Targeting albumin supports production of therapeutic levels of FVIII and functional correction of hemophilia A phenotype. (A) FVIII activity as determined by chromogenic assay in hemophilia A/CD4-deficient mice 2 and 8 weeks after treatment with 1 × 10¹¹ vg of AAV8-mock (red circles), 5 × 10¹⁰ vg of each individual AAV8-ZFN (green circles), and 1 × 10¹¹ vg of donor 2 (see “Methods” section for details). **P = .008, Fisher's exact test. (B) Measurement of clot formation by aPTT prior to and 11 weeks after AAV administration. The aPTT of wild-type (▪) and untreated (●) mice are shown for comparison. **P < .01, 2-tailed Mann-Whitney test.