LAUSR

Background: Breast cancer stem-like cells (BCSCs) are reported to be a major contributing factor for tumor growth and chemotherapy resistance in triple-negative breast cancer (TNBC). We reported that the disialoganglioside GD2 is highly expressed on BCSCs and that targeting GD2 with dinutuximab (chimeric anti-GD2 antibody) in combination with NK cells synergistically reduced tumor volumes in TNBC animal models. Here, we hypothesize that naxitamab targets GD2+ BCSCs and inhibits breast cancer (BC) growth by enhancing macrophage mediated phagocytosis and T cell mediated cytotoxicity. In addition, we explore whether addition of an investigational polymer-engineered IL-15 receptor-agonist, NKTR-255 treated NK cells, can further enhance this anti-GD2 mediated anti-cancer activity. Methods: Naxitamab is a US FDA approved fully humanized anti-GD2 (hu3F8) monoclonal antibody for the treatment of pediatric neuroblastoma. We evaluated the effects of naxitamab treatment on macrophage mediated phagocytosis of BC cells using the live cell imaging system, IncuCyte®. Next, we compared the effects of NKTR-255 treated NK cells with recombinant human IL-15 (rIL-15) treated NK cells in naxitamab induced ADCC in GD2+ BC cells. We also performed immunohistochemistry (IHC) to examine GD2 expression and correlate it with T cell infiltration in primary TNBC patient samples with high and low GD2 levels. The effect of naxitamab treatment on T cell mediated cytotoxicity in BC cells was also observed. Results: When compared to control, naxitamab treatment promoted macrophage mediated phagocytosis of Hs578T and HCC1395 cells in a dose dependent manner (p <0.001). Additionally, when co-cultured with healthy donor derived macrophages, we found a significant reduction in Hs578T spheroids treated with naxitamab in comparison to IgG control (p<0.001). Furthermore, we observed a significantly higher rate of apoptosis in GD2+ Hs578T and HCC1395 breast cancer cells treated with naxitamab and NK cells generated using NKTR-255, compared to rIL-15 treated NK cells (p<0.0001). Interestingly, IHC analysis showed that TNBC patients with high GD2 expression have significantly lower CD3+ T cell infiltration than patients with low GD2 expression (p<0.05). We also observed increased T cell mediated killing of BT549 and T47D cells treated with naxitamab in comparison to IgG control (p<0.001). Conclusion: TNBC with high GD2 expression inhibits immune cell infiltration and naxitamab can inhibit BCSC growth by targeting GD2. Combination of naxitamab with macrophages induced macrophage mediated phagocytosis TNBC cells. NK cells were more stable and cytotoxic when generated with NKTR-255 vs. native IL-15, and naxitamab further enhanced NK cell mediated ADCC of GD2+ BCSCs. The increased T cell mediated killing of breast cancer cells treated with naxitamab further supports the immunomodulatory role of GD2. Citation Format: Vivek Anand, Venkatesh Hegde, Maryam Siddiqui, Anudishi Tyagi, Bolutyfe Oderinde, Mario Marcondes, Willem Overwijk, Venkata Lokesh Battula. Novel humanized anti-GD2 antibody inhibits GD2-mediated immunosuppression by targeting GD2+ breast cancer stem-like cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5115.