RK33 (RK 33) is a first-in-class small molecule inhibitor of DDX3 (a RNA helicase) and causes G1 cell cycle arrest, induces apoptosis, and promotes radiation sensitization in DDX3-overexpressing cells.

RK-33 binds specifically to DDX3, but not to the closely related proteins DDX5 and DDX17. RK-33 inhibits cancer growth and radiosensitizes lung cancer cells in a DDX3-dependent manner. RK-33 has no effect on either mitochondrial respiration or ATP generation. RK-33 curbs proliferation and induces apoptosis in a DDX3-dependent fashion. Wnt signaling is mediated by DDX3 and inhibited by RK-33. RK-33 impairs radiation-induced DNA damage repair by inhibiting NHEJ activity[1].

RK-33 in combination with radiation induces tumor regression in multiple mouse models of lung cancer. RK-33, at the dose used, is non-toxic in SCID mice. RK-33-treated mice do not exhibit any discernable morphological changes[1].

Healthy, 60-70% confluent MDA-MB-231 cells are transduced with shDDX3 lentivirus particles. Knockdown of DDX3 expression is confirmed both by qRT-PCR and immunoblotting. MDA-MB-231 cells are treated with RK-33 (7.5 μM) for 12 h and harvested for RNA. Microarray experiments are performed.(Only for Reference)