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DNA hypomethylating agents (DHA) combined with immune-checkpoint inhibitors (ICI) is a promising strategy to improve the effect of immunotherapy. Providing initial support to this notion, the phase Ib NIBIT-M4 study, a dose-escalation trial of the DHA guadecitabine plus ipilimumab, has shown this regimen to be safe, tolerable and with promising immunomodulatory and anti-tumor activity in advanced melanoma. Here we report the 5-year clinical outcome of NIBIT-M4 patients and its correlation with an integrated multi-omic analysis. The NIBIT-M4 enrolled unresectable Stage III or IV cutaneous melanoma patients. Median Overall Survival (OS), Progression Free Survival (PFS), 5-year OS and PFS rate, and median Duration of Response (DoR) were assessed. Tumor biopsies were performed at baseline and at week 4 and 12 on-treatment. RNA-seq, whole exome sequencing (WES), RRBS methylation profiling, and tumor immune contexture data generated by immunohistochemistry (IHC), were integratively analyzed and correlated with clinical outcome. Patients were classified as responder (R) or non-responder (NR) based on Disease Control. Nineteen patients were enrolled in the NIBIT-M4 study between October 2015, and August 2018. As of July 1, 2022, median OS was 25.6 months (mo) (95% CI, 0.0-52.9), median PFS was 5.2 mo (95% CI, 4.0-6.4); 5-year OS rate was 28.9% and 5-year PFS rate was 5.3 %; median DoR was 20.6 mo (95% CI, 12.4-28.8). Tumor biopsies for correlative analyses were available from 14 patients. Compared to NR, R patients showed higher mutation frequency in NRAS, while NR patients harbored more frequent somatic alterations in genes involved in Epithelial to Mesenchymal Transition (EMT) and chromatin organization pathways. By tumor transcriptome analysis, NR patients showed enrichment for proliferation/differentiation/EMT pathways associated with suppression of INF-ɣ/HLA-II/immune-related transcriptional modules. R patients displayed a dynamic pattern of activated immune signatures related to CD8+ Tex cells, B cells, tertiary lymphoid structures, TFH cells and IFN-ɣ, reaching highest expression levels in week 12 biopsies. Deconvolution of transcriptomic data showed higher CD8+ and NK cell content and higher correlation of TCRB clonality with CD8+ content in R patients. By integration of a genetic immunoediting index (GIE) with an adaptive immunity signature (ICR) lesions were stratified into four distinct subsets. Interestingly, the ICR/GIE classification discriminated 5-year OS and PFS while the classification based on response groups did not. Moreover, patients with a “high ICR/non-GIE” (i.e., without immunoediting) showed lower expression of antigen presentation and processing-related genes associated with defective HLA-class I expression in the lesions, in spite of high CD8+ content. Citation Format: Teresa Noviello, Anna Maria Di Giacomo, Francesca Pia Caruso, Alessia Covre, Giovanni Scala, Luigi Ferraro, Sandra Coral, Wolf H. Fridman, Catherine Sautes-Fridman, Roberta Mortarini, Elena Simonetti, Maria Fortunata Lofiego, Davide Bedognetti, Andrea Anichini, Michele Ceccarelli, Michele Maio. Guadecitabine plus ipilimumab in unresectable melanoma: Five-year follow-up and correlation with integrated, multi-omic analysis in the NIBIT-M4 trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3273.