Why is Palbociclib taken for 21 days and stopped for 7 days?

Palbociclib (Palbociclib) is a targeted therapy for breast cancer. It is usually used in a 21-day cycle. Each cycle includes 21 consecutive days of taking the drug and then 7 days of stopping the drug. Mean maximum observed concentrations are typically observed between 6-12 hours after oral dosing, and the mean absolute bioavailability of palbociclib after an oral 125 mg dose is 46%.

This dosing regimen of palbociclib is to reduce the impact of the drug on bone marrow hematopoietic function. Palbociclib is a cell cycle-specific drug that mainly inhibits the DNA synthesis of tumor cells to prevent their proliferation. However, it may also cause a certain degree of inhibition of DNA synthesis in normal cells, including hematopoietic stem cells. AUC and Cmax generally increase proportionally with dose within the dose range of 25 mg-225 mg. After repeated dosing once daily, a steady state is reached within 8 days. After repeated daily dosing, the median accumulation rate of palbociclib was 2.4.

The original drug of palbociclib has been launched in China and has entered the scope of Class B medical insurance, but reimbursement is limited to patients who meet the indications. The price of each box may be more than more than 4,000 yuan. The price of palbociclib's original drug, 125mg*21 capsules, per box sold overseas may be more than RMB 10,000 (the price may fluctuate due to exchange rates). There are also generic palbociclib drugs produced in other countries. The price of 125mg*21 tablets produced by a Bangladeshi pharmaceutical factory may be around a few hundred yuan per box (the price may fluctuate due to the exchange rate). The price is cheaper. The pharmaceutical ingredients of generic drugs are basically the same as those of domestic and foreign original drugs.