Abstract 3734: Tumoral and systemic immune modulation with neoadjuvant (NeoAd) intratumoral (IT) TAVO-EP (plasmid IL-12 electro gene transfer) and nivolumab (NIVO) in patients (pts) with operable locoregionally advanced melanoma

Abstract Introduction: IT TAVO-EP (tavokinogene telseplasmid delivered by electroporation) results in localized expression of IL12 in the tumor microenvironment (TME). This study (NCT04526730) evaluated NeoAd TAVO-EP and NIVO. All patients provided a written informed consent (Advarra IRB Pro00041794). Biomarkers of tumoral and systemic immune responses were conducted and correlated with clinical outcomes. Methods: NeoAd phase comprised up to 3 × 4-week cycles of IT TAVO-EP and iv NIVO followed by surgery. Endpoints included pathologic complete response (pCR), near pCR, major response (pMR; pCR + near pCR) and nonresponse (pNR). Biospecimens were collected at screening, C1D8, C2D1 (~30 days from treatment start), pre-surgery (~90 days). Slides cut from FFPE tissue were analyzed by chromogenic immunohistochemistry (IHC) for CD8+ tumor infiltrating lymphocytes (TIL) and PD-L1 (22C3 CDx assay). RNA extracted from FFPE tissue was subjected to NanoString’s IO360 transcriptomic analysis, including Tumor Inflammation Signature (TIS). PBMCs were stained and analyzed via flow cytometry on an LSR Fortessa X-20. Serum samples were analyzed for cytokine levels using Luminex® MAGPIX® platform (15-plex). Results: 16 pts were treated; 1 with PR declined surgery, 1 with early distant PD did not have surgery, 14 had surgery: 2 pNR, 3 near pCR, 9 pCR; pMR rate 12/15 (80%). In tumor, at baseline, 9/11 pts tested had 20% CD8+ TIL, 7/11 10% PD-L1 tumor proportion score (TPS) and 6/10 TIS of ≤0, predicting non-response to anti-PD-1. In 5 pts with evaluable matched tissue at baseline and C2D1: 5/5 had increased peritumoral CD8+ T cells, 4/5 increased CD8+ TIL, 2/5 increased PD-L1, 4/5 increased TIS at C2D1 compared to baseline. Tumoral transcriptome profile revealed significant upregulation of genes involved in innate and adaptive immune responses (IFN-gamma, APM, granzymes, CD8, PD-L1, JAK1, chemokines, others) at C2D1. In blood, proliferating Ki-67+/PD-1+/CD8+ T cells expanded at C2D1 while total PD1+/CD8+ cells decreased. Decrease of PD1+CD8+ cells and other subtypes in blood at C2D1 coincided with TME infiltration by CD8+ cells. Serum effector cytokines including IL12, IFN-gamma and IL2, showed no biologically meaningful changes following treatment or differences between responders and non-responders. Conclusions: At baseline, most patients exhibited low CD8+ TIL, PD-L1 and TIS, with enhanced immune activation following treatment in the TME and blood including increased immune-related gene expression, CD8+ TIL, peritumoral CD8+ T cells and TIS. Four of 5 pts with negative predictive baseline biomarkers CD8+TIL/PD-L1/TISlow experienced pCRs supporting activity of IL12/anti-PD1 based regimens in this setting. Citation Format: Ahmad A. Tarhini, Zeynep Eroglu, Jonathan S. Zager, Ricardo J. Gonzalez, Amod A. Sarnaik, C Wayne Cruse, Deanryan B. De Aquino, Edith Abraham, Diana M. Acevedo, Allison Richards, Michael J. Schell, Denise Kalos, Pei-Ling Chen, Jane L. Messina, David A. Canton, Vernon K. Sondak. Tumoral and systemic immune modulation with neoadjuvant (NeoAd) intratumoral (IT) TAVO-EP (plasmid IL-12 electro gene transfer) and nivolumab (NIVO) in patients (pts) with operable locoregionally advanced melanoma abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3734.