Rimiducid is a lipid-permeable tacrolimus analogue, homodimerizing an analogue of human protein fkbp12 and binding to wild-type fkbp12 with 1000-fold lower affinity. Rimiducid is a dimerizer agent that acts by cross-linking the FKBP domains. It dimerizes the Caspase 9 suicide switch and rapidly induces apoptosis.

FKBP:（EC50）0.1 nM

AP1903, a bivalent 'dimerizer' drug that binds FKBP and induces Fas cross-linking.?A single 2-hour treatment eliminated approximately 80% of T cells, and multiple exposures induced further apoptosis.?T cells were eliminated regardless of their proliferation state, suggesting that the AP1903/Fas system, which contains only human components, is a promising alternative to HSV-tk for treating GVHD[2].

Constitutive hGH secretion provides a convenient and accurate way to monitor the number of viable cells in vivo because hGH has a serum half-life of only ≈3 min in mice. Over 3 consecutive days, we implanted these cells i.m. into nude mice, and treated the animals i.v. with various doses of Rimiducid, and then determined serum hGH levels as a measure of the number of surviving cells. Rimiducid (AP1903; i.v.,0.01, 0.1, 1, 10, and 100 mg/kg) elicits a dose-dependent decrease in serum human GH levels, with a half-maximal effective dose of 0.4±0.1 mg/kg[1].