FT576: A Novel Multiplexed Engineered Off-the-Shelf Natural Killer Cell Immunotherapy for the Dual-Targeting of CD38 and Bcma for the Treatment of Multiple Myeloma

Abstract

Multiple myeloma (MM) is a B cell neoplasm that originates from the malignant transformation of plasma cells, with treatment strategies that include chemotherapeutic agents and immunomodulatory drugs. Recently, significant effort has been applied to the development of monoclonal antibody (mAb) and chimeric antigen receptor (CAR) T cell therapies for the treatment of advanced MM. Anti-CD38 mAb therapy is at the forefront of these efforts, with clearly demonstrated clinical benefit and availability of a FDA-approved mAb in daratumumab. Antibody-dependent cellular cytotoxicity (ADCC) is a key mechanism of action of CD38-targeted mAbs; however, high CD38 expression on natural killer (NK) cells results in fratricide, which depletes the NK cells necessary for ADCC. In addition to CD38, targeting of other MM-associated cell-surface proteins has been explored. Of these antigens, the TNF-superfamily member BCMA is among the most researched and is under development by multiple groups as a CAR target. Several clinical trials in MM have shown promising initial results targeting BCMA with CAR T cells, however there remains significant opportunity to improve both relapse rates and treatment of relapsed patients. Collectively, clinical data would suggest that combinatorial targeting of both CD38 and BCMA may improve clinical efficacy compared with targeting either antigen alone. We have developed a multiple-target, adoptive NK cell immunotherapy approach for the treatment of MM. The strategy utilizes our off-the-shelf NK cell platform with four engineered attributes: 1) an anti-BCMA CAR for direct MM targeting, 2) high affinity non-cleavable CD16 (hnCD16) for enhanced ADCC in combination with anti-CD38 mAbs, 3) CD38 deletion for resistance to anti-CD38 mAb induced NK cell depletion, and 4) IL-15/IL-15 receptor α fusion protein (IL-15RF; IL-15 fused to IL-15Rα) for enhanced NK cell persistence. The anti-BCMA CAR consists of a unique single chain variable fragment (scFv) targeting domain with a BCMA binding affinity in the low nanomolar range, providing high functional avidity and efficacy in disease settings where BCMA antigen density is low. Our approach utilizes NK cells derived from a genetically engineered, clonally-derived master pluripotent stem cell line with uniform expression of anti-BCMA CAR, IL-15RF, hnCD16, and CD38 bi-allelic knockout. The engineered master pluripotent stem cell line serves as the starting material for consistent and repeatable manufacture of off-the-shelf NK cells that contain all described attributes in a homogenous manner (termed FT576) and that can be produced at a scale to support multi-dose treatment strategies and on-demand dose availability. In preclinical studies, FT576 NK cells exhibited uniform expression of CD16, CAR, and IL15-RF and did not express CD38 (<1%). In an in vitro fratricide assay, FT576 NK cells were entirely resistant to daratumumab-induced fratricide, with no detectable specific cytotoxicity when exposed to increasing concentrations of daratumumab. Conversely, peripheral blood NK cells were sensitive to daratumumab-induced fratricide (up to 33% cytotoxicity within 3 hrs of daratumumab exposure). FT576 NK cells demonstrated enhanced cytotoxicity against the MM1.S MM cell line during a long-term cytotoxicity assay compared with control NK cells that lacked CAR expression (62% cytotoxicity for FT576 vs 26% for control). In addition, cellular persistence was greater than NK cells lacking the IL-15RF protein, and FT576 NK cells demonstrated the unique ability to expand in vitro absent of exogenous cytokine support (61-fold expansion vs. 4-fold for IL-15RF negative). Importantly, FT576 NK cells remained ADCC competent, as combination with daratumumab enhanced cytotoxicity against MM cell lines in a 2D cytotoxicity assay. Additionally, FT576 mediated direct cytotoxicity against RPMI-8226 MM spheroids, leading to >99% cytotoxicity in a 3D-spheroid culture model. Preclinical studies are ongoing to support the advancement of FT576 as the first-of-kind cellular therapeutic for the combination of anti-BCMA CAR and mAb-directed targeting of MM. Disclosures Bjordahl: Fate Therapeutics, Inc.: Employment. Gaidarova:Fate Therapeutics, Inc: Employment. Goodridge:FATE THERAPEUTICS: Employment. Mahmood:Fate Therapeutics, Inc: Employment. Bonello:Fate Therapeutics, Inc.: Employment. Robinson:Fate Therapeutics, Inc.: Employment. Ruller:Fate Therapeutics, Inc.: Employment. Pribadi:Fate Therapeutics, Inc.: Employment. Lee:Fate Therapeutics, Inc.: Employment. Abujarour:Fate Therapeutics, Inc.: Employment. Dinella:Fate Therapeutics, Inc.: Employment. Huffman:Fate Therapeutics, Inc.: Employment. Chu:FATE THERAPEUTICS: Employment. Valamehr:Fate Therapeutics, Inc: Employment.

From CAR-T Cells to CAR-NK Cells: A Developing Immunotherapy Method for Hematological Malignancies

“…FT596 and FT576, cell products for B-cell malignancies and MM, respectively, are investigational and off-the-shelf CAR-NK cell products derived from a human clonal master iPSC line engineered with anti-tumor abilities. These functional cell products can be manufactured on a large scale to support multi-dose therapeutic strategies and on-demand dose availability (60)(61)(62).…”

“…FT576 NK cells, a CAR-NK cell type derived from iNK cells, exhibit uniform expression of CD16, anti-BCMA CAR, and IL15-receptor a fusion protein (IL-15RF) and did not express CD38 (62). Preclinical trials proved FT576 NK cells enhanced cytotoxicity and persistence, avoidance of self-fratricide, and prevention of antigen loss when combined with other mAbs (e.g., anti-CD38 mAb) in the treatment of MM (61, 62).…”

CART-Cell Therapy: Recent Advances and New Evidence in Multiple Myeloma

“…In addition to donor-derived immune effector cells, induced pluripotent stem cell (iPSC)-derived immune cells are a promising platform for adoptive cellular therapy [ 76 ]. iPSC-derived lymphocytes have three critical advantages: (1) “off the shelf” availability; (2) a unique via clonal selection with a highly selected, multiply gene-edited, and consistent tumor-specific immune cell product; (3) and potent anti-tumor activity similar to conventional CAR T-cells, with maintaining of the innate phenotype, which can translate into fewer concerns about GVHD [ 77 , 78 ]. Another scenario could be represented by CAR NK cells, with a potentially lower CRS risk than conventional CAR T-cells.…”

Multiple Myeloma: An Overview of the Current and Novel Therapeutic Approaches in 2020

“…CAR-T cells are highly being investigated in MM, and we could move from autologous CAR-T cells to allogenic CAR-T cells, which could diminish the fabrication time and provide an ‘off-the-shelf’ therapeutic. Furthermore, CAR-NK could be an alternative to CAR-T cells in the future [ 45 ].…”