Anyah Settle, Scientist at NanoTemper, discussed how she used the Prometheus Panta to explore the physical stability of biologics and the impact of excipients. Given the differences in structures and behaviours under thermal stress, it is difficult to co-formulate two biologic drug products. Settle selected NISTmAb and GLP-1 as her drug products.
The NISTmAb has buried tryptophan within its tertiary structure, meaning when thermal heat is introduced, the only change Settle expected to see was the unfolding of the antibody and the tryptophan becoming exposed to the solvent. Upon heating, one should expect to see the aggregation of GLP-1, and because of this, the tryptophan will become buried.
Settle adopted a systematic approach; she performed individual screens in each component with a number of different excipients with the aim of probing homogeneous interactions within each molecule. Using multiplex optical methods and Prometheus Panta (an automated autosampler) for these experiments. The Prometheus Panta allows for combination DLS, nano DSF, and turbidity measurements with low sample volumes.
The study examined the impact of different excipients (arginine, proline, and salt) on the stability of NISTmAb. It was found that arginine and salt decreased the thermal stability of NISTmAb, while proline had minimal effect. High salt concentrations led to the aggregation of NISTmAb, driven by the unfolding of the Fab domain. Proline did not significantly affect the aggregation or stability of the co-formulated mixture.
Next, Settle investigated aggregation and stability. High salt concentrations led to the aggregation of NISTmAb, driven by the unfolding of the Fab domain. Proline did not significantly affect the aggregation or stability of the co-formulated mixture. Arginine showed the largest increase in viscosity among the excipients tested, while salt and proline had less impact on viscosity. This was notable as salt had the largest effect on the instability of the mixture.
