Nanobody Conjugates for Targeted Cancer Therapy and Imaging

Reforming solid tumor treatment: the emerging potential of smaller format antibody-drug conjugate

In recent years, substantial therapeutic efficacy of antibody-drug conjugates (ADCs) has been validated through approvals of 16 ADCs for the treatment of malignant tumors. However, realization of the maximum clinical use of ADCs requires surmounting extant challenges, mainly the limitations in tumor penetration capabilities when targeting solid tumors. To resolve the hurdle of suboptimal tumor penetration, miniaturized antibody fragments with engineered formats have been harnessed for ADC assembly. By virtue of their reduced molecular sizes, antibody fragment-drug conjugates hold considerable promise for efficacious delivery of cytotoxic agents, thus conferring superior therapeutic outcomes. This review will focus on current advancements in novel ADC development utilizing smaller antibody formats from ~6 to 80 kDa, with particular emphasis on single-domain antibodies, which have been widely applied in novel ADC design. Additionally, strategies to optimize clinical translation are discussed, including half-life extension, acceleration of internalization, and reduction of immunogenic potential.

Targeted drug delivery using nanobodies to deliver effective molecules to breast cancer cells: the most attractive application of nanobodies

Targeted drug delivery is one of the attractive ways in which cancer treatment can significantly reduce side effects. In the last two decades, the use of antibodies as a tool for accurate detection of cancer has been noted. On the other hand, the binding of drugs and carriers containing drugs to the specific antibodies of cancer cells can specifically target only these cells. However, the use of whole antibodies brings challenges, including their large size, the complexity of conjugation, the high cost of production, and the creation of immunogenic reactions in the body. The use of nanobodies, or VHHs, which are a small part of camel heavy chain antibodies, is very popular due to their small size, high craftsmanship, and low production cost. In this article, in addition to a brief overview of the structure and characteristics of nanobodies, the use of this molecule in the targeted drug delivery of breast cancer has been reviewed.

Nanobodies in cytokine‑mediated immunotherapy and immunoimaging (Review)

Cytokines are the main regulators of innate and adaptive immunity, mediating communications between the cells of the immune system and regulating biological functions, including cell motility, differentiation, growth and apoptosis. Cytokines and cytokine receptors have been used in the treatment of tumors and autoimmune diseases, and to intervene in cytokine storms. Indeed, the use of monoclonal antibodies to block cytokine‑receptor interactions, as well as antibody‑cytokine fusion proteins has exhibited immense potential for the treatment of tumors and autoimmune diseases. Compared with these traditional types of antibodies, nanobodies not only maintain a high affinity and specificity, but also have the advantages of high thermal stability, a high capacity for chemical manipulation, low immunogenicity, good tissue permeability, rapid clearance and economic production. Thus, nanobodies have extensive potential for use in the diagnosis and treatment of cytokine‑related diseases. The present review summarizes the application of nanobodies in cytokine‑mediated immunotherapy and immunoimaging.

Preparation of Chromobodies for the Detection of Cell Surface Epitopes

Chromobodies are nanobodies genetically fused to fluorescent proteins, which were developed to visualize endogenous intracellular antigens. These versatile bioimaging nanotools can also be used to detect cell surface epitopes, and we describe here how we use them as an alternative to conjugated antibodies. This way, we routinely test the binding efficiency of nanobodies for their cognate cell surface antigens, before integrating them as sensing domains into complex synthetic receptor architectures.

The Evolving Landscape of Antibody-Drug Conjugates: In Depth Analysis of Recent Research Progress

Antibody-drug conjugates (ADCs) are targeted immunoconjugate constructs that integrate the potency of cytotoxic drugs with the selectivity of monoclonal antibodies, minimizing damage to healthy cells and reducing systemic toxicity. Their design allows for higher doses of the cytotoxic drug to be administered, potentially increasing efficacy. They are currently among the most promising drug classes in oncology, with efforts to expand their application for nononcological indications and in combination therapies. Here we provide a detailed overview of the recent advances in ADC research and consider future directions and challenges in promoting this promising platform to widespread therapeutic use. We examine data from the CAS Content Collection, the largest human-curated collection of published scientific information, and analyze the publication landscape of recent research to reveal the exploration trends in published documents and to provide insights into the scientific advances in the area. We also discuss the evolution of the key concepts in the field, the major technologies, and their development pipelines with company research focuses, disease targets, development stages, and publication and investment trends. A comprehensive concept map has been created based on the documents in the CAS Content Collection. We hope that this report can serve as a useful resource for understanding the current state of knowledge in the field of ADCs and the remaining challenges to fulfill their potential.

Single domain antibodies specific for HER2 dimerization domain effectively disrupts HER2 dimerization

Dimer-dependent phosphorylation of HER2 receptor is a key event for the signal transduction of HER family of receptors which correlates with tumor invasion and metastasis. New generation of therapies based on dimerization domain inhibition using monoclonal or fragment antibodies was introduced. A potent method for manufacturing antibodies and antibody fragments is the phage display antibody library method. A recombinant phage was generated using the phage display method from synthetic dAb library. Subtractive biopanning was performed on sepharose 4b resin. Evaluation of success of subtractive biopanning was confirmed by the PCR fingerprinting after the fourth round of biopanning. The fourth round of biopanning results in the isolation of several dimerization domain reactive clones based on the polyclonal phage ELISA results. Monoclonal phage cell ELISA was used to select the positive clones with the highest affinity, and they were subsequently employed for functional tests. Cell-ELISA, MTT assay and dimerization inhibition test revealed that the reactivity and specificity of the selected monoclonal phage to dimerization domain of HER2. Further, Annexin V/PI staining and gene expression analysis showed that increased apoptosis rates. Also, in silico binding of the selected clones to conformational structure of HER2 was applied, using protein-protein docking tool of the ICM-Pro software, and showed sdAbs were specifically interacted with dimerization domain of the receptor. In conclusion, we have identified a single domain targeting HER2 dimerization, which represents a promising therapeutic and diagnostic candidate for HER2-positive cancers. Purified sdAb needs to more research to evaluate it both in vivo and in vitro via functional tests to determine if it can be applied for treatment and diagnostics.

Penetration of Nanobody-Dextran Polymer Conjugates through Tumor Spheroids

Here we report the generation of nanobody dextran polymer conjugates (dextraknobs) that are loaded with small molecules, i.e., fluorophores or photosensitizers, for potential applications in cancer diagnostics and therapy. To this end, the molecules are conjugated to the dextran polymer which is coupled to the C-terminus of an EGFR-specific nanobody using chemoenzymatic approaches. A monovalent EGFR-targeted nanobody and biparatopic version modified with different dextran average molecular weights (1000, 5000, and 10,000) were probed for their ability to penetrate tumor spheroids. For monovalent Cy5-labeled dextraknobs, the utilization of smaller sized dextran (MW 5000 vs. 10,000) was found to be beneficial for more homogeneous penetration into A431 tumor spheroids over time. For the biparatopic dual nanobody comprising MW 1000, 5000, and 10,000 dextran labeled with photosensitizer IRDye700DX, penetration behavior was comparable to that of a direct nanobody-photosensitizer conjugate lacking a dextran scaffold. Additionally, dextraknobs labeled with IRDye700DX incubated with cells in 2D and 3D showed potent cell killing upon illumination, thus inducing photodynamic therapy (PDT). In line with previous results, monovalent nanobody conjugates displayed deeper and more homogenous penetration through spheroids than the bivalent conjugates. Importantly, the smaller size dextrans did not affect the distribution of the conjugates, thus encouraging further development of dextraknobs.

NANOBODY® Molecule, a Giga Medical Tool in Nanodimensions

Although antibodies remain the most widely used tool for biomedical research, antibody technology is not flawless. Innovative alternatives, such as Nanobody® molecules, were developed to address the shortcomings of conventional antibodies. Nanobody® molecules are antigen-binding variable-domain fragments derived from the heavy-chain-only antibodies of camelids (VHH) and combine the advantageous properties of small molecules and monoclonal antibodies. Nanobody® molecules present a small size (~15 kDa, 4 nm long and 2.5 nm wide), high solubility, stability, specificity, and affinity, ease of cloning, and thermal and chemical resistance. Recombinant production in microorganisms is cost-effective, and VHH are also building blocks for multidomain constructs. These unique features led to numerous applications in fundamental research, diagnostics, and therapy. Nanobody® molecules are employed as biomarker probes and, when fused to radioisotopes or fluorophores, represent ideal non-invasive in vivo imaging agents. They can be used as neutralizing agents, receptor-ligand antagonists, or in targeted vehicle-based drug therapy. As early as 2018, the first Nanobody®, Cablivi (caplacizumab), a single-domain antibody (sdAb) drug developed by French pharmaceutical giant Sanofi for the treatment of adult patients with acquired thrombocytopenic purpura (aTTP), was launched. Nanobody® compounds are ideal tools for further development in clinics for diagnostic and therapeutic purposes.

Targeted Alpha Therapy (TAT) with Single-Domain Antibodies (Nanobodies)

The persistent threat of cancer necessitates the development of improved and more efficient therapeutic strategies that limit damage to healthy tissues. Targeted alpha therapy (TαT), a novel form of radioimmuno-therapy (RIT), utilizes a targeting vehicle, commonly antibodies, to deliver high-energy, but short-range, alpha-emitting particles specifically to cancer cells, thereby reducing toxicity to surrounding normal tissues. Although full-length antibodies are often employed as targeting vehicles for TαT, their high molecular weight and the presence of an Fc-region lead to a long blood half-life, increased bone marrow toxicity, and accumulation in other tissues such as the kidney, liver, and spleen. The discovery of single-domain antibodies (sdAbs), or nanobodies, naturally occurring in camelids and sharks, has introduced a novel antigen-specific vehicle for molecular imaging and TαT. Given that nanobodies are the smallest naturally occurring antigen-binding fragments, they exhibit shorter relative blood half-lives, enhanced tumor uptake, and equivalent or superior binding affinity and specificity. Nanobody technology could provide a viable solution for the off-target toxicity observed with full-length antibody-based TαT. Notably, the pharmacokinetic properties of nanobodies align better with the decay characteristics of many short-lived α-emitting radionuclides. This review aims to encapsulate recent advancements in the use of nanobodies as a vehicle for TαT.

G protein-coupled receptor-targeting antibody-drug conjugates: Current status and future directions

In recent years, antibody-drug conjugates (ADCs) have emerged as promising anti-cancer therapeutic agents with several having already received market approval for the treatment of solid tumor and hematological malignancies. As ADC technology continues to improve and the range of indications treatable by ADCs increases, the repertoire of target antigens has expanded and will undoubtedly continue to grow. G protein-coupled receptors (GPCRs) are well-characterized therapeutic targets implicated in many human pathologies, including cancer, and represent a promising emerging target of ADCs. In this review, we will discuss the past and present therapeutic targeting of GPCRs and describe ADCs as therapeutic modalities. Moreover, we will summarize the status of existing preclinical and clinical GPCR-targeted ADCs and address the potential of GPCRs as novel targets for future ADC development.

Specific Detection of Proteins by a Nanobody-Functionalized Nanopore Sensor

Nanopores are label-free single-molecule analytical tools that show great potential for stochastic sensing of proteins. Here, we described a ClyA nanopore functionalized with different nanobodies through a 5-6 nm DNA linker at its periphery. Ty1, 2Rs15d, 2Rb17c, and nb22 nanobodies were employed to specifically recognize the large protein SARS-CoV-2 Spike, a medium-sized HER2 receptor, and the small protein murine urokinase-type plasminogen activator (muPA), respectively. The pores modified with Ty1, 2Rs15d, and 2Rb17c were capable of stochastic sensing of Spike protein and HER2 receptor, respectively, following a model where unbound nanobodies, facilitated by a DNA linker, move inside the nanopore and provoke reversible blockade events, whereas engagement with the large- and medium-sized proteins outside of the pore leads to a reduced dynamic movement of the nanobodies and an increased current through the open pore. Exploiting the multivalent interaction between trimeric Spike protein and multimerized Ty1 nanobodies enabled the detection of picomolar concentrations of Spike protein. In comparison, detection of the smaller muPA proteins follows a different model where muPA, complexing with the nb22, moves into the pore, generating larger blockage signals. Importantly, the components in blood did not affect the sensing performance of the nanobody-functionalized nanopore, which endows the pore with great potential for clinical detection of protein biomarkers.

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.

Delivery of Drugs into Cancer Cells Using Antibody-Drug Conjugates Based on Receptor-Mediated Endocytosis and the Enhanced Permeability and Retention Effect

Innumerable people worldwide die of cancer every year, although pharmaceutical therapy has actualized many benefits in human health. For background, anti-cancer drug development is difficult due to the multifactorial pathogenesis and complicated pathology of cancers. Cancer cells excrete hydrophobic low-molecular anti-cancer drugs by overexpressed efflux transporters such as multiple drug resistance 1 (MDR1) at the apical membrane. Mutation-driven drug resistance is also developed in cancer. Moreover, the poor distribution of drug to cancer cells is a serious problem, because patients suffer from off-target side effects. Thus, highly selective and effective drug delivery into solid cancer cells across the membrane should be established. It is known that substances (10-100 nm in diameter) such as monoclonal antibodies (mAbs) (approximately 14.2 nm in diameter) or nanoparticles spontaneously gather in solid tumor stroma or parenchyma through the capillary endothelial fenestration, ranging from 200-2000 nm, in neovasculatures due to the enhanced permeability and retention (EPR) effect. Furthermore, cancer antigens, such as HER2, Nectin-4, or TROP2, highly selectively expressed on the surface of cancer cells act as a receptor for receptor-mediated endocytosis (RME) using mAbs against such antigens. Thus, antibody-drug conjugates (ADCs) are promising anti-cancer pharmaceutical agents that fulfill accurate distribution due to the EPR effect and due to antibody-antigen binding and membrane permeability owing to RME. In this review, I introduce the implementation and possibility of highly selective anti-cancer drug delivery into solid cancer cells based on the EPR effect and RME using anti-cancer antigens ADCs with payloads through suitable linkers.

Nanobodies for the Early Detection of Ovarian Cancer

Ovarian cancer ranks fifth in cancer-related deaths among women. Since ovarian cancer patients are often asymptomatic, most patients are diagnosed only at an advanced stage of disease. This results in a 5-year survival rate below 50%, which is in strong contrast to a survival rate as high as 94% if detected and treated at an early stage. Monitoring serum biomarkers offers new possibilities to diagnose ovarian cancer at an early stage. In this study, nanobodies targeting the ovarian cancer biomarkers human epididymis protein 4 (HE4), secretory leukocyte protease inhibitor (SLPI), and progranulin (PGRN) were evaluated regarding their expression levels in bacterial systems, epitope binning, and antigen-binding affinity by enzyme-linked immunosorbent assay and surface plasmon resonance. The selected nanobodies possess strong binding affinities for their cognate antigens (K_D~0.1-10 nM) and therefore have a pronounced potential to detect ovarian cancer at an early stage. Moreover, it is of utmost importance that the limits of detection (LOD) for these biomarkers are in the pM range, implying high specificity and sensitivity, as demonstrated by values in human serum of 37 pM for HE4, 163 pM for SLPI, and 195 pM for PGRN. These nanobody candidates could thus pave the way towards multiplexed biosensors.