Immune responses and association with clinical outcome of advanced colorectal cancer patients treated with the multi-peptide vaccine IMA910.

2522 Background: IMA910 is a novel multi-peptide cancer vaccine consisting of 10 HLA class I and 3class II tumor-associated peptides (TUMAPs), which were selected based on natural presentation on colorectal tumors by the XPRESIDENT antigen discovery platform. Methods: 92 HLA-A*02+ advanced colorectal cancer (aCRC) patients (pts) with stable or responding disease after 12 weeks of first-line oxaliplatin-based therapy were enrolled in this phase I/II trial. After pre-treatment with cyclophosphamide (300 mg/m2), patients were immunized intradermally with IMA910 plus the immune modulator GM-CSF without (cohort 1; n=66) or with (cohort 2; n=26) topically applied imiquimod, another immune modulator acting via toll-like receptor 7 on antigen presenting cells. T-cell responses to individual IMA910 peptides were analyzed by HLA multimer and intracellular cytokine staining (ICS) assays. Results: IMA910 elicited immune responses towards multiple class I (43%) and class II TUMAPs (65%). 34% of pts responded to multip...