Association of immune cells in mesothelioma microenvironment with response to nivolumab plus ipilimumab

Recently, immune checkpoint inhibitor (ICI) treatment was approved for malignant pleural mesothelioma (MPM). Since ICI treatment is not effective in all patients and may lead to side effects, there is a need to identify patients who might have response. Analysis of a phase 2 trial in The Netherlands found that cell densities of CD4+, CD8+, FoxP3+, and PD1+ immune cells in the MPM microenvironment in baseline biopsies were associated with response to nivolumab plus ipilimumab. This association was not seen in a phase 2 study of nivolumab monotherapy. On-treatment biopsies (after 6 weeks of treatment) in both trials did not show significant changes when compared to baseline biopsies. The authors conclude that these observations are a first step in exploring the tumor microenvironment as predictor or response of MPM to ICI treatment.