Adenoviral vector-mediated expression of physiologic levels of human factor VIII in nonhuman primates

An E1-, E2a-, E3-deleted adenoviral vector (Av3H82) encoding an epitope-tag ged B domain-deleted human factor VIII cDNA (flagged FVIII) was evaluated i n nonhuman primates. Twelve cynomolgus monkeys received intravenous adminis tration of Av3H82; 6 monkeys received 6 x 10(11) particles/kg and another 6 received 3 x 10(12) particles/kg. Adenoviral vector transduction of the li ver was efficient, reproducible, and linearly dose dependent. Physiologic l evels of flagged:FVIII were readily detected in plasma samples obtained fro m monkeys that received the higher dose of vector and human FVIII mRNA was detected in their livers. Expression of transgene mRNA was restricted to th e liver by, the albumin promoter. Although vector DNA was readily detected in the liver of monkeys that received the lower dose, neither human FVIII m RNA nor flagged FVIII protein could be detected, Vector distribution was wi despread, with the highest levels observed in liver and spleen. Histopathol ogy, hematology, and serum chemistry analysis identified the liver and bloo d a's major sites of toxicity, Transient mild serum elevations of liver enz ymes were observed, along with a dose-dependent inflammatory response in th e liver. In addition; mild lymphoid hyperplasia was observed in the spleen, Mild anemia and a transient decrease in platelet count were observed, as w as marrow hyperplasia and extramedullary hematopoiesis.