What is palbociclib/palbociclib?

Pfizer's Palbociclib is used in adults to treat hormone receptor-positive, HER2-negative breast cancer that is advanced or has spread in the body (metastasis). It is used in combination with a type of hormone therapy called an aromatase inhibitor in postmenopausal women or men who have not previously been treated with hormone therapy. It is also approved in combination with fulvestrant in patients whose disease has worsened after taking an aromatase inhibitor.

Aromatase inhibitors include drugs such as anastrozole (Arimidex), exemestane (Aromasin) and letrozole (Femara). Palbociclib was used with letrozole in postmenopausal women in clinical studies, but is approved by the FDA for use as first-line treatment with any aromatase inhibitor. Fulvestrant (Faslodex) is considered an estrogen receptor antagonist. Palbociclib belongs to the CDK 4/6 inhibitor class of drugs. CDK stands for cyclin-dependent kinase, an enzyme important for cell division. By blocking these enzymes, palbociclib slows the cell division that leads to the growth of new cancer cells.

Some cancers, such as hormone receptor-positive breast cancer, are more likely to have overactive and unregulated CDK4/6 activity, and CDK 4/6 inhibitors such as palbociclib may be used to treat this. Research suggests palbociclib may increase the time people have before their cancer spreads. More evidence is needed to determine their impact on overall survival. Palbociclib is usually taken with other drugs (such as aromatase inhibitors or fulvestrant) for 21 consecutive days. This cycle repeats every 28 days, as long as you respond positively to the medication and tolerate the side effects well.