Safety and antibody immune response of CHP-NY-ESO-1 vaccine combined with poly-ICLC in advanced or recurrent esophageal cancer patients.

The nanoparticle complex of cholesteryl pullulan (CHP) and NY-ESO-1 antigen protein (CHP-NY-ESO-1) presents multiple epitope peptides to MHC class I and II pathways, leading to CD8+ and CD4+ T cell responses. Poly-ICLC is a synthetic, double-stranded RNA, an agonist of toll-like receptor (TLR)-3, and a cytoplasmic receptor of melanoma differentiation-associated gene (MDA)-5. It should be a suitable immune adjuvant of cancer vaccine to overcome the inhibitory tumor microenvironment. We conducted a phase 1 clinical trial of CHP-NY-ESO-1 with poly-ICLC in patients with advanced or recurrent esophageal cancer. CHP-NY-ESO-1/poly-ICLC (µg/mg) was administered at a dose of 200/0.5 or 200/1.0 (cohorts 1 and 2, respectively) every 2 weeks for a total of six doses. The primary endpoints were safety and immune response. The secondary endpoint was tumor response. In total, 16 patients were enrolled, and six patients in each cohort completed the trial. The most common adverse event (AE) was injection site skin reaction (86.7%). No grade 3 or higher drug-related AEs were observed. No tumor responses were observed, and three patients (30%) had stable disease. The immune response was comparable between the two cohorts, and all patients (100%) achieved antibody responses with a median of 2.5 vaccinations. Comparing CHP-NY-ESO-1 alone to the poly-ICLC combination, all patients in both groups exhibited antibody responses, but the titers were higher in the combination group. In a mouse model, adding anti-PD-1 antibody to the combination of CHP-NY-ESO-1/poly-ICLC suppressed the growth of NY-ESO-1-expressing tumors. Combining the vaccine with PD-1 blockade holds promise in human trials.