Adi Diab, MD:We obtained longitudinal blood and tumor biopsies from the PIVOT-02 trial of melanoma patients. We used these blood markers and tumor markers to ask questions that we had already identified. We wanted to know how NKTR-214 and nivolumab affected the immune system. We found that NKTR-214, by harnessing the IL-2 [interleukin-2] pathway, leads to activation and proliferation of the immune system in the blood. This rapid activation of the immune system was noticed all the time, after each cycle, and continued for as long as we treated patients with these drugs. We saw that these episodes of lymphocytosis increase after a transient episode of lymphopenia, followed immediately by the rapid expansion of T cells after each cycle of NKTR-214.
We’ve seen a similar impact in the NKTR-214 monotherapy trial that we performed. The EXCEL trial with NKTR-214 without nivolumab indicated that this type of pharmacodynamics on the T cells and the lymphocytes was mediated mostly by NKTR-214. We noticed that when you look at the peak of the lymphocytosis, at day 8, after you infuse NKTR-214, you see that these T cells are proliferating. When you evaluate the proliferation by looking at the proliferation marker Ki-67, [you] notice that the proliferation includes the CD4s, CD8s, and natural killers. When we look at the activation marker, we notice that these proliferating cells also upregulate ICOSs [inducible T-cell costimulators]. ICOSs, especially when upregulated in CD4, has been recognized in certain published trials to be associated with positive outcomes. We noticed upregulation of ICOS in not only the CD4 T cells but also CD8 cells.
We also asked about what type of cells are related to proliferation. Is it naïve T cells or some of the cells that have seen antigens or that could be antigen specific? We looked at the marker that is well accepted as a surrogate marker for antigen-experienced T cells (HLA-DR) and noticed that the proliferating cells also upregulated HLA-DR. This indicates that some of these T cells are benefiting and proliferating and are activated by the combination of NKTR-214 and nivolumab. This could be an antigen experience, which is what we want in order to fight a cancer properly and attack the cancer tumor microenvironment properly. You want those antigen-specific T cells to benefit from NKTR-214 and nivolumab.
And certainly, looking at HLA-DR, it’s a surrogate marker for antigen-experienced T cells. When we look into the tumor microenvironment, which is very important, as my boss always says, “The tissue is the issue.” When looking at the tumors, we notice that there is an increase in the number of T cells after you treat with NKTR-214 and nivolumab. We assess that number by looking at 2 different assays. One of them is multiplex immunofluorescence. We looked at different markers and saw that CD8 and CD3 cells are increased when you take a biopsy 3 weeks after you start treatment. There are other markers that were upregulated in the immunofluorescence, such as PD-1 [programmed cell death protein 1], CD6, and CD8.
With an increase of CD3s and CD8s in the tumor microenvironment, we noticed a decrease in the melanoma markers in some of the patients. We noticed that when we saw an increase of the CD8 cells, the increase of the T cells was maybe associated with a decrease in tumor burden. We verified this by looking at the traditional immunohistochemistry, and we’ve also seen this in scenarios where patients had an increase in their T-cell counts after receiving the treatment. So we really verified the increase of T cells in the tumor microenvironment in multiple assays.
Transcript edited for clarity.