Detailed immunogenomic analysis of high dose IL-2 pharmacodynamic effects: A benchmark for next-generation IL-2-based immunotherapies.

e16501 Background: High-dose interleukin-2 (HD IL-2) was the first approved immune-oncology (IO) agent based on proven clinical efficacy in renal cell carcinoma (RCC) and metastatic melanoma, but its use was limited due to significant toxicities. Multiple next-generation IL-2 agents designed to retain efficacy while improving tolerability are in development. Yet, understanding of genomic markers that define optimized target pharmacology is incomplete. Newer evaluation techniques not available at the time of previous HD IL-2 experience may allow for identification of pertinent genomic markers. In this retrospective study, we report for the first time, RNA sequencing (RNAseq) of peripheral blood mononuclear cell (PBMC) samples from metastatic (mRCC) patients before, during and after HD IL-2 treatment. Detailed immunogenomic responses to HD IL-2 treatment with insight into traditional flow cytometry (FC) are presented. Methods: PBMC samples were collected for n = 23 HD IL-2 treated mRCC patients between 2009 and 2015 on Day 1, 3 and 5. Patient samples underwent prior FC analysis described elsewhere (Foureau et al, 2014; Cancer Immunol. Immunother. 63(12)). RNAseq was performed using NovaSeq6000 (Illumina) paired end sequencing on bulk PBMC samples from immediately before (Day 1), during (Day 3) and post-treatment (Day 5) Cycle 1 and/or Cycle 2 of the first course of HD IL-2. Individual genes and signatures for immune and proliferation differences were analyzed. Results: RNAseq analysis of PBMC samples demonstrated that CD8+ T cells transiently decreased in the blood during treatment but recovered to baseline on Day 5, and CD4 Treg cells increased on Day 3 and Day 5, which confirmed prior FC findings. TCR clonality was unchanged which indicates that T cell recovery and expansion is widespread and not driven by a specific subset of T cells. Additional notable insights included increased monocytes at Day 3, with the opposite for NK and B cells (Day 3 decrease and Day 5 expansion). Using a novel GeneCentric proliferation signature, increased expression was noted on Day 3 and Day 5 vs. Day 1, reflecting pronounced IL-2 induced proliferation. Conclusions: Immunogenomics provided further detail regarding IL-2 activity in addition to recapitulating several parameters from FC. Expression analysis of minimally invasive PBMC samples demonstrates the importance of this novel genomic approach to understand the pharmacology of IL-2 and related derivatives.