A GPC3-targeting Bispecific Antibody, GPC3-S-Fab, with Potent Cytotoxicity

This protocol describes the construction and functional studies of a bispecific antibody (bsAb), GPC3-S-Fab. bsAbs can recognize two different epitopes ...

Sun Yat-sen University

IL-15 has been actively investigated for its potential in tumor immunotherapy. To enhance the anti-tumor activity of IL-15, the novel PFC-1 construct was designed, which comprises the following 3 parts: (1) IL-15Rα fused with IL-15 to enhance IL-15 activity, (2) an Fc fragment to increase protein half-life, and (3) an integrin-targeting RGD peptide to enhance tumor targeting. PFC-1 showed tumor cell targeting without compromising IL-15 activity. PFC-1 also had potent anti-tumor activities in xenograft models, suggesting the potential application of this multi-functional fusion protein in tumor therapy. 

A targeted IL-15 fusion protein with potent anti-tumor activity.

Among different cancer immunotherapy approaches, bispecific antibodies (BsAbs) are of great interest due to their ability to recruit immune cells to kill tumor cells directly. Various BsAbs against Her2 tumor cells have been proposed with potent cytotoxic activities. However, most of these formats require extensive processing to obtain heterodimeric bispecific antibodies. In this study, we describe a bispecific antibody, BiHC (bispecific Her2-CD3 antibody), constructed with a single-domain anti-Her2 and a single-chain Fv (variable fragment) of anti-CD3 in an IgG-like format. In contrast to most IgG-like BsAbs, the two arms in BiHC have different molecular weights, making it easier to separate hetero- or homodimers. BiHC can be expressed in Escherichia coli and purified via Protein A affinity chromatography. The purified BiHC can recruit T cells and induce specific cytotoxicity of Her2-expressing tumor cells in vitro. The BiHC can also efficiently inhibit the tumor growth in vivo. Thus, BiHC is a promising candidate for the treatment of Her2-positive cancers.

BiHC, a T-Cell-Engaging Bispecific Recombinant Antibody, Has Potent Cytotoxic Activity Against Her2 Tumor Cells.

Human epidermal growth factor receptor 2 (HER2) is frequently overexpressed and activated in metastatic breast cancers. Monoclonal antibodies targeting Her2, such as trastuzumab and pertuzumab, have become important targeted therapies for patients with HER2-positive breast cancer. Both trastuzumab and pertuzumab can reduce Her2 positive tumor burden by inhibiting Her2 signaling and inducing ADCC activities (antibody dependent cell-mediated cytotoxicity). In this study, we have generated a bispecific antibody, Her2(Per)-S-Fab, by linking the pertuzumab Fab to an anti-CD16 single domain antibody. The Her2(Per)-S-Fab can be expressed and purified efficiently from Escherichia coli. In vitro and in vivo experiments showed Her2(Per)-S-Fab had potent cytotoxicity against Her2-positive tumor cells. Thus, Her2(Per)-S-Fab may provide an alternative to treat Her2-positive cancer patients.

A Bispecific Antibody Based on Pertuzumab Fab Has Potent Antitumor Activity.

Muc1 is one of the most studied tumor antigens. However, antibodies or antibody-toxin conjugates against Muc1 have not shown significant efficacy for tumors with Muc1 overexpression. In this study, we employed bispecific antibody approach to target Muc1 positive tumor cells. A novel bispecific antibody, Muc1-Bi-1, was constructed by linking single domain antibodies, anti-Muc1-VHH and anti-CD16-VHH. Muc1-Bi-2, the humanized form of Muc1-Bi-1, was also constructed by grafting. Both Muc1-Bi bispecific antibodies can be efficiently expressed and purified from bacteria. In vitro, the Muc1-Bi bispecific antibodies can recruit Natural Killer (NK) cells to drive potent and specific cell killing of Muc1-overexpressing tumor cells. In xenograft model, the Muc1-Bi bispecific antibodies can suppress tumor growth in the presence of human peripheral blood mononuclear cells (PBMC). These data suggested that the single domain based Muc1-Bi may provide a valid strategy for targeting tumors with Muc1 overexpression.

Single domain based bispecific antibody, Muc1-Bi-1, and its humanized form, Muc1-Bi-2, induce potent cancer cell killing in muc1 positive tumor cells.

Human epidermal growth factor receptor 2 (HER2) is overexpressed in approximately 20% to 30% of breast cancers and various other types of cancers, which plays a vital role in the cancer progression. Monoclonal antibodies targeting Her2 are now used in the clinic to treat Her2 overexpression cancer patients. However, relapse or resistance is frequent with the current therapies. To generate a new treatment avenue against Her2, we immunized and selected a specific anti-Her2 single domain antibody C3 for further studies. The C3-Fc antibody drove antibody-dependent cell-mediated cytotoxicity against Her2-positive tumor cells in vitro and resulted in potent antitumor growth in vivo. These data suggest that the C3-Fc antibody may provide an alternative avenue for Her2-positive cancer therapy.

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

Bispecific antibodies that engage immune cells to kill cancer cells are actively pursued in cancer immunotherapy. Different types of bispecific antibodies, including single-chain fragments, Fab fragments, nanobodies, and immunoglobulin Gs (IgGs), have been studied. However, the low molecular weight of bispecific antibodies with single-chain or Fab fragments generally leads to their rapid clearance in vivo, which limits the therapeutic potential of these bispecific antibodies.

Site-specific PEGylation of an anti-CEA/CD3 bispecific antibody improves its antitumor efficacy.

Bispecific antibodies have been actively studied for cancer therapy due to their potent cytotoxicity against tumor cells. A number of bispecific antibody formats have exhibited strong tumor cytotoxicity  and . However, effective production of bispecific antibodies remains challenging for the majority of bispecific antibody formats. In the present study, a bispecific antibody was designed that links a conventional antigen-binding fragment (Fab) against cluster of differentiation 3 antigen (CD3) to a camel single domain antibody (VHH) against human epidermal growth factor receptor 2 (HER2). This bispecific antibody may be secreted and purified efficiently from  culture medium. The purified bispecific antibody is able to trigger T cell-mediated HER2-specific cytotoxicity  and . The data gathered in the present study suggest that this bispecific format may be applied to other tumor antigens to produce bispecific antibodies more efficiently.

Jiayu Liu

School of Pharmaceutical Sciences,
Center for Cellular & Structural Biology

Sun Yat-sen University

A GPC3-targeting Bispecific Antibody, GPC3-S-Fab, with Potent Cytotoxicity

Jiayu Liu

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Sun Yat-sen University

A GPC3-targeting Bispecific Antibody, GPC3-S-Fab, with Potent Cytotoxicity

School of Pharmaceutical Sciences,
Center for Cellular & Structural Biology