs and effector domains, thereby improving the specificity and efficacy of the therapy. Up to date, a wide variety of nanobodies have been developed for a broad range of molecular targets and have played a significant role in patients with a broad spectrum of diseases. In this review, we aim to outline the current state-of-the-art research on the nanobodies for medical applications and then discuss the challenges and strategies for their further clinical translation.

Targeted nanobody complex enhanced photodynamic therapy for lung cancer by overcoming tumor microenvironment

Background

To investigate the efficacy of a PLGA-based nanobody complex in photodynamic therapy (PDT) and NIR-II imaging in A549 tumor hypoxic model.

Method

IR1048-MZ was firstly synthesized by conjugating a nitro imidazole group to IR1048. IR1048-MZ and Cat were then encapsulated in PLGA-SH solution. Anti-EGFR-Nanobody was also expressed and purified, and finally Anti-EGFR-Nanobody@PLGA-IR1048MZ-Cat (Nb@IC-NPs) nanobody complex was obtained based on the formation of desulfide bond between PLGA-SH and Anti-EGFR-Nanobody. Size distribution and morphology were characterized by TEM and DLS. Spectrum of Nb@IC-NPs towards NTR was measured by UV and fluorescence, while the particle’s selective response was studied using fluorescence. The uptake of Nb@IC-NPs in A549 cells was observed by flow cytometry and CLSM. In the meantime, its’ catalytic ability that decomposes H₂O₂ both extra-and intra-cellular was observed by fluorescence and CLSM. In vitro photodynamic toxicity of Nb@IC-NPs was examined by MTT, Live/Dead Cell Staining, Flow Cytometry and Apoptosis Assay. Tumor-bearing model was constructed to observe a semi-quantitative fluorescent distribution and the possibility of NIR-II fluorescence/photoacoustic (PA) imaging. Effect of Nb@IC-NPs on enhancing A549 tumor hypoxia and expression profile of HIF-1α was investigated in the presence of NIR. An A549 tumor metastasis model was also constructed to confirm the complex’ potential to destroy primary tumor, inhibit lung metastasis, and prolong mice’ survival. Lastly, impact of Nb@IC-NPs on mice’ main organs and blood indices was observed.

Results

Nb@IC-NPs was successfully fabricated with good homogeneity. The fluorescent absorbance of Nb@IC-NPs showed a linear relationship with the concentration of NTR, and a higher concentration of NTR corresponded to a stronger photoacoustic signal. In addition, Nb@IC-NPs showed a stable selectivity toward NTR. Our results also suggested a high efficient uptake of Nb@IC-NPs in A549 cells, which was more efficient than IC-NPs and IR1048-MZ alone. In vitro assays confirmed the effects of Nb@IC-NPs on catalytic O₂ generation even in hypoxic cells. The cell viability was upregulated with the nanocomplex at the absence of the laser, whereas it was dramatically declined with laser treatment that excited at 980 nm. Nb@IC-NPs achieved tumor hypoxia NIR-II/PA imaging through assisting A549 gathering. When NIR was applied, Nb@IC-NPs can significantly relieve A549 cellular/tumor hypoxia by generating more reactive oxygen species (ROS), which in turn helps lower the expression level of HIF-1α. In summary, Nb@IC-NPs based PDT can efficiently decimate A549 primary tumor, inhibit metastatic lung cancer, and prolong the lifespan of the mice under tolerable dosage. At last, in vivo toxicity tests of the nanocomplex showed its biosafety to the main organs and normal blood indices values.

Conclusion

Nb@IC-NPs improves tumor hypoxia through catalytic reaction and lowers the expression level of HIF-1α. It achieves tumor PA imaging through intensified NIR-II fluorescence signal that caused by response of the complex to the lesion’s nitroreductase (NTR). Nb@IC-NPs based PDT can efficiently kill A549 primary tumor, inhibit a lung metastasis, as well as prolong mice’ survival cycle.

The Therapeutic Potential of Nanobodies

Today, bio-medical efforts are entering the subcellular level, which is witnessed with the fast-developing fields of nanomedicine, nanodiagnostics and nanotherapy in conjunction with the implementation of nanoparticles for disease prevention, diagnosis, therapy and follow-up. Nanoparticles or nanocontainers offer advantages including high sensitivity, lower toxicity and improved safety—characteristics that are especially valued in the oncology field. Cancer cells develop and proliferate in complex microenvironments leading to heterogeneous diseases, often with a fatal outcome for the patient. Although antibody-based therapy is widely used in the clinical care of patients with solid tumours, its efficiency definitely needs improvement. Limitations of antibodies result mainly from their big size and poor penetration in solid tissues. Nanobodies are a novel and unique class of antigen-binding fragments, derived from naturally occurring heavy-chain-only antibodies present in the serum of camelids. Their superior properties such as small size, high stability, strong antigen-binding affinity, water solubility and natural origin make them suitable for development into next-generation biodrugs. Less than 30 years after the discovery of functional heavy-chain-only antibodies, the nanobody derivatives are already extensively used by the biotechnology research community. Moreover, a number of nanobodies are under clinical investigation for a wide spectrum of human diseases including inflammation, breast cancer, brain tumours, lung diseases and infectious diseases. Recently, caplacizumab, a bivalent nanobody, received approval from the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA) for treatment of patients with thrombotic thrombocytopenic purpura.

Cell targeting strategy affects the intracellular trafficking of liposomes altering loaded doxorubicin release kinetics and efficacy in endothelial cells

Targeting nanocarrier drug delivery systems, that deliver drug payloads to the site of disease action, are frequently viewed as the future of nanocarrier based therapies but have struggled to breakthrough to the clinic in comparison to non-targeting counterparts. Using unilamellar liposomes as model nanocarriers, we show that cell targeting strategy (electrostatic, ligand and antigen) influences both the intracellular fate of the liposomes and the corresponding efficacy of the loaded drug, doxorubicin, in endothelial cells. We show that increased liposome uptake by cells does not translate to improved efficacy in this scenario but that liposome intracellular trafficking, particularly distribution between recycling endosomes and lysosomes, influences in vitro efficacy. Choosing targeting strategies that promote desired nanocarrier intracellular trafficking may be a viable strategy to enhance the in vivo efficacy of drug delivery systems.

Nanobody click chemistry for convenient site-specific fluorescent labelling, single step immunocytochemistry and delivery into living cells by photoporation and live cell imaging

While conventional antibodies have been an instrument of choice in immunocytochemistry for some time, their small counterparts known as nanobodies have been much less frequently used for this purpose. In this study we took advantage of the availability of nanobody cDNAs to site-specifically introduce a non-standard amino acid carrying an azide/alkyne moiety, allowing subsequent Cu(I)-catalyzed Azide-Alkyne Click Chemistry (CuAAC). This generated a fluorescently labelled nanobody that can be used in single step immunocytochemistry as compared to conventional two step immunocytochemistry. Two strategies were explored to label nanobodies with Alexa Fluor 488. The first involved enzymatic addition of an alkyne-containing peptide to nanobodies using sortase A, while the second consisted of incorporating para-azido phenylalanine at the nanobody C-terminus. Through these approaches, the fluorophore was covalently and site-specifically attached. It was demonstrated that cortactin and β-catenin, cytoskeletal and adherens junction proteins respectively, can be imaged in cells in this manner through single step immunocytochemistry. However, fixation and permeabilization of cells can alter native protein structure and form a dense cross-linked protein network, encumbering antibody binding. It was shown that photoporation prior to fixation not only allowed delivery of nanobodies into living cells, but also facilitated β-catenin nanobody Nb86 imaging of its target, which was not possible in fixed cells. Pharmacological inhibitors are lacking for many non-enzymatic proteins, and it is therefore expected that new biological information will be obtained through photoporation of fluorescent nanobodies, which allows the study of short term effects, independent of gene-dependent (intrabody) expression.

Folate decorated polymeric micelles for targeted delivery of the kinase inhibitor dactolisib to cancer cells

One of the main challenges in clinical translation of polymeric micelles is retention of the drug in the nanocarrier system upon its systemic administration. Core crosslinking and coupling of the drug to the micellar backbone are common strategies to overcome these issues. In the present study, polymeric micelles were prepared for tumor cell targeting of the kinase inhibitor dactolisib which inhibits both the mammalian Target of Rapamycin (mTOR) kinase and phosphatidylinositol-3-kinase (PI3K). We employed platinum(II)-based linker chemistry to couple dactolisib to the core of poly(ethylene glycol)-b-poly(acrylic acid) (PEG-b-PAA) polymeric micelles. The formed dactolisib-PEG-PAA unimers are amphiphilic and self-assemble in an aqueous milieu into core-shell polymeric micelles. Folate was conjugated onto the surface of the micelles to yield folate-decorated polymeric micelles which can target folate receptor over-expressing tumor cells. Fluorescently labeled polymeric micelles were prepared using a lissamine-platinum complex linked in a similar manner as dactolisib. Dactolisib polymeric micelles showed good colloidal stability in water and released the coupled drug in buffers containing chloride or glutathione. Folate decorated micelles were avidly internalized by folate-receptor-positive KB cells and displayed targeted cellular cytotoxicity at 50-75 nM IC₅₀. In conclusion, we have prepared a novel type of folate-receptor targeted polymeric micelles in which platinum(II) linker chemistry modulates drug retention and sustained release of the coupled inhibitor dactolisib.

EGFR-Targeted Nanobody Functionalized Polymeric Micelles Loaded with mTHPC for Selective Photodynamic Therapy

meta-Tetra(hydroxyphenyl)chlorin (mTHPC) is one of the most potent second-generation photosensitizers, clinically used for photodynamic therapy (PDT) of head and neck squamous cell carcinomas. However, improvements are still required concerning its present formulation (i.e., Foscan, a solution of mTHPC in ethanol/propylene glycol (40:60 w/w)), as mTHPC has the tendency to aggregate in aqueous media, e.g., biological fluids, and it has limited tumor specificity. In the present study, polymeric micelles with three different diameters (17, 24, and 45 nm) based on benzyl-poly(ε-caprolactone)-b-poly(ethylene glycol) (PCL_n-PEG; n = 9, 15, or 23) were prepared with mTHPC loadings ranging from 0.5 to 10 wt % using a film-hydration method as advanced nanoformulations for this photosensitizer. To favor the uptake of the micelles by cancer cells that overexpress the epidermal growth factor receptor (EGFR), the micelles were decorated with an EGFR-targeted nanobody (named EGa1) through maleimide-thiol chemistry. The enhanced binding of the EGFR-targeted micelles at 4 °C to EGFR-overexpressing A431 cells, compared to low-EGFR-expressing HeLa cells, confirmed the specificity of the micelles. In addition, an enhanced uptake of mTHPC-loaded micelles by A431 cells was observed when these were decorated with the EGa1 nanobody, compared to nontargeted micelles. Both binding and uptake of targeted micelles were blocked by an excess of free EGa1 nanobody, demonstrating that these processes occur through EGFR. In line with this, mTHPC loaded in EGa1-conjugated PCL₂₃-PEG (EGa1-P₂₃) micelles demonstrated 4 times higher photocytotoxicity on A431 cells, compared to micelles lacking the nanobody. Importantly, EGa1-P₂₃ micelles also showed selective PDT against A431 cells compared to the low-EGFR-expressing HeLa cells. Finally, an in vivo pharmacokinetic study shows that after intravenous injection, mTHPC incorporated in the P₂₃ micelles displayed prolonged blood circulation kinetics, compared to free mTHPC, independently of the presence of EGa1. Thus, these results make these micelles a promising nanomedicine formulation for selective therapy.

Extra-Small Gold Nanospheres Decorated With a Thiol Functionalized Biodegradable and Biocompatible Linear Polyamidoamine as Nanovectors of Anticancer Molecules

Gold nanoparticles are elective candidate for cancer therapy. Current efforts are devoted to developing innovative methods for their synthesis. Besides, understanding their interaction with cells have become increasingly important for their clinical application. This work aims to describe a simple approach for the synthesis of extra-small gold nanoparticles for breast cancer therapy. In brief, a biocompatible and biodegradable polyamidoamine (named AGMA1-SH), bearing 20%, on a molar basis, thiol-functionalized repeat units, is employed to stabilize and coat extra-small gold nanospheres of different sizes (2.5, 3.5, and 5 nm in gold core), and to generate a nanoplatform for the link with Trastuzumab monoclonal antibody for HER2-positive breast cancer targeting. Dynamic light scattering, transmission electron microscopy, ultraviolet visible spectroscopy, X-ray powder diffraction, circular dichroism, protein quantification assays are used for the characterization. The targeting properties of the nanosystems are explored to achieve enhanced and selective uptake of AGMA1-SH-gold nanoparticles by in vitro studies against HER-2 overexpressing cells, SKBR-3 and compared to HER-2 low expressing cells, MCF-7, and normal fibroblast cell line, NIH-3T3. In vitro physicochemical characterization demonstrates that gold nanoparticles modified with AGMA1-SH are more stable in aqueous solution than the unmodified ones. Additionally, the greater gold nanoparticles size (5-nm) is associated with a higher stability and conjugation efficiency with Trastuzumab, which retains its folding and anticancer activity after the conjugation. In particular, the larger Trastuzumab functionalized nanoparticles displays the highest efficacy (via the pro-apoptotic protein increase, anti-apoptotic components decrease, survival-proliferation pathways downregulation) and internalization (via the activation of the classical clathrin-mediated endocytosis) in HER-2 overexpressing SKBR-3 cells, without eliciting significant effects on the other cell lines. The use of biocompatible AGMA1-SH for producing covalently stabilized gold nanoparticles to achieve selective targeting, cytotoxicity and uptake is completely novel, offering an important advancement for developing new anticancer conjugated-gold nanoparticles.

Theranostics in immuno-oncology using nanobody derivatives

Targeted therapy and immunotherapy have become mainstream in cancer treatment. However, only patient subsets benefit from these expensive therapies, and often responses are short‐lived or coincide with side effects. A growing modality in precision oncology is the development of theranostics, as this enables patient selection, treatment and monitoring. In this approach, labeled compounds and an imaging technology are used to diagnose patients and select the best treatment option, whereas for therapy, related compounds are used to target cancer cells or the tumor stroma. In this context, nanobodies and nanobody-directed therapeutics have gained interest. This interest stems from their high antigen specificity, small size, ease of labeling and engineering, allowing specific imaging and design of therapies targeting antigens on tumor cells, immune cells as well as proteins in the tumor environment. This review provides a comprehensive overview on the state-of-the-art regarding the use of nanobodies as theranostics, and their importance in the emerging field of personalized medicine.

Selective Cytotoxicity to HER2 Positive Breast Cancer Cells by Saporin-Loaded Nanobody-Targeted Polymeric Nanoparticles in Combination with Photochemical Internalization

In cancer treatment, polymeric nanoparticles (NPs) can serve as a vehicle for the delivery of cytotoxic proteins that have intracellular targets but that lack well-defined mechanisms for cellular internalization, such as saporin. In this work, we have prepared PEGylated poly(lactic acid- co-glycolic acid- co-hydroxymethyl glycolic acid) (PLGHMGA) NPs for the selective delivery of saporin in the cytosol of HER2 positive cancer cells. This selective uptake was achieved by decorating the surface of the NPs with the 11A4 nanobody that is specific for the HER2 receptor. Confocal microscopy observations showed rapid and extensive uptake of the targeted NPs (11A4-NPs) by HER2 positive cells (SkBr3) but not by HER2 negative cells (MDA-MB-231). This selective uptake was blocked upon preincubation of the cells with an excess of nanobody. Nontargeted NPs (Cys-NPs) were not taken up by either type of cells. Importantly, a dose-dependent cytotoxic effect was only observed on SkBr3 cells when these were treated with saporin-loaded 11A4-NPs in combination with photochemical internalization (PCI), a technique that uses a photosensitizer and local light exposure to facilitate endosomal escape of entrapped nanocarriers and biomolecules. The combined use of saporin-loaded 11A4-NPs and PCI strongly inhibited cell proliferation and decreased cell viability through induction of apoptosis. Also the cytotoxic effect could be reduced by an excess of nanobody, reinforcing the selectivity of this system. These results suggest that the combination of the targeting nanobody on the NPs with PCI are effective means to achieve selective uptake and cytotoxicity of saporin-loaded NPs.

Multi-targeted approach by 2-benzimidazolylquinoxalines-loaded cationic arginine liposomes against сervical cancer cells in vitro

Multi-targeted approaches for inhibition of сervical cancer cells in vitro were developed by implementing two different strategies and drug combination for creation of new therapeutic target agents and for nanotechnological-enhancement of intracellular delivery. New 2-benzimidazolylquinoxalines derivatives were synthesized and characterized by combining two different pharmacophores - benzimidazole and quinoxaline rings directly bonded in their structures. Spectrophotometric technique for determination of content of compounds in various media was developed to evaluate their solubility in water and micellar solutions of surfactants. The bioavailability of poorly water-soluble 2-benzimidazolylquinoxalines was improved by PEGylated liposomes as antitumor drug delivery carriers. 2-benzimidazolylquinoxalines-loaded PEGylated liposomes, with size close to 100 nm and negative zeta potential ranging from -13 mV to -27 mV, were time-stable at room temperature. The design of liposomal formulations for improving cellular uptake and in vitro antitumor efficacy was performed by modification of liposome surface with the new arginine surfactant. The cell viability of 2-benzimidazolylquinoxalines-loaded arginine liposomes on human cancer M-Hela cells was 16% at the concentration 0.15 mg/ml. Moreover, these liposomes showed a lower toxicity (40%) against normal human Gang liver cells both at the lowest and highest tested concentrations.

Differentially expressed coding and noncoding RNAs in CoCl2-induced cytotoxicity of C2C12 cells

Aim: We aimed to explore potential regulators of coding and noncoding RNAs (ncRNAs) in Co(II) ion-induced myo cytotoxicity. Materials & methods: We confirmed the toxic effects of Co(II) on mouse skeletal C2C12 myotubes by CoCl2, and performed the expression profiles of circular RNAs (circRNAs), long noncoding RNAs (lncRNAs) and mRNAs using microarray analysis. We constructed co-expression, competing endogenous RNA and cis/trans regulation networks for ncRNAs, and filtered 71 candidate circRNAs with coding potential. Results: We identify 605 differentially expressed circRNAs, 4409 long noncoding RNAs and 3965 mRNAs. We also provided several ncRNAs regulation networks and presumed functions of circRNAs with coding potential. Conclusion: Our findings may reveal novel regulatory mechanisms underlying the noxious effects of CoCl2 in skeletal muscle.

Nanomaterial Preparation by Extrusion through Nanoporous Membranes

Template synthesis represents an important class of nanofabrication methods. Herein, recent advances in nanomaterial preparation by extrusion through nanoporous membranes that preserve the template membrane without sacrificing it, which is termed as "non-sacrificing template synthesis," are reviewed. First, the types of nanoporous membranes used in nanoporous membrane extrusion applications are introduced. Next, four common nanoporous membrane extrusion strategies: vesicle extrusion, membrane emulsification, precipitation extrusion, and biological membrane extrusion, are examined. These methods have been utilized to prepare a wide range of nanomaterials, including liposomes, emulsions, nanoparticles, nanofibers, and nanotubes. The principle and historical context of each specific technology are discussed, presenting prominent examples and evaluating their positive and negative features. Finally, the current challenges and future opportunities of nanoporous membrane extrusion methods are discussed.

Recombinant phosphatidylserine-binding nanobodies for targeting of extracellular vesicles to tumor cells: a plug-and-play approach

Extracellular vesicles (EVs) are increasingly being recognized as candidate drug delivery systems due to their ability to functionally transfer biological cargo between cells. However, manipulation of targeting properties of EVs through engineering of the producer cells can be challenging and time-consuming. As a novel approach to confer tumor targeting properties to isolated EVs, we generated recombinant fusion proteins of nanobodies against the epidermal growth factor receptor (EGFR) fused to phosphatidylserine (PS)-binding domains of lactadherin (C1C2). C1C2-nanobody fusion proteins were expressed in HEK293 cells and isolated from culture medium with near-complete purity as determined by SDS-PAGE. Fusion proteins specifically bound PS and showed no affinity for other common EV membrane lipids. Furthermore, C1C2 fused to anti-EGFR nanobodies (EGa1-C1C2) bound EGFR with high affinity and competed with binding of its natural ligand EGF, as opposed to C1C2 fused to non-targeting control nanobodies (R2-C1C2). Both proteins readily self-associated onto membranes of EVs derived from erythrocytes and Neuro2A cells without affecting EV size and integrity. EV-bound R2-C1C2 did not influence EV-cell interactions, whereas EV-bound EGa1-C1C2 dose-dependently enhanced specific binding and uptake of EVs by EGFR-overexpressing tumor cells. In conclusion, we developed a novel strategy to efficiently and universally confer tumor targeting properties to PS-exposing EVs after their isolation, without affecting EV characteristics, circumventing the need to modify EV-secreting cells. This strategy may also be employed to decorate EVs with other moieties, including imaging probes or therapeutic proteins.

Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications

In order to translate nanotechnology into medical practice, magnetic nanoparticles (MNPs) have been presented as a class of non-invasive nanomaterials for numerous biomedical applications. In particular, MNPs have opened a door for simultaneous diagnosis and brisk treatment of diseases in the form of theranostic agents. This review highlights the recent advances in preparation and utilization of MNPs from the synthesis and functionalization steps to the final design consideration in evading the body immune system for therapeutic and diagnostic applications with addressing the most recent examples of the literature in each section. This study provides a conceptual framework of a wide range of synthetic routes classified mainly as wet chemistry, state-of-the-art microfluidic reactors, and biogenic routes, along with the most popular coating materials to stabilize resultant MNPs. Additionally, key aspects of prolonging the half-life of MNPs via overcoming the sequential biological barriers are covered through unraveling the biophysical interactions at the bio-nano interface and giving a set of criteria to efficiently modulate MNPs' physicochemical properties. Furthermore, concepts of passive and active targeting for successful cell internalization, by respectively exploiting the unique properties of cancers and novel targeting ligands are described in detail. Finally, this study extensively covers the recent developments in magnetic drug targeting and hyperthermia as therapeutic applications of MNPs. In addition, multi-modal imaging via fusion of magnetic resonance imaging, and also innovative magnetic particle imaging with other imaging techniques for early diagnosis of diseases are extensively provided.

Nanobodies and Nanobody-Based Human Heavy Chain Antibodies As Antitumor Therapeutics

Monoclonal antibodies have revolutionized cancer therapy. However, delivery to tumor cells in vivo is hampered by the large size (150 kDa) of conventional antibodies. The minimal target recognition module of a conventional antibody is composed of two non-covalently associated variable domains (VH and VL). The proper orientation of these domains is mediated by their hydrophobic interface and is stabilized by their linkage to disulfide-linked constant domains (CH1 and CL). VH and VL domains can be fused via a genetic linker into a single-chain variable fragment (scFv). scFv modules in turn can be fused to one another, e.g., to generate a bispecific T-cell engager, or they can be fused in various orientations to antibody hinge and Fc domains to generate bi- and multispecific antibodies. However, the inherent hydrophobic interaction of VH and VL domains limits the stability and solubility of engineered antibodies, often causing aggregation and/or mispairing of V-domains. Nanobodies (15 kDa) and nanobody-based human heavy chain antibodies (75 kDa) can overcome these limitations. Camelids naturally produce antibodies composed only of heavy chains in which the target recognition module is composed of a single variable domain (VHH or Nb). Advantageous features of nanobodies include their small size, high solubility, high stability, and excellent tissue penetration in vivo. Nanobodies can readily be linked genetically to Fc-domains, other nanobodies, peptide tags, or toxins and can be conjugated chemically at a specific site to drugs, radionuclides, photosensitizers, and nanoparticles. These properties make them particularly suited for specific and efficient targeting of tumors in vivo. Chimeric nanobody-heavy chain antibodies combine advantageous features of nanobodies and human Fc domains in about half the size of a conventional antibody. In this review, we discuss recent developments and perspectives for applications of nanobodies and nanobody-based human heavy chain antibodies as antitumor therapeutics.

Nanobody-Based Delivery Systems for Diagnosis and Targeted Tumor Therapy

The development of innovative targeted therapeutic approaches are expected to surpass the efficacy of current forms of treatments and cause less damage to healthy cells surrounding the tumor site. Since the first development of targeting agents from hybridoma’s, monoclonal antibodies (mAbs) have been employed to inhibit tumor growth and proliferation directly or to deliver effector molecules to tumor cells. However, the full potential of such a delivery strategy is hampered by the size of mAbs, which will obstruct the targeted delivery system to access the tumor tissue. By serendipity, a new kind of functional homodimeric antibody format was discovered in camelidae, known as heavy-chain antibodies (HCAbs). The cloning of the variable domain of HCAbs produces an attractive minimal-sized alternative for mAbs, referred to as VHH or nanobodies (Nbs). Apart from their dimensions in the single digit nanometer range, the unique characteristics of Nbs combine a high stability and solubility, low immunogenicity and excellent affinity and specificity against all possible targets including tumor markers. This stimulated the development of tumor-targeted therapeutic strategies. Some autonomous Nbs have been shown to act as antagonistic drugs, but more importantly, the targeting capacity of Nbs has been exploited to create drug delivery systems. Obviously, Nb-based targeted cancer therapy is mainly focused toward extracellular tumor markers, since the membrane barrier prevents antibodies to reach the most promising intracellular tumor markers. Potential strategies, such as lentiviral vectors and bacterial type 3 secretion system, are proposed to deliver target-specific Nbs into tumor cells and to block tumor markers intracellularly. Simultaneously, Nbs have also been employed for in vivo molecular imaging to diagnose diseased tissues and to monitor the treatment effects. Here, we review the state of the art and focus on recent developments with Nbs as targeting moieties for drug delivery systems in cancer therapy and cancer imaging.

Identification of a nanobody specific to human pulmonary surfactant protein A

Nanobody (Nb) is a promising vector for targeted drug delivery. This study aims to identify an Nb that can specifically target the lung by binding human pulmonary surfactant protein A (SP-A). Human lung frozen tissue sections were used for 3 rounds of biospanning of our previously constructed Nb library for rat SP-A to establish a sub-library of Nb, which specifically bound human lung tissues. Phage-ELISA was performed to screen the sub-library to identify Nb4, which specifically bound human SP-A. The binding affinity Kd of Nb4 to recombinant human SP-A was 7.48 × 10⁻⁷ M. Nb4 (19 kDa) was stable at 30 °C–37 °C and pH 7.0–7.6 and specifically bound the SP-A in human lung tissue homogenates, human lung A549 cells, and human lung tissues, whereas didn’t react with human liver L-02 cells, kidney 293T cells, and human tissues from organs other than the lung. Nb4 accumulated in the lung of nude mice 5 minutes after a tail vein injection of Nb4 and was excreted 3 hours. Short-term exposure (one month) to Nb4 didn’t cause apparent liver and kidney toxicity in rats, whereas 3-month exposure resulted in mild liver and kidney injuries. Nb4 may be a promising vector to specifically deliver drugs to the lung.

Recent progress in protein-protein interaction study for EGFR-targeted therapeutics

INTRODUCTION

Epidermal growth factor receptor (EGFR) expression is upregulated in many tumors and its aberrant signaling drives progression of many cancer types. Consequently, EGFR has become a clinically validated target as extracellular tumor marker for antibodies as well as for tyrosine kinase inhibitors. Within the last years, new mechanistic insights were uncovered and, based on clinical experience as well as progress in protein engineering, novel bio-therapeutic approaches were developed and tested.

AREAS COVERED

The potential therapeutic targeting arsenal in the fight against cancer now encompasses bispecific or biparatopic antibodies, DARPins, Adnectins, Affibodies, peptides and combinations of these binding molecules with viral- and nano-particles. We review past and recent binding proteins from the literature and include a brief description of the various targeting approaches. Special attention is given to the binding modes with the EGFR. Expert commentary: Clinical data from the three approved anti EGFR antibodies indicate that there is room for improved therapeutic efficacy. Having choices in size, affinity, avidity and the mode of EGFR binding as well as the possibility to combine various effector functions opens the possibility to rationally design more effective therapeutics.

Characterization and in vitro evaluation of nimotuzumab conjugated with cisplatin-loaded liposomes

In this paper, we report the conjugation of the humanized monoclonal antibody nimotuzumab with cisplatin-loaded liposomes and the in vitro evaluation of its affinity for tumor cells. The conjugation procedure was performed through derivatization of nimotuzumab with N-succinimidyl S-acetylthioacetate (SATA) followed by a covalent attachment with maleimide groups at the end of PEG-DSPE chains located at the membrane of pre-formed liposomes. Confocal microscopy was performed to evaluate the immunoliposome affinity for EGFR antigens from human epidermoid carcinoma (A-431) and normal lung (MRC-5) cell lines. Results showed that the procedures implemented in this work do not affect the capability of the nimotuzumab-immunoliposomes to recognize the tumor cells, which overexpress the EGFR antigens.

Targeting Colorectal Cancer Stem-Like Cells with Anti-CD133 Antibody-Conjugated SN-38 Nanoparticles

Cancer stem-like cells play a key role in tumor development, and these cells are relevant to the failure of conventional chemotherapy. To achieve favorable therapy for colorectal cancer, PEG-PCL-based nanoparticles, which possess good biological compatibility, were fabricated as nanocarriers for the topoisomerase inhibitor, SN-38. For cancer stem cell therapy, CD133 (prominin-1) is a theoretical cancer stem-like cell (CSLC) marker for colorectal cancer and is a proposed therapeutic target. Cells with CD133 overexpression have demonstrated enhanced tumor-initiating ability and tumor relapse probability. To resolve the problem of chemotherapy failure, SN-38-loaded nanoparticles were conjugated with anti-CD133 antibody to target CD133-positive (CD133(+)) cells. In this study, anti-CD133 antibody-conjugated SN-38-loaded nanoparticles (CD133Ab-NPs-SN-38) efficiently bound to HCT116 cells, which overexpress CD133 glycoprotein. The cytotoxic effect of CD133Ab-NPs-SN-38 was greater than that of nontargeted nanoparticles (NPs-SN-38) in HCT116 cells. Furthermore, CD133Ab-NPs-SN-38 could target CD133(+) cells and inhibit colony formation compared with NPs-SN-38. In vivo studies in an HCT116 xenograft model revealed that CD133Ab-NPs-SN-38 suppressed tumor growth and retarded recurrence. A reduction in CD133 expression in HCT116 cells treated with CD133Ab-NPs-SN-38 was also observed in immunohistochemistry results. Therefore, this CD133-targeting nanoparticle delivery system could eliminate CD133-positive cells and is a potential cancer stem cell targeted therapy.