Category: Formulation and Quality
Purpose: Long acting drug depot are designed for extended drug release of time ranging from weeks to months or even years. During the extended drug release timeframe, it is critical to closely monitor the degradation change and aggregation is typically the main degradation for high concentrated formulations. It can effectively minimize the aggregation growth by optimizing formulations with appropriated excipient selection. However, it is generally a resource consuming process to differentiate the formulation performance due to its designed slow drug released profile. It will be essential to develop an accelerated testing method to facilitate the formulation evaluation process. This method can not only benefit for formulation screening, but also assure the drug product quality control from batch-to-batch variation. In this study, a long acting peptide formulation, GNE-X, was chosen for this development. The team selected pH alteration and elevated temperature to accelerate the rate of drug degradation. The correlation between the developed accelerated method and real-time stability profile was assessed and the results suggests the degradation profile of 3-week in accelerated settings is comparable with the results of 6-month real time condition.
Methods: A 3-week study was proposed to evaluate the stability of peptide drug GNE-X and optimize the time interval of investigation. Three formulations were chosen for this study: 1) Controlled Formulation: GNE-X without excipient, 2) GNE-X with excipient A, and 3) GNE-X with excipient B. All three formulations were tested under real-time condition and accelerated condition. For real time condition: the formulations maintained in their original pH (~5.5) and incubated at 37 °C. For accelerated condition: the pH of formulations was titrated to 7.0 and incubated at 50°C. Degradation and biophysical stability of the formulations at various timepoints were then evaluated and compared to real-time data.
Results: In this study, we selected pH adjustment and temperature elevation as our accelerated conditions to facilitate the peptide degradation process. In order to evaluate the peptide degradation, several analytical methods were utilized for characterization. Physical degradation was validated by using size exclusion chromatography (SEC) for aggregations and reversed phase liquid chromatography (RP-LC) for chemical degradation, including oxidation and deamidation. Biophysical stability of the formulations was characterized using Circular Dichroism (CD) for conformational change and thioflavin T florescence assay for fibril findings.
In the real-time condition, it reached to 60% aggregation at week 24 for control formulations, 26% for GNE-X with excipient A, and 18% for GNE-X with excipient B (Figure 1).
Figure 2 has shown that aggregations were significantly expedited in the accelerated condition. By week 3 aggregations were already comparable to real-time aggregation profile at week 24 (shown in Figure 1 and 2). Rate constant of each formulation at both conditions were calculated and shown in Table 1 as linear functions. Scaling factors show the correlation between 37°C and accelerated 50°C are 5.1, 4.4 and 3.5 for controlled formulation, GNE-X with excipient A and B, respectively. The chemical degradation and biophysical stability were also further evaluated between drug products in real-time and accelerated conditions. The results suggest the degradation property were comparable in both conditions.
Conclusion: A 3-week forced degradation testing was developed by adjusting pH and elevating temperature. The accelerated aggregation profile correlates well with its respective real-time aggregation profiles, which indicates the degrading mechanisms is similar at both conditions. As a result, this developed testing method can be adopted for formulation screening and evaluate quality attributes to assure product performance.
Chloe Hu– South San Francisco, California
Chloe Hu– South San Francisco, California
Chun-Wan Yen– South San Francisco, California
Robert Kuhn– South San Francisco, California
Dennis Leung– Genentech, Inc., South San Francisco, California