Mechanism of action of sirolimus

Sirolimus (sirolimus) is a lipophilic macrolide that, like tacrolimus, binds to members of the FK-binding protein (FKBP) family. The SRL/FKBP complex binds the protein kinase mTOR. Binding to mTOR blocks the activation of signal transduction pathways, causing cell cycle arrest in the G1 phase. mTOR is a major regulator of cell growth and proliferation. Sirolimus does not interact with calcineurin and is therefore less nephrotoxic than calcineurin inhibitors.

The immunosuppressive properties of sirolimus are mainly due to blocking T cell proliferation induced by interleukin-2 (IL-2). Its antiproliferative effects on lymphocytes, vascular endothelial cells, and renal tubular cells and its inhibitory effect on fibrosis contribute to the range of toxicity observed with sirolimus. Sirolimus is available as an oral solution or tablets, both formulations are bioequivalent, it is fat-soluble and water-insoluble. Sirolimus has lower oral bioavailability. Compared with tablets, sirolimus solution reaches maximum plasma concentration in 2 hours, while tablets require 6 hours.

SirolimusThe original drug has been launched in China and has entered the scope of Class B medical insurance. SpecificationsThe price of each box of 1mg*10 tablets is about 400 yuan. The domestic drug is only available to patients with anti-rejection reactions in organ transplantation. Patients who do not meet the conditions may not be able to purchase this drug. The original sirolimus drug has also been launched overseas. The price of the Turkish version of Specifications1mg*100 tablets per box is around RMB 2,000 (the price may fluctuate due to exchange rates). The ingredients of the original drugs marketed in China are basically the same as those of foreign original drugs. Currently, there are no generic sirolimus drugs produced in other countries.