Background: Clinically, prophylactic anti-recurrence treatments for hepatocellular carcinoma (HCC) patients after radical surgery are extremely limited. Neoantigen based vaccine can generate robust anti-tumor immune response in several solid tumors but whether it could induce anti-tumor immune response in HCC and serve as a safe and effective prophylactic strategy for preventing postoperative HCC recurrence still remain largely unclear.Methods: Personalized neoantigen vaccine was designed and immunized for 10 HCC patients with high risk of postoperative recurrence in a prime-boost schedule. The safety and immune response were assessed through adverse events, tissue sequencing, ELISpot, TCR sequencing. The clinical response was evaluated by recurrence-free survival (RFS) and personalized circulating tumor DNA (ctDNA) sequencing.Results: In the 10 enrolled patients, no obvious adverse events were observed during neoantigen vaccinations. Until the deadline of clinical trial, 8 of 10 patients were confirmed with clinical relapse by imaging, the other 2 patients remained relapse-free. From receiving first neoantigen vaccination, the median RFS of 10 patients were 7.4 months. Among 7 patients received all planned neoantigen vaccinations, 5 of them demonstrated neoantigen-induced T cell responses and have significantly longer RFS after radical surgery than other 5 patients without responsive neoantigens or only with prime vaccination and propensity scores matching control patients (p = 0.035). Moreover, tracking personalized neoantigen mutations in ctDNA could provide real-time evaluation of clinical response in HCC patients during neoantigen vaccination and follow up.Conclusion: Personalized neoantigen vaccine is proved as a safe, feasible and effective strategy for HCC anti-recurrence, and its progression could be sensitively monitored by corresponding neoantigen mutations in ctDNA, and thus provided solid information for individualized medicine in HCC.Trial registration: This study was registered at Chinese Clinical Trial Registry; Registration number:ChiCTR1900020990.

Hepatocellular carcinoma (HCC) commonly emerges in an immunologically “cold” state, thereafter protects it away from cytolytic attack by tumor‐infiltrating lymphocytes, resulting in poor response to immunotherapy. Herein, an acidic/photo‐sensitive dendritic cell (DCs)‐based neoantigen nano‐vaccine has been explored to convert tumor immune “cold” state into “hot”, and remodel tumor‐associated neutrophils to potentiate anticancer immune response for enhancing immunotherapy efficiency. The nano‐vaccine is constructed by SiPCCl₂‐hybridized mesoporous silica with coordination of Fe(III)‐captopril, and coating with exfoliated membrane of matured DCs by H22‐specific neoantigen stimulation. The nano‐vaccines actively target H22 tumors and induce immunological cell death to boost tumor‐associated antigen release by the generation of excess ¹O₂ through photodynamic therapy, which act as in situ tumor vaccination to strengthen antitumor T‐cell response against primary H22 tumor growth. Interestingly, the nano‐vaccines are also home to lymph nodes to directly induce the activation and proliferation of neoantigen‐specific T cells to suppress the primary/distal tumor growth. Moreover, the acidic‐triggered captopril release in tumor microenvironment can polarize the protumoral N2 phenotype neutrophils to antitumor N1 phenotype for improving the immune effects to achieve complete tumor regression (83%) in H22‐bearing mice and prolong the survival time. This work provides an alternative approach for developing novel HCC immunotherapy strategies.