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A Real-time Potency Assay for Chimeric Antigen Receptor T Cells Targeting Solid and Hematological Cancer Cells
Published on: November 12, 2019
Pre-Clinical Development of a Humanized Anti-CD47 Antibody with Anti-Cancer Therapeutic Potential
Jie Liu1, Lijuan Wang1, Feifei Zhao1
1Institute for Stem Cell Biology and Regenerative Medicine and the Ludwig Cancer Center, Stanford University School of Medicine, Stanford, California, United States of America.
Abstract:
CD47 is a widely expressed cell surface protein that functions as a regulator of phagocytosis mediated by cells of the innate immune system, such as macrophages and dendritic cells. CD47 serves as the ligand for a receptor on these innate immune cells, SIRP-alpha, which in turn delivers an inhibitory signal for phagocytosis. We previously found increased expression of CD47 on primary human acute myeloid leukemia (AML) stem cells, and demonstrated that blocking monoclonal antibodies directed against CD47 enabled the phagocytosis and elimination of AML, non-Hodgkin's lymphoma (NHL), and many solid tumors in xenograft models. Here, we report the development of a humanized anti-CD47 antibody with potent efficacy and favorable toxicokinetic properties as a candidate therapeutic. A novel monoclonal anti-human CD47 antibody, 5F9, was generated, and antibody humanization was carried out by grafting its complementarity determining regions (CDRs) onto a human IgG4 format. The resulting humanized 5F9 antibody (Hu5F9-G4) bound monomeric human CD47 with an 8 nM affinity. Hu5F9-G4 induced potent macrophage-mediated phagocytosis of primary human AML cells in vitro and completely eradicated human AML in vivo, leading to long-term disease-free survival of patient-derived xenografts. Moreover, Hu5F9-G4 synergized with rituximab to eliminate NHL engraftment and cure xenografted mice. Finally, toxicokinetic studies in non-human primates showed that Hu5F9-G4 could be safely administered intravenously at doses able to achieve potentially therapeutic serum levels. Thus, Hu5F9-G4 is actively being developed for and has been entered into clinical trials in patients with AML and solid tumors (ClinicalTrials.gov identifier: NCT02216409).
Insights
A new humanized antibody, Hu5F9-G4, targets CD47, a protein overexpressed on cancer cells. This therapy promotes phagocytosis, effectively eliminating acute myeloid leukemia (AML) and non-Hodgkin
Area of Science:
- Immunology
- Oncology
- Therapeutic Antibody Development
Background:
- CD47 is a cell surface protein regulating innate immune cell phagocytosis via SIRP-alpha receptor interaction.
- Increased CD47 expression on cancer stem cells, including acute myeloid leukemia (AML), promotes immune evasion.
- Blocking CD47 antibodies have shown potential in eliminating various cancer types in preclinical models.
Purpose of the Study:
- To develop a humanized anti-CD47 antibody with enhanced therapeutic potential and favorable safety profile.
- To evaluate the efficacy of the humanized antibody, Hu5F9-G4, in preclinical models of hematological malignancies and solid tumors.
Main Methods:
- Generation of a novel anti-human CD47 antibody (5F9) and subsequent humanization using CDR grafting onto a human IgG4 framework.
- Characterization of Hu5F9-G4 binding affinity to CD47 and assessment of its ability to induce macrophage-mediated phagocytosis in vitro.
- In vivo efficacy studies in patient-derived xenograft models of AML and non-Hodgkin's lymphoma (NHL), including combination therapy with rituximab.
- Toxicokinetic evaluation of Hu5F9-G4 in non-human primates to determine safe intravenous dosing.
Main Results:
- The humanized antibody Hu5F9-G4 demonstrated high affinity (8 nM) for monomeric CD47.
- Hu5F9-G4 potently induced phagocytosis of primary AML cells and achieved complete eradication of AML in vivo, resulting in long-term survival.
- Hu5F9-G4 synergized with rituximab to eliminate NHL and cure xenografted mice.
- Toxicokinetic studies supported safe intravenous administration of Hu5F9-G4 at potentially therapeutic serum levels.
Conclusions:
- Hu5F9-G4 is a potent humanized anti-CD47 antibody with significant preclinical efficacy against AML and NHL.
- The favorable safety and efficacy profile supports the ongoing clinical development of Hu5F9-G4 for AML and solid tumors.
- Hu5F9-G4 represents a promising therapeutic candidate targeting the CD47 immune checkpoint.
