BIOM-39. P-ERK ASSOCIATION WITH OVERALL SURVIVAL IN RECURRENT GBM PATIENTS TREATED WITH INTRACEREBRAL ADMINISTRATION OF PD-1 AND CTLA-4 BLOCKING ANTIBODIES

Abstract INTRODUCTION Anti-PD-1 immunotherapy induces clinical responses in a subset of glioblastoma (GBM) patients. We previously reported that ERK1/2 phosphorylation (p-ERK) pre-treatment tumor samples is predictive overall survival (OS) following adjuvant anti-PD-1 therapy two independent cohorts recurrent GBM METHODS Following the Remark criteria for biomarker validation, we investigated p-ERK as OS 24 evaluable patients from trial. These underwent intracerebral administration immune checkpoint inhibitors part phase I trial where ipilimumab (10 mg) or (5 and nivolumab followed by postsurgical intravenous was evaluated (NCT03233152; Duerinck J, et al. JITC, 2021). quantified cell density p-ERK+ cells regions. For exploratory purposes, were divided 3 groups (n=8 per group) bases on density. RESULTS observed an incremental with high exhibiting median 81.6 weeks (95% CI 33.86-NA), intermediate 43.1 33.14-NA), low group 19.3 16.14-NA). A Cox proportional hazards model adjusted age IDH mutant status showed trend association favorable (HR= 0.77, 95% 0.6-=1.01, P=0.056). CONCLUSIONS While number analyzed relatively small, this study suggests potential power prospective cohort treated alternative unique approach blockade.