Abstract
Anticytotoxic T lymphocyte-associated protein 4 (CTLA4) antibodies have shown potent antitumor activity, but systemic immune activation leads to severe immune-related adverse events, limiting clinical usage. We developed novel, conditionally active biologic (CAB) anti-CTLA4 antibodies that are active only in the acidic tumor microenvironment. In healthy tissue, this binding is reversibly inhibited by a novel mechanism using physiological chemicals as protein-associated chemical switches (PaCS). No enzymes or potentially immunogenic covalent modifications to the antibody are required for activation in the tumor. The novel anti-CTLA4 antibodies show similar efficacy in animal models compared to an analog of a marketed anti-CTLA4 biologic, but have markedly reduced toxicity in nonhuman primates (in combination with an anti-PD1 checkpoint inhibitor), indicating a widened therapeutic index (TI). The PaCS encompass mechanisms that are applicable to a wide array of antibody formats (e.g., ADC, bispecifics) and antigens. Examples shown here include antibodies to EpCAM, Her2, Nectin4, CD73, and CD3. Existing antibodies can be engineered readily to be made sensitive to PaCS, and the inhibitory activity can be optimized for each antigen's varying expression level and tissue distribution. PaCS can modulate diverse physiological molecular interactions and are applicable to various pathologic conditions, enabling differential CAB antibody activities in normal versus disease microenvironments.
Keywords: CTLA4; conditionally active biologics; immunooncology; monoclonal antibodies; protein-associated chemical switches.
Copyright © 2021 the Author(s). Published by PNAS.
MeSH terms
- 5'-Nucleotidase / antagonists & inhibitors
- 5'-Nucleotidase / genetics
- 5'-Nucleotidase / immunology
- Animals
- Antibodies, Monoclonal / chemistry
- Antibodies, Monoclonal / pharmacology*
- Antibodies, Monoclonal, Humanized / chemistry
- Antibodies, Monoclonal, Humanized / pharmacology*
- Antibodies, Neoplasm / chemistry
- Antibodies, Neoplasm / pharmacology*
- B7-H1 Antigen / antagonists & inhibitors*
- B7-H1 Antigen / genetics
- B7-H1 Antigen / immunology
- Bicarbonates / chemistry
- CD3 Complex / antagonists & inhibitors
- CD3 Complex / genetics
- CD3 Complex / immunology
- CTLA-4 Antigen / antagonists & inhibitors*
- CTLA-4 Antigen / genetics
- CTLA-4 Antigen / immunology
- Cell Adhesion Molecules / antagonists & inhibitors
- Cell Adhesion Molecules / genetics
- Cell Adhesion Molecules / immunology
- Colonic Neoplasms / genetics
- Colonic Neoplasms / immunology
- Colonic Neoplasms / pathology
- Colonic Neoplasms / therapy*
- Epithelial Cell Adhesion Molecule / antagonists & inhibitors
- Epithelial Cell Adhesion Molecule / genetics
- Epithelial Cell Adhesion Molecule / immunology
- GPI-Linked Proteins / antagonists & inhibitors
- GPI-Linked Proteins / genetics
- GPI-Linked Proteins / immunology
- Gene Expression
- Humans
- Hydrogen Sulfide / chemistry
- Hydrogen-Ion Concentration
- Immunotherapy / methods*
- Macaca fascicularis
- Mice
- Neoplasm Proteins / antagonists & inhibitors
- Neoplasm Proteins / genetics
- Neoplasm Proteins / immunology
- Protein Engineering / methods
- Receptor, ErbB-2 / antagonists & inhibitors
- Receptor, ErbB-2 / genetics
- Receptor, ErbB-2 / immunology
- T-Lymphocytes, Cytotoxic / drug effects
- T-Lymphocytes, Cytotoxic / immunology
- T-Lymphocytes, Cytotoxic / pathology
- Tumor Burden / drug effects
- Tumor Microenvironment / drug effects
- Xenograft Model Antitumor Assays
Substances
- Antibodies, Monoclonal
- Antibodies, Monoclonal, Humanized
- Antibodies, Neoplasm
- B7-H1 Antigen
- Bicarbonates
- CD274 protein, human
- CD3 Complex
- CTLA-4 Antigen
- CTLA4 protein, human
- Cell Adhesion Molecules
- EPCAM protein, human
- Epithelial Cell Adhesion Molecule
- GPI-Linked Proteins
- Neoplasm Proteins
- NECTIN4 protein, human
- atezolizumab
- ERBB2 protein, human
- Receptor, ErbB-2
- 5'-Nucleotidase
- NT5E protein, human
- Hydrogen Sulfide