A breast cancer targeted photodynamic degrader to activate immunotherapy through EGFR degradation mediated PD-L1 downregulation.

• Development of photodynamic degrader targeting breast cancer through EGFR. • Targeted degradation of EGFR using afatinib and ROS produced in situ. • EGFR inhibition mediated PD-L1 downregulation to reverse immunosuppression. • Immunogenic induction and intensive immune activation for metastatic tumor eradication. Spatiotemporal downregulation of immune checkpoint provides a promising strategy to activate anti-tumor immunity. In this work, a breast cancer targeted photodynamic degrader (designated as EIpro) is constructed to activate immunotherapy through EGFR degradation mediated PD-L1 downregulation. To be specific, we develop a chimeric peptide, comprising the photosensitizer Protoporphyrin IX (PpIX) and EGFR targeting peptide (QRHKPRE), to encapsulate an EGFR inhibitor afatinib (AFA) forming nanomicelle, namely EIpro. EIpro has a favorable stability and uniform nanosize distribution, preferring to accumulate in EGFR overexpressed breast cancer cells to amplify the chemotherapeutic effect and photodynamic elimination behavior. More interestingly, photodynamic therapy (PDT) produced reactive oxygen species (ROS) is able to damage breast cancer cells and induce immunogenic cell death (ICD) to release tumor associated antigens (TAAs), thereby degrading the nearby EGFR to downregulate PD-L1 and activate anti-tumor immunity. Beneficially, the multi-synergistic effects of EIpro show a robust therapeutic efficacy against primary and metastatic breast cancer with negligible systemic toxicity. This work provides a spatiotemporal strategy for protein degradation, which might inspire the development of sophisticated nanomedicine for effective tumor treatment. [ABSTRACT FROM AUTHOR]