(627f) Mapping the Aggregation Behaviour of Biopharmaceuticals: A New Approach

Mapping the Aggregation
Behaviour of Biopharmaceuticals: A New Approach

S. Hedberg,
J. Heng, D. Williams                       

ABSTRACT

Protein aggregation is a critical problem for the
safety of biopharmaceuticals as they are linked to adverse immunologically
related responses in patients. Much effort has been made to gain a better
understanding of aggregation, however, the mechanisms leading to protein
aggregation are still not fully understood. Protein-protein molecular
interactions in solution are known to be involved in protein solution
aggregation behaviour and are a common issue for the manufacturing of biopharmaceuticals
such as monoclonal antibodies, mAbs.  Therefore, a major industrial and academic challenge
is the development of fast and reliable methods, either theoretically or
experimentally driven, which allow formulation scientists to identify optimal
biopharmaceutical species and solution conditions which deliver stable solution
products, thus avoiding aggregation.

In this work we will describe a SIC (self-interaction
chromatography) method for determining the osmotic second virial
coefficient (B₂₂), where B₂₂ describes the thermodynamics
of protein-protein interactions in solution. This experimental biophysical
approach allows solution stability maps including solution pH and salt
concentration effects to be obtained using mg
quantities of species such as mAbs. The approach has
been validated against traditional size-exclusion chromatographic methods on
samples that were aged over many weeks at elevated temperature. Both methods
gave similar stability condition maps, with the SIC method delivering results within
days compared with traditional stability trials which would typically take many
months.  Over a wide range of test conditions
good correlations were found between experimental B₂₂ values and experimentally
measured aggregation rates.

Similarly, the conformational and structural
changes were investigated for a number of selected conditions over a longer
time at continuously increasing temperature. The results proved that SIC easily
could predict the conformational changes of mAbs too.
From this study it was concluded that improvement in the SIC methods reported
here allows accurate and robust mapping of solution stability conditions as
well as a good prediction of conformational stability.