Complete response in a patient with advanced melanoma following anti-PD-1 therapy is associated with high frequency of melanoma-infiltrating CXCR3+ resident memory CD8+ T cells and multiple chemokine pathways.

The use of immune checkpoint inhibitors (ICI), such as anti-programmed cell death-1 (PD-1) antibodies, has profoundly changed melanoma prognosis. However, only 35% to 45% of patients experience durable responses, highlighting the need to improve our understanding of the mechanisms underlying clinical benefit from anti-PD-1 therapy.1 The extent to which PD-1 blockade boosts CD8+ T-effector cell responses, particularly at the invasive tumor margin, is a critical determinant of anti-PD-1 efficacy.