Abstract 6418: xWU-NK-101 as salvage therapy post immune checkpoint blockade (ICB)

Abstract ICB therapy has transformed cancer treatment; durable responses in difficult-to-treat cancers have been observed. Despite this most patients (pts) don’t respond to ICB (primary resistance), and many pts who initially respond eventually relapse (acquired resistance). Primary resistance is associated with tumor cell extrinsic factors, e.g., the immunosuppressive nature of the tumor microenvironment (TME), while acquired resistance is associated with tumor intrinsic factors, e.g., downregulation of MHC1, preventing T cell recognition. Treatments to overcome ICB resistance are necessary. WU-NK-101 is a PBMC-derived, cytokine-reprogrammed, expanded, and cryopreserved off-the-shelf memory NK cell product. WU-NK-101 cells capture the memory-like NK cell biology of cytokine-induced memory-like (CIML) NK cells, exhibiting enhanced cytotoxicity, metabolic fitness/flexibility, and resistance to TME immunosuppression (Muth et al. EHA 2022; Rutella et al. ESMO 2022). Bone marrow biopsies, collected from R/R AML pts who received CIML-NK cells (NCT01898793), were interrogated using immune gene expression (GE) profiling and spatially resolved proteomics (IO360® panel, n = 740 genes, and GeoMx® DSP; NanoString Technologies). Higher T-cell infiltration was noted post CIML-NK. CIBERSORT deconvoluted GE data inferred higher abundance of macrophages, γδT cells and activated dendritic cells on day 28 post-treatment. GE signatures showed downregulation of NFIL3 and FAM30A (log2 fold-change <1.0; p<0.05) post CIML-NK. TIDE algorithm modelling indicated that lower expression of NFIL3 and FAM30A correlated with high CTL infiltration and improved outcomes in many TCGA tumors (Jiang et al. Nat. Med. 2018). Hence, CIML-NK treatment led to modifications in the TME towards a more T-cell amenable environment. Deleting MHC1 on NALM6 cells significantly improved WU-NK-101 killing compared to WT (p<0.0001), highlighting one mechanism whereby WU-NK-101 overcomes acquired ICB resistance. In transwell assays, co-incubation of tumor cells with WU-NK-101 in the lower chamber led to dose dependent killing; in the upper chamber (tumor cells alone), viability was preserved but a dose-dependent increase of MHC1/PDL1 expression was noted. Similar results were observed using cell-free conditioned media from WU-NK-101 cytotoxicity assays, suggesting that soluble factors released from WU-NK-101 augment MHC1/PDL1 expression. Treatment of tumor cells with IFNγ alone led to similar increases in MHC1/PDL1 expression. Importantly, in vivo experiments revealed that residual tumor cells post WU-NK-101 treatment exhibited higher levels of MHC1/PDL1. Overall, these data highlight a further mechanism through which WU-NK-101 overcomes acquired ICB resistance. In summary, WU-NK-101 has the potential to reverse primary and acquired mechanisms of ICB resistance. A Phase 1b clinical trial of WU-NK-101 as salvage therapy post-ICB is in development. Citation Format: Tom A. Leedom, Barbara Muz, Jaykumar Vadakekolathu, John J. Muth, Xiao-Hua Li, Gregory Watson, Kristaan Magee, Ryan P. Sullivan, Melissa Berrien-Elliott, Todd Fenigher, Sergio Rutella, Matthew L. Cooper, Ayman Kabakibi, Jan K. Davidson-Moncada. xWU-NK-101 as salvage therapy post immune checkpoint blockade (ICB) [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 6418.