High expression of indoleamine 2,3-dioxygenase 1 (IDO1) is a major cause of tumor induced immunosuppression, and appears to be associated with poor prognosis in human colorectal cancer and some others. In this study, we construct a bifunctional liposome by self-assembly of oxaliplatin-prodrug (Oxa(IV)) conjugated phospholipid and alkylated NLG919 (aNLG), an IDO1 inhibitor, together with other commercial lipids. The obtained aNLG/Oxa(IV)-Lip can not only release cytotoxic oxaliplatin inside the reductive cytosol to trigger immunogenic cell death (ICD) of cancer cells, but also efficiently retard the degradation of tryptophan to immunosuppressive kynurenine via the NLG919 mediated inhibition of IDO1. Moreover, in vivo pharmacokinetic studies indicate that such aNLG/Oxa(IV)-Lip has a long blood circulation time, thereby enables highly-efficient passive tumor homing. Upon tumor accumulation, such aNLG/Oxa(IV)-Lip presents superior synergistic antitumor efficacies to both subcutaneous and orthotopic CT26 tumors, ascribing to significantly primed anti-tumor immunity of enhanced intratumoral infiltration of CD8+ T cells, scretion of cytotoxic cytokines and downregulation of immunosuppressive regulatory T cells. This work highlights that such bifunctional aNLG/Oxa(IV)-Lip is a potent candidate for future clinical translation owing to its excellent biocompatibility and high therapeutic efficacy.
Keywords: Chemo-immunotherapy; Colorectal cancer; IDO inhibition; Modulation of immunosuppressive tumor microenvironment; Oxaliplatin prodrug.
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