A Single Domain-Based Anti-Her2 Antibody Has Potent Antitumor Activities

Development of a new affinity maturation protocol for the construction of an internalizing anti-nucleolin antibody library

Over the last decades, monoclonal antibodies have substantially improved the treatment of several conditions. The continuous search for novel therapeutic targets and improvements in antibody's structure, demands for a constant optimization of their development. In this regard, modulation of an antibody's affinity to its target has been largely explored and culminated in the discovery and optimization of a variety of molecules. It involves the creation of antibody libraries and selection against the target of interest. In this work, we aimed at developing a novel protocol to be used for the affinity maturation of an antibody previously developed by our group. An antibody library was constructed using an in vivo random mutagenesis approach that, to our knowledge, has not been used before for antibody development. Then, a cell-based phage display selection protocol was designed to allow the fast and simple screening of antibody clones capable of being internalized by target cells. Next generation sequencing coupled with computer analysis provided an extensive characterization of the created library and post-selection pool, that can be used as a guide for future antibody development. With a single selection step, an enrichment in the mutated antibody library, given by a decrease in almost 50% in sequence diversity, was achieved, and structural information useful in the study of the antibody-target interaction in the future was obtained.

A novel nanobody-based HER2-targeting antibody exhibits potent synergistic antitumor efficacy in trastuzumab-resistant cancer cells

Human epithelial growth factor receptor-2 (HER2) plays an oncogenic role in numerous tumors, including breast, gastric, and various other solid tumors. While anti-HER2 therapies are approved for the treatment of HER2-positive tumors, a necessity persists for creating novel HER2-targeted agents to resolve therapeutic resistance. Utilizing a synthetic nanobody library and affinity maturation, our study identified four anti-HER2 nanobodies that exhibited high affinity and specificity. These nanobodies recognized three distinct epitopes of HER2-ECD. Additionally, we constructed VHH-Fc and discovered that they facilitated superior internalization and showed moderate growth inhibition. Compared to the combination of trastuzumab and pertuzumab, the VHH-Fc combos or their combination with trastuzumab demonstrated greater or comparable antitumor activity in both ligand-independent and ligand-driven tumors. Most remarkably, A9B5-Fc, which targeted domain I of HER2-ECD, displayed significantly enhanced trastuzumab-synergistic antitumor efficacy compared to pertuzumab under trastuzumab-resistant conditions. Our findings offer anti-HER2 nanobodies with high affinity and non-overlapping epitope recognition. The novel nanobody-based HER2-targeted antibody, A9B5-Fc, binding to HER2-ECD I, mediates promising receptor internalization. It possesses the potential to serve as a potent synergistic partner with trastuzumab, contributing to overcoming acquired resistance.

Reviving a Classic Antigen with a Cutting-Edge Approach: Nanobodies for HER2+ Breast Cancer

The serendipitous discovery of nanobodies (NBs) around two decades ago opened the door to new possibilities for innovative strategies, particularly in cancer treatment. These antigen-binding fragments are derived from heavy-chain-only antibodies naturally found in the serum of camelids and sharks. NBs are an appealing agent for the progress of innovative therapeutic strategies because they combine the advantageous assets of smaller molecules and conventional monoclonal antibodies (mAbs). Moreover, the possibility to produce NBs using bacterial systems reduces manufacturing expenses and speeds up the production process, making them a feasible option for the development of new bio-drugs. Several NBs have been developed over the past 10 years and are currently being tested in clinical trials for various human targets. Here, we provide an overview of the notable structural and biochemical characteristics of NBs, particularly in their application against HER2, an extracellular receptor that often gets aberrantly activated during breast cancer tumorigenesis. The focus is on the recent advancements in diagnostic and therapeutic research up to the present date.

A novel multifunctional anti-PD-L1-CD16a-IL15 induces potent cancer cell killing in PD-L1-positive tumour cells

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Anti-PD-L1 single-domain antibodies were identified from hPD-L1-immunized camels.

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Three novel multifunctional antibodies, anti-PD-L1-CD16a, anti-PD-L1-IL15, and anti-PD-L1-CD16a-IL15, target PD-L1-positive cancer cells.

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Anti-PD-L1-IL15 and anti-PD-L1-CD16a-IL15, but not anti-PD-L1-CD16a, stimulate immune cell proliferation in vitro.

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The anti-PD-L1 antibodies can bind PD-L1-positive cells.

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Anti-PD-L1-CD16a-IL15 has the strongest antitumour activity, both in vitro and in vivo.

Cancer is the most acute disease and the leading cause of patient death worldwide. Both chemotherapy and molecular-based therapies play an important role in curing cancer. However, the median and overall survival of patients is poor. To date, immune therapies have changed the treatment methods for cancer patients. Programmed death ligand 1 (PD-L1, also known as B-H1, CD274) is a well-studied tumor antigen. PD-L1 is overexpressed in colon cancer, lung cancer, and so on and plays a vital role in cancer development. In this study, anti-PD-L1 single-domain antibodies were identified from recombinant human PD-L1 (rhPD-L1)-immunized llamas. Then, we generated a novel multifunctional anti-PD-L1-CD16a-IL15 antibody targeting PD-L1-positive tumor cells. Anti-PD-L1-CD16a-IL15 was constructed by linking the Interleukin-2 (IL-2) signal peptide, anti-PD-L1 single domain antibody (anti-PD-L1-VHH) and anti-cluster of differentiation 16a single domain antibody (anti-CD16a-VHH), and Interleukin-15/Interleukin-15 receptor alpha (IL15/IL-15Rα). This anti-PD-L1-CD16a-IL15 fusion protein can be expressed and purified from HEK-293F cells. In vitro, our data showed that the anti-PD-L1-CD16a-IL15 fusion protein can recruit T cells and drive natural killer cells (NK) with specific killing of PD-L1-overexpressing tumor cells. Furthermore, in the xenograft model, the anti-PD-L1-CD16a-IL15 fusion protein inhibited tumor growth with human peripheral blood mononuclear cells (PBMCs). These data suggested that the anti-PD-L1-CD16a-IL15 fusion protein has a latent function in antitumour activity, with better guidance for future cancer immunotherapy.

Unique aspects of adaptive immunity in camelids and their applications

Members of the Camelidae have unique adaptive immunological features that are not widely observed in other species. All camelids are known to have three distinct IgG isotypes - IgG1, IgG2 and IgG3. While IgG1 has a conventional antibody structure, both IgG2 and IgG3 are devoid of light chains and instead possess hypervariable regions in their heavy chain (VHH), while lacking the typical CH1 domain found in heavy chains. VHH domains are increasingly being utilized as "next generation" antibodies, as they have unique biochemical and structural properties including high pH stability as well as a lower molecular weight allowing for increased tissue penetration. These features of VHH domains offer a number of advantages for both biotechnology and clinical applications and are commonly termed "nanobodies". A second unique aspect of the camelid adaptive response is involves T cell-mediated immunity. Characterization of gamma delta (ꝩδ) T cells in camelid species has found they use somatic hypermutation in their T cell receptor gamma (TRG) and delta (TRD) loci to increase the structural stability of their ꝩδ T receptor. The use of somatic hyper mutation to increase the diversity of their T cell repertoire, is a feature that has not been observed in other mammalian species. In addition, in alpacas there is a unique subset of ꝩδ T cells called Vꝩ9Vδ2 T cells. Activation of these cells is dependent upon phosphoantigen (PAg)-mediated interaction with B7-like butyrophilin molecules (BTN-3). This makes alpacas the first species outside of primates to be identified with this unique subset and activation mechanism. Here we review some fundamentals of camelid adaptive immunity that make them distinct from other vertebrate species and their potential applications to human therapies.

Generation of a nanobody against HER2 tyrosine kinase using phage display library screening for HER2-positive breast cancer therapy development

Human epidermal growth factor receptor 2 (HER2) protein overexpression is found in ~30% of invasive breast carcinomas and in a high proportion of noninvasive ductal carcinomas in situ. Targeted cancer therapy is based on monoclonal antibodies and kinase inhibitors and reflects a new era of cancer therapy. However, delivery to tumor cells in vivo is hampered by the large size (150 kDa) of conventional antibodies. Furthermore, there are many disadvantages with the current anti-HER2 drug, including drug resistance and adverse effects. Nanobodies (15 kDa), single-domain antibody (sdAb) fragments, can overcome these limitations. This study produced the recombinant sdAb against the HER2-tyrosine kinase (HER2-TK) domain using phage display technology. Three specific anti-HER2-TK sdAbs were selected for further characterization. Hallmark VHH residue identification and amino acid sequence analysis revealed that clone numbers 4 and 22 were VH antibodies, whereas clone number 17 was a VH H antibody (nanobody). The half-maximal inhibitory concentration of VHH17 exhibited significantly greater HER2 kinase-inhibition activity than the other clones. Consistent with these results, several charges and polar residues of the HER2-TK activation loop that were predicted based on mimotope analysis also appeared in the docking result and interacted via the CDR1, CDR2 and CDR3 loops of VHH17. Furthermore, the cell-penetrable VHH17 (R9 VHH17) showed cell-penetrability and significantly decreased HER2-positive cancer cell viability. Thus, the VH H17 could be developed as an effective therapeutic agent to treat HER2-positive breast cancer.

Biologicals to direct nanotherapeutics towards HER2-positive breast cancers

HER2-positive breast cancer, an aggressive cancer, is treated with combinations of conventional anticancer drugs viz., cytotoxic drugs, nibs, and mAbs. Major limitations associated with this therapy are patient non-compliance due to the adverse drug reactions and rapid development of resistance by the HER2-positive malignant cells. While the former is addressed by the nano-formulations of the anticancer-drugs to some extent, the latter is still at large. This is because the nanocarriers of the anticancer drugs, by and large, lack the target specificity and selectivity. Thus, nowadays, to overcome these problems, various safe and efficacious biological agents are being used to direct the nanotherapeutics towards the HER2-positive breast cancers. The present review describes the potentials of such biological agents.

Expression and In Vitro Function of Anti-Breast Cancer Llama-Based Single Domain Antibody VHH Expressed in Tobacco Plants

Overexpression of human epidermal growth factor receptor type 2 (HER2) is considered as a prognostic factor of breast cancer, which is positively associated with recurrence when cancer metastasizes to the lymph nodes. Here, we expressed the single variable domain on a heavy chain (VHH) form of anti-HER2 camelid single domain antibody in tobacco plants and compared its in vitro anticancer activities with the anti-HER2 full size antibody. The gene expression cassette containing anti-HER2 camelid single domain antibody VHH fused to human IgG Fc region with KDEL endoplasmic reticulum (ER) (VHH-FcK) was transferred into the tobacco plant via the Agrobacterium-mediated transformation. The transformants were screened with polymerase chain reaction and Western blot analyses. Enzyme-linked immunosorbent assay (ELISA) confirmed the binding of the purified anti-HER2 VHH-FcK to the HER2-positive breast cancer cell line, SK-BR-3. Migration assay results confirmed anticancer activity of the plant-derived anticancer camelid single chain antibody. Taken together, we confirmed the possibility of using anti-HER2 VHH-FcK as a therapeutic anticancer agent, which can be expressed and assembled and purified from a plant expression system as an alternative antibody production system.

Bp-Bs, a Novel T-cell Engaging Bispecific Antibody with Biparatopic Her2 Binding, Has Potent Anti-tumor Activities

Patients with Human epidermal growth factor receptor type 2 (Her2) overexpression are associated with aggressive tumor growth and poor clinical outcomes. Bispecific antibodies targeting Her2 have recently exhibited potent effects on Her2 signal inhibition. In this study, a novel biparatopic anti-Her2 bispecific antibody (Bp-Bs) was constructed by linking a single anti-CD3 Fab with two different anti-Her2 single-domain antibodies targeting non-overlapping epitopes of Her2. The Bp-Bs demonstrated strong binding on Her2-positive cells and potent cytotoxicity on Her2-positive tumor cells, even Her2-low expression cells, suggesting that biparatopic bispecific antibodies may have improved therapeutic benefits on broad Her2 patient populations.

Human Domain Antibodies to Conserved Epitopes on HER2 Potently Inhibit Growth of HER2-Overexpressing Human Breast Cancer Cells In Vitro

The FDA approval of two anti-HER2 monoclonal antibodies, trastuzumab and pertuzumab, and an antibody-drug conjugate, trastuzumab emtansine, has transformed clinical practice for HER2-positive cancers. However, not all patients respond to therapy, and the majority of responders eventually develop resistance. In addition, cardiotoxicity is a major safety concern for their clinical use. Thus, there remains a need for the discovery and development of novel classes of HER2-targeted therapeutics with high efficacy and specificity. In this study, we report the identification and characterization of fully human single-domain antibodies (dAbs) targeting HER2 epitopes that are highly conserved among various species and non-overlapping with those of trastuzumab and pertuzumab. An Fc-fusion protein of the best binder demonstrated much higher inhibitory activity against HER2-amplified human breast cancer cell lines than trastuzumab and pertuzumab. Unlike the latter, however, it did not have an effect on gastric and ovarian cancer cell lines with HER2 overexpression. The dAb-Fc fusion protein showed poor pharmacokinetics in mice, thus limiting its potential for therapeutic use. It could be useful as an agent for the exploration of functionally important conserved structures on HER2 with implications for the design of novel therapeutics and elucidation of mechanisms of HER2-mediated tumorigenesis.

Nanobodies: New avenues for imaging, stabilizing and modulating GPCRs

The family of G protein-coupled receptors (GPCRs) is the largest class of membrane proteins and an important drug target due to their role in many (patho)physiological processes. Besides small molecules, GPCRs can be targeted by biologicals including antibodies and antibody fragments. This review describes the use of antibodies and in particular antibody fragments from camelid-derived heavy chain-only antibodies (nanobodies/VHHs/sdAbs) for detecting, stabilizing, modulating and therapeutically targeting GPCRs. Altogether, it becomes increasingly clear that the small size, structure and protruding antigen-binding loops of nanobodies are favorable features for the development of selective and potent GPCRs-binding molecules. This makes them attractive tools to modulate GPCR activity but also as targeting modalities for GPCR-directed therapeutics. In addition, these antibody-fragments are important tools in the stabilization of particular conformations of these receptors. Lastly, nanobodies, in contrast to conventional antibodies, can also easily be expressed intracellularly which render nanobodies important tools for studying GPCR function. Hence, GPCR-targeting nanobodies are ideal modalities to image, stabilize and modulate GPCR function.