Verucopeptin is a potent HIF-1 (IC50=0.22 µM) inhibitor and decreases the expression of HIF-1 target genes and HIF-1alpha protein levels. Verucopeptin strongly inhibits v-ATPase activity by directly targeting the v-ATPase ATP6V1G subunit but not ATP1V1B2 or ATP6V1D. Verucopeptin exhibits antitumor activity against multidrug resistance (MDR) cancers and can be used for cancer research.