Generation and in vivo characterization of a novel high-affinity human antibody targeting carcinoembryonic antigen

There are no effective treatment options for most patients with metastatic colorectal cancer (mCRC). mCRC remains a leading cause of tumor-related death, with a five-year survival rate of only 15%, highlighting the urgent need for novel pharmacological products. Current standard drugs are based on cytotoxic chemotherapy, VEGF inhibitors, EGFR antibodies, and multikinase inhibitors. The antibody-based delivery of pro-inflammatory cytokines provides a promising and differentiated strategy to improve the treatment outcome for mCRC patients. Here, we describe the generation of a novel fully human monoclonal antibody (termed F4) targeting the carcinoembryonic antigen (CEA), a tumor-associated antigen overexpressed in colorectal cancer and other malignancies. The F4 antibody was selected by antibody phage display technology after two rounds of affinity maturation. F4 in single-chain variable fragment format bound to CEA in surface plasmon resonance with an affinity of 7.7 nM. Flow cytometry and immunofluorescence on human cancer specimens confirmed binding to CEA-expressing cells. F4 selectively accumulated in CEA-positive tumors, as evidenced by two orthogonal in vivo biodistribution studies. Encouraged by these results, we genetically fused murine interleukin (IL) 12 to F4 in the single-chain diabody format. F4-IL12 exhibited potent antitumor activity in two murine models of colon cancer. Treatment with F4-IL12 led to an increased density of tumor-infiltrating lymphocytes and an upregulation of interferon γ expression by tumor-homing lymphocytes. These data suggest that the F4 antibody is an attractive delivery vehicle for targeted cancer therapy.

Selection of a PD-1 blocking antibody from a novel fully human phage display library

Programmed cell death protein 1 (PD-1) is an immunoregulatory target which is recognized by different monoclonal antibodies, approved for the therapy of multiple types of cancer. Different anti-PD-1 antibodies display different therapeutic properties and there is a pharmaceutical interest to generate and characterize novel anti-PD-1 antibodies. We screened multiple human antibody phage display libraries to target novel epitopes on the PD-1 surface and we discovered a unique and previously undescribed binding specificity (termed D12) from a new antibody library (termed AMG). The library featured antibody fragments in single-chain fragment variable (scFv) format, based on the IGHV3-23*03 (VH ) and IGKV1-39*01 (Vκ) genes. The D12 antibody was characterized by surface plasmon resonance (SPR), cross-reacted with the Cynomolgus monkey antigen and bound to primary human T cells, as shown by flow cytometry. The antibody blocked the PD-1/PD-L1 interaction in vitro with an EC50 value which was comparable to the one of nivolumab, a clinically approved antibody. The fine details of the interaction between D12 and PD-1 were elucidated by x-ray crystallography of the complex at a 3.5 Å resolution, revealing an unprecedented conformational change at the N-terminus of PD-1 following D12 binding, as well as partial overlap with the binding site for the cognate PD-L1 and PD-L2 ligands which prevents their binding. The results of the study suggest that the expansion of antibody library repertoires may facilitate the discovery of novel binding specificities with unique properties that hold promises for the modulation of PD-1 activity in vitro and in vivo.

Use of uteroglobin for the engineering of polyvalent, polyspecific fusion proteins

We report a novel strategy to engineer and express stable and soluble human recombinant polyvalent/polyspecific fusion proteins. The procedure is based on the use of a central skeleton of uteroglobin, a small and very soluble covalently linked homodimeric protein that is very resistant to proteolytic enzymes and to pH variations. Using a human recombinant antibody (scFv) specific for the angiogenesis marker domain B of fibronectin, interleukin 2, and an scFv able to neutralize tumor necrosis factor-alpha, we expressed various biologically active uteroglobin fusion proteins. The results demonstrate the possibility to generate monospecific divalent and tetravalent antibodies, immunocytokines, and dual specificity tetravalent antibodies. Furthermore, compared with similar fusion proteins in which uteroglobin was not used, the use of uteroglobin improved properties of solubility and stability. Indeed, in the reported cases it was possible to vacuum dry and reconstitute the proteins without any aggregation or loss in protein and biological activity.

Antibody-cytokine fusion proteins: applications in cancer therapy

BACKGROUND

Antibody-cytokine fusion proteins consist of cytokines fused to an antibody to improve antibody-targeted cancer immunotherapy. These molecules have the capacity to enhance the tumoricidal activity of the antibodies and/or activate a secondary antitumor immune response.

OBJECTIVE

To review the strategies used to develop antibody-cytokine fusion proteins and their in vitro and in vivo properties, including preclinical and clinical studies focusing on IL-2, IL-12 and GM-CSF.

METHODS

Articles were found by searching databases such as PubMed and Clinical Trials of the US National Institutes of Health.

RESULTS/CONCLUSION

Multiple antibody-cytokine fusion proteins have demonstrated significant antitumor activity as direct therapeutics or as adjuvants of cancer vaccines in preclinical studies, paving the way for their clinical evaluation.