CDH17 nanobodies facilitate rapid imaging of gastric cancer and efficient delivery of immunotoxin

Nanobody-based immunotoxins: A precision tool in the treatment of solid tumors

Solid tumors, the main cause of cancer-related death, represent a significant therapeutic challenge due to the high-density microenvironment and intolerance to conventional treatments. Nanobody-based immunotoxins (NbITs) are an exciting candidate, combining the ultimate specificity of nanobodies (single-domain antibody fragments of camelid antibodies) and detrimental effects of the toxin. These nanobodies are small (one-tenth of conventional antibody size), thermostable with high specificity, high antigen binding affinity which give it the ability to penetrate into solid tumors. Specific delivery to tumor cells is achieved through conjugating nanobodies with cytotoxic agents of bacterial origin or synthetic drugs. This phenomenon is initially attracted to the cells by the antigen-antibody interaction that is further enhanced by receptor-mediated internalization and cytotoxic payload release that subdues essential cellular processes and, as a consequence, damages the cells. This review discusses the mechanisms that underlie the effectiveness of NbITs, such as tumor antigen recognition, toxin release, and cellular signaling pathways elicited by the internalized toxins. We also discuss the application of NbITs in treating cancers such as HER2-positive breast cancer and EGFR-overexpressing lung cancer, and other cancers, highlighting their ability to address limitations of conventional therapies. Key challenges in NbIT development, including stability, immunogenicity, and efficient delivery, are critically evaluated. Current advances such as the creation of bispecific nanobody constructs, optimization of linker strategies, as well as the incorporation of nanoparticle-based delivery systems are maximizing the therapeutic potential of these molecules. This review synthesizes recent progress and addresses current obstacles in NbIT development, showcasing their transformative potential as a targeted therapeutic approach for solid tumors. It also covers future opportunities to develop and advance this emerging treatment strategy.

Chemoenzymatic Site-Specific Lysine Modification of Nanobodies and Subsequent Bioconjugation via Potassium Acyltrifluoroborate (KAT) Ligations

Single chain camelid antigen binding domains, often called nanobodies, have emerged as powerful tools for diagnostics and therapy. Methods for their site-specific modification offer immense potential for enhancing their therapeutic applications, but established approaches, such as fusion proteins, have well-known limitations in the nanobody format. Here, we report a convenient and broadly applicable method for site-specifically functionalizing a single residue near the C-terminus of VHH nanobodies by employing lysine acylation using conjugating enzymes (LACE) to transfer short peptides bearing functional group handles for potassium acyltrifluoroborate (KAT) ligations onto a single lysine residue of the expressed nanobodies. This approach requires a LACE tag (4 residues or 11 residues) in the recombinant nanobodies and enables direct elaboration of the products via a rapid amide forming reaction. In this study, VHH nanobodies expressed in Escherichia coli could be efficiently modified through the transfer of specific chemical handles, enabling their conjugation to small molecules, nanobodies, and antibodies by chemoselective, amide-forming KAT ligations that operate at micromolar concentrations.

GRP78 Nanobody-Directed Immunotoxin Activates Innate Immunity Through STING Pathway to Synergize Tumor Immunotherapy

The lack of targetable antigens poses a significant challenge in developing effective cancer-targeted therapies. Cell surface translocation of endoplasmic reticulum (ER) chaperones, such as glucose-regulated protein 78 (GRP78), during malignancy, drug resistance, and ER stress induced by therapies, offers a promising pan-cancer target. To target GRP78, nanobody C5, identified from a phage library and exhibiting high affinity for human and mouse GRP78, is utilized to develop the Pseudomonas exotoxin (PE) immunotoxin C5-PE38. C5-PE38 induced ER stress, apoptosis and immunogenic cell death in targeted cells and showed antitumor efficacy against colorectal cancer and melanoma models without obvious toxicity. Mechanistically, transcriptome profiling showed that C5-PE38 reshaped the tumor immune microenvironment with enhanced innate and adaptive immune response and response to interferon beta. Moreover, C5-PE38-induced cell death could trans-activate STING pathway in dendritic cells and macrophages, promoting CD8+ T cell infiltration. It also sensitizes both primary and metastatic melanomas to anti-PD1 therapy, partly through STING activation. Overall, this study unveils a feasible GRP78 nanobody-directed therapy strategy for single or combinatorial cancer intervention. This work finds that C5-PE38-induced cell death stimulates STING-dependent cytosolic DNA release to promote antitumor immunity, a mechanism not previously reported for PE38, providing valuable insights for its clinical use.

Nanobody Engineered and Photosensitiser Loaded Bacterial Outer Membrane Vesicles Potentiate Antitumour Immunity and Immunotherapy

Bacterial outer membrane vesicles (OMVs) are promising as antitumour agents, but their clinical application is limited by toxicity concerns and unclear mechanisms. We engineered OMVs with cadherin 17 (CDH17) tumour-targeting nanobodies, enhancing tumour selectivity and efficacy while reducing adverse effects. These engineered OMVs function as natural stimulator of interferon genes (STING) agonists, activating the cyclic GMP-AMP synthase (cGAS)-STING pathway in cancer cells and tumour-associated macrophages (TAMs). Loading engineered OMVs with photoimmunotherapy photosensitisers further enhanced tumour inhibition and STING activation in TAMs. Combining nanobody-engineered OMV-mediated photoimmunotherapy with CD47 blockade effectively suppressed primary and metastatic tumours, establishing sustained antitumour immune memory. This study demonstrates the potential of nanobody-engineered OMVs as STING agonists and provides insights into novel OMV-based immunotherapeutic strategies harnessing the innate immune system against cancer. Our findings open new avenues for OMV applications in tumour immunotherapy, offering a promising approach to overcome current limitations in cancer treatment.

Challenges and opportunities in single-domain antibody-based tumor immunotherapy

Single-domain antibodies (sdAbs) have emerged as a promising tool in tumor immunotherapy, garnering significant attention in recent years due to their unique structure and superior properties. Unlike traditional antibodies, sdAbs exhibit several advantages, including small molecular weight, high stability, strong affinity, and high specificity. These characteristics enable sdAbs to effectively target and eliminate tumor cells within the complex tumor microenvironment. Moreover, their structural advantages enhance tissue penetration and reduce immunogenicity, thereby increasing their potential for clinical application. The potential applications of sdAbs include novel immune checkpoint inhibitors, bispecific antibody drugs, innovative immune cell therapies, antibody-drug conjugate therapies, and tumor molecular imaging diagnostics. Despite the promising prospects, several challenges of sdAb-based tumor immunotherapy still require further investigation. This review aims to summarize the status of sdAb-based immunotherapy, identify the challenges encountered, and evaluate the clinical research and application potential of sdAbs in this field.

Pure drug nanomedicines - where we are?

Pure drug nanomedicines (PDNs) encompass active pharmaceutical ingredients (APIs), including macromolecules, biological compounds, and functional components. They overcome research barriers and conversion thresholds associated with nanocarriers, offering advantages such as high drug loading capacity, synergistic treatment effects, and environmentally friendly production methods. This review provides a comprehensive overview of the latest advancements in PDNs, focusing on their essential components, design theories, and manufacturing techniques. The physicochemical properties and in vivo behaviors of PDNs are thoroughly analyzed to gain an in-depth understanding of their systematic characteristics. The review introduces currently approved PDN products and further explores the opportunities and challenges in expanding their depth and breadth of application. Drug nanocrystals, drug-drug cocrystals (DDCs), antibody-drug conjugates (ADCs), and nanobodies represent the successful commercialization and widespread utilization of PDNs across various disease domains. Self-assembled pure drug nanoparticles (SAPDNPs), a next-generation product, still require extensive translational research. Challenges persist in transitioning from laboratory-scale production to mass manufacturing and overcoming the conversion threshold from laboratory findings to clinical applications.

Nanobodies targeting the tumor microenvironment and their formulation as nanomedicines

Among the emerging strategies for cancer theranostics, nanomedicines offer significant promise in advancing both patients' diagnosis and treatment. In combination with nanobodies, nanomedicines can potentially enhance the precision and efficiency of drug or imaging agent delivery, addressing key limitations of current approaches, such as off-target toxicities. The development of nanomedicines will be further accelerated by the creation of smart nanoparticles, and their integration with immunotherapy. Obviously, the success of nano-immunotherapy will depend on a comprehensive understanding of the tumor microenvironment, including the complex interplay of mechanisms that drive cancer-mediated immunosuppression and immune escape. Hence, effective therapeutic targeting of the tumor microenvironment requires modulation of immune cell function, overcoming resistance mechanisms associated with stromal components or the extracellular matrix, and/or direct elimination of cancer cells. Identifying key molecules involved in cancer progression and drug resistance is, therefore, essential for developing effective therapies and diagnostic tools that can predict patient responses to treatment and monitor therapeutic outcomes. Current nanomedicines are being designed with careful consideration of factors such as the choice of carrier (e.g., biocompatibility, controlled cargo release) and targeting moiety. The unique properties of nanobodies make them an effective engineering tool to target biological molecules with high affinity and specificity. In this review, we focus on the latest applications of nanobodies for targeting various components of the tumor microenvironment for diagnostic and therapeutic purposes. We also explore the main types of nanoparticles used as a carrier for cancer immunotherapies, as well as the strategies for formulating nanoparticle-nanobody conjugates. Finally, we highlight how nanobody-nanoparticle formulations can enhance current nanomedicines.

Radioiodinated Nanobody immunoPET probe for in vivo detection of CD147 in pan-cancer

BACKGROUND

To develop the extracellular matrix metalloproteinase inducer (CD147)-targeting therapeutic strategies, accurate detection of CD147 expression in tumors is crucial. Owing to their relatively low molecular weights and high affinities, nanobodies (Nbs) may be powerful candidates for cancer diagnosis and therapy. In this study, we developed a novel CD147-targeted nanobody radiotracer, [124I]I-NB147, which provides guidance for the noninvasive detection of CD147-overexpressing cancers.

METHODS

CD147 expression in human cancers was detected via immunohistochemistry (IHC) on tissue microarrays (TMAs). Western blot (WB) and flow cytometry were used to screen CD147-positive malignant melanoma (MM), triple-negative breast cancer (TNBC), and pancreatic cancer (PCA) cell lines. The CD147 nanobody (NB147) was labeled with [124I]INa using Iodogen as the oxidizing agent and was purified by the PD-10 column. The physicochemical properties, affinity, metabolic characteristics, biodistribution, and immunoPET imaging of [124I]I-NB147 were evaluated Moreover, [18F]F-FDG was used as a control. Finally, CD147 expression analysis was performed via multiplex immunofluorescence (MxIF) and autoradiography on human cancer specimens and tumor-bearing mice tissues.

RESULTS

TMAs results revealed that CD147 is highly expressed in MM, TNBC, and PCA. A CD147-specific nanobody, NB147, was successfully generated with excellent in vitro binding characteristics. [124I]I-NB147 was obtained with high radiochemical yield and purity, and was stable for at least 4 h in vitro. WB and FCM revealed that CD147 was positive in A375, MDA-MB-435 and ASPC1 cells, whereas SK-MEL-28, 4T1 and BXPC3 cells presented low expression levels. The radio-ELISA results indicated that [124I]I-NB147 had a high binding affinity to CD147. The uptake of [124I]I-NB147 was significantly different between CD147 high-expression cells and CD147 low-expression cells (P < 0.001). The biological half-life of the distribution and clearance phases were 0.05 h and 1.58 h, respectively. In CD147-positive tumor models, the [124I]I-NB147 accumulated in A375, MDA-MB-435, and ASPC1 tumors, and the uptake value was significantly higher than that of [18F]F-FDG. Uptake in SK-MEL-28, BXPC3, and 4T1 tumors was not clearly observed. Finally, through autoradiography and histological studies, the correlation analysis between tumor uptake and CD147 expression level was determined.

CONCLUSIONS

The high expression of CD147 in MM, TNBC, and PCA tissuesand in tumor cells was verified. The CD147 nanobody, NB147 was produced and radiolabeled to obtain the immunoPET probe, [124I]I-NB147, which showed high affinity to CD147 and precise visualization for accurate diagnosis of CD147-expressing lesions in different cancers. These results provide insight into the imaging and binding properties of nanobody NB147 over extended periods of time, reinforcing its potential in developing radionuclide therapies for CD147-positive cancer patients.

From antibodies to nanobodies: The next frontier in cancer theranostics for solid tumors

The field of cancer therapeutics has witnessed significant advancements over the past decades, particularly with the emergence of immunotherapy. This chapter traces the transformative journey from traditional antibody-based therapies to the innovative use of nanobodies in the treatment and diagnosis of solid tumors. Nanobodies are the smallest fragments of antibodies derived from camelid immunoglobulins and have redefined the possibilities in cancer theranostics due to their unique structural and functional properties. We provide an overview of the biochemical characteristics of nanobodies that make them particularly suitable for theranostic applications, such as their small size, high stability, enhanced infiltration into the complex tumor microenvironment (TME) and ability to bind with high affinity to epitopes that are inaccessible to conventional antibodies. Further, their ease of modification and functionalization has enabled the development of nanobody-based drug conjugates/toxins and radiolabeled compounds for precise imaging and targeted radiotherapy. We elucidate how nanobodies are being served as valuable tools for prognostic assessment, enabling clinicians to predict disease aggressiveness, monitor treatment response, and stratify patients for personalized therapeutic interventions.

Discovery of nanobodies: a comprehensive review of their applications and potential over the past five years

Nanobodies (Nbs) are antibody fragments derived from heavy-chain-only IgG antibodies found in the Camelidae family as well as cartilaginous fish. Their unique structural and functional properties, such as their small size, the ability to be engineered for high antigen-binding affinity, stability under extreme conditions, and ease of production, have made them promising tools for diagnostics and therapeutics. This potential was realized in 2018 with the approval of caplacizumab, the world's first Nb-based drug. Currently, Nbs are being investigated in clinical trials for a broad range of treatments, including targeted therapies against PDL1 and Epidermal Growth Factor Receptor (EGFR), cardiovascular diseases, inflammatory conditions, and neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. They are also being studied for their potential for detecting and imaging autoimmune conditions and infectious diseases such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A variety of methods are now available to generate target-specific Nbs quickly and efficiently at low costs, increasing their accessibility. This article examines these diverse applications of Nbs and their promising roles. Only the most recent articles published in the last five years have been used to summarize the most advanced developments in the field.

Multiomics2Targets identifies targets from cancer cohorts profiled with transcriptomics, proteomics, and phosphoproteomics

The availability of data from profiling of cancer patients with multiomics is rapidly increasing. However, integrative analysis of such data for personalized target identification is not trivial. Multiomics2Targets is a platform that enables users to upload transcriptomics, proteomics, and phosphoproteomics data matrices collected from the same cohort of cancer patients. After uploading the data, Multiomics2Targets produces a report that resembles a research publication. The uploaded matrices are processed, analyzed, and visualized using the tools Enrichr, KEA3, ChEA3, Expression2Kinases, and TargetRanger to identify and prioritize proteins, genes, and transcripts as potential targets. Figures and tables, as well as descriptions of the methods and results, are automatically generated. Reports include an abstract, introduction, methods, results, discussion, conclusions, and references and are exportable as citable PDFs and Jupyter Notebooks. Multiomics2Targets is applied to analyze version 3 of the Clinical Proteomic Tumor Analysis Consortium (CPTAC3) pan-cancer cohort, identifying potential targets for each CPTAC3 cancer subtype. Multiomics2Targets is available from https://multiomics2targets.maayanlab.cloud/.

Nanobody-Engineered Biohybrid Bacteria Targeting Gastrointestinal Cancers Induce Robust STING-Mediated Anti-Tumor Immunity

Bacteria can be utilized for cancer therapy owing to their preferential colonization at tumor sites. However, unmodified non-pathogenic bacteria carry potential risks due to their non-specific targeting effects, and their anti-tumor activity is limited when used as monotherapy. In this study, a biohybrid-engineered bacterial system comprising non-pathogenic MG1655 bacteria modified with CDH17 nanobodies on their surface and conjugated with photosensitizer croconium (CR) molecules is developed. The resultant biohybrid bacteria can efficiently home to CDH17-positive tumors, including gastric, pancreatic, and colorectal cancers, and significantly suppress tumor growth upon irradiation. More importantly, biohybrid bacteria-mediated photothermal therapy (PTT) induced abundant macrophage infiltration in a syngeneic murine colorectal model. Further, that the STING pathway is activated in tumor macrophages by the released bacterial nucleic acid after PTT is revealed, leading to the production of type I interferons. The addition of CD47 nanobody but not PD-1 antibody to the PTT regimen can eradicate the tumors and extend survival. This results indicate that bacteria endowed with tumor-specific selectivity and coupled with photothermal payloads can serve as an innovative strategy for low-immunogenicity cancers. This strategy can potentially reprogram the tumor microenvironment by inducing macrophage infiltration and enhancing the efficacy of immunotherapy targeting macrophages.

Cadherin-17 as a target for the immunoPET of adenocarcinoma

PURPOSE

Cadherin-17 (CDH17) is a calcium-dependent cell adhesion protein that is overexpressed in several adenocarcinomas, including gastric, colorectal, and pancreatic adenocarcinoma. High levels of CDH17 have been linked to metastatic disease and poor prognoses in patients with these malignancies, fueling interest in the protein as a target for diagnostics and therapeutics. Herein, we report the synthesis, in vitro validation, and in vivo evaluation of a CDH17-targeted 89Zr-labeled immunoPET probe.

METHODS

The CDH17-targeting mAb D2101 was modified with an isothiocyanate-bearing derivative of desferrioxamine (DFO) to produce a chelator-bearing immunoconjugate - DFO-D2101 - and flow cytometry and surface plasmon resonance (SPR) were used to interrogate its antigen-binding properties. The immunoconjugate was then radiolabeled with zirconium-89 (t1/2 ~ 3.3 days), and the serum stability and immunoreactive fraction of [89Zr]Zr-DFO-D2101 were determined. Finally, [89Zr]Zr-DFO-D2101's performance was evaluated in a trio of murine models of pancreatic ductal adenocarcinoma (PDAC): subcutaneous, orthotopic, and patient-derived xenografts (PDX). PET images were acquired over the course of 5 days, and terminal biodistribution data were collected after the final imaging time point.

RESULTS

DFO-D2101 was produced with a degree of labeling of ~ 1.1 DFO/mAb. Flow cytometry with CDH17-expressing AsPC-1 cells demonstrated that the immunoconjugate binds to its target in a manner similar to its parent mAb, while SPR with recombinant CDH17 revealed that D2101 and DFO-D2101 exhibit nearly identical KD values: 8.2 × 10-9 and 6.7 × 10-9 M, respectively. [89Zr]Zr-DFO-D2101 was produced with a specific activity of 185 MBq/mg (5.0 mCi/mg), remained >80% stable in human serum over the course of 5 days, and boasted an immunoreactive fraction of >0.85. In all three murine models of PDAC, the radioimmunoconjugate yielded high contrast images, with high activity concentrations in tumor tissue and low uptake in non-target organs. Tumoral activity concentrations reached as high as >60 %ID/g in two of the cohorts bearing PDXs.

CONCLUSION

Taken together, these data underscore that [89Zr]Zr-DFO-D2101 is a highly promising probe for the non-invasive visualization of CDH17 expression in PDAC. We contend that this radioimmunoconjugate could have a significant impact on the clinical management of patients with both PDAC and gastrointestinal adenocarcinoma, most likely as a theranostic imaging tool in support of CDH17-targeted therapies.

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.

Cadherin 17 Nanobody-Mediated Near-Infrared-II Fluorescence Imaging-Guided Surgery and Immunotoxin Delivery for Colorectal Cancer

Surgery and targeted therapy are of equal importance for colorectal cancer (CRC) treatment. However, complete CRC tumor resection remains challenging, and new targeted agents are also needed for efficient CRC treatment. Cadherin 17 (CDH17) is a membrane protein that is highly expressed in CRC and, therefore, is an ideal target for imaging-guided surgery and therapeutics. This study utilizes CDH17 nanobody (E8-Nb) with the near-infrared (NIR) fluorescent dye IRDye800CW to construct a NIR-II fluorescent probe, E8-Nb-IR800CW, and a Pseudomonas exotoxin (PE)-based immunotoxin, E8-Nb-PE38, to evaluate their performance for CRC imaging, imaging-guided precise tumor excision, and antitumor effects. Our results show that E8-Nb-IR800CW efficiently recognizes CDH17 in CRC cells and tumor tissues, produces high-quality NIR-II images for CRC tumors, and enables precise tumor removal guided by NIR-II imaging. Additionally, fluorescent imaging confirms the targeting ability and specificity of the immunotoxin toward CDH17-positive tumors, providing the direct visible evidence for immunotoxin therapy. E8-Nb-PE38 immunotoxin markedly delays the growth of CRC through the induction of apoptosis and immunogenic cell death (ICD) in multiple CRC tumor models. Furthermore, E8-Nb-PE38 combined with 5-FU exerts synergistically antitumor effects and extends survival. This study highlights CDH17 as a promising target for CRC imaging, imaging-guided surgery, and drug delivery. Nanobodies targeting CDH17 hold great potential to construct NIR-II fluorescent probes for surgery navigation, and PE-based toxins fused with CDH17 nanobodies represent a novel therapeutic strategy for CRC treatment. Further investigation is warranted to validate these findings for potential clinical translation.

A humanized trivalent Nectin-4-targeting nanobody drug conjugate displays potent antitumor activity in gastric cancer

BACKGROUND

Gastric cancer represents a highly lethal malignancy with an elevated mortality rate among cancer patients, coupled with a suboptimal postoperative survival prognosis. Nectin-4, an overexpressed oncological target for various cancers, has been exploited to create antibody-drug conjugates (ADCs) to treat solid tumors. However, there is limited research on Nectin-4 ADCs specifically for gastric cancer, and conventional immunoglobulin G (IgG)-based ADCs frequently encounter binding site barriers. Based on the excellent tumor penetration capabilities inherent in nanobodies (Nbs), we developed Nectin-4-targeting Nb drug conjugates (NDCs) for the treatment of gastric cancer.

RESULTS

An immunized phage display library was established and employed for the selection of Nectin-4-specific Nbs using phage display technology. Subsequently, these Nbs were engineered into homodimers to enhance Nb affinity. To prolong in vivo half-life and reduce immunogenicity, we fused an Nb targeting human serum albumin (HSA), resulting in the development of trivalent humanized Nbs. Further, we site-specifically conjugated a monomethyl auristatin E (MMAE) at the C-terminus of the trivalent Nbs, creating Nectin-4 NDC (huNb26/Nb26-Nbh-MMAE) with a drug-to-antibody ratio (DAR) of 1. Nectin-4 NDC demonstrated excellent in vitro cell-binding activities and cytotoxic efficacy against cells with high Nectin-4 expression. Subsequent administration of Nectin-4 NDC to mice bearing NCI-N87 human gastric cancer xenografts demonstrated rapid tissue penetration and high tumor uptake through in vivo imaging. Moreover, Nectin-4 NDC exhibited noteworthy dose-dependent anti-tumor efficacy in in vivo studies.

CONCLUSION

We have engineered a Nectin-4 NDC with elevated affinity and effective tumor uptake, further establishing its potential as a therapeutic agent for gastric cancer.

Engineered polyspecific antibodies: A new frontier in the field of immunotherapeutics

The 21st-century beginning remarked with the huge success of monospecific MAbs, however, in the last couple of years, polyspecific MAbs (PsAbs) have been an interesting topic and show promise of being biobetter than monospecific MAbs. Polyspecificity, in which a single antibody serves multiple specific target binding, has been hypothesized to contribute to the development of a highly effective antibody repertoire for immune defence. This polyspecific MAb trend represents an explosion that is gripping the whole pharmaceutical industry. This review is concerned with the current development and quality enforcement of PsAbs. All provided literature on monospecific MAbs and polyspecific MAbs (PsAbs) were searched using various electronic databases such as PubMed, Google Scholar, Web of Science, Elsevier, Springer, ACS, Google Patent and books via the keywords Antibody engineering, Polyspecific antibody, Conventional antibody, non-conventional antibody, and Single domain antibody. In the literature, there are more than 100 different formats to construct PsAb by quadroma technology, chemical conjugation and genetic engineering. Till March 2023, nine PsAb have been approved around the world, and around 330 are in advanced developmental stages, showing the dominancy of PsAb in the growing health sector. Recent advancements in protein engineering techniques and the fusion of non-conventional antibodies have made it possible to create complex PsAbs that demonstrate higher stability and enhanced potency. This marks the most significant achievement for cancer immunotherapy, in which PsAbs have immense promise. It is worth mentioning that seven out of the nine PsAbs have been approved as anti-cancer therapy. As PsAbs continue to acquire prominence, they could pave the way for the development of novel immunotherapies for multiple diseases.

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.

Precise Photodynamic Therapy by Midkine Nanobody-Engineered Nanoparticles Remodels the Microenvironment of Pancreatic Ductal Adenocarcinoma and Potentiates the Immunotherapy

Pancreatic ductal adenocarcinoma (PDAC) is notorious for its resistance against chemotherapy and immunotherapy due to its dense desmoplastic and immunosuppressive tumor microenvironment (TME). Traditional photodynamic therapy (PDT) was also less effective for PDAC owing to poor selectivity, insufficient penetration, and accumulation of photosensitizers in tumor sites. Here, we designed a light-responsive novel nanoplatform targeting the TME of PDAC through tumor-specific midkine nanobodies (Nbs), which could efficiently deliver semiconducting polymeric nanoparticles (NPs) to the TME of PDAC and locally produce abundant reactive oxygen species (ROS) for precise photoimmunotherapy. The synthesized nanocomposite can not only achieve multimodal imaging of PDAC tumors (fluorescence and photoacoustic imaging) but also lead to apoptosis and immunogenic cell death of tumor cells via ROS under light excitation, ultimately preventing tumor progression and remodeling the immunosuppressive TME with increased infiltration of T lymphocytes. Combined with a PD-1 checkpoint blockade, the targeted PDT platform showed the best antitumor performance and markedly extended mice survival. Conclusively, this work integrating Nbs with photodynamic NPs provides a novel strategy to target formidable PDAC to achieve tumor suppression and activate antitumor immunity, creating possibilities for boosting efficacy of immunotherapy for PDAC tumors through the combination with precise local PDT.

Heavy chain-only antibodies with a stabilized human VH in transgenic chickens for therapeutic antibody discovery

Heavy chain-only antibodies have found many applications where conventional heavy-light heterodimeric antibodies are not favorable. Heavy chain-only antibodies with their single antigen-binding domain offer the advantage of a smaller size and higher stability relative to conventional antibodies, and thus, the potential for novel targeting modalities. Domain antibodies have commonly been sourced from camelids with ex-vivo humanization or transgenic rodents expressing heavy chains without light chains, but these host species are all mammalian, limiting their capacity to elicit robust immune responses to conserved mammalian targets. We have developed transgenic chickens expressing heavy chain-only antibodies with a human variable region to combine the superior target recognition advantages of a divergent, non-mammalian host with the ability to discover single-domain binders. These birds produce robust immune responses, consisting of antigen-specific antibodies targeting diverse epitopes with a range of affinities. Biophysical attributes are favorable, with good developability profiles and low predicted immunogenicity.

Targeted delivery of organic small-molecule photothermal materials with engineered extracellular vesicles for imaging-guided tumor photothermal therapy

Imaging-guided photothermal therapy (PTT) for cancers recently gathered increasing focus thanks to its precise diagnosis and potent therapeutic effectiveness. Croconaine (CR) dyes demonstrate potential in expanding utility for near infrared (NIR) dyes in bio-imaging/theranostics. However, reports on CR dyes for PTT are scarce most likely due to the short of the efficacious delivery strategies to achieve specific accumulation in diseased tissues to induce PTT. Extracellular vesicles (EVs) are multifunctional nanoparticle systems that function as safe platform for disease theragnostics, which provide potential benefits in extensive biomedical applications. Here, we developed a novel delivery system for photothermal molecules based on a CR dye that exerts photothermal activity through CDH17 nanobody-engineered EVs. The formed CR@E8-EVs showed strong NIR absorption, excellent photothermal performance, good biological compatibility and superb active tumor-targeting capability. The CR@E8-EVs can not only visualize and feature the tumors through CR intrinsic property as a photoacoustic imaging (PAI) agent, but also effectively retard the tumor growth under laser irradiation to perform PTT. It is expected that the engineered EVs will become a novel delivery vehicle of small organic photothermal agents (SOPTAs) in future clinical PTT applications.

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.

Albumin-binding photosensitizer capable of targeting glioma via the SPARC pathway

BACKGROUND

Malignant glioma is among the most lethal and frequently occurring brain tumors, and the average survival period is 15 months. Existing chemotherapy has low tolerance and low blood-brain barrier (BBB) permeability; therefore, the required drug dose cannot be accurately delivered to the tumor site, resulting in an insufficient drug effect.

METHODS

Herein, we demonstrate a precision photodynamic tumor therapy using a photosensitizer (ZnPcS) capable of binding to albumin in situ, which can increase the permeability of the BBB and accurately target glioma. Albumin-binding ZnPcS was designed to pass through the BBB and bind to secreted protein acidic and rich in cysteine (SPARC), which is abundant in the glioma plasma membrane.

RESULTS

When the upper part of a mouse brain was irradiated using a laser (0.2 W cm^- 2) after transplantation of glioma and injection of ZnPcS, tumor growth was inhibited by approximately 83.6%, and the 50% survival rate of the treatment group increased by 14 days compared to the control group. In glioma with knockout SPARC, the amount of ZnPcS entering the glioma was reduced by 63.1%, indicating that it can target glioma through the SPARC pathway.

CONCLUSION

This study showed that the use of albumin-binding photosensitizers is promising for the treatment of malignant gliomas.

Aptamers and nanobodies as alternatives to antibodies for ligand-targeted drug delivery in cancer

Targeted drug delivery (TDD) is the selective delivery of a therapeutic agent specifically to the site of action to avoid adverse effects and systemic toxicity and to reduce the dose required. Ligand TDD or active TDD involves using a ligand-drug conjugate comprising a targeting ligand linked to an active drug moiety that can either be free or encapsulated within a nanocarrier (NC). Aptamers are single-stranded oligonucleotides that bind to specific biomacromolecules because of their 3D conformation. Nanobodies are the variable domains of unique heavy chain-only antibodies (HcAbs) produced by animals of the Camelidae family. Both these types of ligand are smaller than antibodies and have been used to efficiently target drugs to particular tissues or cells. In this review, we describe the applications of aptamers and nanobodies as ligands for TDD, their advantages and disadvantages compared with antibodies, and the various modalities for targeting cancers using these ligands. Teaser: Aptamers and nanobodies are macromolecular ligands that can actively chaperone drug molecules to particular cancerous cells or tissues in the body to target their pharmacological effects and improve their therapeutic index and safety.