Basic Science and Experimental Study A Pharmacokinetic Analysis of Molecular Cardiac Surgery With Recirculation Mediated Delivery of bARKct Gene Therapy: Developing a Quantitative Definition of the Therapeutic Window

Background: Two major problems for translating gene therapy for heart failure therapy are: safe and efficient delivery and the inability to establish a relationship between vector exposure and in vivo effects. We present a pharmacokinetics (PK) analysis of molecular cardiac surgery with recirculating delivery (MCARD) of scAAV6-bARKct. MCARD’s stable cardiac specific delivery profile was exploited to determine vector exposure, half-life, and systemic clearance. Methods and Results: Five naive sheep underwent MCARD with 10 14 genome copies of scAAV6bARKct. Blood samples were collected over the recirculation interval time of 20 minutes and evaluated with quantitative polymerase chain reaction (qPCR). C(t) curves were generated and expressed on a log scale. The exposure, half-life, and clearance curves were generated for analysis. qPCR and Western blots were used to determine biodistribution. Finally, all in vivo transduction data was plotted against MCARD’s PK to determine if a relationship existed. Vector concentrations at each time point were (cardiac and systemic, respectively): 5 minutes: 9.16 6 0.15 and 3.21 6 0.38; 10 minutes: 8.81 6 0.19 and 3.62 6 0.37; 15 minutes: 8.75 6 0.12 and 3.69 6 0.31; and 20 minutes: 8.66 6 0.22 and 3.95 6 0.26; P ! .00001. The half life of the vector was 2.66 6 0.24 minutes. PK model data revealed that only 0.61 6 0.43% of the original dose remained in the blood after delivery, and complete clearance from the system was achieved at 1 week. A PK transfer function revealed a positive correlation between exposure and in vivo transduction. Robust bARKct expression was found in all cardiac regions with none in the liver. Conclusion: MCARD may offer a viable method to establish a relationship between vector exposure and in vivo transduction. Using this methodology, it may be possible to address a critical need for establishing an effective therapeutic window. (J Cardiac Fail 2011;17:691e699)