Sorbitol crystallization-induced aggregation in frozen mAb formulations.

Sorbitol crystallization-induced aggregation of mAbs in the frozen state was evaluated. The effect of protein aggregation resulting from sorbitol crystallization was measured as a function of formulation variables such as protein concentration and pH. Long-term studies were performed on both IgG1 and IgG2 mAbs over the protein concentration range of 0.1-120 mg/mL. Protein aggregation was measured by size-exclusion HPLC (SE-HPLC) and further characterized by capillary-electrophoresis SDS. Sorbitol crystallization was monitored and characterized by subambient differential scanning calorimetry and X-ray diffraction. Aggregation due to sorbitol crystallization is inversely proportional to both protein concentration and formulation pH. At high protein concentrations, sorbitol crystallization was suppressed, and minimal aggregation by SE-HPLC resulted, presumably because of self-stabilization of the mAbs. The glass transition temperature (Tg ') and fragility index measurements were made to assess the influence of molecular mobility on the crystallization of sorbitol. Tg ' increased with increasing protein concentration for both mAbs. The fragility index decreased with increasing protein concentration, suggesting that it is increasingly difficult for sorbitol to crystallize at high protein concentrations.

A case study of nondelamination glass dissolution resulting in visible particles: implications for neutral pH formulations.

Visible particles were unexpectedly observed in a neutral-pH placebo formulation stored in glass vials but were not observed in the same formulation composition that contained protein. The particles were identified as silica gel (SiO2 ) and polysorbate 20, suggesting dissolution of the glass vial. Time course studies were performed to assess the effect of variables such as pH, excipients, storage temperature, and duration on particle formation. Data suggest that glass dissolution occurred during the storage in the liquid state, as shown by increased Si levels in solution. Upon freezing, the samples underwent freeze concentration and likely became supersaturated, which resulted in the appearance of visible silica particles upon thawing. The glass degradation described here is unique and differs from the more commonly reported delamination, defined by the presence of reflective, shard-like glass flakes in solution that are often termed lamellae. This case study underscores the importance of an early assessment (during formulation development) of potential incompatibility of the formulation with the primary container.