A chimeric antigen receptor uniquely recognizing MICA/B stress proteins provides an effective approach to target solid tumors

BACKGROUND

The advent of chimeric antigen receptor (CAR) T cell therapies has transformed the treatment of hematological malignancies; however, broader therapeutic success of CAR T cells has been limited in solid tumors because of their frequently heterogeneous composition. Stress proteins in the MICA and MICB (MICA/B) family are broadly expressed by tumor cells following DNA damage but are rapidly shed to evade immune detection.

METHODS

We have developed a novel CAR targeting the conserved α3 domain of MICA/B (3MICA/B CAR) and incorporated it into a multiplexed-engineered induced pluripotent stem cell (iPSC)-derived natural killer (NK) cell (3MICA/B CAR iNK) that expressed a shedding-resistant form of the CD16 Fc receptor to enable tumor recognition through two major targeting receptors.

FINDINGS

We demonstrated that 3MICA/B CAR mitigates MICA/B shedding and inhibition via soluble MICA/B while simultaneously exhibiting antigen-specific anti-tumor reactivity across an expansive library of human cancer cell lines. Pre-clinical assessment of 3MICA/B CAR iNK cells demonstrated potent antigen-specific in vivo cytolytic activity against both solid and hematological xenograft models, which was further enhanced in combination with tumor-targeted therapeutic antibodies that activate the CD16 Fc receptor.

CONCLUSIONS

Our work demonstrated 3MICA/B CAR iNK cells to be a promising multi-antigen-targeting cancer immunotherapy approach intended for solid tumors.

FUNDING

Funded by Fate Therapeutics and NIH (R01CA238039).

117 FT536 Path to IND: Ubiquitous targeting of solid tumors with an off-the-shelf, first-of-kind MICA/B-specific CAR-iNK cellular immunotherapy

Background

Chimeric antigen receptor (CAR)-T cell therapy has revolutionized cancer treatment, but it is associated with significant dose-limiting toxicities, restricted tumor targeting (limited by specific antigen expression), and, notably, a lack of multi-antigen targeting capability to mitigate tumor associated immune evasion and heterogeneity. Furthermore, dysfunctional starting material, product inconsistency, and small manufacturing lot size limits the application and on-demand availability of CAR-T cell therapy.

Methods

To overcome these considerable limitations, we have developed FT536, a first-of-kind, induced pluripotent stem cell (iPSC)-derived NK (iNK) cell with a novel CAR that ubiquitously targets cancer cells through canonical stress ligand recognition. We have previously reported FT536 recognizes the conserved α3 domain of the pan-tumor associated antigens MICA and MICB (MICA/B), and is derived from a renewable master iPSC line that contains multiplexed genetic edits to enhance effector cell functionality, persistence, and multi-antigen targeting capabilities via high affinity non cleavable CD16 (hnCD16) mediated antibody dependent cellular cytotoxicity (ADCC). Here we preview the nonclinical study for the investigational new drug (IND) application for FT536.

Results

Utilizing a manufacturing process analogous to pharmaceutical drug product development, we demonstrate FT536 can be consistently and uniformly produced with a greater than 4x10E7 fold cellular expansion per manufacturing campaign. Furthermore, FT536 can be cryopreserved at clinical scale to support off-the-shelf clinical application, with rapid product thaw and immediate patient infusion in an out-patient setting. Functional evaluation demonstrated that FT536 uniquely possesses potent and persistent antigen specific cytolytic activity against an array of solid and hematological tumor lines. Through its hnCD16 modality, FT536 can be utilized in combination with monoclonal antibodies to provide multi-antigen targeting capabilities and in conjunction with chemotherapeutics and/or radiation that augment surface MICA/B expression. In addition, directly thawed and infused FT536 demonstrated significant tumor growth inhibition in multiple solid and liquid in vivo xenograft models, in which tumor control was further enhanced in combination with a therapeutic antibody (figure 1). Finally, ongoing studies utilizing a lung adenocarcinoma model have highlighted the sustained persistence of FT536 in lung tissue up to 33 days following a single dose infusion without the need for exogenous cytokine support.

Abstract 117 Figure 1

FT536 provides statistically significant in vivo anti-tumor activity which is enhanced in combination with ADCC active monoclonal antibody therapy. (A-B) FT536 significantly reduced the number of lung and liver (not shown) metastases compared to CAR negative iNK control cells in a murine metastatic melanoma model using B16-F10 cells engineered to overexpress human MICA. (C-D) FT536 alone, and in combination with Herceptin, demonstrate significant tumor growth inhibition (TGI) compared to Herceptin alone in an orthotopic xenograft model of human lung adenocarcinoma.

Conclusions

Collectively, these studies demonstrate that FT536 is a highly potent, multi-tumor targeting CAR-iNK cell product that is uniform in composition and can be effectively and safely used off-the-shelf for on-demand treatment of multiple solid and hematological malignancies. An IND submission is planned for 2021, with an initial Phase 1 clinical trial to follow.

Abstract 332: Chimeric fusion receptors provide a CD3-mediated activation signal to off-the-shelf iPSC-derived TCR-less CAR-T cells for enhanced efficacy

T cells require a combination of signals to properly activate and exhibit their full potential; signal 1 from the T cell receptor (TCR), signal 2 from costimulatory receptors and signal 3 from cytokine receptors can shape the function of T cells. Second generation chimeric antigen receptor (CAR) T-cells targeting CD19 have shown success in hematologic malignancies, in part because signals 1 and 2 are provided by the CAR endodomain. As previously reported, we have developed an off-the-shelf iPSC-derived CAR19 T (CAR19-iT) cell product where the CAR is inserted into the T cell receptor alpha constant (TRAC) locus for enhanced efficacy and disruption of surface TCR expression. While the TCR-less CAR19-iT cells are ideal for allogeneic CAR-T cell therapies, as a consequence, they lack CD3 surface expression and the means by which to mediate CD3 signaling.

To further improve CAR-iT cell performance and facilitate combinatorial strategies with T cell engagers such as bispecific T cell engagers (BiTEs), we designed chimeric fusion receptors (CFRs) comprising an ectodomain of CD3 or CD28, a transmembrane domain of CD28, and various endodomains that provide combinations of signals 1, 2, and 3. In addition to providing co-stimulatory signaling, the CFR designs can be controlled via agonistic antibodies or BiTEs to initiate signal transduction for precision control of the cell product. Furthermore, a series of CFRs with various CD3 endodomains were also developed to augment costimulatory signaling and the ER retention and endocytosis motifs found in CD3 endodomains were mutated to prevent downregulation of the CFRs from the cell surface of TCR-less cells.

Selected CFRs were engineered into TRAC knockout Jurkat cells expressing a luciferase based NFAT reporter gene. After 48 hours, surface expression of the CFRs was confirmed by flow cytometry. Signal transduction via the CFRs was evaluated following exposure to agonistic antibodies or BiTEs. Measurement of the luciferase activity showed comparable levels to activated wildtype reporter cells. After construct validation, the CFRs were introduced into TCR-less CAR19-iT cells and co-cultured overnight with Nalm6 target cells in the presence of agonistic antibodies. Compared to control CAR19-iT cells, the armed CFR-CAR19 iT cells demonstrated superior killing of target cells. These results support the notion that enhancing signal 1 can increase CAR-T cell efficacy with current studies underway to investigate CFRs with endodomains that provide additional signal 2 or 3. We expect these constructs to further enhance CAR-iT cell persistence and engagement with BiTEs for activation and multi-antigen targeting. Collectively, the data suggest that TRC-less CAR-iT cells can be further armed with CFRs containing appropriate endodomains to provide superior antitumor function in a regulated manner.

Citation Format: Eigen Peralta, Dan Lu, Mark Landon, Helen Chu, Shohreh Sikaroodi, Emily Carron, Natalie Navarrete, Alec Witty, Tom Lee, Anhco Nguyen, Bahram Valamehr. Chimeric fusion receptors provide a CD3-mediated activation signal to off-the-shelf iPSC-derived TCR-less CAR-T cells for enhanced efficacy [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 332.

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

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 <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 <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.

Abstract 1497: A unique strategy to arm iPSC-derived CAR-T cells to perform antibody-directed cellular cytotoxicity to facilitate multi-antigen targeting

Although chimeric antigen receptor (CAR)-T cells have been transformational for several liquid tumors, their effectiveness in treating a variety of solid tumors has been limited in part because the heterogeneity of tumor-associated antigens found in many bulky tumors represents a major obstacle to the development and the delivery of effective CAR-T cell therapies in cancer.

Here we demonstrate that iPSC-derived CAR-T (CAR-iT) cells are an ideal off-the-shelf approach that can be engineered to perform antibody-dependent cell-mediated cytotoxicity (ADCC) to facilitate multi-antigen targeting with the introduction of various monoclonal antibodies (mAbs). Under this strategy, while the CAR is equipped to predominantly target antigen 1, targeting additional tumor associated antigens through the use of various mAbs can be leveraged through ADCC. To this end, CAR-iT cells were genetically edited at the iPSC stage to uniformly express a novel high-affinity variant (158V), non-cleavable CD16A (hnCD16) Fc receptor to recognize and bind to the Fc fragment of mAbs and facilitate ADCC. When combined with therapeutic mAbs targeting HER2, EGFR, or PDL1, the cytolytic efficacy of hnCD16+ CAR-iT cells was significantly enhanced compared to parental CAR-iT cells in several tumor models, including ovarian, HER2+ breast, and triple-negative breast cancers, underscoring the flexibility of a combined CAR and ADCC – mediated targeting approach. Importantly, although both CD16A and CAR signaling share common CD3ζ pathways, simultaneous activation did not appreciably attenuate the activation and effector function of CAR-iT cells. Moreover, hnCD16+ CAR-iT cells demonstrated enhanced control in an established triple negative breast cancer solid tumor xenograft model. The control of antigenically heterogenous tumors by hnCD16+ CAR-iT cells was also significantly improved when compared to parental CAR-iT cells. To confirm selectivity and avoidance of immunoglobulin interference with functional output, various in vitro cellular cytotoxicity assays were conducted with IgG1 to confirm that hnCD16 requires crosslinking to elicit ADCC while maintaining full potentiation of CAR function. Additional in vitro and in vivo studies are ongoing and will be presented.

Collectively, the data demonstrates that CAR-iT cells can be further modified with hnCD16 Fc receptor to elicit ADCC and the combination of CAR and hnCD16 is a unique approach to tackling tumor heterogeneity often found in bulky tumors.

Citation Format: Martin Hosking, Soheila Shirinbak, Joy Grant, Wen-I Yeh, Yijia Pan, Mochtar Pribadi, Amit Mehta, Amanda Yzaguirre, Philip Chu, Shohreh Sikaroodi, Angela Gentile, Bruce Walcheck, Jianming Wu, Anhco Nguyen, Bahram Valamehr. A unique strategy to arm iPSC-derived CAR-T cells to perform antibody-directed cellular cytotoxicity to facilitate multi-antigen targeting [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 1497.