Updated project metadata. Protein neddylation modification is catalyzed by a neddylation activating enzyme (NAE, E1), an E2 conjugating enzyme and an E3 ligase. In various types of human cancers, the neddylation pathway was abnormally activated. Our previous study validated that neddylation E2 UBE2F is a promising lung cancer target. However, although NAE inhibitor MLN4924/pevonedistat is currently in few clinical trials for anticancer application, no small molecule was reported that targets UBE2F. Here, we report, for the first time, the discovery, via structure-based virtual screen and chemical optimization, of such a small molecule, designated as HA-9104. HA-9104 binds to UBE2F, reduces its protein levels, and consequently inhibits cullin-5 neddylation to inactivate CRL5 (cullin-RING ligase-5) ligase, leading to accumulation of CRL5 substrate, NOXA, to induce apoptosis. Moreover, HA-9104 appears to form the DNA adduct via its 7-azaindole group to induce DNA damage and G2/M arrest. Biologically, HA-9104 effectively suppresses the growth and survival of lung cancer cells and confers radiosensitization in both in vitro cell culture and in vivo xenograft tumor models. Taken together, our study discovered a small molecule HA-9104 that targets the UBE2F-CRL5 axis with anticancer activity alone or in combination with radiation.