Palbociclib is a drug for the treatment of ER-positive and HER2-negative breast cancer developed by Pfizer. It is a selective inhibitor of the cyclin-dependent kinases CDK4 and CDK6.[1][2] Palbociclib was the first CDK4/6 inhibitor to be approved as a cancer therapy by any organization.

In the G1 phase of the cell cycle, mammalian cells must pass a checkpoint known as the restriction point, R, in order to complete the cell cycle and divide. CDK4 and CDK6 complex with cyclin D to drive the phosphorylation of the retinoblastoma protein, Rb, which allows the cell to pass R and commit to division. Regulation of one or more proteins involved in this checkpoint is lost in many cancers. However, by inhibiting CDK4/6 palbociclib ensures that the cyclin D-CDK4/6 complex cannot aid in phosphorylating Rb. This prevents the cell from passing R and exiting G1, and in turn from proceeding through the cell cycle.

In February 2017, the National Institute for Health and Care Excellence (NICE) in the United Kingdom published a statement stating that the cost of Ibrance (approximately $3700 USD/28 days) did not make the added health benefits worth the cost. Though the committee acknowledged Ibrance's ability to extend patient life by approximately 10 months, it was stated that with the side effects caused by Ibrance, it was not a cost effective medication for NICE to endorse. At the time, a year's treatment with palbociclib and a drug such as fulvestrant was priced at $106,105 USD (£79,650). In November 2017 NICE announced that, after negotiation with Pfizer, the price would be discounted, and the drug would be recommended for use.

Formal Chemical Name (IUPAC)
6-acetyl-8-cyclopentyl-5-methyl-2-((5-(piperazin-1-yl)pyridin-2-yl)amino)pyrido[2,3-d]pyrimidin-7(8H)-one

References

https://en.wikipedia.org/wiki/Palbociclib