Abstract P2-04-10: High-affinity activated natural killer (haNK) cells augment trastuzumab efficacy in a mouse model of HER2-positive human metastatic breast cancer (2017)

Abstract Background. The ability of NK cells to kill cancer cells makes them an attractive choice for clinical immunotherapy. Early phase clinical trials in patients (pts) with advanced cancers have demonstrated the safety of activated NK (aNK [NK-92]) cells, an investigational cell line that was established from the peripheral blood mononuclear cells of a pt with non-Hodgkin lymphoma. NK cells can participate in antibody-dependent cellular cytotoxicity (ADCC) mediated by recognition of the Fc fragment of the target-bound antibody (IgG1) via the CD16 Fc receptor. Among pts with HER2-positive breast cancer treated with trastuzumab (IgG1) the high-affinity CD16 V/V genotype was significantly correlated with better clinical outcomes (Musolino. JCO. 2008;26:1789-96). To enhance the killing activity of aNK cells, we modified aNK cells to stably express high-affinity CD16 and evaluated the resulting haNK cells in combination with trastuzumab in a mouse xenograft model of HER2-positive human breast cancer. Methods. haNK cells were generated by transfection of aNK cells with a bicistronic plasmid coding for CD16 (158V) and an intracellular form of IL-2, which enables haNK cells to grow in the absence of exogenous IL-2. Female, 7 to 8-week-old NOD-scid IL2Rgammanull (NSG) mice were inoculated subcutaneously in the left and right flank area with 0.1mL of 1x108/mL MDA-MB-453 human breast cancer cells in 50% Matrigel. When tumors reached ≥100mm3, mice were randomly assigned to 10 groups of 4 mice per group and dosed (IV) with PBS, 1 or 3mg/kg IgG1 isotype control, 1 or 3mg/kg trastuzumab (determined from a dose range finding study), 1x107 non-irradiated haNK cells, or non-irradiated haNK cells in combination with IgG1 or trastuzumab. The dosing schedules were: PBS/haNK cells twice weekly for 4 weeks; IgG1/trastuzumab once weekly for 4 weeks. For the combination treatments, mice received antibodies at least 3h prior to the injection of haNK cells. Tumor growth and animal weights were measured twice weekly. Results: Results obtained after 4 weeks of treatment are shown in the table. haNK alone and both doses of trastuzumab alone significantly inhibited the growth of human MDA-MB-453 breast tumors. The combination of haNK plus 1mg/kg trastuzumab was synergistic with a T/C value of -60.1%. Conclusions: The combination of haNK cells and trastuzumab was synergistic at 1mg/kg trastuzumab resulting in tumor regressions and significantly better efficacy vs each agent alone. Trastuzumab monotherapy at 3mg/kg was very effective and likely masked any synergistic effect of haNK. This study illustrates the potential for combining haNK cells with trastuzumab in a clinical trial of pts with HER2-positive metastatic breast cancer. ResultsGroupTreatmentT/C (%)BWC (%)APBS--0.6BIgG1 (1mg/kg)40.8-4.7CTrastuzumab (1mg/kg)-34.5-2.8DhaNK (1x107)-20.3-15.9EIgG1 (1mg/kg) + haNK (1x107)-10.7-16.0FTrastuzumab (1mg/kg) + haNK (1x107)-60.1-16.6GIgG1 (3mg/kg)39.1-0.4HTrastuzumab (3mg/kg)-95.2-1.8IIgG1 (3mg/kg)+ haNK (1x107)-26.4-16.7JTrastuzumab (3mg/kg) + haNK (1x107)-93.8-18.3%T/C, percent treated/control; BWC, body weight change. Citation Format: Rabizadeh S, Zhou L, Toneguzzo F, Boissel L, Soon-Shiong P, Niazi K, Klingemann H. High-affinity activated natural killer (haNK) cells augment trastuzumab efficacy in a mouse model of HER2-positive human metastatic breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-04-10.