Profile of buparlisib and its potential in the treatment of breast cancer: evidence to date.

Alteration of the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin signaling pathway is key for the growth and survival of several cancers, including breast cancer. In addition, dysregulation of PI3K signaling may contribute to resistance to several anticancer agents. PI3K inhibitors may, therefore, be effective as antineoplastic therapy. Buparlisib is a potent and highly specific oral inhibitor of the pan-class I PI3K family. Buparlisib specifically inhibits class I PIK3 in the PI3K/AKT kinase signaling pathway in an ATP-competitive manner, thus inhibiting the production of the secondary messenger phosphatidylinositol (3,4,5)-trisphosphate and activation of the PI3K signaling pathway. This may induce inhibition of tumor cell growth and survival in susceptible tumor cell populations. Buparlisib is currently under investigation in patients with a variety of solid tumors, including breast cancer. Buparlisib has been validated as a promising anticancer agent, and tremendous efforts have been taken to develop it. However, buparlisib monotherapy has resulted in humble benefit so far. Results from studies combining buparlisib with different anticancer agents - namely, endocrine therapy, anti-HER2 therapy, and chemotherapy - have showed variable efficacy with consistent substantial toxicity.