Abstract 4209: CD38KO K-NK cells prevent NK cell fratricide effect and improve isatuximab-mediated cytotoxicity against multiple myeloma cells

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Abstract Multiple myeloma (MM) is a plasma cell malignancy characterized by clonal accumulation of malignant plasma cells in the bone marrow. CD38 is highly expressed on MM cells, and antibodies targeting CD38 (such as Isatuximab and Daratumumab) induce MM cell killing though several mechanisms, particularly by NK cell-mediated antibody dependent cellular cytotoxicity (ADCC). However, NK cells also express CD38 and treatment with anti-CD38 antibodies results in a rapid decrease of NK cells presumably due to fratricide, which may potentially limit NK cell mediated ADCC and reduce the efficacy of anti-CD38 antibody treatment. NK cells lacking CD38 in combination with Daratumumab have been shown to be resistant to NK cell fratricide and have improved ADCC. Here, we investigated the effect of knocking out CD38 in K-NK cells (CD38KO K-NK) in combination with Isatuximab. Peripheral blood NK cells were isolated from healthy donors and expanded using Kiadis PM21 particle technology (Oyer et al, Cytotherapy 2016) to produce highly activated K-NK cells. To produce CD38KO K-NK cells, CRISPR gene editing was applied during NK cell expansion by electroporating with Cas9/RNP complexes targeting CD38, and successful deletion of CD38 was confirmed by flow cytometry analysis. Analysis of key NK cell receptors by flow cytometry evidenced very similar receptor profiles between WT and CD38KO K-NK cells, suggesting that CD38 deletion does not affect the potent activation state of the K-NK cells. Importantly, CD38KO K-NK cells were found to be resistant to Isatuximab-induced fratricide. The cytotoxic activity of CD38KO K-NK cells in combination with Isatuximab against LP-1 and H929 MM cell lines was also measured. Calcein release assay and Incucyte based analysis revealed that cytotoxicity of CD38KO K-NK cells is enhanced in presence of Isatuximab, and that CD38KO K-NK cells are more cytotoxic than WT when combined with Isatuximab. Furthermore, the effect of Isatuximab/CD38KO K-NK cells combination also in association with SAR444245 (also termed THOR-707; Ptacin et al, Nat Commun 2021), an engineered non-α binding IL-2 that promotes NK cell activation and proliferation, was tested. Cytotoxicity of WT or CD38KO NK cells is enhanced in the presence of SAR444245. Indeed, addition of SAR444245 was found to further enhance the cytotoxic activity of CD38KO K-NK cells against LP-1 MM cells when combined with Isatuximab, resulting in an overall superior and sustained cytotoxicity. These data suggest that deletion of CD38 mitigates NK cell fratricide and improves Isatuximab-mediated ADCC against MM cells, and provide evidence for the therapeutic potential of the triple combination CD38KO NK cells, Isatuximab and SAR444245 in the setting of MM. Citation Format: Marco Meloni, Pauline Perrin, Erik Slinger, Chrissta Maracle, Alain Fournier, Nicole Acuff, Jill Mooney, Robert Y. Igarashi, Angela Virone-Oddos, Marielle Chiron. CD38KO K-NK cells prevent NK cell fratricide effect and improve isatuximab-mediated cytotoxicity against multiple myeloma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4209.