Effect of a single FG-4497 dose on serum Epo concentration in P4h-tm null, Hif-p4h-2 hypomorphic, and Hif-p4h-3 null mice. The P4h-tm^−/− (A), Hif-p4h-2^gt/gt (B), Hif-p4h-3^−/− (C), and wild-type mice received a single oral dose of FG-4497 (100 mg/kg), and serum Epo concentration was analyzed after 6 hours. Statistical significance is shown only for the comparison of the values between the FG-4497–treated gene-modified and wild-type mice (*P = .02, **P < .005). The values in the vehicle-treated wild-type and gene-modified mice were less than 3% of those in the FG-4497–treated wild-type mice. In (A) n = 3 for the 2 vehicle-treated groups, n = 7 for the FG-4497–treated wild-type mice and n = 5 for the FG-4497–treated null mice, in (B) n = 3 for each group, and in (C) n = 2 for the 2 vehicle-treated groups and n = 3 for the 2 FG-4497–treated groups. Error bars represent SEM.