palbociclib + ribociclib + abemaciclib

This drug is a **combination** of three cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors: **palbociclib**, **ribociclib**, and **abemaciclib**. These are targeted small-molecule inhibitors developed to block cell cycle progression in cancer cells by selectively inhibiting CDK4 and CDK6. Each is approved as an individual agent (in combination with endocrine therapy) for the treatment of hormone receptor–positive, HER2-negative advanced or metastatic breast cancer. All three drugs act to inhibit phosphorylation of the retinoblastoma (Rb) protein, arresting the cell cycle at the G1/S transition, and thus suppressing tumor cell proliferation. They differ in pharmacokinetics, dosing schedules, and some aspects of side effect profiles. There is no approved or studied use for the direct combined administration of all three agents together in a single regimen or formulation[2][4][5][7].