Role of
Cosolutes in the Aggregation Kinetics of Monoclonal
Antibodies
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Abstract
We propose a general strategy based
on kinetic analysis to investigate
how cosolutes affect the aggregation behavior of therapeutic proteins.
We apply this approach to study the impact of NaCl and sorbitol on
the aggregation kinetics of two monoclonal antibodies, an IgG1 and
an IgG2. By using a combination of size exclusion chromatography and
light scattering techniques, we study the impact of the cosolutes
on the monomer depletion, as well as on the formation of dimers, trimers,
and larger aggregates. We analyze these macroscopic effects in the
frame of a kinetic model based on Smoluchowski’s population
balance equations modified to account for nucleation events. By comparing
experimental data with model simulations, we discriminate the effect
of cosolutes on the elementary steps which contribute to the global
aggregation process. In the case of the IgG1, it is found that NaCl
accelerates the kinetics of aggregation by promoting specifically
aggregation events, while sorbitol delays the kinetics of aggregation
by specifically inhibiting protein unfolding. In the case of the IgG2,
whose monomer depletion kinetics is limited by dimer formation, NaCl
and sorbitol are found respectively to accelerate and inhibit conformational
changes and aggregation events to the same extent