PX 866 is a ring-opened analog of wortmannin that potently and irreversibly inhibits PI3K (IC50 = 0.1-88 nM). It less potently blocks the activity of mammalian target of rapamycin (mTOR, IC50 = 3.1 μM). PX 866 exhibits single agent in vivo anti-tumor activity and increases the anti-tumor effects of cisplatin and radiation treatment. In cancer cells grown in three-dimensional cultures, PX 866 reduces cell growth and motility without causing cytotoxicity. Consistent with having cytostatic effects, PX 866 dosing is associated with prolonged stable disease in cancer patients.
