IPI-549 (1693758-51-8) is a potent and highly selective inhibitor of PI3K-γ in both biochemical (IC50?= 16 nM) and cellular (IC50?= 12.2 nM) assays.1?Macrophage PI3K-γ has been found to be a critical switch between immune stimulation and suppression.2?IPI-549 has been used to reshape tumor immune microenvironments and promote cytotoxic T-cell-mediated tumor regression. Resistance to immune checkpoint blockade in 4T1 and B16-GMCSF tumors was overcome when anti-PD-1 or anti-CTLA4 therapies were combined with PI3K-γ inhibition via IPI-549.3?IPI-549 mono-treatment also resulted in tumor growth inhibition in several cancer cell lines.3?IPI-549 has also been shown to modulate P-glycoprotein-mediated multidrug resistance.4