Specifically, she and her colleagues are evaluating the effects of treatment on immune-related biomarkers, measuring tumor-specific mutations and mutant neoantigens recognized by patient T cells in tumor biopsies, evaluating changes in the frequency of T cells recognizing tumor-specific mutant neoantigens in peripheral blood lymphocytes pre- and posttherapy, and looking at epigenetic changes pre- and posttherapy.
These preliminary findings suggest that the combination of entinostat and nivolumab with or without ipilimumab is safe and tolerable, with expected rates of immune-related adverse events, Dr. Connolly said, noting that the recommended phase 2 dose to be used in the dose expansion phase of the study has yet to be determined.
The findings, should they be confirmed as the trial progresses, could have important implications because immune checkpoint inhibitors, which work best in patients with immunogenic cancers that naturally attract T-cell infiltration into their tumor microenvironment, have limited single-agent activity in tumors, such as breast cancer, that are not believed to be immunogenic, she reported. Such cancers have thus far had only modest responses to single-agent immune checkpoint inhibition in advanced triple-negative and HER2+ breast cancer, with overall response rates of 5%-20%.
However, women who do respond to immune checkpoint inhibition tend to have durable and sustainable responses, she said, explaining that suboptimal immune responsiveness is likely a result of a lack of tumor antigen expression and/or recognition, as well as multiple suppressive signals in the tumor microenvironment.