Abstract 4053: A mesothelin targeting chimeric antigen receptor macrophage (CAR-M) for solid tumor immunotherapy: pre-clinical development of CT-1119

While adoptive cell therapies have seen significant success in the treatment of hematological malignancies, solid tumors remain challenging for the field. A significant obstacle is the exclusion of T cells from the tumor microenvironment (TME). In contrast, monocytes/macrophages are naturally recruited to the TME. These cells then have the potential to phagocytose tumor cells, activate the TME, and prime a broad anti-tumor adaptive immune response via T cell recruitment and activation. We have previously developed CT-0508, a chimeric antigen receptor macrophage (CAR-M) targeting HER2 which showed efficacy in a variety of pre-clinical models and is currently in a Phase I clinical trial for patients with HER2+ solid tumors. Mesothelin is overexpressed in a variety of solid tumors, including mesothelioma, lung, pancreatic, and ovarian cancers. To leverage tumor biology with myeloid cells, we engineered primary human macrophages using the chimeric adenoviral vector Ad5f35 to express a CAR containing a human scFv against human mesothelin. We used both in vitro cell based assays and in vivo xenograft models to assess the activity of CT-1119. CAR-M engineered with an Ad5f35 vector demonstrated high CAR expression, high viability, upregulated M1 (anti-tumor) macrophage markers, and downregulated M2 (pro-tumor) macrophage markers. CT-1119 specifically phagocytosed multiple mesothelin expressing tumor cell lines in a CAR-dependent and antigen-dependent manner. CT-1119 demonstrated robust in vitro killing of the relevant tumor cell lines A549 and MES-OV expressing mesothelin. CAR engagement also induced the release of pro-inflammatory cytokines such as TNFα following stimulation with mesothelin in both cell-free and cell-based contexts in a dose-dependent manner. In vivo, CT-1119 significantly reduced tumor burden in a murine xenograft model of lung cancer. Similarly, human monocytes targeting mesothelin were successfully generated using the same Ad5f35 vector and demonstrated specific activity against mesothelin positive tumor cells. The presented results demonstrate that CT-1119, an autologous human anti-mesothelin CAR-M, can cause phagocytosis, tumor cell killing, and pro-inflammatory cytokine release in response to stimulation with mesothelin. These results show that CAR-M is a feasible approach for the treatment of mesothelin expressing sold tumors via the potential for induction of a systemic anti-tumor response.

Citation Format: Nicholas R. Anderson, Brinda Shah, Alison Worth, Rashid Gabbasov, Brett Menchel, Kerri Ciccaglione, Daniel Blumenthal, Stefano Pierini, Sabrina Ceeraz DeLong, Sascha Abramson, Thomas Condamine, Michael Klichinsky. A mesothelin targeting chimeric antigen receptor macrophage (CAR-M) for solid tumor immunotherapy: pre-clinical development of CT-1119. [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 4053.

Abstract 582: Pre-clinical development of CAR Monocytes (CAR Mono) for solid tumor immunotherapy

Introduction: Engineered cell therapies have demonstrated significant clinical activity against hematologic malignancies, but responses have been rare in solid tumors. Our previously developed human chimeric antigen receptor macrophage (CAR-M) platform has shown potent anti-tumor activity in pre-clinical solid tumor models1, and the anti-HER2 CAR-M CT-0508 is currently being evaluated in a Phase I trial. The use of myeloid cells as a platform for cell therapy provides the tools to overcome critical solid tumor challenges such as infiltration, immunosuppression within the tumor microenvironment, lymphocyte exclusion, and target antigen heterogeneity. Currently, CAR-M are generated in a week-long ex-vivo process in which peripheral blood monocytes are differentiated into macrophages prior to genetic manipulation. Here, we demonstrate the production feasibility, phenotype, pharmacokinetics, cellular fate, specificity, and anti-tumor activity of human CD14+ CAR monocytes.

Experimental: Using the chimeric adenoviral vector Ad5f35, we engineered primary human CD14+ monocytes to express a CAR (CAR-mono) targeted against HER2. We established a process that allowed for same day manufacturing (from Leukopak to cryopreserved CAR-mono cell product).

Results: CAR-mono showed high CAR expression and viability (>90%), and efficiently differentiated into CAR-expressing macrophages. Adenoviral transduction led to pre-conditioning of CAR-mono, resulting in a strong M1 phenotype upon differentiation into CAR-M. CAR-mono derived macrophages demonstrated potent anti-tumor activity regardless of exposure to GM-CSF or M-CSF, and were protected against M2 switching by immunosuppressive factors. Treating CAR-mono with GM-CSF and IL-4 resulted in their differentiation to monocyte-derived CAR-DCs with an activated phenotype, indicating that these cells retained their myeloid differentiation potential. In vivo, CAR-mono induced anti-tumor activity in various HER2+ solid tumor xenograft models. Following IV administration, CAR-mono demonstrated the ability to traffic to both GM-CSFhigh and GM-CSFlow expressing tumors. Notably, CAR-mono showed long-term CAR expression and persistence (>180 days) in both NSG and NSG-S mouse models, demonstrating lasting persistence irrespective of human cytokine support.

Conclusions: The CAR-mono platform enables an automated, same-day manufacturing process while maintaining the key characteristics of CAR-M therapy. The use of Ad5f35 for human monocyte transduction primes the cells toward M1 macrophage differentiation and produces a cell population phenotypically and functionally similar to our established CAR-M platform. These data provide strong pre-clinical support to advance the CAR-mono platform into clinical testing.1Klichinsky M, et al. Human chimeric antigen receptor macrophages for cancer immunotherapy. Nature Biotechnology. March 2020.

Citation Format: Daniel Blumenthal, Linara Gabitova, Brett Menchel, Patricia Reyes-Uribe, Sabrina Ceeraz DeLong, Sascha Abramson, Michael Klichinsky. Pre-clinical development of CAR Monocytes (CAR Mono) for solid tumor immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 582.

104 Development and characterization of human chimeric antigen receptor monocytes (CAR-Mono), a novel cell therapy platform

Background

Engineered cell therapies have demonstrated significant clinical activity against hematologic malignancies, but solid tumors remain an intractable challenge. We have previously developed a human chimeric antigen receptor macrophage (CAR-M) platform for adoptive cell therapy and shown potent anti-tumor activity in pre-clinical solid tumor models.1 CAR-M overcome critical solid tumor challenges such as tumor infiltration, immunosuppression within the tumor microenvironment, lymphocyte exclusion, and target antigen heterogeneity. Currently, CAR-M are generated in a week-long ex-vivo process in which peripheral blood monocytes are differentiated into macrophages prior to genetic manipulation. Here, we demonstrate the production feasibility, phenotype, pharmacokinetics, cellular fate, specificity, and anti-tumor activity of human CD14+ CAR monocytes.

Methods

Using the chimeric adenoviral vector Ad5f35, we engineered primary human CD14+ monocytes to express a CAR targeted against human epidermal growth factor receptor 2 (HER2) (CAR-mono). Using a partially automated approach, we established a process that allowed for same day manufacturing (from Leukopak to cryopreserved CAR-mono cell product).

Results

CAR expression and cell viability exceeded 90%, and cells efficiently differentiated into CAR-expressing macrophages. The adenoviral based gene modification method led to pre-conditioning of CAR-mono cells resulting in a strong M1 phenotype upon differentiation, and potent anti-tumor activity regardless of exposure to GM-CSF, M-CSF, or immunosuppressive factors. Treating CAR-mono cells with GM-CSF and IL-4 resulted in their differentiation to monocyte-derived CAR-DCs, indicating that these cells retain their myeloid differentiation potential. In vivo, CAR-mono treatment induced anti-tumor activity in various HER2+ solid tumor xenograft models. Following intravenous administration, CAR-mono demonstrated the ability to traffic to both GM-CSF < sup >high</sup > and GM-CSF< sup >low</sup >expressing tumors. Notably, CAR-mono showed long-term CAR expression and persistence (>100 days) in both NSG and NSG-S mouse models, demonstrating lasting persistence irrespective of human cytokine support.

Conclusions

The CAR-mono platform allows for a rapid, same-day manufacturing process while maintaining the key characteristics of CAR-M therapy. Ad5f35 engineered human monocytes are primed toward M1 macrophage differentiation and produce a cell population highly similar to our established CAR-M platform. Collectively, these findings provide strong pre-clinical support to advance the CAR-mono platform into clinical testing.

Reference

Klichinsky M, et al. Human chimeric antigen receptor macrophages for cancer immunotherapy. Nature Biotechnology March 2020.

Abstract 1530: Anti-HER2 CAR monocytes demonstrate targeted anti-tumor activity and enable a single day cell manufacturing process

Recent advances in cell therapy have led to significant efficacy in hematologic malignancies, but solid tumors remain an intractable challenge. We have previously developed a CAR macrophage (CAR-M) adoptive cell therapy platform and demonstrated potent anti-tumor activity in pre-clinical models. CAR-M overcome several of the barriers to efficacy in the solid tumor setting - trafficking, immunosuppression, lymphocyte exclusion, and antigen heterogeneity. Currently, CAR-M are generated via ex vivo differentiation of peripheral blood monocytes into macrophages prior to genetic manipulation. In order to streamline the manufacturing process, improve cell yields, and potentially improve tumor infiltration, we sought to evaluate the feasibility of directly engineering CD14+ monocytes to express CAR. Using the chimeric adenoviral vector Ad5f35, we engineered primary human CAR-monocytes to target tumors overexpressing HER2. CAR expression and viability both exceeded 90%. Anti-HER2 CAR-monocytes produced pro-inflammatory cytokines in response to antigen, specifically phagocytosed HER2 overexpressing target cells, and eradicated HER2-overexpressing tumor cells in a time and dose-dependent manner. CAR-monocytes efficiently differentiated into CAR-expressing macrophages in response to various maturation factors and cytokines within 3-5 days. Adenoviral based gene modification resulted in the upregulation of several pro-inflammatory markers on CAR-monocytes and pre-conditioned these cells to differentiate into M1 macrophages in the absence of exogenous M1 polarization factors. The M1 phenotype was maintained when CAR-monocytes were challenged with immunosuppressive cytokines in vitro. These cells demonstrated potent effector function after differentiation into macrophages, regardless of exposure to GM-CSF, M-CSF, or immunosuppressive factors. Anti-HER2 CAR monocytes carried broadly expressed myeloid chemokine receptors and responded to a panel of chemotactic factors. In order to optimize the cell manufacturing process associated with CAR-M, we established a closed-system, ultra-rapid CAR monocyte process. This process enabled same day manufacturing of the final CAR monocyte cell product, significantly reducing the cost of goods associated with autologous cell therapy as well as “vein to vein” time. This study demonstrated the successful development of CAR-monocytes with direct anti-tumor activity and capacity to differentiate into M1 polarized CAR-M. In addition, we established an ultra-rapid same-day CAR monocyte manufacturing process. The CAR-monocyte platform represents an advance in the field of adoptive cell therapy.

Citation Format: Linara Gabitova, Brett Menchel, Rashid Gabbasov, Stefano Pierini, Andrew Best, Kayleigh Ross, Yumi Ohtani, Daniel Blumenthal, Sascha Abramson, Thomas Condamine, Michael Klichinsky. Anti-HER2 CAR monocytes demonstrate targeted anti-tumor activity and enable a single day cell manufacturing process [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 1530.