周期蛋白依賴性激酶（CDK）4/6是細胞周期的關(guān)鍵調(diào)節(jié)因子，能夠觸發(fā)細胞周期從生長期（G₁期）向DNA復(fù)制期（S₁期）轉(zhuǎn)變。在雌激素受體陽性（ER⁺）乳腺癌中，CDK4/6的過度活躍非常頻繁。palbocicib是一種口服的CDK4/6抑制劑，能夠選擇性抑制CDK4/6，恢復(fù)細胞周期控制，阻斷腫瘤細胞增殖。從Ⅱ期臨床實驗結(jié)果來看，palbociclib的臨床療效具有非常明顯的優(yōu)勢。

Cycle dependent protein kinase (CDK) 4/6 is the key regulatory factor to cell cycle, and can trigger cell cycle phase to change from growth period (G₁ phase) to the DNA replication period (S₁ phase). In the estrogen receptor (ER⁺) breast cancer, the hyperactivity of CDK4/6 is very frequent. Palbocicib is an oral CDK4/6 inhibitor, which can selectively inhibit CDK4/6, and restore the control of cell cycle, therefore to block the proliferation of tumor cells. From the results of Ⅱ period clinical trials, the clinical efficacy of palbociclib has obvious advantages.