Generation and characterization of a novel human IgG1 antibody against vascular endothelial growth factor receptor 2

A VEGFR2-MICA bispecific antibody activates tumor-infiltrating lymphocytes and exhibits potent anti-tumor efficacy in mice

MHC class I-related chain A (MICA) is one of the major ligands for natural killer group 2 member D (NKG2D), which is an activating NK receptor. MICA is expressed on the surface of human epithelial tumor cells, and its shedding from tumor cells leads to immunosuppression. To activate immune response in the tumor microenvironment, we designed an anti-VEGFR2-MICA bispecific antibody (JZC01), consisting of MICA and an anti-VEGFR2 single chain antibody fragment (JZC00) and explored its potential anti-tumor activity. JZC01 targeted vascular endothelial growth factor receptor 2 (VEGFR2) and inhibited tumorigenesis by blocking the VEGFR2 signaling pathway. Additionally, JZC01 promoted NK and CD8⁺ T cells to release IFN-γ and engaged activated lymphocytes to lysis of VEGFR2-expressing tumor cells. The in vivo anti-tumor activity of JZC01 was investigated by establishing a Lewis lung cancer cell-transplanted mouse model. It effectively reduced the tumor vascular density and increased the infiltration and activation of NK and CD8⁺ T cells in the tumor microenvironment. Thus, JZC01 functions in anti-tumor angiogenesis and anti-tumor immune activation, and showed improved anti-tumor efficacy combined with docetaxel, which provides a new insight into anti-tumor therapy.

Anti-CD24 Antibody-Nitric Oxide Conjugate Selectively and Potently Suppresses Hepatic Carcinoma

Nitric oxide (NO) has a wide range of potential applications in tumor therapy. However, a targeted delivery system for NO donors has remained elusive, creating a bottleneck that limits its druggability. The antibody-drug conjugate (ADC) is a targeted drug delivery system composed of an antibody linked to an active cytotoxic drug. This design may compensate for the weak targeting ability and various biological functions of the NO donor. In this study, we designed the NO donor HL-2, which had a targeted, cleaved disulfide bond and an attachable maleimide terminal. We conjugated HL-2 with an antibody that targeted CD24 through a thioether bond to generate an ADC-like immunoconjugate, antibody-nitric oxide conjugate (ANC), which we named HN-01. HN-01 showed efficient internalization and significantly increased the release of NO in hepatic carcinoma cells in vitro. HN-01 induced apoptosis of tumor cells and suppressed tumor growth in hepatic carcinoma-bearing nude mice through antibody-dependent co-toxicity; HN-01 also increased NO levels in tumor cells. Collectively, this study expands the concept of ADC and provides an innovative NO donor and ANC to address current challenges in targeted delivery of NO. This new inspiration for an ANC design can also be used in future studies for other molecules with intracellular targets. SIGNIFICANCE: This study is the first to expand the concept of ADC with an antibody-nitric oxide conjugate that suppresses hepatic carcinoma in vitro and in vivo.

A Novel Fusion Antibody Exhibits Antiangiogenic Activity and Stimulates NK Cell-mediated Immune Surveillance Through Fused NKG2D Ligand

A single-chain variable fragment (scFv) targeting vascular endothelial growth factor receptor 2 was previously generated from a phage display library in our laboratory. However, it has shortened half-life and lacks Fc fragment for effector cell recognition. To address these challenges, a ligand of NK-cell receptor NKG2D was fused to the scFv and created a fusion protein scFv-major histocompatibility complex class I-related chain A (MICA), which is expected to recognize tumor cells through the scFv moiety and stimulate NK cells through the MICA. The fusion protein demonstrated specific binding to both vascular endothelial growth factor receptor 2 and NKG2D in protein-based and cell-based assays. In addition, it demonstrated antiangiogenic activities including restraining the proliferation, migration, transwell invasion, and tube formation of human umbilical vein endothelial cells. Furthermore, the fusion protein exhibited significant cytotoxicity on K562, MDA-MB-435, and B16F10 cells and triggered NK92 cell-mediated cytotoxicity on MDA-MB-435 cells by stimulating the release of significant cytokines. The fusion protein targeting strategy, therefore, provides a means to engage lymphocyte effector cells against tumor specific antigen overexpressing tumor cells.

VEGFR2-targeted fusion antibody improved NK cell-mediated immunosurveillance against K562 cells

MHC class I polypeptide-related sequence A (MICA), which is normally expressed on cancer cells, activates NK cells via NK group 2-member D pathway. However, some cancer cells escape NK-mediated immune surveillance by shedding membrane MICA causing immune suppression. To address this issue, we designed an antibody-MICA fusion targeting tumor-specific antigen (vascular endothelial growth factor receptor 2, VEGFR2) based on our patented antibody (mAb04) against VEGFR2. In vitro results demonstrate that the fusion antibody retains both the antineoplastic and the immunomodulatory activity of mAb04. Further, we revealed that it enhanced NK-mediated immunosurveillance against K562 cells through increasing degranulation and cytokine production of NK cells. The overall data suggest our new fusion protein provides a promising approach for cancer-targeted immunotherapy and has prospects for potential application of chronic myeloid leukemia.

VEGFR2 targeted antibody fused with MICA stimulates NKG2D mediated immunosurveillance and exhibits potent anti-tumor activity against breast cancer

Binding of MHC class I-related chain molecules A and B (MICA/B) to the natural killer (NK) cell receptor NK group 2, member D (NKG2D) is thought critical for activating NK-mediated immunosurveillance. Angiogenesis is important for tumor growth and interfering with angiogenesis using the fully human IgG1 anti-VEGFR2 (vascular endothelial growth factor receptor 2) antibody (mAb04) can be effective in treating malignancy. In an effort to make mAb04 more effective we have generated a novel antibody fusion protein (mAb04-MICA) consisting of mAb04 and MICA. We found that mAb04-MICA maintained the anti-angiogenic and antineoplastic activities of mAb04, and also enhanced immunosurveillance activated by the NKG2D pathway. Moreover, in human breast tumor-bearing nude mice, mAb04-MICA demonstrated superior anti-tumor efficacy compared to combination therapy of mAb04 + Docetaxel or Avastin + Docetaxel, highlighting the immunostimulatory effect of MICA. In conclusion, mAb04-MICA provided new inspiration for anti-tumor treatment and had prospects for clinical application.

A humanized anti-DLL4 antibody promotes dysfunctional angiogenesis and inhibits breast tumor growth

Blockage of Delta-like 4 (DLL4)-directed Notch signaling induces excessive tip cell formation and endothelial proliferation resulting in dysfunctional angiogenesis in tumors. MMGZ01, as a murine anti-human DLL4 monoclonal antibody, specifically binds to human DLL4 and blocks Notch pathway. Here, the structure of MMGZ01 variable fragment (Fv) was established and framework region (FR) residues which supported complementarily determining region (CDR) loop conformation were identified. Important residues interactions were also identified through docking MMGZ01 Fv with antigen epitope in DLL4. To humanize the murine antibody, we modified MMGZ01 Fv through CDR grafting and the reconstructed antibody (H₃L₂) maintained similar structure and binding affinity to parental MMGZ01 after back mutation of 12 canonical murine residues in the FRs. Meanwhile, H₃L₂ promoted human umbilical vein endothelial cell (HUVEC) proliferation through inhibiting DLL4-directed Notch pathway. Moreover, in MDA-MB-231-bearing nude mice, H₃L₂ induced dysfunctional angiogenesis and tumor cell apoptosis and showed superior anti-tumor activity. In conclusion, H₃L₂ is an ideal humanized antibody that inhibits tumor growth through targeting DLL4-Notch pathway and has attracting potentials for clinical applications.

A novel bispecific diabody targeting both vascular endothelial growth factor receptor 2 and epidermal growth factor receptor for enhanced antitumor activity

Epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor 2 (VEGFR2) are receptor tyrosine kinases known to play critical roles in the development and progression of tumors. Based on the cross-talk between EGFR and VEGFR2 signal pathways, we designed and produced a bispecific diabody (bDAb) targeting both EGFR and VEGFR2 simultaneously. The bispecific molecule (EK-02) demonstrated that it could bind to HUVEC (VEGFR2 high-expressing) and A431 (EGFR overexpressing) cells. Additionally, similar to the parental antibodies, it was able to inhibit proliferation and migration, and induced apoptosis in these cells (HUVECs and A431), demonstrating that it had retained the functional properties of its parental antibodies. Furthermore, the efficacy of EK-02 was evaluated using the human colon adenocarcinoma cell line HT29 (VEGFR2 and EGFR coexpressing). In vitro assay showed that EK-02 could bind to HT29 cells, restrain cell growth and migration, and induce apoptosis with enhanced efficacy compared to both parental antibodies. Further, it inhibited the neovascularization and tumor formation on an HT29 cell bearing chicken chorioallantoic membrane (CAM) tumor model in vivo. In conclusion, these data suggest that the novel bDAb (EK-02) has antiangiogenesis and antitumor capacity both in vitro and in vivo, and can possibly be used as cotargeted therapy for the treatment of EGFR and VEGFR2 overexpressing tumors. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:294-302, 2016.

A bispecific protein rG7S-MICA recruits natural killer cells and enhances NKG2D-mediated immunosurveillance against hepatocellular carcinoma

MHC class I-related chain A (MICA) is a principal immunoligand of the natural killer (NK) cell receptor NK group 2, member D (NKG2D) and plays a key role in NK cell-mediated immune recognition. Shedding of MICA from tumor cells leads to immunosuppression. To reconstitute the immunosurveilance function of NK cells, we constructed a fusion protein rG7S-MICA and explored its potential anti-tumor activity against hepatocellular carcinoma (HCC). rG7S-MICA consists of human MICA and a single-chain antibody fragment (scFv) targeting the tumor-associated antigen cluster of differentiation 24 (CD24). In vitro, rG7S-MICA engaged both NK cells and CD24(+) human HCC cells, and triggered NK cell-mediated cytolysis. Furthermore, in CD24(+) HCC-bearing nude mice, rG7S-MICA specifically targeted to the tumor tissue, where it effectively recruited NK cells and induced the release of cytokines, and showed superior anti-tumor activity. In conclusion, rG7S-MICA provides a new approach for HCC-targeting immunotherapy and has attracting potentials for clinical applications.

MMGZ01, an anti-DLL4 monoclonal antibody, promotes nonfunctional vessels and inhibits breast tumor growth

Increasing evidence suggests that DLL4 (Delta-like 4)-Notch signaling plays a critical role in cell fate determination and differentiation in tissues. Blocking DLL4-Notch signaling results in inhibition of tumor growth, which is associated with increased nonfunctional vessels and poor perfusion in the tumor. We successfully generated a human DLL4 monoclonal antibody MMGZ01 that binds specifically to DLL4 to disrupt the interaction between DLL4 and Notch1. MMGZ01 showed high affinity to DLL4 to inhibit the DLL4-mediated human umbilical vein endothelial cell (HUVEC) phenotype. Furthermore, MMGZ01 stimulated HUVEC vessel sprouting and tubule formation in vitro. In addition, MMGZ01 had a pronounced effect in promoting immature vessels and reduced breast cancer cell growth in vivo. Finally, MMGZ01 treatment inhibited the proliferation of breast cancer cells, induced tumor cell apoptosis, suppressed mammosphere formation, decreased CD44(+)/CD24(-) cell population, and reduced epithelial mesenchymal transition (EMT). These findings suggest that antagonism of the DLL4-Notch signaling pathway might provide a potential therapeutic approach for breast cancer treatment.

A human IgG-like bispecific antibody co-targeting epidermal growth factor receptor and the vascular endothelial growth factor receptor 2 for enhanced antitumor activity

Both Epidermal Growth Factor Receptor (EGFR) and the Vascular Endothelial Growth Factor Receptor 2 (VEGFR2) play critical roles in tumorigenesis. We hypothesized co-targeting EGFR and VEGFR2 using a bispecific antibody might have significant therapeutic potential. Here,we designed and produced a human IgG-like bispecific antibody (Bi-Ab) based on the variable regions of cetuximab (an anti-EGFR antibody) and mAb-04 (an anti-VEGFR2 antibody developed in our lab) . The Bi-Ab was found to inhibit the proliferation, survival and invasion of cancer cells via ablating phosphorylation of receptor and downstream signaling. In vivo efficacy was demonstrated against established HT-29 and SKOV-3 xenografts grown in nude mice. Studies revealed our Bi-Ab was able to restrain xenografted tumor growth and prolong survival of mice through inhibiting cell proliferation,promoting apoptosis and anti-angiogenesis. In contrast to cetuximab or mAb-04 alone, our Bi-Ab exhibits enhanced antitumor activity and has equal or slightly superior activity to their combination (Combi). It shows promise as a therapeutic agent, especially for use against tumors EGFR and/or VEGFR2 over-expressing malignancies.

Design of liposomal formulations for cell targeting

Liposomes have gained extensive attention as carriers for a wide range of drugs due to being both nontoxic and biodegradable as they are composed of substances naturally occurring in biological membranes. Active targeting for cells has explored specific modification of the liposome surface by functionalizing it with specific targeting ligands in order to increase accumulation and intracellular uptake into target cells. None of the Food and Drug Administration-licensed liposomes or lipid nanoparticles are coated with ligands or target moieties to delivery for homing drugs to target tissues, cells or subcellular organelles. Targeted therapies (with or without controlled drug release) are an emerging and relevant research area. Despite of the numerous liposomes reviews published in the last decades, this area is in constant development. Updates urgently needed to integrate new advances in targeted liposomes research. This review highlights the evolution of liposomes from passive to active targeting and challenges in the development of targeted liposomes for specific therapies.