T cell (Tc) receptor (TCR)-based cell therapies have shown clinical efficacy across many cancer types and represent an attractive strategy for targeting solid tumors. However, the immunosuppressive tumor microenvironment, downregulation of target antigen and HLA, and the need for an autologous source limit the efficacy and the accessibility of TCR-Tc therapies. Early clinical trials have shown the potential of natural killer cells (NKs) as a therapy to treat hematological and solid cancers. Allogeneic NKs, engineered to express a TCR, represent a novel and promising strategy overcoming the limitations of T and NKs therapies. Here we describe the development of a product consisting of NKs engineered to express an affinity-enhanced TCR recognizing MAGE-A4, a clinically validated tumor antigen expressed across several solid tumors. The introduction of the TCR does not disrupt the innate functionality of NKs and adds TCR-mediated specific killing of antigen-positive targets. In fact, the innate potential of the NKs appears to be enhanced by the presence of the CD3-TCR complex, creating NKs with increased potency. TCR-NKs are faster, more potent than TCR-Tc and retain killing activity in the absence of TCR target antigen thus potentially overcoming tumor heterogeneity and/or antigen loss. Lastly, TCR-NKs are not activated when co-cultured with normal cells, displaying a safe profile. Combining the innate cytotoxicity of NKs with MAGE-A4-specific targeting of an affinity-enhanced TCR, results in a potent and safe cellular product representing a promising and novel therapeutic off-the-shelf paradigm for the treatment of many solid cancers.

Abstract T cell receptor (TCR)-T based therapies, such as MAGE-A4 TCR-T cells, have shown compelling data demonstrating effective infiltration into and targeting of solid tumors with clinical responses across various solid cancers. However, heterogeneity and down-regulation of target antigen and HLA expression limit the durability and curative potential of these types of treatments. On the other hand, owing to their clinical potency, favorable safety profile and applicability as “off the shelf” therapy, natural killer (NK) cells have emerged as promising modalities in recent years. Unguided NK cells have shown limited potential against solid cancers, due to lacking infiltration into tumors. With our proprietary TCR-NK platform, we combine the solid tumor targeting capabilities of TCRs with the pan-cancer sensing and cytotoxic potential of highly potent killer cells, redirecting and arming NK cells with a fully functional TCR-CD3 complex. Here we present our lead product, an optimized TCR-NK cell product, ZI-MA4-1a, expressing an affinity enhanced TCR (KVL-a) directed to the HLA class I-restricted clinically validated cancer-testis antigen MAGE-A4, that is broadly expressed across solid tumors. The KVL-a TCR was successfully engineered from a naturally occurring wild-type TCR, increasing the affinity to MAGE-A4-peptide-HLA complex and resulting in enhanced recognition of tumor cells expressing the target antigen. ZI-MA4-1a is produced by transducing healthy peripheral blood derived NK cells with the full CD3 complex, the KVL-a TCR and a CD8 coreceptor. The process has been optimized to enrich TCR-NK cells, increasing process robustness, diminishing the impact of donor variability, and producing a higher performing TCR-NK cell product. We show the dual functionality of ZI-MA4-1a: TCR driven cytotoxicity as well as innate NK sensing of antigen knockout or HLA negative cancers. We demonstrate killing of heterogenous tumor cell models in vitro, as well as the multifunctionality of ZI-MA4-1a with killing, degranulation and multicytokine secretion. Interestingly, we observe enhanced proliferation of ZI-MA4-1a cells after activation by MAGE-A4 expressing tumor cells, indicating that TCR-NK cells acquire further proliferative capacity when the TCR is triggered. Finally, we demonstrate higher activity of ZI-MA4-1a compared to KVL-a and benchmark TCR transduced T cells against antigen positive targets, and activity against antigen negative tumor cells escaping TCR-T cell recognition. Citation Format: Sarah Vollmers, Artur Cieslar-Pobuda, Justyna Kmiecik, Giulia Malachin, Michelle L. Sætersmoen, Frida Høsøien Haugen, Margherita Boieri, Maja Sandve, Dennis Clement, Ines Cardoso, Pimthanya Wanichawan, Martha E. Haugstøyl, Anja Oldenburg, Liliane Christ, Pranav Oberoi, Luz Mora-Velandia, Anders Holm, Namir J. Hassan, Emilie Gauthy, Julia Ino, Sylvie Pollmann, Luise U. Weigand. Development of the first optimised “off the shelf” MAGE-A4 targeting TCR-NK cells for advancement into the clinic for the treatment of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1329.

Background T cell receptor (TCR)-T based therapies, such as MAGE-A4 TCR-T cells, have shown compelling data demonstrating effective infiltration into and targeting of solid tumours with clinical responses across various solid cancers.1 However, heterogeneity and down-regulation of target expression limit the durability and curative potential of these types of treatments. On the other hand, owing to their clinical potency, favourable safety profile and applicability as 'off the shelf' therapy, natural killer (NK) cells have emerged as promising modalities in recent years. Unguided NK cells have shown limited potential against solid cancers, due to lacking infiltration into tumours. With our proprietary TCR-NK platform, we combine the solid tumour targeting capabilities of TCRs with the pan-cancer cytotoxic potential of highly potent killer cells, redirecting and arming NK cells with a fully functional TCR-CD3 complex. Here we present our lead, an optimised TCR-NK cell product, ZI-MA4–1, expressing an affinity enhanced TCR directed to the HLA class I-restricted clinically validated cancer-testis antigen MAGE-A4, broadly expressed across solid tumours. Methods The ZI-MA4–1 TCR was successfully engineered from a naturally occurring wild-type TCR increasing the affinity to MAGE-A4-peptide-HLA complex and resulting in enhanced recognition of tumour cells expressing the target antigen. ZI-MA4–1 is produced by transducing healthy peripheral blood derived NK cells (PB-NK) with the full CD3 complex and a CD8 coreceptor. The process has been optimised to enrich CD3/TCR expression on NK, increasing process robustness, diminishing the impact of donor variability, and producing higher performing TCR-NK cells. Results We show for the first time, that affinity enhancing a TCR increases the anti-tumour activity of TCR-NK cells compared to the wild-type TCR. Specificity analysis of the affinity enhanced TCR shows an absence of off-target cross-reactivity against normal tissue human cells and iCells. Furthermore, we show the dual functionality of TCR-NK cells: TCR driven cytotoxicity as well as innate NK recognition of antigen knockout or HLA negative cancers. Finally, we demonstrate higher activity of TCR-NKs compared to benchmark TCR-Ts against antigen positive targets, and activity against antigen negative tumour cells escaping TCR-T cell recognition. Conclusions Taken together, these data demonstrate the feasibility and potential of generating optimised TCR-NK cells from PB-NK resulting in a highly potent cell product combining TCR-mediated and innate NK killing functions. Based on the potency and safety profile, ZI-MA4–1 has advanced into manufacturing with a preclinical package underway to enable a clinical trial for treatment of patients with advanced solid tumours. Reference David S Hong, Brian A Van Tine, Swethajit Biswas, Cheryl McAlpine, Melissa L Johnson, Anthony J Olszanski, Jeffrey M Clarke, Dejka Araujo, George R Blumenschein, Partow Kebriaei, Quan Lin, Alex J Tipping, Joseph P Sanderson, Ruoxi Wang, Trupti Trivedi, Thejo Annareddy, Jane Bai, Stavros Rafail, Amy Sun, Lilliam Fernandes, Jean-Marc Navenot, Frederic D Bushman, John K Everett, Derin Karadeniz, Robyn Broad, Martin Isabelle, Revashnee Naidoo, Natalie Bath, Gareth Betts, Zohar Wolchinsky, Dzmitry G Batrakou, Erin Van Winkle, Erica Elefant, Armin Ghobadi, Amanda Cashen, Anne Grand'Maison, Philip McCarthy, Paula M Fracasso, Elliot Norry, Dennis Williams, Mihaela Druta, David A Liebner, Kunle Odunsi, Marcus O Butler, Autologous T cell therapy for MAGE-A4+ solid cancers in HLA-A*02+ patients: a phase 1 trial. Nature Medicine. 2023;29:104–114.

T-cell receptor (TCR) redirected T cells are considered as the next generation of care for the treatment of numerous solid tumors. KRAS mutations are driver neoantigens that are expressed in over 25% of all cancers and are thus regarded as ideal targets for Adoptive Cell Therapy (ACT). We have isolated four KRAS-specific TCRs from a long-term surviving pancreatic cancer patient vaccinated with a mix of mutated KRAS peptides. The sequence of these TCRs could be identified and expressed in primary cells. We demonstrated stable expression of all TCRs as well as target-specific functionality when expressing T cells were co-incubated with target cells presenting KRAS peptides. In addition, these TCRs were all partially co-receptor independent since they were functional in both CD4 and CD8 T cells, thus indicating high affinity. Interestingly, we observed that certain TCRs were able to recognize several KRAS mutations in complex with their cognate Human leukocyte antigen (HLA), suggesting that, here, the point mutations were less important for the HLA binding and TCR recognition, whereas others were single-mutation restricted. Finally, we demonstrated that these peptides were indeed processed and presented, since HLA-matched antigen presenting cells exogenously loaded with KRAS proteins were recognized by TCR-transduced T cells. Taken together, our data demonstrate that KRAS mutations are immunogenic for CD4 T cells and are interesting targets for TCR-based cancer immunotherapy.

The original version of this article unfortunately included a mistake in Fig. 2b where the images of mice in the tumour control group (right), day 30 (bottom) should be removed as the wrong images (duplicate of day 17) were inserted by mistake. At this time point the tumour control mice were no longer alive and the images were replaced by black areas.

T cell receptor (TCR)-engineered T cell therapy is a promising cancer treatment approach. Human telomerase reverse transcriptase (hTERT) is overexpressed in the majority of tumors and a potential target for adoptive cell therapy. We isolated a novel hTERT-specific TCR sequence, named Radium-4, from a clinically responding pancreatic cancer patient vaccinated with a long hTERT peptide. Radium-4 TCR-redirected primary CD4(+) and CD8(+) T cells demonstrated in vitro efficacy, producing inflammatory cytokines and killing hTERT(+) melanoma cells in both 2D and 3D settings, as well as malignant, patient-derived ascites cells. Importantly, T cells expressing Radium-4 TCR displayed no toxicity against bone marrow stem cells or mature hematopoietic cells. Notably, Radium-4 TCR+ T cells also significantly reduced tumor growth and improved survival in a xenograft mouse model. Since hTERT is a universal cancer antigen, and the very frequently expressed HLA class II molecules presenting the hTERT peptide to this TCR provide a very high (>75%) population coverage, this TCR represents an attractive candidate for immunotherapy of solid tumors.

Off-target toxicity due to the expression of target antigens in normal tissue or TCR cross-reactivity represents a major risk when using T cell receptor (TCR)-engineered T cells for treatment of solid tumours. Due to the inherent cross-reactivity of TCRs it is difficult to accurately predict their target recognition pre-clinically. It has become evident that direct testing in a human being represents the best evaluation of the risks. There is, therefore, a clear unmet need for assessing the safety of a therapeutic TCR in a more controllable manner than by the injection of permanently modified cellular products. Using transiently modified T cells combined with dose escalation has already been shown feasible for chimeric antigen receptor (CAR)-engineered T cells, but nothing is yet reported for TCR. We performed a preclinical evaluation of a therapeutic TCR transiently expressed in T cells by mRNA electroporation. We analyzed if the construct was active in vitro, how long it was detectable for and if this expression format was adapted to in vivo efficacy assessment. Our data demonstrate the potential of mRNA engineered T cells, although less powerful than permanent redirection, to induce a significant response. Thus, these findings support the development of mRNA based TCR-therapy strategies as a feasible and efficacious method for evaluating TCR safety and efficacy in first-in-man testing.

T cells modified to express chimeric antigen receptor (CAR) targeting CD19 (CD19CAR) have produced remarkable clinical responses in patients with relapsed/refractory B-cell acute lymphoblastic leukemia. CD19CAR T-cell therapy has also demonstrated prominent effects in B-cell non-Hodgkin lymphoma (B-NHL) patients. However, a subset of patients who relapse after CD19CAR T-cell therapy have outgrowth of CD19- tumor cells. Hence, development of alternative CARs targeting other B-cell markers represents an unmet medical need for B-cell acute lymphoblastic leukemia and B-NHL. Here, we confirmed previous data by showing that, overall, B-NHL has high expression of CD37. A second-generation CD37CAR was designed, and its efficacy in T cells was compared with that of CD19CAR. In vitro assessment of cytotoxicity and T-cell function upon coculture of the CAR T cells with different target B-cell lymphoma cell lines demonstrated comparable efficacy between the 2 CARs. In an aggressive B-cell lymphoma xenograft model, CD37CAR T cells were as potent as CD19CAR T cells in controlling tumor growth. In a second xenograft model, using U2932 lymphoma cells containing a CD19- subpopulation, CD37CAR T cells efficiently controlled tumor growth and prolonged survival, whereas CD19CAR T cells had limited effect. We further show that, unlike CD19CAR, CD37CAR was not sensitive to antigen masking. Finally, CD37CAR reactivity was restricted to B-lineage cells. Collectively, our results demonstrated that CD37CAR T cells also can effectively eradicate B-cell lymphoma tumors when CD19 antigen expression is lost and support further clinical testing for patients with relapsed/refractory B-NHL.