Novel engineered regulatory macrophages combined with ICIs for post-transplant recurrence after liver transplantation for HCC.

e14582 Background: Liver transplantation is the most effective treatment for early-stage hepatocellular carcinoma (HCC), but post-transplant recurrence limits the efficacy of surgery and affects the patient prognosis. Most of the current attempts to apply immune checkpoint inhibitors (ICIs) to posttransplant recurrence have resulted in either acute allograft rejection or tumor progression, which may be related to the disruption of the immune balance that maintains immune tolerance and enhances immune activation. Methods: Therefore, we constructed an engineered regulatory macrophages (Mregs) with anti-tumor capacity in the transplant setting using reprogrammed liposomes to precisely regulate the immune microenvironment of post-transplant recurrence, in order to create suitable conditions for the safe use of ICIs. Results: Experimentally, Mregs were shown to prolonged allograft survival without promoting tumor development. Through fusing with the Mregs membrane, reprogrammed liposomes insert an anti-CD47 lipid shell onto the surface, enhancing phagocytosis against tumor. The drug-loaded inner core entered into the cytoplasm to reprogram Mregs. Tomivosertib downregulated the expression of PD-L1 and attenuated the immunosuppressive effect. Pexidartinib inhibited the polarization of the M2 pathway and upregulated the expression of CD80, CD86, and MHC II, enhancing the ability of antigen presentation. Combination with anti-PD-L1 antibodies can enhance anti-tumor effect without accelerating allograft rejection. Both in vivo and in vitro results demonstrate that engineered Mregs provide conditions for the safe use of anti-PD-L1 antibodies in the context of transplantation. Conclusions: Engineered Mregs combined with ICIs enhances immunotherapeutic efficacy and provides a viable therapeutic approach for posttransplant recurrence after liver transplantation for HCC.