buparlisib + ribociclib

Buparlisib + ribociclib is an experimental combination therapy composed of buparlisib, a pan-class I phosphoinositide 3-kinase (PI3K) inhibitor, and ribociclib, a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor. Both are small molecule drugs. Buparlisib inhibits PI3K signaling, blocking cell proliferation and survival pathways, while ribociclib selectively inhibits CDK4/6, leading to cell cycle arrest. This combination was evaluated primarily in postmenopausal women with hormone receptor–positive, HER2-negative advanced or metastatic breast cancer, aiming to delay resistance to endocrine therapies. Clinical development found that combining these agents, often with fulvestrant or letrozole, raised toxicity concerns, leading to early trial discontinuation in some studies.