Effect Of Dexamethasone In Glioblastoma (Gbm) Patients On Systemic And Intratumoral T-Cell Responses Induced By Personalized Neoantigen-Targeting Vaccine.

2020Background: The impact of individualized neoepitope vaccination targeting neoantigens arising from tumor-specific mutations for GBM, a low mutation burden tumor with an immunologically cold tumor microenvironment, as well as that of concurrently administered dexamethasone (dex), are unknown. Methods: Individualized vaccination of up to 20 synthetic, long neoepitope peptides with high predicted HLA binding affinity admixed with poly-ICLC, were administered subcutaneously using a prime-boost schedule after RT to newly diagnosed, MGMT unmethylated, at least partially resected, GBM patients without progression after radiation (RT) in our phase 1b study. Results: 9 of 10 screened patients had sufficient (≥ 10) identified neoepitope peptides. 8 patients without progression after RT received vaccine consisting of a median of 12 peptides (range, 7-20) beginning a median of 18.6 wks (range 16.0-23.2) after surgery. Adverse events were limited to infrequent grade 1/2 local reactions and fatigue. Median PFS and ...