Abstract Immune checkpoint inhibitors (ICI) have revolutionized treatment for various cancers; however, durable response is limited to only a subset of patients. Discovery of blood-based biomarkers that reflect dynamic change of the tumor microenvironment, and predict response to ICI will markedly improve current treatment regimens. Here, we investigated a role of CX3C chemokine receptor 1 (CX3CR1), a marker of T-cell differentiation, in predicting response to ICI therapy. Successful treatment of tumor-bearing mice with ICI increased the frequency and T-cell receptor clonality of the peripheral CX3CR1 + CD8 + T-cell subset that included an enriched repertoire of tumor-specific and tumor-infiltrating CD8 + T cells. Furthermore, an increase in the frequency of the CX3CR1 + subset in circulating CD8 + T cells early after initiation of anti-PD-1 therapy correlated with response and survival in patients with non-small cell lung cancer (NSCLC). Taken together, these data support T-cell CX3CR1 expression as a blood-based dynamic biomarker to predict response to ICI therapy.

A circulating T-cell differentiation marker to predict response to immune checkpoint inhibitors