Engineered CAR T cell therapy for solid tumors

The adoptive transfer of T cells redirected to tumor-associated antigens via transgenic expression of chimeric antigen receptors (CARs) has produced impressive clinical responses in patients with hematologic malignances. However the successful extension of this therapy to solid tumors has proven challenging due to i) the paucity of target antigens that are tumor selective, leading to a heightened risk of “on-target, off-tumor” toxicities and, ii) the suppressive tumor microenvironment, which subverts T cell effector function. Therefore, to overcome these limitations we have programmed T cells with a combination of receptors that recognize a gene expression pattern that is unique to the tumor site and whose endodomains deliver intracellular signals 1, 2 and 3 (antigen, co-stimulation and cytokine) required for optimal T cell activation and protection from suppressive factors present at the tumor site. The current presentation will not only highlight our T cell engineering improvements but also our process optimization, including the incorporation of the G-Rex device, to facilitate the clinical and commercial development of potentially curative therapie

CAR T cell therapy for breast cancer: harnessing the tumor milieu to drive T cell activation

Abstract Background The adoptive transfer of T cells redirected to tumor via chimeric antigen receptors (CARs) has produced clinical benefits for the treatment of hematologic diseases. To extend this approach to breast cancer, we generated CAR T cells directed against mucin1 (MUC1), an aberrantly glycosylated neoantigen that is overexpressed by malignant cells and whose expression has been correlated with poor prognosis. Furthermore, to protect our tumor-targeted cells from the elevated levels of immune-inhibitory cytokines present in the tumor milieu, we co-expressed an inverted cytokine receptor linking the IL4 receptor exodomain with the IL7 receptor endodomain (4/7ICR) in order to transform the suppressive IL4 signal into one that would enhance the anti-tumor effects of our CAR T cells at the tumor site. Methods First (1G - CD3ζ) and second generation (2G - 41BB.CD3ζ) MUC1-specific CARs were constructed using the HMFG2 scFv. Following retroviral transduction transgenic expression of the CAR±ICR was assessed by flow cytometry. In vitro CAR/ICR T cell function was measured by assessing cell proliferation and short- and long-term cytotoxic activity using MUC1+ MDA MB 468 cells as targets. In vivo anti-tumor activity was assessed using IL4-producing MDA MB 468 tumor-bearing mice using calipers to assess tumor volume and bioluminescence imaging to track T cells. Results In the IL4-rich tumor milieu, 1G CAR.MUC1 T cells failed to expand or kill MUC1+ tumors and while co-expression of the 4/7ICR promoted T cell expansion, in the absence of co-stimulatory signals the outgrowing cells exhibited an exhausted phenotype characterized by PD-1 and TIM3 upregulation and failed to control tumor growth. However, by co-expressing 2G CAR.MUC1 (signal 1 - activation + signal 2 - co-stimulation) and 4/7ICR (signal 3 - cytokine), transgenic T cells selectively expanded at the tumor site and produced potent and durable tumor control in vitro and in vivo. Conclusions Our findings demonstrate the feasibility of targeting breast cancer using transgenic T cells equipped to thrive in the suppressive tumor milieu and highlight the importance of providing transgenic T cells with signals that recapitulate physiologic TCR signaling – [activation (signal 1), co-stimulation (signal 2) and cytokine support (signal 3)] - to promote in vivo persistence and memory formation

Additional file 1: of CAR T cell therapy for breast cancer: harnessing the tumor milieu to drive T cell activation

Figure S1. Generation of 2nd generation CAR.MUC1 T cells. (A) Schematic of 2nd generation CAR.MUC1 (2G) retroviral construct. (B) Co-expression of 4/7ICR and 2G CAR as detected by mOrange and anti-IgG, respectively. Summary data (right panel) shows percentage of double-positive cells (mean ± SEM, n = 4). (PPTX 298 kb

Optimizing the production of suspension cells using the G-Rex “M” series

Broader implementation of cell-based therapies has been hindered by the logistics associated with the expansion of clinically relevant cell numbers ex vivo. To overcome this limitation, Wilson Wolf Manufacturing developed the G-Rex, a cell culture flask with a gas-permeable membrane at the base that supports large media volumes without compromising gas exchange. Although this culture platform has recently gained traction with the scientific community due to its superior performance when compared with traditional culture systems, the limits of this technology have yet to be explored. In this study, we investigated multiple variables including optimal seeding density and media volume, as well as maximum cell output per unit of surface area. Additionally, we have identified a novel means of estimating culture growth kinetics. All of these parameters were subsequently integrated into a novel G-Rex “M” series, which can accommodate these optimal conditions. A multicenter study confirmed that this fully optimized cell culture system can reliably produce a 100-fold cell expansion in only 10 days using 1L of medium. The G-Rex M series is linearly scalable and adaptable as a closed system, allowing an easy translation of preclinical protocols into the good manufacturing practice