Improved formulation and lyophilization cycle for rBCG vaccine

To improve the conventional BCG vaccine in cake appearance and integrity, a new formulation with corresponding freeze drying cycle was developed for a recombinant BCG vaccine. The new formulation contains mannitol as a bulking agent, and trehalose, sucrose and sodium glutamate as stabilizers. The formulation and freeze drying cycle were tested with different super cooling rates and secondary drying temperatures, with or without an annealing process. Thermodynamic behavior was characterized using differential scanning calorimetry (DSC). Varying the secondary drying temperature and presence/absence of an annealing step caused marked differences in cake thermodynamic profiles irrespective of different cooling rates. The annealing process allowed efficient crystallization of the mannitol. Failure to crystallize the bulking agent had the potential to depress the Tg′ and compromise storage stability in the final lyophile by crystallizing from the solid during storage, even when the secondary drying temperature was as high as 40 °C. The improved formulation and freeze drying cycle resulted in good recovery of 53.2% during lyophilization and a higher survival rate of 61.7% in an accelerated stability study than the conventional BCG formulation and cycle. In summary, full crystallization was necessary for the mannitol bulking formulation. The freeze dried rBCG vials obtained using the formulation and drying cycle developed here met the requirements of BCG vaccine in good cake appearance, high viability post freeze drying and heat stability during storage.