Drug-drug conjugates self-assembled nanomedicines triggered photo−/immuno- therapy for synergistic cancer treatments

Although immunotherapies have made progress in cancer treatment, their clinical response rates vary widely and are typically low due to sparse immune cell infiltration (immune "cold") and suppressive tumor immune microenvironment (TIME). A simple yet effective approach that integrates a variety of immune-stimulating and TIME-modulating functions could potentially address this clinical challenge. Herein, we conjugate two small molecules, including a photosensitizer (pyropheophorbide-a, PA) and a Toll-like receptor 7/8 agonist (resiquimod, R848), into prodrug (PA-R848) that self-assembles into PA-R848 esterase responsive nanoparticles (PARE NPs) with 100% drug composition and synergistic photo−/immune- therapeutic effects. In PARE NPs, PA exhibits strong phototherapeutic effects which ablate the primary tumor directly and elicits immunogenic cell death (ICD) to promote the immune response. R848 effectively polarizes the M2-type tumor-associated macrophage (TAM) to M1-type TAM, consequently reversing the "cold" and suppressive TIME when working together with phototherapy. The PARE NPs can efficiently pare down the tumor development by two synergisms, including i) synergistic immunotherapy between ICD and TAM polarization; ii) and the antitumor effects between phototherapy and immunotherapy. On a head-neck squamous cell carcinoma mouse model, PARE NPs combined with PD-1 antibody eliminate primary tumors, and significantly inhibit the progress of distant tumors thanks to the robust antitumor immunity enhanced by the PARE NPs.