Abstract A37: Development and future of CAR T cell therapy for pancreatic ductal adenocarcinoma and triple negative breast cancer
Authors: Mukherjee Pinku , Zhou Ru , Yazdanifar Mahboubeh , Lopamudra Das Roy 
Published: December 2017

Rationale and Background: Immunotherapy of cancer has gained much attention in the past decade with the development of immune checkpoint inhibitors and chimeric antigen receptor (CAR) technology that can activate and redirect patient T cells to kill tumors that over-express a specific antigen. CARs are fusion receptors that are comprised of an antibody-derived single-chain variable fragment (scFv) coupled via hinge and transmembrane elements to a T cell signaling and co-stimulatory domain. This technology is in its early stages of development and has not been fully exploited for the treatment of metastatic epithelial cancers. We focus our studies on Pancreatic Ductal Adenocarcinomas (PDAC) and Triple Negative Breast Cancer (TNBC). However, if successful, the studies will be applicable to other epithelial tumors. For CAR-T cells to work, and to avoid off target toxicities, both the target antigen and the antibody recognizing the target have to be highly specific. The challenge is that there are few such antigen-antibody combinations for solid tumors. We have recently developed a novel patented antibody (designated TAB 004) that specifically recognizes ONLY the tumor-associated form of MUC1 (tMUC1) but not the normal form of MUC1 (nMUC1) in several subtypes of breast cancers including TNBC and in PDAC. We show compelling data that TAB004 recognizes tMUC1 in &gt;90% of human TNBCs and 85% of PDAC but spares all normal epithelial tissues. The antigenic isoform that TAB004 recognizes is completely hidden in normal epithelia making it extremely safe for development of CAR-T cells.

Hypothesis: TNBC and PDAC can be specifically targeted with the tMUC1-CAR-engineered T cells, whilst sparing normal organs.

Methodology and Results: We have engineered several TAB-specific CAR constructs using the scFv fragment of TAB 004. Six constructs are developed, 3 for human T cells and 3 for mouse T cells: 1. TAB- CD28-CD3zeta (2nd generation CAR), 2. TAB-CD28-41BB-CD3zeta (3rd generation CAR), and 3. TAB-CD28-OX40-CD3zeta (3rd generation CAR). Data shows that we can successfully engineer human T cells to express the TAB-CAR on their surface and that these engineered T cells can bind specifically to tumor cells expressing the unique tMUC1 epitope, become activated, and effectively kill the tumor cells. We show that these engineered T cells only minimally bind and kill normal epithelial cell lines. However, some of the cell lines are more resistant than others. We are therefore conducting combination therapy with various drugs that are known to enhance immune based therapies including checkpoint inhibitors, COX-2 inhibitors, cyclophosphamide and others. We may also have data to show that the engineered TAB-CAR T cells kill tMUC1-expressing TNBC and PDAC cells in vivo. We will show data that TAB-CAR-T cell kill human PDAC and TNBC cells in vitro and propose to conduct the same in vivo xenograft model of human PDAC and metastatic TNBC. In the following months, we will test if TAB-CAR-T cell retards tumor growth in an orthotopic syngeneic mouse model of PDAC and metastatic BC in human MUC1.Tg immune competent mice. We further propose to demonstrate that the TAB-CAR-T cell can mediate apoptosis in the immune competent KCM mice (KC X human MUC1.Tg mice) that develop spontaneous PDAC and the MMT mice (PyVMT X human MUC1.Tg mice) that develop spontaneous mammary gland tumors. Both models mimic the human disease progression and express human MUC1 in a tissue specific manner. This is important since all normal epithelia in these mice express the nMUC1 except the tumors that expresses the target, tMUC1.

Impact: If successful, this project will have a major impact and accelerate progress toward a clinical trial for PDAC and metastatic TNBC. This will be the first attempt to test the efficacy of a CAR-T cell in an immune competent, human MUC1.Tg mouse model that develops spontaneous tumors within the appropriate stromal and hormonal microenvironment.

Citation Format: Pinku Mukherjee, Ru Zhou, Mahboubeh Yazdanifar, Das Roy Lopamudra. Development and future of CAR T cell therapy for pancreatic ductal adenocarcinoma and triple negative breast cancer [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr A37.