Schematic drawing of the BAX 335 expression cassette. The recombinant vector genome of BAX 335 is designed to express a codon-optimized FIX Padua (R338L) cDNA from the liver-specific murine transthyretin (TTR) promoter/enhancer. The intron fragment from minute virus of mice (MVM) and the bovine growth hormone (BGH) polyadenylation (pA) sequence help improve expression. The expression cassette is flanked by 1 AAV2 wild-type inverted terminal repeat (ITR) sequence (3′ITR) and 1 mutated AAV2 ITR (MUT 5′ITR) to direct preferential replication and packaging of self-complementary (sc) vector DNA. The overall size of the resulting sc genome is 4806 nucleotides (nt). The BAX 335 nucleotide sequence including ITRs is provided in supplemental Figure 1.