Therapeutic advantage of combinatorial CAR T cell and chemo-therapies.

Chimeric antigen receptor (CAR) T cell therapies have transformed outcomes for many patients with hematological malignancies. However, some patients do not respond to CAR T cell treatment, and adapting CAR T cells for solid and brain tumors has been met with many challenges including a hostile tumor microenvironment and poor CAR T cell persistence. Thus, it is unlikely that CAR T cell therapy alone will be sufficient for consistent, complete tumor clearance across cancer patients. Combinatorial therapies of CAR T cells and chemotherapeutics are a promising approach for overcoming this as chemotherapeutics could augment CAR T cells for improved anti-tumor activity or work in tandem with CAR T cells to clear tumors. Herein, we review efforts towards achieving successful CAR T cell and chemical drug combination therapies. We focus on combination therapies with approved chemotherapeutics as these will be more easily translated to the clinic, but also review non-approved chemotherapeutics and drug screens designed to reveal promising new CAR T cell and chemical drug combinations. Together, this review highlights the promise of CAR T cell and chemotherapy combinations with specific focus on how combinatorial therapy overcomes challenges faced by either monotherapy and supports the potential of this therapeutic strategy to improve outcomes for cancer patients. Significance Statement Improving currently available CAR T cell products via combinatorial therapy with chemotherapeutics has the potential to drastically expand the types of cancers and number of patients that could benefit from these therapies when neither alone has been sufficient to achieve tumor clearance. Herein, we provide a thorough review of the current efforts towards studying CAR T and chemotherapy combinatorial therapies and provide perspectives on optimal ways to identify new and effective combinations moving forward.