Humanized anti-CD33 CAR-T cells and antibody-drug conjugates for targeted therapy in acute myeloid leukemia.

[BACKGROUND] Acute myeloid leukemia (AML) is a malignant disorder originating from myeloid hematopoietic stem and progenitor cells. Despite the availability of current treatment options, a significant number of patients fail to achieve complete remission after initial chemotherapy. CD33, a transmembrane protein highly expressed on AML cells, serves as a promising therapeutic target. This study aimed to develop and evaluate chimeric antigen receptor T cells (CAR-T) and antibody-drug conjugates (ADC) based on humanized antibodies, specifically targeting CD33, to assess their potential efficacy against AML.

[METHODS] Monoclonal antibodies specific to human CD33 were generated by immunizing mice and then humanized. These humanized antibodies were then used to construct CAR-T cells and ADCs, and their cytotoxic properties were evaluated both and . In the in vivo experiments, mice bearing Molm13-Luciferase tumor cells were assigned to different treatment groups and were administered with saline, Gemtuzumab-MMAE, or Clone3HM-MMAE.

[RESULTS] The experiments revealed that several antibody clones, including Clone2HM, Clone3HM, Clone5HM, Clone6HM, and Clone7HM, displayed strong cytotoxic effects against Molm13-Luciferase tumor cells when conjugated with MMAE, outperforming the positive control antibody Gemtuzumab-MMAE. In the studies, mice treated with Clone3HM-MMAE showed a significant reduction in tumor signals, which nearly disappeared in the latter stages of the experiment. This led to a substantially longer survival time compared to other groups. Additionally, the body weight of mice in all treatment groups remained stable throughout the treatment period, indicating a favorable safety profile.

[CONCLUSION] The CAR-T cells and ADCs developed in this study, based on humanized antibodies, showed significant anti-tumor efficacy in the AML model. Clone3HM-MMAE, in particular, demonstrated excellent anti-tumor activity along with a strong safety profile. These results strongly support the further development of targeted therapeutic strategies for AML.