BAY-1082439 is an orally bioavailable inhibitor of the class I phosphoinositide 3-kinase (PI3K) alpha and beta isoforms with potential antineoplastic activity. PI3K alpha/beta inhibitor BAY1082439 selectively inhibits both PI3K alpha, including mutated forms of PIK3CA, and PI3K beta in the PI3K/Akt/mTOR pathway, which may result in tumor cell apoptosis and growth inhibition in PI3K-expressing and/or PTEN-driven tumor cells. By specifically targeting class I PI3K alpha and beta, this agent may be more efficacious and less toxic than pan PI3K inhibitors. Dysregulation of the PI3K/Akt/mTOR pathway is frequently found in solid tumors and results in increased tumor cell growth, survival, and resistance to chemotherapy and radiotherapy. PIK3CA, one of the most highly mutated oncogenes, encodes the p110-alpha catalytic subunit of the class I PI3K. PTEN, a tumor suppressor protein and negative regulator of PI3K activity, is often mutated in a variety of cancer cells.

BAY-87-2243 is a potent and selective hypoxia-inducible factor-1 (HIF-1) inhibitor. BAY 87-2243 inhibits HIF-1 reporter gene activity and CA9 protein expression with IC50 of 0.7 nM and 2 nM, respectively. In hypoxic lung cancer H460 cells, BAY-87-2243 suppresses HIF target gene expression, and inhibits HIF-1α protein accumulation. BAY-87-2243 showed dose-dependent in vivo antitumor efficacy in the H460 lung tumor xenograft model accompanied by a suppression of HIF-1a protein and HIF-1 target genes without any signs of toxicity or body weight loss. Further mode-of-action analyses revealed that BAY-87-2243 exerts its effect on the HIF pathway by blocking mitochondrial complex I activity and thereby reducing HIF protein levels under hypoxia. BAY-87-2243 had been in phase I clinical trials by Bayer for the treatment of malignancies. However, this study has been terminated for the drug-related adverse events.