S14161 inhibits D-cyclin transactivation by inhibition of phosphoinositide 3-kinase (PI3K) activity. S14161 is a pan-class I PI3K inhibitor. S14161 inhibited the activity of all 4 isoforms of the PI3K class I family, and unlike LY294002, had little effect on class IV enzymes mechanistic target of rapamycin (mTOR) and DNA-PKcs (DNA-dependent protein kinase, catalytic subunit), or on AKT-1, -2, or -3 or PDK1. S14161 inhibited the expression of cyclins D1, D2, and D3, leading to the arrest of cells at the G0/G1 phase, and has exhibited anti-myeloma and anti-leukemia activity with no gross toxicity.