AP1903的生物活性 AP1903 is a homodimer binding to FKBP; elicites potent and dosedependent apoptotic death of engineered cell line HT1080 in culture with an EC50 of? 0.1 nM. IC50 value: 0.1 nM (EC50, HT1080) [1] Target: FKBP regulator AP1903 is a ideal reagents for controlling the activities of cells that have been modified by gene therapy procedures, without interference from endogenous FKBP. 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 (22, 23). Over 3 consecutive days, we implanted these cells i.m. into nude mice, treated the animals i.v. with various doses of AP1903, and then determined serum hGH levels as a measure of the number of surviving cells. Fig. 5B shows that AP1903 elicited a dosedependent decrease in serum hGH levels, with a half-maximal effective dose of 0.4 6 0.1 mg/kg [1]. No drug-related adverse events were observed at any of the dose levels with the possible exception of facial flushing in 1 volunteer at the 1.0 mg/kg dose level. AP1903 plasma levels were directly proportional to the administered dose, with mean Cmax values ranging from approximately 10 to 1,275 ng/mL over the 0.01 to 1.0 mg/kg dose range [2].