CD70 CAR T cells secreting an anti-CD33/anti-CD3 dual-targeting antibody overcome antigen heterogeneity in AML
Harrison J Silva1, Grace Martin1, Filippo Birocchi1
1Cellular Immunotherapy Program, Cancer Center, Massachusetts General Hospital, Boston, MA.
Abstract:
CD70 has emerged as a promising target in acute myeloid leukemia (AML), and we have previously demonstrated the potency of an optimized CD70-targeted ligand-based chimeric antigen receptor (CAR). However, here, we identify in vivo CD70 antigen escape as a limitation of single-antigen targeting. Combination targeting of CD70 and CD33 may overcome AML antigen heterogeneity. We hypothesized that modifying our CD70 CAR platform to secrete a bispecific T-cell engaging antibody molecule (TEAM) targeting CD33 (7033) would create a therapeutic window whereby AML heterogeneity could be addressed without increasing tissue toxicity. We found that CD33 TEAMs mediated specific cytotoxicity across AML cell lines, including CD33 or CD70 single-antigen knockout tumors. 7033 CAR T cells eradicated tumor in an in vivo mixed tumor model of CD70 antigen escape and outperformed the previously optimized CD70 CAR in a patient-derived xenograft. In vivo gene expression profiling of CAR T cells revealed enhanced 7033 CAR T-cell pathway scoring for persistence, activation, and T-cell receptor signaling. Additionally, CD33 TEAMs successfully redirected T cells isolated from patients with AML to activate, secrete cytokines, and kill tumor targets despite exposure to substantial prior cytotoxic therapies. In summary, our findings demonstrate the feasibility of our 7033 CAR to overcome AML heterogeneity and leverage the bystander T cells of patients; this approach warrants further study in patients with this dire clinical need.
Insights
This study introduces a novel bispecific CAR T-cell therapy targeting CD70 and CD33 to overcome antigen escape in acute myeloid leukemia (AML). The 7033 CAR T cells show efficacy against heterogeneous AML, offering a promising new treatment strategy.
Area of Science:
- Immunotherapy
- Oncology
- Hematologic Malignancies
Background:
- CD70 is a promising target for acute myeloid leukemia (AML) treatment.
- Single-antigen targeting with CD70-based chimeric antigen receptor (CAR) T cells faces limitations due to in vivo antigen escape.
- AML exhibits antigen heterogeneity, necessitating combination targeting strategies.
Purpose of the Study:
- To develop and evaluate a novel bispecific CAR T-cell therapy (7033 CAR) targeting both CD70 and CD33.
- To address AML antigen heterogeneity and overcome CD70 antigen escape.
- To assess the therapeutic window and potential for reduced tissue toxicity.
Main Methods:
- Modification of a CD70 CAR platform to secrete a bispecific T-cell engaging antibody molecule (TEAM) targeting CD33.
- Assessment of CD33 TEAM-mediated cytotoxicity in AML cell lines, including antigen-knockout models.
- Evaluation of 7033 CAR T-cell efficacy in vivo using mixed tumor models and patient-derived xenografts.
- In vivo gene expression profiling of CAR T cells.
- Testing of CD33 TEAMs with T cells isolated from AML patients.
Main Results:
- CD33 TEAMs demonstrated specific cytotoxicity against AML cell lines, including those with CD33 or CD70 single-antigen knockout.
- 7033 CAR T cells eradicated tumors in a mixed tumor model of CD70 antigen escape and outperformed the previous CD70 CAR in patient-derived xenografts.
- In vivo gene expression profiling indicated enhanced persistence, activation, and T-cell receptor signaling in 7033 CAR T cells.
- CD33 TEAMs successfully redirected T cells from AML patients to kill tumor targets, even after prior cytotoxic therapies.
Conclusions:
- The 7033 CAR is feasible for overcoming AML heterogeneity.
- This approach effectively leverages bystander T cells from patients.
- The 7033 CAR warrants further investigation for patients with acute myeloid leukemia.
