Phase 2 Trial Of Sl-701 In Relapsed/Refractory (R/R) Glioblastoma (Gbm): Correlation Of Immune Response With Longer-Term Survival.

2058Background: SL-701 is a novel immunotherapy comprised of synthetic peptides designed to elicit an anti-tumor immune response against GBM targets: interleukin-13 receptor alpha-2, EphrinA2 and Survivin. Updated Phase 2 data are reported. Methods: Patients with r/r GBM HLA-A2+, bevacizumab (bev)-naive and KPS u003e 60, enrolled. Stage 1: SL-701 with adjuvants GM-CSF and imiquimod dosed biweekly for 6 months, then q28 days. Stage 2: SL-701 with adjuvant poly-ICLC dosed biweekly with bev (10 mg/kg) for 6 months, then q28 days. Primary objectives: safety, tolerability, investigator assessed objective response rate (ORR, RANO criteria) and 12-month OS rate (OS-12). SL-701-specific CD8+ T-cell frequency was assessed by flow cytometry. PBMCs were isolated by density gradient and stimulated for 4h with SL-701 peptides (1mg/ml/peptide) before intracellular staining with live/dead, CD3, CD4, CD8, IFNγ, TNFα, IL-2, and PD-1. Results: As of 2/7/18, 74 bev-naive patients received median of 8.5 SL-701 doses. Most freque...