A compound of Formula (I): or a pharmaceutically acceptable salt thereof, where: Q can be 1,2,4-triazin-3-yl, pyridazin-3-yl, 6-methylpyridazin-3-yl, or 6-fluoropyridazin-3-yl; R1 can be hydrogen, methoxy, trifluoromethoxy, oxetan-3-yl, 3-fluoroazetidin-1-yl, 3-methoxyazetidin-1-yl, or 3,3-difluoroazetidin-1-yl; R2 can be hydrogen or fluoro; R3 can be hydrogen or methoxy; and R4 can be methoxy, ethoxy, or methoxymethyl; provided that when R1 is hydrogen, methoxy or trifluoromethoxy, then R3 is not hydrogen, and/or R4 is methoxymethyl. The compound of formula (I) can inhibit glutaminase, e.g., GLS1.