LAUSR

Introduction: The anti-CTLA-4 monoclonal antibody (mAb) ipilimumab (Ipi) has firstly shown the therapeutic potential of targeting immune checkpoints in metastatic melanoma (MM) patients (pts), though with limited objective clinical responses, ranging from 10 to 13% (Hodi, NEJM 2010; Ascierto, TLO 2017). Targeting of CTLA-4 is of interest due to its role in the priming phase of the immune response; thus, anti-CTLA-4 mAb are being tested in different combinations to improve their clinical efficacy also by overcoming tumor resistance to treatment. We have thoroughly demonstrated that epigenetic remodelling of cancer cells with DNA hypomethylating agents (DHA) improves tumor immunogenicity and immune recognition (Maio M, CCR 2015). These findings identified DHA as highly intriguing “partner agents” to improve the therapeutic index of checkpoint blockers, including CTLA-4 mAb. This hypothesis is being tested in the ongoing NIBIT-M4 study (NCT02608437). Methods: The NIBIT-M4 is a phase 1b, dose-escalation study sequencing treatment-naive/pre-treated, unresectable Stage III/IV MM pts, with the next generation DHA guadecitabine followed by Ipi. The dose escalation follows a 3+3 design: guadecitabine (at 30, 45 or 60 mg/m2) is administered s.c. on Week (W) 0, 3, 6, 9, days 1-5 and Ipi i.v. at 3 mg/kg on W1, 4, 7 and 10 q21d. Tumor assessment per immune-related response criteria is performed at screening (W0), W12, 18, 24 and q12 weeks. Patients-wise genome-wide methylation, RNA sequencing, whole-exome sequencing, and immunohistochemistry (IHC) analyses were performed on tumor samples collected at W0, 4 and 12. Canonical pathways and upstream regulators were investigated with IPA. Preliminary results: Fourteen out of the 19 planned pts have been enrolled so far, with no dose limiting toxicities. Among the 11 evaluable pts, the objective response rate is 27%. A reduction in tumor CpG sites methylation, from W0 (median 81.18%) to W4 (median 76.54%) and W12 (median 76.89%), was identified in the initial 8 pts enrolled. Transcriptomic analyses identified 3,897 ± 3,577 and 5,414 ± 3,569 differentially expressed genes (DEG) (q  1.0) at W4 and W12 compared to W0, respectively. Among the 137 pathways that were significantly modulated in all tumor samples at either W4 and/or W12, the most frequently activated ones were immune related (i.e., Th1 and Th2, iCOS-iCOSL and CD28 Signaling in T Helper Cells, and Interferon (IFN) Signaling). In addition, the top predicted upstream regulators were genes involved in the interferon IFN pathway (i.e., IFNG, STAT1, IRF7, IFNA2, IRF1). Though limited by the current sample size investigated, a greater number of significantly (p Conclusions: Epigenetic tumor immune-remodeling seems to be a promising strategy to improve the efficacy of CTLA-4 blockade, to be further pursued also with other immunomodulating mAb. *AMDG and AC equally contributed. Citation Format: Anna M. Di Giacomo, Alessia Covre, Francesca Finotello, Dietmar Rieder, Luca Sigalotti, Carolina Fazio, Ornella Cutaia, Christoph Bock, Florent Petitprez, Laetitia Lacroix, James N. Lowder, Wolf H. Fridman, Catherine Sautes-Fridman, Zlatko Trajanoski, Michele Maio. Epigenetic tumor remodelling to improve the efficacy of immune checkpoint blockade: the NIBIT-M4 clinical trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT059.