A Fully Human Recombinant IgG-like Bispecific Antibody to Both the Epidermal Growth Factor Receptor and the Insulin-like Growth Factor Receptor for Enhanced Antitumor Activity

Phage Display as a Medium for Target Therapy Based Drug Discovery, Review and Update

Phage libraries are now amongst the most prominent approaches for the identification of high-affinity antibodies/peptides from billions of displayed phages in a specific library through the biopanning process. Due to its ability to discover potential therapeutic candidates that bind specifically to targets, phage display has gained considerable attention in targeted therapy. Using this approach, peptides with high-affinity and specificity can be identified for potential therapeutic or diagnostic use. Furthermore, phage libraries can be used to rapidly screen and identify novel antibodies to develop immunotherapeutics. The Food and Drug Administration (FDA) has approved several phage display-derived peptides and antibodies for the treatment of different diseases. In the current review, we provided a comprehensive insight into the role of phage display-derived peptides and antibodies in the treatment of different diseases including cancers, infectious diseases and neurological disorders. We also explored the applications of phage display in targeted drug delivery, gene therapy, and CAR T-cell.

Targeted Inhibitors of EGFR: Structure, Biology, Biomarkers, and Clinical Applications

Members of the EGFR family of tyrosine kinase receptors are major regulators of cellular proliferation, differentiation, and survival. In humans, abnormal activation of EGFR is associated with the development and progression of many cancer types, which makes it an attractive target for molecular-guided therapy. Two classes of EGFR-targeted cancer therapeutics include monoclonal antibodies (mAbs), which bind to the extracellular domain of EGFR, and tyrosine kinase inhibitors (TKIs), which mostly target the intracellular part of EGFR and inhibit its activity in molecular signaling. While EGFR-specific mAbs and three generations of TKIs have demonstrated clinical efficacy in various settings, molecular evolution of tumors leads to apparent and sometimes inevitable resistance to current therapeutics, which highlights the need for deeper research in this field. Here, we tried to provide a comprehensive and systematic overview of the rationale, molecular mechanisms, and clinical significance of the current EGFR-targeting drugs, highlighting potential candidate molecules in development. We summarized the underlying mechanisms of resistance and available personalized predictive approaches that may lead to improved efficacy of EGFR-targeted therapies. We also discuss recent developments and the use of specific therapeutic strategies, such as multi-targeting agents and combination therapies, for overcoming cancer resistance to EGFR-specific drugs.

Phage Display Derived Monoclonal Antibodies: From Bench to Bedside

Monoclonal antibodies (mAbs) have become one of the most important classes of biopharmaceutical products, and they continue to dominate the universe of biopharmaceutical markets in terms of approval and sales. They are the most profitable single product class, where they represent six of the top ten selling drugs. At the beginning of the 1990s, an in vitro antibody selection technology known as antibody phage display was developed by John McCafferty and Sir. Gregory Winter that enabled the discovery of human antibodies for diverse applications, particularly antibody-based drugs. They created combinatorial antibody libraries on filamentous phage to be utilized for generating antigen specific antibodies in a matter of weeks. Since then, more than 70 phage–derived antibodies entered clinical studies and 14 of them have been approved. These antibodies are indicated for cancer, and non-cancer medical conditions, such as inflammatory, optical, infectious, or immunological diseases. This review will illustrate the utility of phage display as a powerful platform for therapeutic antibodies discovery and describe in detail all the approved mAbs derived from phage display.

Fine-tuning bispecific therapeutics

Bispecific therapeutics target two distinct antigens simultaneously and provide novel functionalities that are not attainable with single monospecific molecules or combinations of them. The unique potential of bispecific therapeutics is driving extensive efforts to discover synergistic dual targets, design molecular formats to integrate bispecific elements, and accelerate successful clinical translation. In particular, the past decade has witnessed a boom in the design and development of bispecific antibody formats with more than 100 collections to date. Despite the remarkable progress that has been made to expand the number of formats, qualitative fine-tuning of bispecific formats is needed to achieve optimal dual-target engagement based on understanding of the spatiotemporal interdependence of the two physically linked binding specificities and the complex target biology associated with bispecific approaches. This review provides insights into the design parameters - including affinity, valency, and geometry - that need to be considered at an early stage of development in order to take the best advantage of bispecific therapeutics.

Influence of molecular weight on transdermal delivery of model macromolecules using hydrogel-forming microneedles: potential to enhance the administration of novel low molecular weight biotherapeutics

With a view to improve the current monoclonal antibody-based therapies dominating the pharmaceutical market, low molecular weight (MW) protein-based macromolecules, such as recombinant antibody fragments, typically within the range of 10-70 kDa, have been developed. Previously, our group successfully delivered Avastin®, a monoclonal antibody (mAb) across the skin using hydrogel-forming microneedles (MN). However, it is thought that this delivery system can be further enhanced using novel, lower MW biomolecules. To address this perception, in the current study, FITC-dextran of different MWs (10, 70 and 150 kDa) was used to model the transdermal delivery of low MW biotherapeutics and mAbs with MWs of approximately 150 kDa. Conversely, fluorescein sodium was the compound selected to model hydrophilic, low MW drugs. As expected, fluorescein sodium produced the greatest cumulative permeation (637.4 ± 42.69 μg). The amounts of FITC-dextran 10 kDa and 150 kDa which permeated across neonatal porcine skin in vitro were 462.17 ± 65.85 μg and 213.54 ± 15.19 μg after 24 h, respectively. The results collated here suggest that the delivery of emerging novel biotherapeutics, via'super swelling' hydrogel-forming MNs, have the potential to result in greater permeation across human skin, compared to the delivery of mAbs delivered via the same route.

Phage Display Derived Monoclonal Antibodies: From Bench to Bedside

Monoclonal antibodies (mAbs) have become one of the most important classes of biopharmaceutical products, and they continue to dominate the universe of biopharmaceutical markets in terms of approval and sales. They are the most profitable single product class, where they represent six of the top ten selling drugs. At the beginning of the 1990s, an in vitro antibody selection technology known as antibody phage display was developed by John McCafferty and Sir. Gregory Winter that enabled the discovery of human antibodies for diverse applications, particularly antibody-based drugs. They created combinatorial antibody libraries on filamentous phage to be utilized for generating antigen specific antibodies in a matter of weeks. Since then, more than 70 phage-derived antibodies entered clinical studies and 14 of them have been approved. These antibodies are indicated for cancer, and non-cancer medical conditions, such as inflammatory, optical, infectious, or immunological diseases. This review will illustrate the utility of phage display as a powerful platform for therapeutic antibodies discovery and describe in detail all the approved mAbs derived from phage display.

Below the Surface: IGF-1R Therapeutic Targeting and Its Endocytic Journey

Ligand-activated plasma membrane receptors follow pathways of endocytosis through the endosomal sorting apparatus. Receptors cluster in clathrin-coated pits that bud inwards and enter the cell as clathrin-coated vesicles. These vesicles travel through the acidic endosome whereby receptors and ligands are sorted to be either recycled or degraded. The traditional paradigm postulated that the endocytosis role lay in signal termination through the removal of the receptor from the cell surface. It is now becoming clear that the internalization process governs more than receptor signal cessation and instead reigns over the entire spatial and temporal wiring of receptor signaling. Governing the localization, the post-translational modifications, and the scaffolding of receptors and downstream signal components established the endosomal platform as the master regulator of receptor function. Confinement of components within or between distinct organelles means that the endosome instructs the cell on how to interpret and translate the signal emanating from any given receptor complex into biological effects. This review explores this emerging paradigm with respect to the cancer-relevant insulin-like growth factor type 1 receptor (IGF-1R) and discusses how this perspective could inform future targeting strategies.

Diabody-Ig: a novel platform for the generation of multivalent and multispecific antibody molecules

Multivalent mono- or bispecific antibodies are of increasing interest for therapeutic applications, such as efficient receptor clustering and activation, or dual targeting approaches. Here, we present a novel platform for the generation of Ig-like molecules, designated diabody-Ig (Db-Ig). The antigen-binding site of Db-Ig is composed of a diabody in the V_H-V_L orientation stabilized by fusion to antibody-derived homo- or heterodimerization domains, e.g., C_H1/C_L or the heavy chain domain 2 of IgE (EHD2) or IgM (MHD2), further fused to an Fc region. In this study, we applied the Db-Ig format for the generation of tetravalent bispecific antibodies (2 + 2) directed against EGFR and HER3 and utilizing different dimerization domains. These Db-Ig antibodies retained the binding properties of the parental antibodies and demonstrated unhindered simultaneous binding of both antigens. The Db-Ig antibodies could be purified by a single affinity chromatography resulting in a homogenous preparation. Furthermore, the Db-Igs were highly stable in human plasma. Importantly, only one short peptide linker (5 aa) per chain is required to generate a Db-Ig molecule, reducing the potential risk of immunogenicity. The presence of a fully functional Fc resulted in IgG-like pharmacokinetic profiles of the Db-Ig molecules. Besides tetravalent bispecific molecules, this modular platform technology further allows for the generation of other multivalent molecules of varying specificity and valency, including mono-, bi-, tri- and tetra-specific molecules, and thus should be suitable for numerous applications.

Development of a bioassay to detect T-cell-activating impurities for T-cell-dependent bispecific antibodies

T-cell-dependent bispecific antibodies (TDBs) are promising cancer immunotherapies that recruit a patient's T cells to kill cancer cells. There are increasing numbers of TBDs in clinical trials, demonstrating their widely recognized therapeutic potential. Due to the fact that TDBs engage and activate T cells via an anti-CD3 (aCD3) arm, aCD3 homodimer (aCD3 HD) and high-molecular-weight species (HMWS) are product-related impurities that pose a potential safety risk by triggering off-target T-cell activation through bivalent engagement and dimerization of T-cell receptors (TCRs). To monitor and control the level of unspecific T-cell activation, we developed a sensitive and quantitative T-cell-activation assay, which can detect aCD3 HD in TDB drug product by exploiting its ability to activate T cells in the absence of target cells. This assay provides in-vivo-relevant off-target T-cell-activation readout. Furthermore, we have demonstrated that this assay can serve as a platform assay for detecting T-cell-activating impurities across a broad spectrum of aCD3 bispecific molecules. It therefore has the potential to significantly benefit many T-cell-recruiting bispecific programs.

Imaging EGFR and HER3 through 89Zr-labeled MEHD7945A (Duligotuzumab)

Tumor resistance to treatment paved the way toward the development of single agent drugs that target multiple molecular signatures amplified within the malignancy. The discovered crosstalk between EGFR and HER3 as well as the role of HER3 in mediating EGFR resistance made these two receptor tyrosine kinases attractive targets. MEHD7945A or duligotuzumab is a single immunotherapy agent that dually targets both molecular signatures. In this study, a positron emission tomography (PET) companion diagnostic to MEHD7945A is reported and evaluated in pancreatic cancer. Tumor accretion and whole body pharmacokinetics of 89Zr-MEHD7945A were established. Specificity of the probe for EGFR and/or HER3 was further examined.

The making of bispecific antibodies

During the past two decades we have seen a phenomenal evolution of bispecific antibodies for therapeutic applications. The 'zoo' of bispecific antibodies is populated by many different species, comprising around 100 different formats, including small molecules composed solely of the antigen-binding sites of two antibodies, molecules with an IgG structure, and large complex molecules composed of different antigen-binding moieties often combined with dimerization modules. The application of sophisticated molecular design and genetic engineering has solved many of the technical problems associated with the formation of bispecific antibodies such as stability, solubility and other parameters that confer drug properties. These parameters may be summarized under the term 'developability'. In addition, different 'target product profiles', i.e., desired features of the bispecific antibody to be generated, mandates the need for access to a diverse panel of formats. These may vary in size, arrangement, valencies, flexibility and geometry of their binding modules, as well as in their distribution and pharmacokinetic properties. There is not 'one best format' for generating bispecific antibodies, and no single format is suitable for all, or even most of, the desired applications. Instead, the bispecific formats collectively serve as a valuable source of diversity that can be applied to the development of therapeutics for various indications. Here, a comprehensive overview of the different bispecific antibody formats is provided.

Spotlight on necitumumab in the treatment of non-small-cell lung carcinoma

The treatment options for metastatic non-small-cell lung cancer (NSCLC) have expanded dramatically in the last 10 years with the discovery of newer drugs and targeted therapy. Epidermal growth factor receptor (EGFR), when aberrantly activated, promotes cell growth and contributes in various ways to the malignant process. EGFR has become an important therapeutic target in a variety of malignancies. Small-molecule tyrosine kinase inhibitors (TKIs) of EGFR are being used to treat advanced NSCLC and are particularly effective in the presence of EGFR mutations. Monoclonal antibodies have also been developed that block the EGFR at the cell surface and work in conjunction with chemotherapy. Necitumumab is a second-generation fully human IgG1 monoclonal antibody that has shown promise in metastatic NSCLC. The benefit has mostly been restricted to squamous cell lung cancer in the frontline setting. Considering that the survival advantage for these patients was modest, there is a need to discover biomarkers that will predict which patients will likely have the best outcomes. This review focuses on the development and clinical trial experience with necitumumab in NSCLC.

Enhanced tumor-targeting selectivity by modulating bispecific antibody binding affinity and format valence

Bispecific antibodies are considered attractive bio-therapeutic agents owing to their ability to target two distinct disease mediators. Cross-arm avidity targeting of antigen double-positive cancer cells over single-positive normal tissue is believed to enhance the therapeutic efficacy, restrict major escape mechanisms and increase tumor-targeting selectivity, leading to reduced systemic toxicity and improved therapeutic index. However, the interplay of factors regulating target selectivity is not well understood and often overlooked when developing clinically relevant bispecific therapeutics. We show in vivo that dual targeting alone is not sufficient to endow selective tumor-targeting, and report the pivotal roles played by the affinity of the individual arms, overall avidity and format valence. Specifically, a series of monovalent and bivalent bispecific IgGs composed of the anti-HER2 trastuzumab moiety paired with affinity-modulated V_H and V_L regions of the anti-EGFR GA201 mAb were tested for selective targeting and eradication of double-positive human NCI-H358 non-small cell lung cancer target tumors over single-positive, non-target NCI-H358-HER2 CRISPR knock out tumors in nude mice bearing dual-flank tumor xenografts. Affinity-reduced monovalent bispecific variants, but not their bivalent bispecific counterparts, mediated a greater degree of tumor targeting selectivity, while the overall efficacy against the targeted tumor was not substantially affected.

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.

Growth factor expression mediates resistance to EGFR inhibitors in head and neck squamous cell carcinomas

OBJECTIVES

Epidermal growth factor receptor (EGFR)-targeted therapy is frequently used in the treatment of advanced head and neck squamous cell carcinoma (HNSCC). However, constitutive or acquired resistance is common and underlying resistance mechanisms remain poorly understood. We investigated the expression levels of growth factors (GF) in tumor-associated stroma and tumor from HNSCC patients and determined the influence of GFs on EGFR inhibitor efficacy in vitro.

MATERIALS AND METHODS

The Chicago HNC Genomic Cohort (CHGC) was queried for GF and receptor tyrosine kinase (RTK) expression. Viability assays were used to evaluate the effect of EGFR inhibition (gefitinib), GF treatment, or both in HNSCC cell lines. Caspase-based assays were used to measure apoptotic activity. Expression of RTKs was determined and correlated with GF treatment effects.

RESULTS

Amphiregulin (AREG), transforming growth factor (TGFβ1), insulin like growth factor (IGF1), fibroblast growth factors (FGF1/FGF2) and the corresponding RTKs were highly expressed in 30-50% of HNSCC, and expression was usually concurrent. While EGFR inhibition was markedly efficacious in HNC cell lines (HN5/HN13/H400/SCC61), co-treatment with most GFs increased viability up to 100%. Only TGFβ1 treatment was additive to EGFR inhibition. GFs also reduced apoptotic effects of EGFR inhibition. RTK expression showed strong positive correlation with respective GF treatment effect for IGF1-IGF1R, less strong for HGF-MET/AREG-EGFR and a moderate negative correlation for TGFβ1-TGFBR1/2.

CONCLUSION

High expression of GFs/RTKs occurs in HNSCC. Co-expression is common. GF expression contributes to EGFR inhibition resistance in our model system, and may be a common mechanism of constitutive or acquired resistance to EGFR inhibition in HNSCC.

Insights into the molecular basis of a bispecific antibody's target selectivity

Bispecific antibodies constitute a valuable class of therapeutics owing to their ability to bind 2 distinct targets. Dual targeting is thought to enhance biological efficacy, limit escape mechanisms, and increase target selectivity via a strong avidity effect mediated by concurrent binding to both antigens on the surface of the same cell. However, factors that regulate the extent of target selectivity are not well understood. We show that dual targeting alone is not sufficient to promote efficient target selectivity, and report the substantial roles played by the affinity of the individual arms, overall avidity and valence. More particularly, various monovalent bispecific IgGs composed of an anti-CD70 moiety paired with variants of the anti-CD4 mAb ibalizumab were tested for preferential binding and selective depletion of CD4⁺/CD70⁺ T cells over cells expressing only one of the target antigens that resulted from antibody dependent cell-mediated cytotoxicity. Variants exhibiting reduced CD4 affinity showed a greater degree of target selectivity, while the overall efficacy of the bispecific molecule was not affected.

XGFR*, a novel affinity-matured bispecific antibody targeting IGF-1R and EGFR with combined signaling inhibition and enhanced immune activation for the treatment of pancreatic cancer

The epidermal growth factor receptor (EGFR) and the insulin-like growth factor-1 receptor (IGF-1R) play critical roles in tumor growth, providing a strong rationale for the combined inhibition of IGF-1R and EGFR signaling in cancer therapy. We describe the design, affinity maturation, in vitro and in vivo characterization of the bispecific anti-IGF-1R/EGFR antibody XGFR*. XGFR* is based on the bispecific IgG antibody XGFR, which enabled heterodimerization of an IGF-1R binding scFab heavy chain with an EGFR-binding light and heavy chain by the "knobs-into-holes" technology. XGFR* is optimized for monovalent binding of human EGFR and IGF-1R with increased binding affinity for IGF-1R due to affinity maturation and highly improved protein stability to oxidative and thermal stress. It bears an afucosylated Fc-portion for optimal induction of antibody-dependent cell-mediated cytotoxicity (ADCC). Stable Chinese hamster ovary cell clones with production yields of 2-3 g/L were generated, allowing for large scale production of the bispecific antibody. XGFR* potently inhibits EGFR- and IGF-1R-dependent receptor phosphorylation, reduces tumor cell proliferation in cells with heterogeneous levels of IGF-1R and EGFR receptor expression and induces strong ADCC in vitro. A comparison of pancreatic and colorectal cancer lines demonstrated superior responsiveness to XGFR*-mediated signaling and tumor growth inhibition in pancreatic cancers that frequently show a high degree of IGF-1R/EGFR co-expression. XGFR* showed potent anti-tumoral efficacy in the orthotopic MiaPaCa-2 pancreatic xenograft model, resulting in nearly complete tumor growth inhibition with significant number of tumor remissions. In summary, the bispecific anti-IGF-1R/EGFR antibody XGFR* combines potent signaling and tumor growth inhibition with enhanced ADCC induction and represents a clinical development candidate for the treatment of pancreatic cancer.

The application of mathematical modelling to the design of bispecific monoclonal antibodies

Targeting multiple receptors with bispecific antibodies is a novel approach that may prevent the development of resistance to cancer treatments. Despite the initial promise, full clinical benefit of this technology has yet to be realized. We hypothesized that in order to optimally exploit bispecific antibody technology, thorough fundamental knowledge of their pharmacological properties compared to that of single agent combinations was needed. Therefore, we developed a mathematical model for the binding of bispecific antibodies to their targets that accounts for the spatial distribution of the binding receptors and the kinetics of binding, and is scalable for increasing valency. The model provided an adequate description of internal and literature-reported in vitro data on bispecific binding. Simulations of in vitro binding with the model indicated that bispecific antibodies are not always superior in their binding potency to combination of antibodies, and the affinity of bispecific arms must be optimized for maximum binding potency. Our results suggest that this tool can be used for the design and development of the next generation of anti-cancer bispecific compounds.

Contribution of EGFR and ErbB-3 Heterodimerization to the EGFR Mutation-Induced Gefitinib- and Erlotinib-Resistance in Non-Small-Cell Lung Carcinoma Treatments

EGFR mutation-induced drug resistance has become a major threat to the treatment of non-small-cell lung carcinoma. Essentially, the resistance mechanism involves modifications of the intracellular signaling pathways. In our work, we separately investigated the EGFR and ErbB-3 heterodimerization, regarded as the origin of intracellular signaling pathways. On one hand, we combined the molecular interaction in EGFR heterodimerization with that between the EGFR tyrosine kinase and its inhibitor. For 168 clinical subjects, we characterized their corresponding EGFR mutations using molecular interactions, with three potential dimerization partners (ErbB-2, IGF-1R and c-Met) of EGFR and two of its small molecule inhibitors (gefitinib and erlotinib). Based on molecular dynamics simulations and structural analysis, we modeled these mutant-partner or mutant-inhibitor interactions using binding free energy and its components. As a consequence, the mutant-partner interactions are amplified for mutants L858R and L858R_T790M, compared to the wild type EGFR. Mutant delL747_P753insS represents the largest difference between the mutant-IGF-1R interaction and the mutant-inhibitor interaction, which explains the shorter progression-free survival of an inhibitor to this mutant type. Besides, feature sets including different energy components were constructed, and efficient regression trees were applied to map these features to the progression-free survival of an inhibitor. On the other hand, we comparably examined the interactions between ErbB-3 and its partners (EGFR mutants, IGF-1R, ErbB-2 and c-Met). Compared to others, c-Met shows a remarkably-strong binding with ErbB-3, implying its significant role in regulating ErbB-3 signaling. Moreover, EGFR mutants corresponding to poor clinical outcomes, such as L858R_T790M, possess lower binding affinities with ErbB-3 than c-Met does. This may promote the communication between ErbB-3 and c-Met in these cancer cells. The analysis verified the important contribution of IGF-1R or c-Met in the drug resistance mechanism developed in lung cancer treatments, which may bring many benefits to specialized therapy design and innovative drug discovery.

Role of HER2 in brain metastasis of breast cancer: a systematic review and meta-analysis

BACKGROUND

Breast cancer is one of the most common cancers among women worldwide and the HER2 receptor plays an important role in its development and progression. This systematic review aimed to summarize the role of HER2 in brain metastasis in patients with breast cancer.

MATERIALS AND METHODS

We conducted a literature search by advanced search in title field using the Scopus, Pubmed, and Google scholar databases until the end of June 2014. With metastasis, metastatic, HER2, brain, and breast cancer, as terms of search we selected 31 articles, which were reviewed by two independent and blinded expert reviewers. The studies were first selected according to their titles and abstracts. Quality of the studies were then assessed using the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) protocol for observational studies and CONSORT(Consolidation of Standards for Reporting Trials) protocol for clinical trials. For statistical analyses, we used STATA, version 11.0 software. Forest and funnel diagrams were drawn and for heterogeneity, index was also considered. Also we used meta regression analysis.

RESULTS

Finally, we reviewed 10 studies. The prevalence of brain metastasis in HER2- positive breast cancer patients was 24.9%. There was publication bias in the reviewed studies. Meta regression analysis showed that follow up time had no significant effect (p=0.396) on the prevalence of brain metastasis.

CONCLUSIONS

The results showed a high prevalence of brain metastasis in HER2 positive breast cancer patients.

Bi-specific antibodies with high antigen-binding affinity identified by flow cytometry

Using conventional approaches, the antigen-binding affinity of a novel format of bi-specific antibody (BsAb) cannot be determined until purified BsAb is obtained. Here, we show that new lipoprotein A (NlpA)-based bacteria display technology, combined with flow cytometry (FCM), can be used to detect antigen-binding affinity of BsAbs, in the absence of expression and purification work. Two formats of BsAb, scFv2-CH/CL and Diabody-CH/CL, specific for human interleukin 1β (hIL-1β) and human interleukin 17A (hIL-17A), were constructed and displayed in Escherichia coli using NlpA-based bacteria display technology. Conversion of these cells to spheroplasts, and their incubation with fluorescently conjugated antigens resulted in the selective labeling of spheroplasts expressing BsAb; enabling their antigen-binding affinity to be analyzed with FCM. The association and dissociation of BsAbs for binding to hIL-1β and hIL-17A were analyzed using FCM-based assays. The results showed that antigen-binding affinity of Diabody-CH/CL was significantly higher than that of scFv2-CH/CL. To confirm these results of FCM-based assays, BsAbs were expressed, purified and subjected to relative affinity measurements, in vitro and in vivo bioactivity analysis. The results showed that Diabody-CH/CL had greater relative affinities for both antigens, resulting in better blocking bioactivities on cellular level and effects on alleviating joint inflammation, and cartilage destruction and bone damage in collagen induced arthritis (CIA) mice model. These results indicate that BsAbs with good antigen-binding affinity can be identified by FCM-based assays without expression and purification work, and the indentified BsAb can serve as a lead compound for further drug development.

Relationship between insulin-like growth factor-1 receptor and human papillomavirus in patients with oropharyngeal cancer

BACKGROUND

Human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma (SCC) is associated with better prognosis than HPV-negative oropharyngeal SCC. The purpose of this study was to assess the expression of insulin-like growth factor-1 receptor (IGF-1R) in patients with oropharyngeal SCC, its relationship to HPV status and various clinical parameters, and its relationship with clinical outcome.

METHODS

The study subjects were 59 patients with oropharyngeal SCC. IGF-1R expression was examined by immunohistochemistry in paraffin-embedded tumor tissues. HPV status was evaluated by in situ hybridization (ISH) in the same tissues.

RESULTS

IGF-1R did not correlate with clinical parameters, but IGF-1R expression was more common in HPV-negative tumors than in HPV-positive tumors. The prognosis was poorer in patients of the IGF-1R-positive group than in the IGF-1R-negative group.

CONCLUSION

The results suggested that IGF-1R expression in oropharyngeal SCC correlated with poor prognosis in HPV-negative patients. Treatment targeting IGF-1R could potentially improve the survival of patients with HPV-negative oropharyngeal SCC.

A novel glycoengineered bispecific antibody format for targeted inhibition of epidermal growth factor receptor (EGFR) and insulin-like growth factor receptor type I (IGF-1R) demonstrating unique molecular properties

In the present study, we have developed a novel one-arm single chain Fab heterodimeric bispecific IgG (OAscFab-IgG) antibody format targeting the insulin-like growth factor receptor type I (IGF-1R) and the epidermal growth factor receptor (EGFR) with one binding site for each target antigen. The bispecific antibody XGFR is based on the "knob-into-hole" technology for heavy chain heterodimerization with one heavy chain consisting of a single chain Fab to prevent wrong pairing of light chains. XGFR was produced with high expression yields and showed simultaneous binding to IGF-1R and EGFR with high affinity. Due to monovalent binding of XGFR to IGF-1R, IGF-1R internalization was strongly reduced compared with the bivalent parental antibody, leading to enhanced Fc-mediated cellular cytotoxicity. To further increase immune effector functions triggered by XGFR, the Fc portion of the bispecific antibody was glycoengineered, which resulted in strong antibody-dependent cell-mediated cytotoxicity activity. XGFR-mediated inhibition of IGF-1R and EGFR phosphorylation as well as A549 tumor cell proliferation was highly effective and was comparable with a combined treatment with EGFR (GA201) and IGF-1R (R1507) antibodies. XGFR also demonstrated potent anti-tumor efficacy in multiple mouse xenograft tumor models with a complete growth inhibition of AsPC1 human pancreatic tumors and improved survival of SCID beige mice carrying A549 human lung tumors compared with treatment with antibodies targeting either IGF-1R or EGFR. In summary, we have applied rational antibody engineering technology to develop a heterodimeric OAscFab-IgG bispecific antibody, which combines potent signaling inhibition with antibody-dependent cell-mediated cytotoxicity induction and results in superior molecular properties over two established tetravalent bispecific formats.

Construction and production of an IgG-Like tetravalent bispecific antibody, IgG-single-chain Fv fusion

In recent years, both laboratory and clinical studies have demonstrated that bispecific antibodies (BsAbs) may have significant potential application in cancer therapy either by targeting tumor cells with cytotoxic agents including effector cells, radionuclides, drugs, and toxins, or by simultaneously blocking two tumor-associated targets, e.g., tumor growth factors and/or their cell surface receptors. A major obstacle in the development of BsAb has been the difficulty of producing the materials in sufficient quality and quantity by traditional technologies such as the hybrid hybridoma and chemical conjugation methods. The development of recombinant BsAbs as therapeutic agents will depend heavily on the advances made in the design of the constructs (or formats) and production efficiency. Here we describe a recombinant method for the construction and production of a tetravalent IgG-like BsAb molecule, IgG-scFv fusion, in which, a single-chain Fv (scFv) antibody fragment of one antigen specificity is genetically fused to the c-terminal of a conventional IgG of a different antigen specificity.

An alternative chemical redox method for the production of bispecific antibodies: implication in rapid detection of food borne pathogens

Bi-functional antibodies with the ability to bind two unrelated epitopes have remarkable potential in diagnostic and bio-sensing applications. In the present study, bispecific antibodies that recognize human red blood cell (RBC) and the food borne pathogen Listeria monocytogenes (L. monocytogenes) were engineered. The procedure involves initial reduction of a mixture of anti-RBC and anti-Listeria antibodies followed by gradual re-oxidation of the reduced disulphides. This facilitates association of the separated antibody chains and formation of hybrid immunoglobulins with affinity for the L. monocytogenes and human RBC. The bispecific antibodies caused the agglutination of the RBCs only in the presence of L. monocytogenes cells. The agglutination process necessitated the specific presence of L. monocytogenes and the red colored clumps formed were readily visible with naked eyes. The RBC agglutination assay described here provides a remarkably simple approach for the rapid and highly specific screening of various pathogens in their biological niches.

Phase 1b study of safety, tolerability and efficacy of R1507, a monoclonal antibody to IGF-1R in combination with multiple standard oncology regimens in patients with advanced solid malignancies

BACKGROUND

R1507 is a human IgG1 Mab that binds to the insulin-like growth factor-1 receptor (IGF-1R) and inhibits IGF-1- or IGF-2-mediated anchorage-independent growth of malignant cells. A phase 1b study evaluated the safety, tolerability and efficacy of R1507 in combination with multiple standard oncology regimens.

METHODS

R1507 (3, 5, 9, 10 and 16 mg/kg IV, Q2 W or Q3 W) was added to six treatment regimens: gemcitabine + erlotinib (GE); paclitaxel + bevacizumab (PB); carboplatin + etoposide (CE); mFOLFOX6 + bevacizumab (FB); capecitabine + trastuzumab (CT); and sorafenib (S). If tolerable, R1507 dose was escalated utilizing a 3 + 3 + 6 and a 3 + 9 design.

RESULTS

A total of 104 patients enrolled into regimens 1-6: 93 % were non-recent diagnoses. Eighteen withdrew for safety [one death, 17 adverse events (AEs)]. A total of 1,337 AEs any grade, across regimens and doses were nausea, vomiting and diarrhea. A total of 123 had grade ≥3 AEs (n = 28 dose level 1; n = 95 dose level 1) and in 60 patients were myelosuppression, fatigue and mucosal inflammation. ORR (PR plus SD) of evaluable patients across six regimens was 36 % with five PRs: regimens PB (non-small cell lung cancer, nasopharyngeal cancer), CE (melanoma), FB (colon cancer) and S (GIST). The GIST pt (>4 prior therapies) had a PR for 3 years. Three patients (breast cancer, melanoma and adenoid cystic carcinoma) were on study for >1 year; 76 % of patients had SD or better for 4 months.

CONCLUSIONS

R1507 added to six standard oncology regimens was well tolerated with an ORR of 36 %.

The potential role of nanotechnology in therapeutic approaches for triple negative breast cancer

Triple Negative Breast Cancer, TNBC, a highly aggressive and metastatic type of breast cancer, is characterized by loss of expression of the estrogen receptor (ER), progesterone receptor (PR), and a lack of overexpression of the human epidermal growth factor receptor 2 (HER2). It is a heterogeneous group of tumors with diverse histology, molecular uniqueness and response to treatment. Unfortunately, TNBC patients do not benefit from current anti-HER2 or hormone positive targeted breast cancer treatments; consequently, these patients rely primarily on chemotherapy. However, the 5-year survival rate for woman with metastatic TNBC is less than 30%. As a result of ineffective treatments, TNBC tumors often progress to metastatic lesions in the brain and lung. Brain metastases of invasive breast cancer are associated with 1 and 2 year survival rate of 20% and <2% respectively. Because the only current systemic treatment for TNBC is chemotherapy, alternative targeted therapies are urgently needed to improve the prognosis for TNBC patients. This review is focused on opportunities for developing new approaches for filling the current void in an effective treatment for TNBC patients.

A novel bispecific EGFR/Met antibody blocks tumor-promoting phenotypic effects induced by resistance to EGFR inhibition and has potent antitumor activity

Simultaneous targeting of epidermal growth factor receptor (EGFR) and Met in cancer therapy is under pre-clinical and clinical evaluation. Here, we report the finding that treatment with EGFR inhibitors of various tumor cells, when stimulated with hepatocyte growth factor (HGF) and EGF, results in transient upregulation of phosphorylated AKT. Furthermore, EGFR inhibition in this setting stimulates a pro-invasive phenotype as assessed in Matrigel-based assays. Simultaneous treatment with AKT and EGFR inhibitors abrogates this invasive growth, hence functionally linking signaling and phenotype. This observation implies that during treatment of tumors a balanced ratio of EGFR and Met inhibition is required. To address this, we designed a bispecific antibody targeting EGFR and Met, which has the advantage of a fixed 2:1 stoichiometry. This bispecific antibody inhibits proliferation in tumor cell cultures and co-cultures with fibroblasts in an additive manner compared with treatment with both single agents. In addition, cell migration assays reveal a higher potency of the bispecific antibody in comparison with the antibodies' combination at low doses. We demonstrate that the bispecific antibody inhibits invasive growth, which is specifically observed with cetuximab. Finally, the bispecific antibody potently inhibits tumor growth in a non-small cell lung cancer xenograft model bearing a strong autocrine HGF-loop. Together, our findings strongly support a combination treatment of EGFR and Met inhibitors and further evaluation of resistance mechanisms to EGFR inhibition in the context of active Met signaling.

The potential for cancer combination therapy with multi-targeted, single-protein pharmaceuticals

Many diseases and disorders are best treated by a combination of drugs. Unlike small molecules, engineered proteins can be designed to incorporate multiple independent drug activities. Compared with a combination of two or more proteins, the potential benefits of a single biologic that inhibits multiple targets may include lower cost, simplified clinical testing and greater patient convenience. The evolution of HIV combination therapy is a useful point of comparison, as it occurred in an unusual regulatory environment that allowed the testing of combinations when the clinical benefit of component drugs was unproven. The epidermal growth factor receptor family of cancer targets illustrates how a particular single-molecule combination therapy might be used for cancer therapy, so some attempts to construct single-protein agents with multiple activities that include anti-EGFR moieties are reviewed. Protein engineers have created an armory of multiply-targeted antibody derivatives, but such engineered molecules often have a shorter serum half-life than IgG antibodies. New protein engineering approaches may be needed to address this problem. Nonetheless, multiply-targeted single-protein agents may be an economical solution to the problem of antibody combination therapy for cancer.

Bispecific antibody derivatives with restricted binding functionalities that are activated by proteolytic processing

We have designed bispecific antibodies that bind one target (anti-Her3) in a bivalent IgG-like manner and contain one additional binding entity (anti-cMet) composed of one V(H) and one V(L) domain connected by a disulfide bond. The molecules are assembled by fusing a V(H,Cys44) domain via flexible connector peptides to the C-terminus of one H-chain (heavy chain), and a V(L,Cys100) to another H-chain. To ensure heterodimerization during expression in mammalian cells, we introduced complementary knobs-into-holes mutations into the different H-chains. The IgG-shaped trivalent molecules carry as third binding entity one disulfide-stabilized Fv (dsFv) without a linker between V(H) and V(L). Tethering the V(H) and V(L) domains at the C-terminus of the C(H)3 domain decreases the on-rates of the dsFv to target antigens without affecting off-rates. Steric hindrance resolves upon removal of one side of the double connection by proteolysis: this improves flexibility and accessibility of the dsFv and fully restores antigen access and affinity. This technology has multiple applications: (i) in cases where single-chain linkers are not desired, dsFvs without linkers can be generated by addition of furin site(s) in the connector that are processed during expression within mammalian cells; (ii) highly active (toxic) entities which affect expression can be produced as inactive dsFvs and subsequently be activated (e.g. via PreScission cleavage) during purification; (iii) entities can be generated which are targeted by the unrestricted binding entity and can be activated by proteases in target tissues. For example, Her3-binding molecules containing linkers with recognition sequences for matrix metalloproteases or urokinase, whose inactivated cMet binding site is activated by proteolytic processing.

Next generation of antibody therapy for cancer

Monoclonal antibodies (mAbs) have become a major class of therapeutic agents providing effective alternatives to treating various human diseases. To date, 15 mAbs have been approved by regulatory agencies in the world for clinical use in oncology indications. The selectivity and specificity, the unique pharmacokinetics, and the ability to engage and activate the host immune system differentiate these biologics from traditional small molecule anticancer drugs. mAb-based regimens have brought clinical benefits, including improvements in overall survival, to patients with a variety of cancers. Many challenges still remain, however, to fully realize the potential of these new medicines. With our further understanding of cancer biology, mechanism of antibody action, and advancement of antibody engineering technologies, many novel antibody formats or antibody-derived molecules are emerging as promising new generation therapeutics. Carefully designed and engineered, they retain the advantage of specificity and selectivity of original antibodies, but in the meantime acquire additional special features such as improved pharmacokinetics, increased selectivity, and enhanced anticancer efficacy. Promising clinical results are being generated with these newly improved antibody-based therapeutics.

Inhibition of hepatocellular carcinoma cell growth by an anti-insulin-like growth factor-I receptor monoclonal antibody

Hepatocellular carcinoma (HCC) overexpresses insulin-like growth factor-I receptor (IGF-IR), as compared with normal hepatocytes. Since IGF-1R-mediated signaling promotes survival, oncogenic transformation and tumor growth and spread, it represents a potential target for treating HCC. Here, we have generated a murine anti-IGF-1R antibody, 4F2, that recognizes the IGF-IRα subunit and blocks in vitro IGF-I and IGF-II-induced cell proliferation of SMMC-7721 and Bel-7402 HCC cell lines. 4F2 can inhibit IGF-IR autophosphorylation, IRS-1 phosphorylation and the activation of the major downstream signaling molecules AKT and mitogen-activated protein kinase. Additionally, we observed a moderate increase in apoptosis as demonstrated by detection of changes in the expression of the pro-apoptotic and anti-apoptotic proteins Bax and Bcl-2 after 4F2 treatment. Combined treatment with 4F2 and doxorubicin was more effective in reducing cell proliferation and promoting apoptosis than either agent alone. These data support that therapeutic anti-IGF-IR antibodies are potential new agents for treating HCC.

Advances in bispecific biotherapeutics for the treatment of cancer

Conventional monoclonal antibody (mAb) therapeutics interfering with cellular signaling of their respective target antigens are frequently limited in their ability to induce significant anti-tumor activities when administered as single agents in patients with solid tumors. To overcome these limitations, several new technologies are being developed to empower biotherapeutics and to improve their anti-tumor activities, while maintaining their high tumor selectivity and superior safety profiles. The various efficacy enhancement technologies developed for mAbs can be divided broadly into two categories: First, technologies that improve the intrinsic anti-tumor activities of conventional immunoglobulin mAb formats, including the enhancement of effector cell functions and modulations of target binding properties, including interference with multiple signaling pathways. The second category of empowered biologics combines complementary anti-tumor modalities independent of the IgG format, including antibody drug conjugates (ADCs). In addition, bispecific compounds designed to recruit different subsets of inflammatory cells to the tumor environment, also belong to the mechanistic complementation strategy. This approach termed redirected immune cell killing, belongs to one the most promising new biotherapeutic platforms developed in oncology. Over 20 bispecific compounds are currently being developed pre-clinically, and several compounds are undergoing early stage clinical trials. In this report, we review the progress made in the development of bispecific biotherapeutics in the context of ADCs, redirected T- and B-cell killing and targeting of multiple signaling pathways. We also discuss the status of the clinical development of this class of compounds in oncology and the promises and challenges this field is currently facing.

Generating bispecific human IgG1 and IgG2 antibodies from any antibody pair

Bispecific antibodies and antibody fragments are a new class of therapeutics increasingly utilized in the clinic for T cell recruitment (catumaxomab anti-EpCAM/CD3 and blinatumomab anti-CD19/CD3), increase in the selectivity of targeting, or simultaneous modulation of multiple cellular pathways. While the clinical potential for certain bispecific antibody formats is clear, progress has been hindered because they are often difficult to manufacture, may suffer from suboptimal pharmacokinetic properties, and may be limited due to potential immunogenicity issues. Current state-of-the-art human IgG-like bispecific technologies require co-expression of two heavy chains with a single light chain, use crossover domains to segregate light chains, or utilize scFv (single-chain fragment variable)-Fc fusion. We have engineered both human IgG1 and IgG2 subtypes, with minimal point mutations, to form full-length bispecific human antibodies with high efficiency and in high purity. In our system, the two antibodies of interest can be expressed and purified separately, mixed together under appropriate redox conditions, resulting in a formation of a stable bispecific antibody with high yields. With this approach, it is not necessary to generate new antibodies that share a common light chain, therefore allowing the immediate use of an existing antibody regardless of whether it has been generated via standard hybridoma or display methods. We demonstrate the generality of the approach and show that these bispecific antibodies have properties similar to those of wild-type IgGs, and we further demonstrate the utility of the technology with an example of a CD3/CD20 bispecific antibody that effectively depletes B cells in vitro and in vivo.

Development of tetravalent IgG1 dual targeting IGF-1R-EGFR antibodies with potent tumor inhibition

In this study we present novel bispecific antibodies that simultaneously target the insulin-like growth factor receptor type I (IGF-1R) and epidermal growth factor receptor (EGFR). For this purpose disulfide stabilized scFv domains of the EGFR/ADCC antibody GA201 were fused via serine-glycine connectors to the C-terminus of the heavy (XGFR2) or light chain (XGFR4), or the N-termini of the light (XGFR5) or heavy chain (XGFR3) of the IGF-1R antibody R1507 as parental IgG1 antibody. The resulting bispecific IGF-1R-EGFR antibodies XGFR2, XGFR3 and XGFR4 were successfully generated with yields and stability comparable to conventional IgG1 antibodies. They effectively inhibited IGF-1R and EGFR phosphorylation and 3D proliferation of H322M and H460M2 tumor cells, induced strong down-modulation of IGF-1R as well as enhanced EGFR down-modulation compared to the parental EGFR antibody GA201 and were ADCC competent. The bispecific XGFR derivatives showed a strong format dependent influence of N- or C-terminal heavy and light chain scFv attachment on ADCC activity and an increase in receptor downregulation over the parental combination in vitro. XGFR2 and XGFR4 were selected for in vivo evaluation and showed potent anti-tumoral efficacy comparable to the combination of monospecific IGF-1R and EGFR antibodies in subcutaneous BxPC3 and H322M xenograft models. In summary, we have managed to overcome issues of stability and productivity of bispecific antibodies, discovered important antibody fusion protein design related differences on ADCC activity and receptor downmodulation and show that IGF-1R-EGFR antibodies represent an attractive therapeutic strategy to simultaneously target two key components de-regulated in multiple cancer types, with the ultimate goal to avoid the formation of resistance to therapy.

Dual targeting strategies with bispecific antibodies

Monoclonal antibodies are widely used for the treatment of cancer, inflammatory and infectious diseases and other disorders. Most of the marketed antibodies are monospecific and therefore capable of interacting and interfering with a single target. However, complex diseases are often multifactorial in nature, and involve redundant or synergistic action of disease mediators or upregulation of different receptors, including crosstalk between their signaling networks. Consequently, blockade of multiple, different pathological factors and pathways may result in improved therapeutic efficacy. This result can be achieved by combining different drugs, or use of the dual targeting strategies applying bispecific antibodies that have emerged as an alternative to combination therapy. This review discusses the various dual targeting strategies for which bispecific antibodies have been developed and provides an overview of the established bispecific antibody formats.