Quarfloxin (also known as CX-3543) is a fluoroquinolone derivative patented by Cyclene Pharmaceuticals, Inc. as an antitumor agent. Quarfloxin selectively disrupts nucleolin/rDNA G-quadruplex complexes in the nucleolus, thereby inhibiting DNA polymerase I transcription and inducing apoptosis in cancer cells. CX-3543 was evaluated in phase II clinical studies for the treatment of low or intermediate grade neuroendocrine carcinoma, including carcinoid and islet cell cancer. In 2008, a trial for the treatment of chronic lymphocytic leukemia (CLL) was withdrawn prior to patient enrollment. In 2010, phase I clinical studies for the treatment of solid tumors and for the treatment of lymphoma were terminated upon the observation that the modified dose schedule presented no advantage over previously studies schedule solid tumors/ Cylene discontinued development of quarfloxin in 2010.

Chryseriol (Chrysoeriol) is a methoxylated flavone of great scientific interest because of its promising antioxidant, antiinflammatory, antitumor, antimicrobial, antiviral, and free radical scavenging activities. Chryseriol is a promising inhibitor of protein kinase CK2α and CK2α', the catalytic subunits of CK2, with IC50 values of 250 and 34 nM for CK2α and CK2α', respectively. Chrysoeriol produced a noncompetitive and mixed inhibition of pancreatic lipase with IC50=158uM. Chryseriol is a dual c‑Met and VEGFR2 kinase inhibitor. The results of docking experiments revealed that chrysoeriol was able to efficiently bind in the active site cavity of c‑Met and VEGFR2. The results of enzymatic assays showed relatively high binding affinities of chrysoeriol to c‑Met (Kd=12 uM) and VEGFR2 (Kd=11 uM). Chrysoeriol selectively inhibited human recombinant CYP1B1-mediated 7-ethoxyresorufin-O-deethylation (EROD) activity 5-fold more than that of CYP1A1-mediated activity in a competitive manner. Additionally, chrysoeriol inhibited E(2) hydroxylation catalyzed by CYP1B1, but not by CYP1A1. So chrysoeriol is a chemopreventive natural ingredient that can selectively inhibit CYP1B1 activity and prevent the formation of carcinogenic 4-OHE(2) from E(2.). Chrysoeriol was a selective PI3K-AKT-mTOR pathway inhibitor. It restrained the proliferation of human multiple myeloma cells, but didn't affect proliferation of PBMNCs from normal donors. It might exhibit the cell cycle regulatory effect via the inhibition of PI3K-AKT-mTOR signal pathway. The US Food and Drug Administration (FDA) recently granted orphan drug approval for Chrysoeriol, a cannabis-based drug used to treat acute myeloid leukaemia, which was developed by Jamaican scientist Dr Henry Lowe.