Real-time MR imaging with Gadoteridol predicts distribution of transgenes after convection-enhanced delivery of AAV2 vectors.

Gene therapies that utilize convention-enhanced delivery (CED) will require close monitoring of vector infusion in real time and accurate prediction of drug distribution. The magnetic resonance imaging (MRI) contrast agent, Gadoteridol (Gd), was used to monitor CED infusion and to predict the expression pattern of glial cell line-derived neurotrophic factor (GDNF) protein after administration of adeno-associated virus type 2 (AAV2) vector encoding human pre-pro-GDNF complementary DNA. The nonhuman primate (NHP) thalamus was utilized for modeling infusion to allow delivery of volumes more relevant to planned human studies. AAV2 encoding human aromatic L-amino acid decarboxylase (AADC) was coinfused with AAV2-GDNF/Gd to confirm regions of AAV2 transduction versus extracellular GDNF diffusion. There was a close correlation between Gd distribution and GDNF or AADC expression, and the ratios of expression areas of GDNF or AADC versus Gd were both close to 1. Our data support the use of Gd and MRI to monitor AAV2 infusion via CED and to predict the distribution of GDNF protein after AAV2-GDNF administration.