Engineering CD4+ T cells to develop a novel immunotherapy for pancreatic cancer

Project Summary: Pancreatic ductal adenocarcinoma (PDAC) is a solid tumor with limited treatment options and a dismal five-year survival rate of only 12%, necessitating the development of improved therapeutics for this malignancy. While cancer immunotherapy has shown promise in hematological malignancies and some solid tumors, the

application of chimeric antigen receptor (CAR) T cell therapy in PDAC faces obstacles due to its unique characteristics, including desmoplastic stroma and poor T cell infiltration (work by Dr. Lesinski, sponsor). To overcome these challenges, we propose a groundbreaking approach: using CD4+ T cells expressing high levels

of the enzymatically active molecule CD26 and engineering them with a mesothelin-directed CAR. Previous work from the Paulos lab (co-sponsor) has demonstrated that CD26 marks T cells with favorable properties, making them an ideal template for CAR engineering. CD26's enzymatic activity in degrading immunosuppressive

peptides holds promise for remodeling the tumor microenvironment and limiting the myeloid-dominant features in PDAC. We hypothesize that by engineering CD26+CD4+CAR T cells with a mesothelin-targeted CAR (Meso- CAR), we can enhance PDAC immunotherapy efficacy. Preliminary data support this hypothesis, with

CD26+CD4+Meso-CAR T cells showing robust activity against PDAC and other mesothelin-positive tumors in mice. Aim 1 of this grant will focus on assessing the impact of CD26+CD4+Meso-CAR T cells upon remodeling the tumor microenvironment (TME), including chemokines and myeloid cells that are likely altered by the CD26

enzyme. We will use systemic inhibition and genetic knockout of CD26 to determine the importance of its enzymatic activity in TME modulation. Aim 2 will elucidate how CD26+CD4+Meso-CAR T cells engage the endogenous immune response and enhance the efficacy of co-administered, purified CD8+CAR T cells in both

immune-competent and immune-deficient mouse models. The rationale for both aims lies in understanding the interactions between CD26+CD4+Meso-CAR T cells and the endogenous immune response within the complex PDAC microenvironment. We propose to deepen this understanding by using congenic orthotopic mouse models

to systematically evaluate the efficacy of CD26+CD4+Meso-CAR T cells and/or CD8+Meso-CAR T cells with variable CD26 activity (Aim 1) and with alterations in the endogenous host immune system presence (Aim 2). The anticipated impact of our findings is significant, providing proof-of-principle pre-clinical data supporting the

development of CD26+CD4+ based cell therapy approaches for PDAC patients. Because CD26's enzymatic action on immunosuppressive peptides may mitigate myeloid-dominant features in PDAC tumors, this approach offers a promising avenue to improve outcomes in other challenging solid tumors. While we utilize mesothelin

as the target antigen in this proposal, the approach is adaptable to other antigens or neoantigens in PDAC and other solid tumors. Collectively, we seek to validate and characterize an innovative CD26+CAR T cell therapy as a platform that can be used to revolutionize solid tumor immunotherapies in the future.