38P Biomarkers predictive of response to immune checkpoint inhibitor therapy in patients with metastatic melanoma

Results: The patients included: melanoma (n14), NSCLC (n10), endometrial cancer (n4), breast cancer (n3), GI cancer (n 1), head/neck cancer (n1), RCC (n1) and urothelial cancer (n1), treated with ICI alone (n21) or with chemotherapy (n14).At 12 months of follow-up, 47.1% had experienced an irAE with 80.8% grade 1-2 and 19.2% grade 3-4.Neutrophil counts (P0.02) and the neutrophil/lymphocyte ratio (P0.05) were higher at baseline in patients experiencing an irAE.Furthermore increases in the percent of total CD4+ (P0.03),Th1 (P0.04), and Tfh1 (P0.01)cells, coupled with decreases in Th17 (P0.003) and Tfh17 (P0.03) cells in the blood at 8-11 weeks on treatment were significantly associated with an irAE.Conclusions: These results suggest that changes in the relative balance of neutrophils and specific CD4+ T cell subpopulations were linked with an irAE.Our ongoing studies will further investigate changes in cytokine and gene expression profiles to deepen our understanding of these associations.This study marks a first step toward identifying biomarkers that anticipate the onset of an irAE and consequently reduce the need for immunosuppressive treatment that could compromise the efficacy of ICIs.Clinical trial identification: NCT05429866.