YK 4-279 is an inhibitor of RNA Helicase A (RHA) binding to the oncogenic transciption factor EWS-FLI1. YK-4-279 inhibits Ewing's sarcoma family tumor (ESFT) cell growth; YK-4-279 induces apoptosis. IC50 value: Target: RNA Helicase A ES-FLI1 is an oncogenic fusion protein found in Ewing’s sarcoma, a family of undifferentiated tumors that occur throughout the body. The binding of RNA helicase A (RHA) to ES-FLI1 promotes its oncogenic function. YK-4-279 is an inhibitor of protein-protein interactions between ES-FLI1 and RHA. At 10 μM, YK-4-279 blocks RHA binding to ES-FLI1 and induces apoptosis of a panel of Ewing’s sarcoma tumor cell lines with IC50 values ranging from 0.5-2 μM. At 1.5 mg per dose, YK-4-279 reduces the growth of Ewing’s sarcoma orthotopic xenografts in mice after treatment with the inhibitor for two weeks.