Palbociclib works as a highly potent and selective inhibitor of CDK4 and -6 in patients with advanced estrogen receptor positive, HER-2 negative breast cancer. When used in conjunction with anticancer therapy Letrozole, Palbociclib has proven to significantly promote progression-free survival in patients. Studies have determined that In vitro, Palbociclib reduced cellular proliferation of ER-positive breast cancer cells by effectively blocking the progression of the cell from the G1 into S phase of the cell cycle.
Regarding Cardiac Electrophysiology Palbociclib elicited no substantial change in the QTc interval in studies of patients diagnosed with metastatic estrogen receptor positive, HER-2 negative breast cancer. The binding of Palbociclib to plasma proteins in vitro was valued at 85 percent, with no concentration dependence over the expected range of 500 ng/mL to 5000 ng/mL.
Palbociclib is metabolized both in vitro and in vivo via hepatic metabolism in humans. Post oral administration of a one-time dose of 125 milligrams of Palbociclib the primary metabolic pathways have been observed to involve both oxidation and sulfonation, along with with glucuronidation and acylation as contributing minor pathways.
The toxicity of Palbociclib alongside Letrozole was found to be acceptable in extensive and comprehensive studies. Adverse events noted included anemia, neutropenia and fatigue.
Weinberg RA. The Biology of Cancer. 2nd ed. New York: Garland Science; 2014.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4128689/