Enhancing immunotherapy with tumour-responsive nanomaterials

Abstract

The targeted delivery of immunotherapies to tumours using tumour-responsive nanomaterials is a promising area of cancer research with the potential to address the limitations of systemic administration such as on-target off-tumour toxicities and a lack of activity owing to the immunosuppressive tumour microenvironment (TME). Attempts to address these challenges include the design and functionalization of nanomaterials capable of releasing their cargoes in response to specific TME characteristics, thus facilitating the targeted delivery of immune-checkpoint inhibitors, cytokines, mRNAs, vaccines and, potentially, chimaeric antigen receptors as well as of agents that modulate the extracellular matrix and induce immunogenic cell death. In this Review, we describe these various research efforts in the context of the dynamic properties of the TME, such as pH, reductive conditions, reactive oxygen species, hypoxia, specific enzymes, high levels of ATP and locoregional aspects, which can be leveraged to enhance the specificity and efficacy of nanomaterial-based immunotherapies. Highlighting preclinical successes and ongoing clinical trials, we evaluate the current landscape and potential of these innovative approaches. We also consider future research directions as well as the most important barriers to successful clinical translation, emphasizing the transformative potential of tumour-responsive nanomaterials in overcoming the barriers that limit the activity of traditional immunotherapies, thus improving patient outcomes. Immunotherapies, predominantly immune-checkpoint inhibitors and chimaeric antigen receptor T cells, have transformed oncology. Nonetheless, these systemically administered agents have several limitations, including the risk of off-target toxicities and a lack of activity owing to an inability to overcome an immunosuppressive tumour microenvironment (TME). In this Review, the authors describe the potential to overcome these challenges using functionalized nanomaterials that are designed to release a wide range of immunotherapeutic cargoes in response to specific TME characteristics, including hypoxia, differences in pH, the presence of specific enzymes, reactive oxygen species and/or high levels of extracellular ATP.