PICLIB 75 mg Capsules PICLIB contains Palbociclib, a reversible inhibitor of cyclin-dependent kinases 4 and 6 (CDK4 and CDK6). It prevents the phosphorylation of retinoblastoma (Rb) protein, blocking G1-to-S phase cell cycle progression and suppressing tumor cell proliferation. It is indicated for the treatment of hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast cancer, used in combination with an aromatase inhibitor as initial endocrine-based therapy or with fulvestrant following disease progression.