Copanlisib dihydrochloride (BAY 80-6946 dihydrochloride) is a selective and potent inhibitor of pan-class I PI3K. It significantly inhibits the catalytic activity of class I PI3K isoforms α, β, γ, and δ with IC50 of 0.5, 3.7, 6.4, and 0.7 nM, respectively. BAY 80-6946 exhibits potent antitumor activity in multiple cell-line–derived and patient-derived xenograft tumor models.