Abstract 6397: Immune profiling for improving responsiveness to ipilimumab plus nivolumab checkpoint blockade treatment in patients with metastatic melanoma

Abstract Background: aCTLA-4 and aPD-1 combination therapy has significantly improved clinical outcomes in patients with metastatic melanoma, with 50%-60% of patients responding to treatment, but predictors of response and treatment induced immunological effects are poorly characterized. Identifying circulating immune populations as biomarkers could reveal crucial insights into the mechanisms driving treatment success. Methods: Using unbiased single-cell profiling (with cytometry by Time-Of-Flight, CyTOF), we characterized the systemic immune compartments of over 250 peripheral blood mononuclear samples from 89 patients with advanced melanoma before and during combination therapy. We evaluated the association between circulating immune populations and clinical outcome using nonparametric Mann-Whitney tests, and investigated the prognostic values of these features using survival analysis. Additionally, we assessed treatment-induced immunological effects, providing insights into the dynamic changes within the immune system during therapy. Results: We characterized circulating T cells, NK cells, B cells, and monocytes from peripheral blood. Following combination therapy, there was a shift from naïve and central memory T cells to effector populations in both CD4+ and CD8+ T cells compartments. There was also a broad activation observed in both adaptive and innate populations, characterized by an elevation of multiple co-stimulatory and co-inhibitory molecules. Lower CD8+ NK cell populations prior to combination therapy were predictive of durable clinical benefit (DCB). Pre-treatment measurements of Tregs were not predictive of outcome, but higher Tregs one month after starting therapy, as well as increases of Tregs from pre to post treatment, predicted better progression free survival (PFS) and overall survival (OS). Starting from early on treatment, higher “exhausted-like” CD8+ T cells, characterized by positive expression of at least two co-inhibitory markers, is associated with resistance. Conclusions: aCTLA-4 and aPD-1 combination therapy led to a longitudinal shift from naïve and central memory to effector phenotypes in T cells, along with a broad activation in both adaptive and innate populations. Within innate immune compartment, favorable clinical outcome was associated with lower CD8+ NK cells, capable of regulating proliferation and activation of CD4+ T cells. Interestingly, one month after the start of the therapy, the increase in Tregs and a decrease in 'exhausted-like' CD8+ T populations are associated with a better response. Collectively, these analyses suggest potential treatment-specific correlates of efficacy and may enable biomarker-selected patient populations in future. Citation Format: Joanna Baginska, Jiajia Chen, Giuseppe Tarantino, Anita Giobbie-Hurder, Jason L. Weirather, Mariano Severgnini, Michael Manos, Kelly Burke, Janice D. Russell, Martha Brainard, Elizabeth Gabriel, Ryan Brennick, Matthew Nazzaro, Emma Hathaway, Marta Holovatska, Claire Manuszak, Srinika Ranashinge, David Liu, F. Stephen Hodi. Immune profiling for improving responsiveness to ipilimumab plus nivolumab checkpoint blockade treatment in patients with metastatic 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 6397.