Supinoxin (RX-5902) is an orally active inhibitor of phosphorylated-p68 RNA helicase and a potent first-in-class anti-cancer agent, inducing cell apoptosis and inhibiting the growth of TNBC cancer cell lines (IC50s: 10 nM - 20 nM).

Supinoxin inhibits cell growth, MDA-MB-231, Caki-1, UMRC2, PANC-1, A549, MKN-45, HepG2, HCT116, HT29, PC-3, U251, HeLa, SK-MEL-28 and OVCAR-3 (IC50: range from 0.01 μM to 0.021 μM in the growth inhibition of cancer cells). Supinoxin (0-10 μM; 72 hours) is active against cell lines of all TNBC molecular subtypes and is active against cell lines with mutations in p53, RB1, CDKN2A, and loss of PTEN. Supinoxin (20-100 nM; 24 hours) treatment causes a dose-dependent increase in tetraploid cells, consistent with induction of G2–M cell-cycle arrest. Supinoxin (0-100 nM; 24 or 48 hours) reduces MCL-1 expression in a dose-dependent manner in TNBC cell lines sensitive to Supinoxin. Supinoxin (0-100 nM; 72 hours) exhibits no significant induction of apoptosis in cell lines resistant to the antiproliferative effects of Supinoxin. But in sensitive cells, the observed activation of apoptosis begins at 24–48 hours and reaches a peak at 72 hours. The induced apoptosis is treated with a dose of 100 nM [1][2].

Supinoxin (p.o.; 160/320/600 mg/kg; once weekly for 3 weeks) obviously dose-dependent tumor growth inhibition in the MDA-MB-231 model, exhibits TGI of 55.7%, 80.29% and 94.58% at 160 mg/kg, 320 mg/kg and 600 mg/kg, respectively [1].