Effective γδ T‐cell clinical therapies: current limitations and future perspectives for cancer immunotherapy

Abstract

Abstract γδ T cells are a unique subset of T lymphocytes, exhibiting features of both innate and adaptive immune cells and are involved with cancer immunosurveillance. They present an attractive alternative to conventional T cell‐based immunotherapy due, in large part, to their lack of major histocompatibility (MHC) restriction and ability to secrete high levels of cytokines with well‐known anti‐tumour functions. To date, clinical trials using γδ T cell‐based immunotherapy for a range of haematological and solid cancers have yielded limited success compared with in vitro studies. This inability to translate the efficacy of γδ T‐cell therapies from preclinical to clinical trials is attributed to a combination of several factors, e.g. γδ T‐cell agonists that are commonly used to stimulate populations of these cells have limited cellular uptake yet rely on intracellular mechanisms; administered γδ T cells display low levels of tumour‐infiltration; and there is a gap in the understanding of γδ T‐cell inhibitory receptors. This review explores the discrepancy between γδ T‐cell clinical and preclinical performance and offers viable avenues to overcome these obstacles. Using more direct γδ T‐cell agonists, encapsulating these agonists into lipid nanocarriers to improve their pharmacokinetic and pharmacodynamic profiles and the use of combination therapies to overcome checkpoint inhibition and T‐cell exhaustion are ways to bridge the gap between preclinical and clinical success. Given the ability to overcome these limitations, the development of a more targeted γδ T‐cell agonist‐checkpoint blockade combination therapy has the potential for success in clinical trials which has to date remained elusive.

Keywords

• bisphosphonates
• combination therapy
• immunotherapy
• lipid nanocarriers
• nanomedicine
• γδ T cells