Potential predictive biomarkers assessed for ICI benefit in GBM patients include tumor PD-L1/2 expression, CTLA-4 expression, mismatch repair deficiency (MMRd), tumor mutation burden (TMB), tumor-infiltrating lymphocytes, tumor-specific antibodies, and T cell functional markers [123]. Here, CTLA4 is linked to hyperinsulinemic hypoglycemia, familial, 4.