Abstract 1307: Assessment of gene expression in peripheral blood from patients with advanced melanoma using RNA-seq before and after treatment with anti-PD-1 therapy with pembrolizumab (MK-3475)
Authors: Ayers Mark D. , Nebozhyn Michael , Hirsch Heather A. , Cristescu Razvan , Murphy Erin E. , Kang S. Peter , Ebbinghaus Scot W. , McClanahan Terrill K. , Loboda Andrey , Lunceford Jared K. 
Published: August 2015

Abstract
Pembrolizumab (MK-3475) is a humanized monoclonal IgG4 antibody against programmed death receptor 1 (PD-1) that is currently being studied in clinical trials across more than 30 types of cancer. Gene expression profiling was used to explore a less invasive method for gaining new insights into the pembrolizumab mechanism of action and to assess the potential for blood-based predictive biomarkers. RNA-seq data were obtained from the whole blood of 44 patients with advanced melanoma enrolled in the phase 1 KEYNOTE-001 clinical study before and after the first cycle of treatment with pembrolizumab. Objective response rates (ORR) were assessed per RECIST v1.1 by independent central review. The pembrolizumab dose and treatment schedule varied among the patients studied and included 10 mg/kg given once every 3 weeks (Q3W) (n = 21), 10 mg/kg Q2W (n = 12), and 2 mg/kg Q3W (n = 11). Among the 44 patients with melanoma included in the analysis, 75% received previous ipilimumab treatment. The ORR was 32%. Significant posttreatment changes in gene expression were confirmed for the target, PD-1, and its key ligand, programmed death ligand 1 (PD-L1). Changes in PD-1 and PD-L1 gene expression did not, however, show a significant association with ORR. Statistically significant posttreatment changes for an interferon-gamma (IFNG)-related 10-gene signature were observed (P &lt; 0.002, upregulated in 70% of patients), and these changes were also associated with improved clinical outcome in terms of ORR (P = 0.042) and progression-free survival (P = 0.010). There appeared to be a possible association between IFNG gene signature posttreatment changes in blood in tumors with higher PD-L1 expression at baseline. There were no clear differences between posttreatment changes in the IFNG gene signature according to previous ipilimumab treatment. Baseline blood expression levels for PD-1, PD-L1, and the IFNG 10-gene signature were not found to be associated with clinical outcome. Additional post hoc analyses of baseline expression in combination with pathway analysis showed that the more highly ranked genes were linked to oxidative phosphorylation, suggesting that for patients whose tumors are not responding to pembrolizumab, their T cells may not be engaged with glycolysis, which is important for the transcriptional regulation of IFNG. The observation that nonresponders showed a lack of ability to induce activation of IFNG signaling suggests a possible link to defective T-cell effector function and may provide a means by which to monitor patient response to anti-PD-1 therapy.
Citation Format: Mark D. Ayers, Michael Nebozhyn, Heather A. Hirsch, Razvan Cristescu, Erin E. Murphy, S. Peter Kang, Scot W. Ebbinghaus, Terrill K. McClanahan, Andrey Loboda, Jared K. Lunceford. Assessment of gene expression in peripheral blood from patients with advanced melanoma using RNA-seq before and after treatment with anti-PD-1 therapy with pembrolizumab (MK-3475). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1307. doi:10.1158/1538-7445.AM2015-1307