7.3.3　PI3K Inhibitor

The PI3K inhibitor also acts on the PI3K-AKTmTOR pathway and is the upstream PI3K signal transduction factor.In the BELLE-2 study，the median PFS of the PI3K inhibitor Buparlisib in combination with fulvestrant and fluvizide groups in patients with hormone receptor-positive/HER-2 negative advanced breast cancer who were resistant to postmenopausal endocrine therapy.They were 6.9 months and 5.0 months（HR=0.78，P=0.00021）.A large number of drug candidates targeting the PI3K signaling pathway are currently in various clinical research stages.According to different mechanisms of action，they can be divided into three categories：broad-spectrum PI3K inhibitors，subtype-specific PI3K inhibitors，and dual-target inhibitors that act on PI3K and mTOP.(https://www.daowen.com)