Abstract 5001: Personalized neoantigen/cancer-testis antigen nanovaccine for advanced solid tumors, a single-arm, open-label pilot study

Abstract Background: Neoantigens, derived from somatic mutations in tumor cells, have been identified as promising targets of immunotherapy. A personalized neoantigen/cancer-testis antigen (CTA) nanovaccine (PNVAC) platform has been established by us previously, and demonstrated its feasibility, safety and efficacy in preventing recurrence of high-risk resected gastric/gastroesophageal junction (G/GEJ) cancer in both preclinical and clinical studies. This study aims to explore the universality of PNVAC monotherapy or combined with anti-angiogenesis drugs or anti-programmed death 1 (PD-1) in patients with multiple advanced solid malignancies. Methods: Patient-specific neoantigens were selected based on tumor-specific mutations identified by whole-exome sequencing (WES) and RNA sequencing of paired blood and tumor tissues. Bioinformatic analysis for neoantigen prediction, including sequencing read filtering, human leukocyte antigen (HLA) typing and neoantigen filtering was performed. PNVAC is an amphiphiles nanovaccine loaded with multiple personalized neoantigens designed to induce specific T cell responses. PNVAC is administrated to patients with metastatic solid tumors on days 1, 4, 8, 15, 22, 43 (prime phase) and 64, 85 and 169 (boost phase) alone, or combined with anti-angiogenesis or anti-PD-1 drugs. Safety, immunogenicity and clinical efficacy are evaluated. Results: Of the 30 enrolled patients, no treatment-related severe adverse events (AEs) occurred and the vast majority of AEs were limited to grade 1-2, only 1 patient developed grade 3 thrombocytopenia. The objective response rate (ORR) was 26. 7% (8/30), including 2 cases of complete response (CR) and 6 cases of partial response (PR), and a disease control rate (DCR) of 66. 7% achieved. The median progression-free survival (PFS) was 9. 90 months (95% CI, 3. 46-16. 34 months), while the median overall survival (OS) was not reached (range, 0. 80-43. 53 months), and the estimated 1- and 2-year survival rates were 86. 2% and 60. 6%. Notably, among the 21 patients who had relapsed disease after previous ICB and/or anti-angiogenesis, disease control was asserted in 14 (66. 7%) of them (7 of SD, 5 of PR, 2 of CR). ORR of this set was 33. 3% (7/21), higher than that of all the enrolled patients (26. 7%), and the set without prior ICB and/or anti-angiogenesis treatment (11. 1%). For immune analysis, PNVAC elicited robust and persistent immune responses against neoantigens/CTAs. Additionally, peripheral T cells with a cytotoxic phenotype tended to increase after vaccination, and immune memory was also detected in some representative patients. Conclusions: These data supported the safety, immunogenicity, and efficacy of this regimen in patients with advanced solid malignancies, thus broadening the application and combined strategies of neoantigen-based vaccines. Clinical trial information: ChiCTR1800017319. Citation Format: Jia Wei, Qin Liu, Lijing Zhu, Jie Shao, Ju Yang, Guanghui Xu, Nandie Wu, Hanbing Wang, Rutian Li, Huizi Sha, Qiuping Xu, Jie Shen, Li Xie, Lifeng Wang, Juan Du, Lanqi Cen, Manman Tian, Lixia Yu, Baorui Liu. Personalized neoantigen/cancer-testis antigen nanovaccine for advanced solid tumors, a single-arm, open-label pilot study abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 5001.