Abstract 1773: Preclinical characterization of allogeneic Vγ9Vδ2 HER2-TAC T cells for the treatment of HER2-positive solid tumors

Background: The T cell antigen coupler (TAC) is a novel, proprietary chimeric receptor that facilitates the redirection of T cells to tumor cells and activates T cells by co-opting the endogenous T cell receptor complex with the goal to elicit safe and durable anti-tumor responses. TAC01-HER2, a first-in-class, autologous TAC T cell product targeting HER2 (ERBB2), has entered a phase I/II clinical trial in patients with HER2-positive solid tumors. Here, we describe the development of an allogeneic HER2-TAC T cell product based on Vγ9Vδ2 (γδ) T cells which belong to a subset of T cells that recognize target cells in a human leukocyte antigen (HLA) independent manner. Thus, γδ T cells do not cause GvHD and have the potential for allogeneic cell therapy applications.

Materials and Methods: A variety of in vitro and in vivo assays were used to evaluate the potency and safety of HER2-TAC γδ T cells generated from multiple donors. In vitro assays included flow cytometric analysis determining the γδ T cell phenotype, intracellular cytokines, CD69 upregulation, and T cell proliferation. Anti-tumor cytotoxicity was assessed via real-time microscopy-based co-culture assays. Mixed lymphocyte reactions (MLR) were performed to measure cytokine production and proliferation of HER2-TAC γδ T cells in response to HLA mismatches between unrelated donors. In vivo studies examined the anti-tumor effect of HER2-TAC γδ T cells against established solid HER2-expressing tumors.

Results: HER2-TAC γδ T cells selectively reacted to HER2-expressing tumor cells in co-culture, as demonstrated by CD69 upregulation, intracellular cytokine production, increase in proliferation, and cytotoxicity. In contrast, HER2-TAC γδ T cells failed to show activity in MLR assays, potentially indicating that HER2-TAC γδ T cells are free of GvH reactivity. These MLR assays comprised dendritic cells that represent the major HLA subtypes found in North America. In addition, HER2-TAC γδ T cells showed strong anti-tumor efficacy in HER2-positive tumor xenograft models without signs of toxicity.

Conclusions: The in vitro and in vivo data confirm strong and specific activity of HER2-targeted TAC γδ T cells against HER2-expressing tumor models and highlights the potential of the TAC platform in the development of an allogeneic product for therapeutic applications in solid tumors.

Citation Format: Suzanna L. Prosser, Stacey X. Xu, Ling Wang, Ritu R. Randhawa, Sailaja Pirati, Laura Ravensbergen, Seungmi Yoo, Miyoung Jung, Laurentia Gheorghiu, Angel Gomez, Gurleen Sandhu, Chris Ayers, Donna Rill, Christopher W. Helsen, Andreas G. Bader. Preclinical characterization of allogeneic Vγ9Vδ2 HER2-TAC T cells for the treatment of HER2-positive solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1773.

Abstract 3188: Patient-derived TAC01-HER2 TAC T cells produced in Cocoon® Platform is highly functional in models of solid tumors

Background:

The T cell antigen coupler (TAC) is a novel, proprietary chimeric receptor that facilitates the re-direction of T cells to tumor cells and activates T cells by co-opting the endogenous T cell receptor complex with the goal to elicit a safe and durable anti-tumor response. TAC01-HER2, a first-in-class TAC T product targeting HER2 (ERBB2), has entered a Phase I/II clinical trial in patients with HER2-positive solid tumors. Here, we characterized the TAC T cell phenotypes and anti-tumor activity of TAC01-HER2 manufactured using leukocytes from Phase I/II patients in nonclinical in vitro and in vivo assays.

Materials and Methods:

TAC T cell proliferation, activation, and phenotype of patient-derived TAC01-HER2 were assessed by flow cytometric analysis. In vitro anti-tumor cytotoxicity was assessed via a real-time microscopy-based co-culture assay, and in vivo anti-tumor activity of TAC01-HER2 was assessed in mice engrafted with established solid HER2-expressing human tumors.

Results:

Complex phenotype analysis showed that patient-derived TAC01-HER2 products consisted of a high percentage of memory T cells similar to products generated from healthy donors. Patient-derived products had significant proportions of CD4 and CD8 T cells, with CD4 being the predominant population in several of these. In a 5-day in vitro potency assay, patient-derived products showed effective tumor cell killing at low E:T rations (1:1 to 1:20) which was comparable to product generated from healthy donors. Similarly, intravenous administration of patient-derived TAC01-HER2 in mice carrying HER2-positive tumors xenografts led to a complete and sustained tumor clearance.

Conclusion:

The in vitro and in vivo data confirm the potency of patient-derived TAC01-HER2 against HER2-expressing solid tumor models. This work combined with other biomarkers may help correlate nonclinical potency with clinical outcomes.

Citation Format: Ling Wang, Stacey X. Xu, Tania Benatar, Ritu R. Randhawa, Philbert Ip, Prabha Lal, Thanyashanthi Nitya-Nootan, Laura Ravensbergen, Heather MacGregor, Suzy Prosser, Sadhak Sengupta, Christopher W. Helsen, Andreas G. Bader. Patient-derived TAC01-HER2 TAC T cells produced in Cocoon® Platform is highly functional in models of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3188.