Zotarolimus (ABT-578) is a semi-synthetic analogue of rapamycin, made by substituting a tetrazole ring for the native hydroxyl group at position 42 in rapamycin. Zotarolimus is highly effective in inhibiting both smooth muscle cell and endothelial cell proliferation, with IC50 values of 2.9 nM and 2.6 nM, respectively. Zotarolimus is mechanistically similar to sirolimus in having high-affinity binding to the immunophilin FKBP12 and comparable potency for inhibiting in vitro proliferation of both human and rat T cells. Zotarolimus inhibits Con A-induced human T cells and rat T cells proliferation with IC50 of 7.0 nM and 1337 nM respectively.
