Chemoimmunotherapy is reported to activate a robust T cell antitumor immune response by triggering immunogenic cell death (ICD), which has initiated a number of clinical trials. However, current chemoimmunotherapy is restricted to a small fraction of patients due to low drug delivery efficacy and immunosuppression within the tumor microenvironment. A tumor microenvironment‐activatable prodrug vesicle for cancer chemoimmunotherapy using ICD is herein reported. The prodrug vesicles are engineered by integrating an oxaliplatin (OXA) prodrug and PEGylated photosensitizer (PS) into a single nanoplatform, which show tumor‐specific accumulation, activation, and deep penetration in response to the tumoral acidic and enzymatic microenvironment. It is demonstrated that codelivery of OXA prodrug and PS can trigger ICD of the tumor cells by immunogenic cells killing. The combination of prodrug vesicle‐induced ICD with Î ± CD47‐mediated CD47 blockade further facilitates dendritic cell (DC) maturation, promotes antigen presentation by DCs, and eventually propagates the antitumor immunity of ICD. CD47 blockade and ICD induction efficiently inhibit the growth of both primary and abscopal tumors, suppress tumor metastasis, and prevent tumor recurrence. Collectively, these results imply that boosting antitumor immunity using ICD induction and suppressing tumor immune evasion via CD47 blockade might be promising for improved cancer chemoimmunotherapy.

Checkpoint blockade immunotherapy is promising for clinical treatment of various malignant tumors. However, checkpoint blockade immunotherapy suffers from a low response rate due to insufficient tumor immunogenicity and the immunosuppressive tumor microenvironment (ITM). In this study, a tumor-microenvironment-activatable binary cooperative prodrug nanoparticle (BCPN) is rationally designed to improve immunotherapy by synergistically modulating the immune tumor microenvironment. BCPN is purely constructed from a tumor acidity and reduction dual-responsive oxaliplatin (OXA) prodrug for triggering immunogenic cell death (ICD) and eliciting antitumor immunity, and a reduction-activatable homodimer of NLG919 for inactivating indoleamine 2,3-dioxygenase 1, which is a key regulator for ITM. Upon tumor-acidity-triggered cleavage of the poly(ethylene glycol) shell, PN shows negative to positive charge switch for enhanced tumor accumulation and deep penetration. OXA and NLG919 are then activated in the tumor cells via glutathione-mediated reduction. It is demonstrate that activated OXA promotes intratumoral accumulation of cytotoxic T lymphocytes by triggering ICD of cancer cells. Meanwhile, NLG919 downregulates IDO-1-mediated immunosuppression and suppresses regulatory T cells. Most importantly, PN shows much higher efficiency than free OXA or the combination of free OXA and NLG919 to regress tumor growth and prevent metastasis of mouse models of both breast and colorectal cancer.

Photodynamic therapy (PDT) has emerged as a promising clinical modality for cancer therapy due to its ability to initiate an antitumor immune response. However, PDT-mediated cancer immunotherapy is severely impaired by tumor-cell immunosuppression of host T cell antitumor activity through the programmed cell death 1 ligand (PD-L1) and programmed cell death receptor 1 (PD-1) (PD-L1-PD-1) immune checkpoint pathway. Here, we demonstrate that PDT-mediated cancer immunotherapy can be augmented by PD-L1 knockdown (KD) in tumor cells. We rationally designed a versatile micelleplex by integrating an acid-activatable cationic micelle, photosensitizer (PS), and small interfering RNA (siRNA). The micelleplex was inert at physiological pH conditions and activated only upon internalization in the acidic endocytic vesicles of tumor cells for fluorescence imaging and PDT. Compared to PDT alone, the combination of PDT and PD-L1 KD showed significantly enhanced efficacy for inhibiting tumor growth and distant metastasis in a B16-F10 melanoma xenograft tumor model. These results suggest that acid-activatable micelleplexes utilizing PDT-induced cancer immunotherapy are more effective when combined with siRNA-mediated PD-L1 blockade. This study could provide a general strategy for enhancing the therapy efficacy of photodynamic cancer therapy.