Effect of FIX_gla-egf1FVIIa chimera on saphenous vein bleeding in the hemophilia B mouse. Wild-type (control group) or hemophilia B (experimental group) mice were subjected to saphenous vein incision. After initial clot formation, the clot was disrupted repeatedly for 30 minutes and the time for each clot to form was measured; the average time to clot formation was calculated for each mouse. Ten minutes before incision, mFVIIa or mFIXgla-egf1FVIIa was injected into Hemophilia B mice. The hemophilic mice bled continuously during the entire 1800-second duration of the experiment; WT mice have an ATTH of 44 seconds. Each point represents the average of multiple bleeding times in each mouse during the 30-minute observation time. For 2 mg/kg, median ATTH was 37 seconds (n = 4) for mFVIIa-treated hemophilia B mice and 47 seconds for mFIXgla-egf1FVIIa-treated mice (n = 6). The difference in ATTH was not statistically significant (P = .24); both are significantly shorter than untreated hemophilia B mice (P < .05). For 1 mg/kg, mFVIIa-treated hemophilia B mice (n = 5) clotted in an average of 108 seconds; the ATTH was 97 seconds for mFIXgla-egf1FVIIa-treated hemophilia B mice (n = 6) (P = .75). At a dose of 0.25 mg/kg, the median ATTH for mFVIIa-treated mice (n = 5) was 86 seconds, whereas for mFIXgla-egf1FVIIa–treated mice (n = 5) it was 111 seconds (P = .83). All P values were calculated using the nonparametric Mann-Whitney U test. HB, hemophilia B.