Mechanistic Studies and Formulation Mitigations of Adeno-associated Virus Capsid Rupture During Freezing and Thawing: Mechanisms of Freeze/Thaw Induced AAV Rupture

Abstract

Gene therapies delivered using adeno-associated virus (AAV) vectors are showing promise for many diseases. Frozen AAV drug products are exposed to freeze-thaw (F/T) cycles during manufacturing, storage, and distribution. In this work we studied the mechanisms of AAV capsid rupture during F/T. We found that exposure to interfaces, exacerbated by F/T, and the mechanical force of excipient devitrification correlated with AAV capsid rupture during F/T. There was no impact of pH shifts, cryo-concentration, or cold-denaturation. Results were similar for AAV8 and AAV9. With these mechanistic insights we identified three formulation mitigation approaches. Addition of ≥0.0005% w/v poloxamer 188 (P188) eliminated substantial recovery losses (up to ∼60% without P188) and minimized rupture to ≤1% per F/T cycle. Elimination of exothermic devitrification events during rewarming, either by formulating with a low buffer concentration, or by adding a cryoprotectant further reduced rupture during F/T. Rupture of AAV9 was <0.2% per F/T cycle in a formulation with 1 mM phosphate, 4.4 mM dextrose, electrolytes, and 0.001% P188 at pH 7.2. Rupture of AAV8 was not detected when formulated with 4% sucrose, 100 mM salt, and 0.001% P188 at pH 7.4. These results provide insights into effective strategies for stabilizing AAVs against rupture during F/T.