Abstract 1591: FT536: Preclinical development of a novel off-the-shelf CAR-MICA/B NK cell immunotherapy combined with radiation and antibody treatments as a first-of-kind pan-cancer targeting strategy
Authors: Goulding John , Blum Robert , Hancock Bryan , Ge Moyar , Groff Brian , Shirinbak Soheila , Grant Joy , Hosking Martin , Pribadi Mochtar , Pan Yijia , Chui Hui-Yi , Sikaroodi Shohreh , Fong Lauren , Huffman Janel , Yeh Wen-I , Chang Chia-Wei , Dailey Thomas , Meza Miguel , Nguyen Cokey , de Andrade Lucas Ferrari , Lee Tom , Bjordahl Ryan , Wucherpfennig Kai W. , Valamehr Bahram 
Published: July 2021

Abstract
Cancer immunotherapies have revolutionized cancer treatment by showing clinical efficacy across multiple cancer indications. However, tumor heterogeneity and evasion from host immune cell surveillance often limit the durability and efficacy of these strategies as monotherapies. Consequently, it is becoming common practice to combine existing anticancer treatments and novel immunotherapies to maximize clinical efficacy. The pan tumor-associated antigens MICA and MICB (MICA/B) are surface proteins induced by cellular stress, often associated with tumorigenesis, and are recognized by the NK cell activating receptor NKG2D. To evade immune recognition, cancer cells often proteolytically shed the membrane distal domains of MICA/B, leading to reduced NKG2D recognition. To combat this pervasive tumor escape mechanism and create a ubiquitous cancer targeting platform, we have developed a novel CAR-iPSC-derived NK (iNK) cell that targets the conserved α3 domain of MICA/B, rendering it resistant to inhibition by shed MICA/B. To enhance effector cell function, persistence and multi-antigen capacity, further genetic editing at the iPSC stage was conducted to equip the CAR-iNK cells with a unique IL-15/IL-15 receptor fusion, the knockout of CD38 and a novel high-affinity, non-cleavable CD16 (hnCD16) to enhance antibody-dependent cellular cytotoxicity (ADCC). In this study, we evaluated the function of multiplexed engineered MICA/B CAR iNK cells (termed FT536) in combination with monoclonal antibodies (mAbs), to elicit multi-antigen targeting, and radiation therapy, to augment surface MICA/B expression. FT536 showed superior in vitro cytotoxicity and in vivo tumor control against an array of MICA/B expressing tumor lines. Furthermore, ADCC, induced in combination with cetuximab or trastuzumab, enhanced the potency of FT536 against various solid tumor lines (p &lt;0.05). To demonstrate the capability of FT536 to synergize with irradiation therapy, we utilized a panel of tumor lines, divergent in tissue origin and MICA/B expression profiles. This approach highlighted that irradiation of the SK-BR-3 tumor line, a breast adenocarcinoma that expresses low levels of surface MICA/B and high levels of EGFR, induced the upregulation of MICA/B expression (p &lt;0.05). As anticipated, FT536 exhibited enhanced, CAR-dependent cytotoxicity against irradiated SK-BR-3 cells. Ongoing work is focused on the development of in vivo models that combine FT536 with in situ tumor irradiation and mAbs in order to promote durable responses and the elimination of resistant and heterogenous cancer cells. These data demonstrate successful targeting of MICA/B positive tumors by FT536 can be augmented by mAb and radiation therapies as first-of-kind combinatorial strategies to broadly target escape-prone tumors.
Citation Format: John Goulding, Robert Blum, Bryan Hancock, Moyar Ge, Brian Groff, Soheila Shirinbak, Joy Grant, Martin Hosking, Mochtar Pribadi, Yijia Pan, Hui-Yi Chui, Shohreh Sikaroodi, Lauren Fong, Janel Huffman, Wen-I Yeh, Chia-Wei Chang, Thomas Dailey, Miguel Meza, Cokey Nguyen, Lucas Ferrari de Andrade, Tom Lee, Ryan Bjordahl, Kai W. Wucherpfennig, Bahram Valamehr. FT536: Preclinical development of a novel off-the-shelf CAR-MICA/B NK cell immunotherapy combined with radiation and antibody treatments as a first-of-kind pan-cancer targeting strategy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1591.