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Natural killer (NK) cells harbor efficient cytotoxicity against tumor cells without causing life-threatening cytokine release syndrome (CRS) or graft-versus-host disease (GvHD). When compared to chimeric antigen receptor (CAR) technology, Antibody-Cell Conjugation (ACC) technology has been developed to provide an efficient platform to arm immune cells with cancer-targeting antibodies to recognize and attack cancer cells. Recently, we established an endogenous CD16-expressing oNK cell line (oNK) with a favorable expression pattern of NK activation/inhibitory receptors. In this study, we applied ACC platform to conjugate oNK with trastuzumab and an anti-human epidermal growth factor receptor 2 (HER2) antibody. Trastuzumab-conjugated oNK, ACE-oNK-HER2, executed in vitro and in vivo cytotoxicity against HER2-expressing cancer cells and showed enhanced T cell-recruiting capability and secretion of IFNγ. The irradiated and cryopreserved ACE-oNK-HER2, designated as ACE1702, retained superior HER2-specific in vitro and in vivo potency with no tumorigenic potential. In conclusion, this study provides the evidence to support the potential clinical application of ACE1702 as a novel off-the-shelf NK cell therapy against HER2-expressing solid tumors.

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Introduction: CAR-αβT therapies have been shown to improve clinical outcomes in hematological malignancies; however, solid tumors still remain as challenges to CAR-αβT therapies due to tumor microenvironment, limited tumor infiltration or antigen escape. Previous research findings indicate γδ2 T cells are involved in tumor surveillance by responding to phosphoantigen overexpressed by most of cancers. The antibody cell conjugation (ACC) technology has the advantage to link cancer-targeting antibodies on cell surface of immune cells without genetic modification. This study applies ACC technology to generate an off-the-shelf EGFR-targeting γδ2 T cell therapy ACE2016, and presents the promising potency of ACE2016 against EGFR-expressing cancer cells. Methods: γδ2 T cells were expanded from healthy donor PBMCs and αβ T cell population were depleted. Both γδ2 T cells and αEGFR were covalently conjugated to selected DNA aptamers that enable DNA hybridization to generate EGFR-targeting γδ2 T cells, ACE2016. The characteristics and antibody conjugation of ACE2016 was evaluated by flow cytometry, and in vitro cytotoxicity and in vivo anti-tumor potency was investigated using luminescence-based cytotoxicity assay and the orthotopical model with EGFR-expressing cancer cells, respectively. Results: ACE2016 showed nearly 100 % of αEGFR antibody conjugation and exhibited EGFR-specific binding activity. These features conferred ACE2016 with enhanced in vitro cytotoxicity against EGFR-expressing cancer cells compared to unconjugated γδ2 T cells, while ACE2016 and γδ2 T cells showed no significant difference of anti-tumor potency against EGFR-negative cancer cells. Further characterization studies demonstrated that co-cultured with target cells significantly activated ACE2016 along with enhanced degranulation and cytokine production without measurable IL-6 secretion. Moreover, ACE2016 suppressed EGFR-expressing breast cancer cells in vivo in the orthotopic xenograft model without weight loss or toxicological observations. Conclusion: ACE2016, an EGFR-targeting γδ2 T cell product, was successfully generated as an effective off-the-shelf treatment for EGFR-expressing solid tumors. This study provides the evidence for the in vitro and in vivo efficacy of ACE2016 against EGFR-expressing cancer cells to support the clinical application against EGFR-expressing tumors. Citation Format: Hao-Kang Li, Tai-Sheng Wu, Pei-Ru Leng, Yi-Chiu Kuo, Zih-Fei Cheng, Chia-Yun Lee, Yan-Liang Lin, Sai-Wen Tang, Shih-Chia Hsiao. ACE2016: an off-the-shelf EGFR-targeting γδ2 T cell therapy against EGFR-expressing solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB089.

BackgroundAutologous or allogeneic natural killer (NK) cells possess efficient cytotoxicity against tumor cells without severe side effects such as CRS or graft-versus-host disease (GvHD). In addition to chimeric antigen receptor (CAR) strategy, antibody-cell conjugates (ACC) platform provides more efficient way to arm NK cells with binding specificity and enhanced potency against target cells. In this work, we develop a NK cell therapy product ACE1702, a novel NK cell line oNK conjugated with trastuzumab, and assess its potency against HER2+ solid tumors.Methods oNK cells were covalently conjugated with monoclonal antibody Trastuzumab after sublethal irradiation by our patented antibody-cell conjugates (ACC) platform to become our cryopreserved final product ACE1702 compliant with current good manufacturing practice (cGMP). Function of ACE1702 was validated by real-time xCELLigence analyzer and MTT assay in vitro. Efficacy of intraperitoneally (ip.) delivered ACE1702 was evaluated in tumor-bearing female immune compromised NSG mice. Characterization of ACE1702 was analyzed by flow cytometry.ResultsWe demonstrated that the trastuzumab-armed oNK cells, ACE1702, exerted human epidermal growth factor 2 (HER2) binding specificity and enhanced cytotoxicity against various types of cancer cells with different grade of HER2 expressions compared to control oNK cells in vitro. In vivo results in human ovarian cancer cell line SK-OV-3-bearing xenograft mouse model further supported the in vitro observations. Of note, ACE1702 also displayed a better cytotoxicity against HER2+ cancer cells than trastuzumab and its derived antibody-drug conjugate. ACE1702 also remained cytotoxicity against cancer cells in the suppressive tumor microenvironment. Characterization revealed a preferential expression of NK activation receptors, and conjugation of trastuzumab with cell membrane proteins responsible for NK activity capacitated ACE1702 with enhanced cytotoxicity. These results underscore the potency of ACE1702 in eradication of cancer cells.ConclusionsHere we introduced a novel trastuzumab-modified oNK cell product with enhanced specificity against myriad types of HER2+ cancers. Selective conjugation of trastuzumab with membrane proteins contributing to NK activation conferred ACE1702 with enhanced cytotoxicity even in the suppressive tumor microenvironment.AcknowledgementsNoneTrial RegistrationNoneEthics ApprovalThe animal study was conducted according to protocols approved by the Institutional Animal Care and Use Committee of Muragenics.ConsentNone