ROBUST INDUCTION OF TYPE-1 CD8+ T-CELL RESPONSES IN WHO GRADE II LOW-GRADE GLIOMA PATIENTS RECEIVING PEPTIDE-BASED VACCINES IN COMBINATION WITH POLY-ICLC

Abstract

BACKGROUND: WHO grade II low-grade gliomas (LGGs) with high risk factors for recurrence aremostly lethal despite current treatments, and novel approaches are needed. We conducted a phase I study to evaluate the safety and immunogenicity of subcutaneous vaccinations with synthetic peptides for glioma-associated antigen (GAA) epitopes in human leukocyte antigen (HLA)-A2+ adults with high-risk LGGs in the following three cohorts: 1) newly diagnosed patients without prior radiation therapy (RT); 2) newly diagnosed patients with prior RT, and 3) recurrent patients. METHODS: GAAs were interleukin-13 receptor (IL-13R)α2, EphA2, Wilms Tumor (WT)1, and Survivin, and synthetic peptides were emulsified in Montanide-ISA-51 and given every 3 weeks for 8 courses within tramuscular injections of Toll-like receptor 3 agonist Polyinosinic-Polycytidylic Acid Stabilized by Lysine and Carboxymethylcellulose (poly-ICLC), followed by q12-week booster vaccines. Primary endpoints were safety and CD8+ T-cell responses against vaccine-targeted GAAs. RESULTS: Cohorts 1, 2, and 3 enrolled 12, 1, and 10 patients, respectively. No regimen-limiting toxicity has been encountered except for one case with Common Terminology Criteria for Adverse Events (CTCAE) Grade 3 fever (Cohort 1). Enzyme-linked Immuno-SPOT (ELISPOT) assays demonstrated robust and sustained interferon (IFN)-γ responses against at least 3 of the 4 GAA epitopes in 10 and 4 cases of Cohorts 1 and 3, respectively. Cohort 1 patients demonstrated significantly higher IFN-γ ELISPOT responses than Cohort 3 patients, suggesting newly diagnosed patients have superior vaccine-responsiveness to recurrent patients. IFN-γ ELISPOT response levels in this study is significantly higher than those observed in our previous phase I/II study in high-grade glioma patients (Okada et al. JCO 2011). Furthermore, IFN-γ ELISPOT response levels were significantly higher than those for IL-5, indicating effective type-1 skewing by the current regimen. Median progression-free survival (PFS) periods are 21 months (Cohort 1; since diagnosis; range 10-42) and 12 months (Cohort 3; since the 1st vaccine; range 3-26).The only patient with large astrocytoma in Cohort 2 has been progression-free for over 58 months since diagnosis. There was a positive trend between IFN-γ ELISPOT responses and progression-free survival (PFS) in Cohort 3 patients (P = 0.08 by The Cox proportional hazards model). CONCLUSIONS: The current regimen is well tolerated and induces robust GAA-specific responses in WHO grade IILGG patients. These results suggest these patients may be suitable populations for vaccine therapy and warrant further evaluations of this approach.