LC-MS-Based Identification of Polysorbate Degradation Pathways

Polysorbates are commonly used as surfactants in biologic formulations, but their chemical composition and polymeric nature can make degradation behavior complex. Changes in polysorbate content during long-term storage may therefore require targeted analytical investigation to determine the underlying degradation pathway.

In this case, an abnormal polysorbate content was observed in long-term stability samples, raising concerns that polysorbate degradation might have occurred during storage. LC-MS-based analysis was therefore required to investigate the potential degradation pathways.

Because polysorbate is a polymeric material and may undergo different degradation mechanisms, including enzymatic degradation, oxidation, and hydrolysis, Protheragen established separate LC-MS analytical approaches and corresponding MS databases for each potential pathway.

By using a project reference material to simulate the three degradation pathways, the team identified that the polysorbate changes observed under the oxidative degradation pathway were consistent with those detected in the long-term stability samples. Further LC-MS analysis indicated that the long-term stability samples contained three additional oxidation products compared with the reference material.

The Challenge

Limited Optimization Space with the Original Salt-gradient Method

The original CEX method used a salt-gradient elution strategy.

Although salt-gradient CEX methods can be effective for charge variant analysis, the existing method provided limited room for further optimization. As a result, conventional adjustment of the existing salt-gradient conditions was insufficient to adequately address the observed robustness issue.

The key challenges were:

• Significant differences in results between different chromatography columns;
• Insufficient method robustness;
• Limited optimization space within the existing salt-gradient approach; and
• The need to maintain clear separation of acidic, main, and basic charge variants.

The development objective was therefore to identify an alternative CEX method design that could provide better separation and improved robustness.

Multiple Potential Polysorbate Degradation Pathways

Polysorbate is a polymeric surfactant with a complex composition, and its degradation may occur through multiple pathways.

Potential mechanisms considered in the investigation included:

• Enzymatic degradation
• Oxidative degradation
• Hydrolytic degradation

Because different degradation pathways may generate different degradation products, simply analyzing the stability sample using a single LC-MS method would not be sufficient to confidently establish the underlying pathway.

The project therefore required:

1. Separate investigation of each potential degradation pathway;

2. Establishment of corresponding LC-MS analytical methods;

3. Development of MS databases for the degradation products generated through each pathway; and

4. Comparison of the degradation profiles from simulated degradation samples with those observed in long-term stability samples.

The central analytical question was:

Which degradation pathway best explains the polysorbate changes observed in the long-term stability samples?

Our Strategy

• Simulate Potential Degradation Pathways

The project reference material was used to simulate three potential polysorbate degradation pathways:

Enzymatic Degradation: The reference material was subjected to conditions designed to simulate enzymatic degradation and generate representative degradation products.

Oxidative Degradation: Oxidative conditions were used to generate representative oxidation products and establish an oxidation-related polysorbate degradation profile.

Hydrolytic Degradation: Hydrolytic conditions were used to investigate potential degradation products associated with hydrolysis.

This approach allowed the team to establish reference profiles for comparison with the long-term stability samples.

• Establish LC-MS Analytical Methods

Separate LC-MS analytical methods were developed for the simulated degradation pathways.

The objective was to characterize the changes in polysorbate composition and identify degradation-related signals associated with each pathway.

• Build Pathway-specific MS Databases

MS databases were established for the degradation products associated with the investigated pathways.

These databases provided reference information for comparing LC-MS profiles from the simulated degradation samples with those from the long-term stability samples.

This database-supported approach enabled the team to move beyond simply observing changes in polysorbate content and instead investigate which degradation pathway generated a profile consistent with the stability samples.

• Compare Simulated Degradation Profiles with Stability Samples

The LC-MS profiles of the long-term stability samples were compared with those generated from the simulated degradation studies.

The comparison showed that the changes in polysorbate observed in the long-term stability samples were consistent with the changes generated under the oxidative degradation pathway.

This provided analytical evidence supporting oxidation as the degradation pathway associated with the observed polysorbate changes.

Results

Comparison of the LC-MS profiles showed that the polysorbate changes observed in the long-term stability samples were consistent with those observed for the reference material under the oxidative degradation pathway.

This result supported oxidation as the degradation pathway associated with the observed polysorbate changes during storage.

Key Development Strategy

Key Outcomes

Before vs. Investigation

Project Outcome

The project successfully investigated the abnormal polysorbate changes observed in long-term stability samples using a multi-pathway LC-MS analytical strategy.

Three potential degradation pathways-enzymatic degradation, oxidative degradation, and hydrolysis-were investigated using the project reference material. Corresponding LC-MS analytical methods and MS databases were established to characterize and compare the resulting degradation profiles.

The comparison demonstrated that the polysorbate changes observed in the long-term stability samples were consistent with those observed under the oxidative degradation pathway. LC-MS analysis further identified three additional oxidation products in the long-term stability samples compared with the reference material.

The investigation therefore provided analytical evidence supporting the association between the observed polysorbate changes and oxidative degradation during storage.

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