MAO A/HSP90-IN-1 (4-b) is a MAO A/HSP90 dual inhibitor with IC₅₀ value of 1.77 μM and 0.019 μM in Glioblastoma (GBM) GL26 cells and HSP90α, respectively. MAO A/HSP90-IN-1 (4-b) can inhibit MAO A activity, HSP90 binding and the expression of HER2 and phospho-Akt to inhibit the growth of GBM, they also reduce PD-L1 expression, which inhibits T cell activation. MAO A/HSP90-IN-1 (4-b) have potential to inhibit tumor immune escape. MAO A/HSP90-IN-1 (4-b) can be used for brain tumor-related diseases research^[1].