CD4+ T cells in PBMC to predict the outcome of anti-PD-1 therapy.

Abstract

11525 Background: Antibody blockade of programmed death 1 (PD-1), has led to durable responses and significant prolongation of overall survival in metastatic cancers including non-small cell lung cancer (NSCLC). However, in clinical trials, response rates were as low as 20 %, and approximately 50 % of the patients did not achieve benefits to prolong progression free survival. These results bring us a hypothesis that there are subgroups with distinct pre-existing anti-tumor immunity resulting in different responses to anti-PD-1 therapy. We reported that effector T cells, which are capable of mediating antitumor reactivity, are primed in LNs draining growing tumors and that these T cells exclusively belong to the T cells that down-regulated CD62L (CD62Llow) subpopulation. In the absence of purified tumor antigenic proteins or peptides on many tumors, the expression of the homing molecule CD62L on T cells may serve as a surrogate marker for identifying tumor-specific immune cells. Methods: We analyzed the peripheral blood mononuclear cells (PBMC) of 50 consecutive NSCLC patients who were planned to be treated with anti-PD-1 Ab, Nivolumab after obtaining written informed consent. The patients received Nivolumab at a dose of 3 mg per kilogram of body weight every 2 weeks. Tumor response was assessed with the use of the Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1, at week 8 and every 8 weeks thereafter. Results: The NSCLC patients who achieved partial response (PR) or stable disease (SD) had significantly (p = 4.1x10-7) more CD62Llow CD4+ T cells in PBMC than progressive disease (PD) patients. The percentages of CD62Llow in CD4+ T cells provided sensitivity 92.9 %, and specificity 96.7 % to predict the patients who had PD. Moreover, SD patients had significantly (p = 0.0067) less regulatory T cell subpopulation than PR patients, thus, it was possible to predict PR from SD. Conclusions: These results show that the major differences in pre-existing immunity among PR, SD, and PD patients to anti-PD-1 Ab existed in CD4+ T cell balance between primed effector and regulatory T cells. Further characterization of CD62Llow CD4+ T cells including mRNA microarray, checkpoint molecules, and chemokine receptors is going on.