Three new glycosylated phenazine derivatives, named izuminosides A-C (1-3) have been isolated from the ethyl acetate extract of Streptomyces sp. IFM 11260. The structures of the new compounds were determined on the basis of their spectral data. Compounds 1-3 were evaluated for their activity in overcoming tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) resistance in human gastric adenocarcinoma cells. Compounds 2 (10 μM) and 3 (60 μM) in combination with TRAIL showed synergistic activity in sensitizing TRAIL-resistance AGS cells.