Safety of direct myocardial administration of an adenovirus vector encoding vascular endothelial growth factor 121

A gene therapy strategy involving direct myocardial administration of an ad enovirus (Ad) vector encoding the vascular endothelial growth factor 121 cD NA (Ad(GV)VEGF121.10) has been shown to be capable of "biological revascula rization" of ischemic myocardium in an established porcine model [Mack, C.A . (1998). J. Thorac. Cardiovasc. Surg. 115, 168-177]. The present study eva luates the local and systemic safety of this therapy in this porcine ischem ia model and in normal mice. Myocardial ischemia was induced in Yorkshire s wine with an ameroid constrictor 21 days prior to vector administration. Ad GVVEGF121.10 (10(9) or 10(10) PFU), Ad5 wild type (10(9) PFU), AdNull (cont rol vector with no transgene; 10(9) PFU), saline, or no injection (naive) w as administered in 10 sites in the ischemic, circumflex distribution of the myocardium. Toxicity was assessed by survival, serial echocardiography, bl ood analyses, and myocardial and liver histology at 3 and 28 days after vec tor administration. All pigs survived to sacrifice, except for one animal i n the AdGVVEGF121.10 (1010 PFU) group, which died as a result of oversedati on. Echocardiograms of Ad(GV)VEGF121.10-treated pigs demonstrated no differ ences in pericardial effusion, mitral valve regurgitation, or regional wall motion compared with control pigs. Intramyocardial administration of Ad(GV )VEGF121.10 included only minimal myocardial inflammation and necrosis, and no hepatic inflammation or necrosis. Only a mild elevation of the white bl ood cell count was encountered on day 3, which was transient and self-limit ed in the Ad(GV)VEGF121.10 group as compared with the saline-treated animal s. As a measure of inadvertent intravascular administration of vector, norm al C57/BL6 mice received intravenous Ad(GV)VEGF121.10 (10(4), 10(6), 5 x 10 (7), or 10(9) PFU), AdNull (5 x 107 or 109 PFU), or saline. Toxicity was as sessed by survival, blood analyses, and organ histology at 3 and 7 days aft er vector administration. A separate group of C57/BL6 mice received intrave nous AdmVEGF164 (Ad vector encoding the murine VEGF164 cDNA), Ad(GV)VEGF121 .10, AdNull (10(8) PFU each group), or saline to assess duration of express ion and safety of a homologous transgene. All mice survived to sacrifice ex cept for 40% of the mice in the highest (10(9) PFU; a dose more than 10(3)- fold higher by body weight than the efficacious dose in pigs) Ad(GV)VEGF121 .10 dose group, which died on days 5-6 after vector administration. The onl y differences seen in the blood analyses between treated and control mice w ere in the very high Ad(GV)VEGF121.10 dose group (109 PFU), which demonstra ted an anemia as well as an increase in alkaline phosphatase when compared with all other treatment groups. Hepatic VEGF levels by ELiSA in AdmVEGF164 -treated mice did not persist beyond 14 days after vector administration, s uggesting that persistent expression of a homologous VEGF gene transferred with an Ad vector is not a significant safety risk. Although this is not a chronic toxicity study, these data demonstrate the safety of direct myocard ial administration of Ad(GV)VEGF121.10, and support the potential use of th is strategy to treat human myocardial ischemia.