Personalized peptide vaccines induce predicted T cell responses against signet ring cell carcinoma—a case report

T cell-based immunotherapies increasingly include personalized neoantigen vaccines that target tumor-specific mutations. However, despite their promise, current neoantigen vaccines show limited and unpredictable clinical benefit, with T cell responses observed in only a subset of patients. To overcome these limitations, we developed the VERDI (Vaccine Epitopes Ranked by Digital Intelligence) System—a cloud-based computational platform that integrates a patient’s human leukocyte antigen (HLA) class I and II genotype with selected tumor-associated antigens (TAAs), including cancer-testis antigens (CTAs), to identify peptides with high predicted immunogenicity and low risk of immune-related adverse events (irAEs). Using the VERDI System, we designed ten personalized peptide vaccines for a patient with metastatic signet ring cell carcinoma (SRCC), a rare and aggressive gastric cancer with limited treatment options. All ten VERDI vaccines were well tolerated and consistently induced tumor-specific T cell responses following a single administration, without the need for checkpoint inhibitors. The patient survived for 15 months—substantially longer than the reported median survival of 5.6 months in metastatic SRCC—highlighting the potential of this individualized, predictive vaccine platform to improve outcomes in advanced cancer.