CD33 CAR NK Cell Therapy Shows Improved Targeting in Acute Myeloid Leukemia

An investigational cell therapy that combines with wide expression of CD33 with the safety of natural killer (NK) cells has shown efficacy and safety in a small population of patients with relapsed/refractory acute myeloid leukemia (r/r AML).

The findings were presented at the 2022 European Hematology Association (EHA) Annual Meeting, June 9-17, 2022, by Ruihao Huang, of the Medical Center of Hematology, Xinqiao Hospital of Army Medical University, in Chongqing, China.

“One of the main challenges is that current targets for myeloid malignancies are either widely expressed on healthy hemopoietic stem cells such as CD33 or specific for a group of tumor cells presented as Lewis Y antigen, which could cause lasting bone marrow depression induced by ‘on target, off tumor’ side-effect or target negative relapse,” Huang and colleagues wrote.

Based on this, Huang and colleagues developed a CD33 CAR that recognized AML cells that is carried by NK cells to the tumor site.

A total of 5 patients with r/r AML were enrolled (age 18-65, median=43) and underwent infusions with the anti-CD33 CAR NK cells in 1 of 2 dose groups: dose group 1, 6×10⁸, 1.2×10⁹, or 1.8×10⁹ cells; or dose group 2, 1.8×10⁹ cells, following preconditioning with fludarabine (30mg/m²) and cytoxan 300-500mg/m² for 3 days to 5 days. End points included response rate at day 28 and adverse events.

Among the enrolled participants, a median tumor burden of 31% was observed. In dose group 1, 3 patients received 3 rounds of infusions of the CAR NK product (interval, 7 days after last round). One patient developed grade 1 cytokine release syndrome following infusion with the highest dose but resolved within 24 hours following treatment. In that cohort, patient 1 and patient 2 reached minimum residual disease (MRD)-negative complete response (CR) at day 14 and 21, respectively; however, patient 1 relapsed at day 43 following the initial infusion.

In the second dose group, patient 4 and patient 5 received a single dose of the highest cell infusion, which resulted in patient 5 developing grade 2 cytokine release syndrome, which resolved after 5mg intravenous dexamethasone. Both patients 4 and 5 reached MRD CR at day 14, and in total, 3 patients remain in MRD CR at time of reporting.

The investigators hope to collect longer follow-up and enroll more patients to expand upon the efficacy and safety exploration of this therapy in r/r AML.

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REFERENCE

Huang R, Wen Q, Wang X, et al. Off the shelf CD33 CAR NK cell therapy for relapse/refractory AML: First in human phase 1 trial. Presented at: European Hematology Association Annual Meeting. June 9-17, 2022; Vienna, Austria, and virtual.