Cytokine Armored CAR-NK Cell Therapy for Advanced Ovarian Cancer

Immunotherapy using chimeric antigen receptor (CAR) expressing NK cells engineered via viral vectors has shown exceptional efficacy against hematologic cancers in clinical trials. This method, however, is limited in cargo capacity and large-scale manufacturing for clinical use is cost-prohibitive to most academic centers. We have addressed these shortcomings by engineering CAR-NK cells using non-viral transposon engineering that can be paired with concurrent CRISPR/Cas9 editing. We believe that this approach avails opportunities that will allow researchers to address some of the more difficult solid tumor types.

Here, we developed a CAR-NK therapy with specific advantages to killing mesothelin-positive ovarian cancers which tend to form solid tumors, a new area for CAR NK cells. We started by testing 3 different mesothelin binders named SS1, 121, and M912. Our transposon vector also encodes for secretion of the cytokine IL15 for increased persistence and function of CAR-NK cells. The SS1, 121, and M912 CAR NK cells with soluble IL15 (Armored-NK) were tested in vitro and in vivo. No CAR variant dominated during the in vitro testing, so all three proceeded into a pilot in vivo study. In this experiment, NSG mice were engrafted with a mesothelin high tumor cell line, A1847, engineered to express Luciferase. A1847 cells were injected 14 days prior to the Armored CAR NK injection. Both tumor cells and Armored CAR NK cells were delivered via intraperitoneal (IP) injection.

At week 6, control mice, 121 treated, and M912 treated mice had tumors beginning to grow exponentially while the SS1 CAR controlled tumor growth. This trend continued for 3 more weeks as the SS1-treated mice did not see significant tumor growth while all other mice had to be euthanized due to tumor burden. SS1 mice survived long term with the only detectable tumor being a mass that grew at the injection site, outside of the IP space. With these results, we plan to test additional edits and modifications to SS1 cytokine-armored CAR-NK cells before proceeding with a phase 1 clinical trial. We believe these edits will enable cytokine-armored CAR-NK cells to treat solid tumors.

Key Learning Objectives:
Natural killer (NK) cells offer an off-the-shelf therapy for cancer immunotherapy
NK cells can be efficiently engineered using non-viral DNA transposons delivered as GenCircle plasmids
Transposon-engineered, cytokine-armored CAR-NK cells are effective against ovarian cancer in vitro and in vivo