If available, tumour tissue following progression of disease will also be tested for immune and genetic markers. Early work has indicated these biomarkers may be predictive of responders to study treatment. In a phase 1 study of 90 patients receiving nivolumab at different dose levels, high pre-treatment NY-ESO-1 and MART-1-specific CD8+ T cells were associated with progression of disease. At week 12, increased peripheral-blood T regulatory cells and decreased antigen-specific T cells were associated with progression. PD-L1 tumour staining was associated with responses to nivolumab, but negative staining did not rule out a response.