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    Myeloma Novel Drug Targets and agents

    Category: Myeloma Novel Drug Targets and agents

    Fueling the Fighters: Cytokine-Driven Optimization of Allogeneic NK Cells for Multiple Myeloma Immunotherapy

    (PA-283) Fueling the Fighters: Cytokine-Driven Optimization of Allogeneic NK Cells for Multiple Myeloma Immunotherapy

    Thursday, September 18, 2025

    Introduction:      Allogeneic NK cells are promising candidates for cell-based immunotherapy against multiple myeloma (MM), readily obtainable from peripheral blood. Their therapeutic application is further enhanced by the low risk of GvHD. However, clinical applications are hampered by donor heterogeneity and a lack of standardized ex vivo expansion protocols. This study aimed to develop an optimized ex vivo expansion protocol suitable for NK cells obtained from the majority of donors.

    Methods:   Isolated primary NK cells from healthy donors were expanded over five weeks in Miltenyi NK MACS medium supplemented with three combinations of interleukins (ILs) IL-2, IL-15, and IL-21. We established a comprehensive pipeline to assess NK cell fitness, phenotype, and functionality against MM cell lines. First, we evaluated proliferation and viability, followed by analysis of key surface receptor expression related to NK cell activation, inhibition, and exhaustion. Lastly, we assessed pivotal NK metabolic fitness, degranulation, and cytotoxicity.

    Results:   The continuous NK cell profiling during ex vivo culture revealed donor-specific responses to IL combinations. Based on their expansion and viability profiles in different IL conditions, NK cells were classified into three functional groups. Group 1 exhibited enhanced proliferation and viability in IL-15 + IL-21, with increased expression of activation markers during culture. However, when cultured in IL-2 + IL-15, the same cells demonstrated moderate proliferation but higher degranulation and cytotoxicity (e.g., 74% vs. 47% on day 7). Group 2 maintained robust growth in both IL-15 + IL-21 and IL-2 + IL-15 conditions, showing no significant differences in key marker expression, but cytotoxicity was significantly higher in IL-15 + IL-21 (e.g., 86% vs. 26% on day 14), alongside increased degranulation. Group 3 showed superior expansion and viability in IL-2 + IL-15 conditions. This group demonstrated downregulation of inhibitory CD161, with upregulation of activation markers CD69 and NKG2D. Although degranulation did not vary significantly across conditions, cytotoxicity was markedly higher in IL-2 + IL-15 (e.g., 64% vs. 12% on day 7). Moreover, a combination of IL-2 and IL-21 did not sustain NK cells beyond two weeks, whereas IL-15 proved to be crucial for NK cell proliferation and maintenance.

    Conclusions:   

    Robust NK cell expansion while preserving cytotoxic function is critical for developing reliable “off-the-shelf” immunotherapies, particularly in the context of CAR-NK cell therapies against MM and other hematological malignancies. Our findings emphasize substantial primary NK cell donor-to-donor variability and distinct functional responses to different IL combinations during long-term ex vivo expansion. Our findings warrant further analysis in a larger donor cohort to refine and validate expansion protocols that ensure consistent potency and clinical applicability of primary NK cell-based therapies for MM.