Impact of Initial Aggregate Level on Aggregation Potential of Monoclonal Antibodies in Different Buffer Systems

This study investigates the stability and kinetics of degradation when monoclonal antibodies (mAbs) process intermediates are stored in commonly used Protein A elution buffers, including citrate, acetate, and glycine, at varying pre-existing aggregates levels (low: 1-5%, moderate: 5-15% and high: 15-25%) at 4°C and 30°C to simulate standard and worst-case conditions.

mAb samples were subjected to thermal stress to achieve different levels of initial aggregates. The pre-aggregated samples were then incubated in different buffers at 4°C and 30°C to assess aggregation rates and stability. Aggregates were quantified using dynamic light scattering (DLS) integrated with machine learning (ML).

At 30°C, half-life reductions for citrate, acetate, and glycine buffers were 6.30-fold, 6.48-fold, and 9.64-fold, respectively, compared to 4°C, with glycine buffer offering the best stability, while citrate buffer provides the least. At higher initial aggregate levels, half-lives decreased by 2.15-, 1.95-, and 1.73-fold for citrate, acetate, and glycine buffers, respectively, compared to lower initial aggregates. Second-order kinetics dominated in samples having lower initial aggregate levels, while first-order kinetics prevailed in medium and high initial aggregate levels. Glycine buffer at 4°C with low initial aggregates achieved the highest half-life of 129 days, whereas citrate buffer at 30°C with high initial aggregate exhibited the lowest stability, with a half-life of 3.5 days.

The findings highlight the significance of using an optimal buffer system and appropriate storage conditions for in-process intermediates during mAb manufacturing to have a robust process that delivers safe and efficacious biotherapeutic products.