Stability of adenoviral vectors used in gene therapy

Abstract

Background & Aim Adenoviral vectors (AdV) are still the most widely used for both in vivo administration and in vitro genetic modification of cellular therapy products. CAGT has manufactured 51 clinical grade AdV for either in vivo or in vitro use. In both cases it is important to obtain stability data on the AdV both upon thawing for in vivo use and during long-term cryopreservation, since factors, such as exposure to atmospheric carbon dioxide, have been shown to affect the titers. Methods, Results & Conclusion Three AdVs were thawed and held at 2-8°C for up to 24 hours. The titer (ifu/ml) was measured at these intervals using the Adeno-X™ Rapid Titer Kit. The titers were expressed as a percentage of the starting titer. The results showed a slow decline over the 24 hours to a minimum 72% of the initial value (Figure 1). In the next experiment, AdV was thawed and held at 2-8°C for 4, 24, 48 and 72 hours at which times the titers were measured. The results, shown in Figure 2, demonstrate that the activity decreased by 13%, 26%, 30%, and 36% over the respective time interval. We evaluated the stability of AdV during 4 freeze/thaw cycles (Figure 3) and found that a second cycle reduced the titer by 8% and subsequent cycles resulted in reductions of 16%, 23% and 40% from the initial value. We also examined the stability of seven AdV stored at -80°C for up to 11 years. The results (not shown) demonstrated that there was generally good maintenance of titer over this time period. .