CX-4945 is a first-in-class small-molecule targeted cancer therapeutic derived from the validated fluoroquinolone class of drugs. This drug was rationally designed to target a G-quadruplex (QPLX) DNA structure and disrupt protein-DNA interactions essential to cancer cells. The QPLX targeted by quarfloxin forms within ribosomal DNA (rDNA) and the QPLX is bound by the nucleolin protein.This Phase 1 study of CX-3543 is designed to test the safety, tolerability and highest safe dose level of this drug in patients with advanced solid tumor cancers.