Pidnarulex (CX-5461) is an inhibitor of rRNA synthesis, selectively inhibits Pol I-driven transcription of rRNA with IC50 of 142 nM in HCT-116, A375, and MIA PaCa-2 cells, has no effect on Pol II, and possesses 250- to 300-fold selectivity for inhibition of rRNA transcription versus DNA replication and protein translation.
