USF2690 was found to be an inhibitor of β-hexosaminidase release and tumor necrosis factor (TNF)-α, and 9nterleukin (IL)-4 secretion from rat basophilic leukemia (RBL-2H3) cells, with IC50 values of 2.8, 2.9, and 2.8 μM, respectively. Here, TNF is linked to acute basophilic leukemia.