Programmed cell death protein 1 (PD-1) inhibitors have modest efficacy as a monotherapy in hepatocellular carcinoma (HCC). A personalized therapeutic cancer vaccine (PTCV) may enhance responses to PD-1 inhibitors through the induction of tumor-specific immunity. We present results from a single-arm, open-label, phase 1/2 study of a DNA plasmid PTCV (GNOS-PV02) encoding up to 40 neoantigens coadministered with plasmid-encoded interleukin-12 plus pembrolizumab in patients with advanced HCC previously treated with a multityrosine kinase inhibitor. Safety and immunogenicity were assessed as primary endpoints, and treatment efficacy and feasibility were evaluated as secondary endpoints. The most common treatment-related adverse events were injection-site reactions, observed in 15 of 36 (41.6%) patients. No dose-limiting toxicities or treatment-related grade ≥3 events were observed. The objective response rate (modified intention-to-treat) per Response Evaluation Criteria in Solid Tumors 1.1 was 30.6% (11 of 36 patients), with 8.3% (3 of 36) of patients achieving a complete response. Clinical responses were associated with the number of neoantigens encoded in the vaccine. Neoantigen-specific T cell responses were confirmed in 19 of 22 (86.4%) evaluable patients by enzyme-linked immunosorbent spot assays. Multiparametric cellular profiling revealed active, proliferative and cytolytic vaccine-specific CD4⁺ and CD8⁺ effector T cells. T cell receptor β-chain (TCRβ) bulk sequencing results demonstrated vaccination-enriched T cell clone expansion and tumor infiltration. Single-cell analysis revealed posttreatment T cell clonal expansion of cytotoxic T cell phenotypes. TCR complementarity-determining region cloning of expanded T cell clones in the tumors following vaccination confirmed reactivity against vaccine-encoded neoantigens. Our results support the PTCV’s mechanism of action based on the induction of antitumor T cells and show that a PTCV plus pembrolizumab has clinical activity in advanced HCC. ClinicalTrials.gov identifier: NCT04251117.

程序性细胞死亡蛋白 1 (PD-1) 抑制剂作为单一疗法治疗肝细胞癌 (HCC) 的疗效有限。个性化治疗性癌症疫苗 (PTCV) 可以通过诱导肿瘤特异性免疫来增强对 PD-1 抑制剂的反应。我们展示了一项单臂、开放标签、1/2 期研究的结果，该研究针对编码多达 40 种新抗原的 DNA 质粒 PTCV (GNOS-PV02) 与质粒编码的白细胞介素 12 加派姆单抗共同给药于既往接受过治疗的晚期 HCC 患者与多酪氨酸激酶抑制剂。安全性和免疫原性作为主要终点进行评估，治疗效果和可行性作为次要终点进行评估。最常见的治疗相关不良事件是注射部位反应，在 36 名患者中观察到 15 名 (41.6%)。未观察到剂量限制性毒性或治疗相关的≥3级事件。根据实体瘤疗效评估标准 1.1 的客观缓解率为 30.6%（36 名患者中的 11 名），其中 8.3%（36 名患者中的 3 名）达到完全缓解。临床反应与疫苗中编码的新抗原的数量有关。通过酶联免疫吸附斑点测定，22 名可评估患者中的 19 名 (86.4%) 证实了新抗原特异性 T 细胞反应。多参数细胞分析揭示了活性、增殖性和溶细胞性疫苗特异性 CD4 ⁺和 CD8 ⁺效应 T 细胞。 T 细胞受体 β 链 (TCRβ) 批量测序结果表明，疫苗接种后 T 细胞克隆扩增和肿瘤浸润。单细胞分析揭示了细胞毒性 T 细胞表型的治疗后 T 细胞克隆扩增。疫苗接种后肿瘤中扩增的 T 细胞克隆的 TCR 互补决定区克隆证实了针对疫苗编码的新抗原的反应性。我们的结果支持 PTCV 基于抗肿瘤 T 细胞诱导的作用机制，并表明 PTCV 联合派姆单抗在晚期 HCC 中具有临床活性。 ClinicalTrials.gov 标识符：NCT04251117。