Plasma clearance of vector and human FIX expression after peripheral vein administration of scAAV2/8 in macaques. (A) Clearance of the vector from rhesus plasma was determined using a Q-PCR assay on samples collected on days 1, 3, and 7 after peripheral vein administration of scAAV2/8 (□) or scAAV2/5 (▪) vector. Standards consisting of serial dilutions of scAAV2/8-LP1-hFIXco in rhesus plasma were used to define the sensitivity of the assay. Results are expressed as mean transgene copy number per microgram of plasma derived from the 3 animals in each of the serotype 5 and 8 cohorts. (B) Human FIX concentration in rhesus plasma was determined at the indicated time points after administration of 1 × 10¹² vg/kg (M5-sc, ○; M6-sc, □; and M7-sc, ▵) serotype 8–pseudotyped scAAV-LP1-hFIXco into the peripheral vein of 3 rhesus macaques. Each sample was independently evaluated on at least 3 separate occasions, and the results are depicted as an average together with the standard error of the mean.