Prolonged survival and expression of FVIII:Ag from genetically modified BOECs implanted into the omentum. Hemophilia dog #2 was 10 months old and weighed 9.4 kg when the procedure was performed. Approximately 4.5 × 10⁷ cells were injected into each of 11 sites. In vitro these cells expressed 1.5 IU of cFVIII per 10⁶ cells over 24 hours. To prevent bleeding problems, the dog received multiple infusions of canine cryoprecipitate (black arrows) before and after the procedure, including 3 infusions of 56, 48, and 140 U FVIII on days 100, 113, and 133, respectively. Plasmas samples were obtained at the indicated time points. (A) FVIII activity (FVIII:C) and FVIII antigen (FVIII:Ag) levels were measured, and the results were compared with pooled normal canine plasma samples that were arbitrarily set at 100%. Plasma samples from 13 untreated hemophilia A dogs showed no detectable FVIII:Ag. (B) Levels of inhibitory antibodies were measured by a Bethesda assay, and anti-FVIII IgG1 and IgG2 antibodies were measured by ELISA.