Simple formulations with only excipients for stable lyophilization and ambient-temperature storage of adeno-associated viral vectors.

In the present study, we newly attempted the stable lyophilization of adeno-associated viral (AAV) vectors under simple formulations with only excipients containing no buffer, salt, or surfactant. An in vitro transfection study demonstrated that the intrinsic gene expression activity of AAV vectors was completely lost after lyophilization with no excipient, whereas it was partly maintained after lyophilization with some excipients, the efficacy of which was in the following order: cellulose derivatives and dileucine (diLeu) ≥ trehalose > other carbohydrates and dipeptides > amino acids. Methyl cellulose (MC), a cellulose derivative, almost completely maintained the intrinsic gene expression activity of AAV vectors with various serotypes after lyophilization up to a vector content of 8 × 1010 genome copies/mg excipient. In an in vivo transfection study through intratracheal or intranasal administration to mice, AAV vectors lyophilized with MC exhibited a similar gene expression pattern in the nose or lungs to the original AAV vectors with MC, causing no body weight loss. Furthermore, diLeu alone or its combination with MC prolonged the gene expression activity of lyophilized AAV vectors for at least 4 weeks after their storage at room temperature.