Correlation of survival with tumor antigen expression in patients with newly diagnosed glioblastoma receiving a multi-epitope pulsed dendritic cell vaccine

2087 Background: This study evaluated the safety and immune responses to an autologous dendritic cell vaccine pulsed with class I peptides from tumor associated antigens (TAA) expressed on gliomas and overexpressed in their cancer stem cell population (ICT-107). These TAA epitodes AIM-2. TRP-2, HER2 and AIM-2, are also overexpressed on glioblastoma multiforme (GBM) cancer stem cells. Methods: TAA epitopes included HER2, TRP-2, gp100, MAGE-1, IL13Rα2, and AIM-2. HLA-A1 and/or HLA-A2 positive glioblastoma (GBM) patients with gross total resection were eligible. Mononuclear cells from leukapheresis were differentiated into dendritic cells, pulsed with TAA peptides, and administered intradermally three times at two-week intervals in the axilla region after a standard treatment with concurrent temozolomide (TMZ) and radiation therapy for newly diagnosed (ND-GBM). Results: Twenty-one patients were enrolled with 17 ND-GBM and three recurrent GBM patients and one brainstem glioma. Immune response data on 15 newly diagnosed patients showed 33% responders. TAA expression by qRT-PCR showed all patient tumors expressed at least three TAA with 75% expressing all six. Correlations of increased PFS and quantitative expression of MAGE1, AIM-2, gp100 and HER2 were observed. A decrease or absence of CD133 expression was seen in five patients who underwent a second resection. As of February 1, 2012, six of 16 ND-GBM patients showed no evidence of tumor recurrence (44-63 months). Median progressive free survival (PFS) in newly diagnosed patients was 16.9 months with a two-year PFS rate was 43.8% (95%CI,19.8-66.0 ). The median overall survival rate (OS) was 38.4 months and a two-year OS was 80.3% (95%CI,58.6-96.7). Conclusions: Expression of four ICT-107 targeted antigens in the pre-vaccine tumors correlated with prolonged overall survival and PFS in ND-GBM patients. The goal of targeting tumor antigens highly expressed on glioblastoma cancer stem cells is supported by the observation of decreased or absent CD133 expression in the recurrent areas of gadolinium-enhanced tumor.