Ro 5-3335 is core binding factor (CBF) inhibitor; preferentially kills human leukemia cell lines with CBF fusion proteins (IC50 = 1.1 μM). It represses RUNX1/CBFβ-dependent transactivation in reporter assays and inhibits transcriptional regulation by RUNX1 and CBFβ. It also reduces the leukemia burden in a mouse model. Attenuates RUNX1-dependent hematopoiesis in zebrafish embryos. It also is a Tat antagonist and inhibits HIV-1 replication in vitro.