Semiconducting polymer nano-PROTACs for activatable photo-immunometabolic cancer therapy

Immunometabolic intervention has been applied to treat cancer via inhibition of certain enzymes associated with intratumoral metabolism. However, small-molecule inhibitors and genetic modification often suffer from insufficiency and off-target side effects. Proteolysis targeting chimeras (PROTACs) provide an alternative way to modulate protein homeostasis for cancer therapy; however, the always-on bioactivity of existing PROTACs potentially leads to uncontrollable protein degradation at non-target sites, limiting their in vivo therapeutic efficacy. We herein report a semiconducting polymer nano-PROTAC (SPN pro ) with phototherapeutic and activatable protein degradation abilities for photo-immunometabolic cancer therapy. SPN pro can remotely generate singlet oxygen ( 1 O 2 ) under NIR photoirradiation to eradicate tumor cells and induce immunogenic cell death (ICD) to enhance tumor immunogenicity. Moreover, the PROTAC function of SPN pro is specifically activated by a cancer biomarker (cathepsin B) to trigger targeted proteolysis of immunosuppressive indoleamine 2,3-dioxygenase (IDO) in the tumor of living mice. The persistent IDO degradation blocks tryptophan (Trp)-catabolism program and promotes the activation of effector T cells. Such a SPNpro-mediated in-situ immunometabolic intervention synergizes immunogenic phototherapy to boost the antitumor T-cell immunity, effectively inhibiting tumor growth and metastasis. Thus, this study provides a polymer platform to advance PROTAC in cancer therapy. Proteolysis targeting chimeras (PROTACs) is an effective alternative to modulate protein homeostasis but can lead to uncontrollable protein degradation and off-target side effects. Here, the authors developed semiconducting polymer nano-PROTACs with phototherapeutic and activatable protein degradation abilities for photo-immunometabolic cancer therapy.