STAT5B and central nervous system cancer: Promisingly, SH-4-54 is small molecule STAT3/STAT5 inhibitor based on salicylic acid with excellent BBB penetration that was found to potently induce apoptosis in GSCs and inhibit growth of gliomas in a murine xenograft model, although it should be noted that these were subcutaneously implanted tumors [237,238].