Hypoxia alleviation-triggered enhanced photodynamic therapy in combination with IDO inhibitor for preferable cancer therapy

Abstract Photodynamic therapy (PDT) has attracted growing attention in the field of cancer therapy due to its non-invasive intervention and initiation of antitumor immune responses by use of non-toxic photosensitizers (PS) and topical light irradiation. However, inherent hypoxia and immunosuppression mediated by checkpoints in tumors severally impair the efficacy of PDT and PDT-induced immunity. Herein, a multi-functional nanoplatform is rationally constructed by fluorinated polymer nanoparticle saturated with oxygen in advance, which simultaneously encapsulated PS (Ce6) and an indoleamine 2,3-dioxygenase (IDO) inhibitor (NLG919). In particular, the tumor hypoxic microenvironment is obviously relieved and much more reactive oxygen species (ROS) is generated by fluorinated nanoparticle compared with alkylated polymer nanoparticle as a control in vitro and in vivo , this is mainly because the fluorinated polymers are endowed with high oxygen carrying capacity which also contributed to the relief of hypoxia. Meanwhile, compared to PDT alone, the co-encapsulation of IDO inhibitor and PS can further greatly enhance efficacy for inhibiting the growth of primary and abscopal tumors via enhanced T cell infiltration. This study can provide a convenient and practical strategy for enhancing the therapeutic effect of PDT and relieving immune suppression, in turn affording clinical benefits for cancer treatment.