Tumor growth experiments conducted in syngeneic mice inoculated with MC38 cells using PD-1 immune checkpoint inhibitors demonstrated that while BEBT-908 (a dual HDAC/PI3K inhibitor) alone could delay the growth of MC38 tumors, its efficacy was significantly enhanced when combined with anti-PD-1 antibodies, with some host mice surviving for extended periods. This evidence concerns the gene HDAC9 and neoplasm.