A fluoroquinolone derivative with antineoplastic activity. Quarfloxin disrupts the interaction between the nucleolin protein and a G-quadruplex DNA structure in the ribosomal DNA (rDNA) template, a critical interaction for rRNA biogenesis that is overexpressed in cancer cells; disruption of this G-quadruplex DNA:protein interaction in aberrant rRNA biogenesis may result in the inhibition of ribosome synthesis and tumor cell apoptosis. Check foractive clinical trials using this agent.