Body-weight gain in rhesus monkeys after a single AAV9.hIDUA intrathecal injection at 4 weeks of age. Body weight was monitored regularly and compared to historical controls. Dashed lines represent the average body weight ±2 SD from historical controls. F, female; M, male; AAV9, adeno-associated virus serotype 9; hIDUA, human α-L-iduronidase; SD, standard deviation.