Excipients are utilized during drug manufacture for a variety of purposes, including stabilization, bulking up or enhancing of the active pharmaceutical ingredient (API). Polysorbate-80 (PS-80) is a surfactant commonly used as an excipient to improve API stability. However, degradation of PS-80 can lead to decreased drug potency or stability, and there is inconsistency in the quality and composition of PS-80 provided by different vendors. To address these issues, Catalent developed a two-method approach to quantitate and characterize PS-80 supplied by multiple vendors and exposed to a variety of environmental stressors. Using high-performance liquid chromatography (HPLC) and charged aerosol detection (CAD), Catalent was able to detect degradation and differences in chemical composition in treated samples. This novel approach has multiple applications for drug developers looking to utilize PS-80 in their final product.
PS-80 is commonly used in biologic drugs to minimize surface adsorption/interfacial interaction and stabilize protein against stress-induced aggregation. However, PS-80 is a heterogenous mixture of varying chain lengths, structural-related materials and impurities. Therefore, there is lot-to-lot variability among manufacturers. Additionally, there is difficulty in quantitating the amount of PS-80 in solution due to lack of a universal standard. Finally, PS-80 can degrade over time when exposed to the environment, leading to detrimental effects on drug potency and stability. Catalent needed to develop a method to measure PS-80 quantity and quality as an excipient in biologic development and manufacture.
The Catalent Solution
Catalent utilized HPLC and CAD to develop two complementary analytical methods enabling PS-80 quantitation and characterization. First, degraded PS-80 solutions were prepared using 0.1% w/v PS-80 subjected to each of the following: thermal stress, base hydrolysis, oxidation and UV/Fluorescent light exposure. Bovine Serum Albumin (BSA) or IgG monoclonal antibody were spiked into the degraded PS-80 solution to a final concentration of 5 mg/ml.
For PS-80 quantitation, Catalent utilized mixed-mode chromatography via Waters Oasis MAX column. PS-80 components were eluted via step gradient of 80% water to 100% isopropanol. PS-80 concentration was calculated by comparing to a standard curve ranging from 12.5 µg/ml to 100 µg/ml. A decrease in PS-80 was observed in stressed samples when compared to protected or untreated samples, indicating that the method can successfully quantitate PS-80 in the product formulation (Figure 1).
Figure 1. Change of PS-80 content in stressed samples by quantitation method. (A) Thermal stress (B) Base hydrolysis (C) AAPH oxidation (D) Light exposure.
For PS-80 characterization, protein was removed from the PS-80 via Waters Oasis HLB SPE cartridges for solid-phase extraction. The resultant PS-80 components were separated by Agilent Zorbax SB-CN column. Degradation was observed to affect sorbitan POE esters, while POE sorbitan was relatively unaffected in most conditions. Base hydrolysis products oleic acid and POE sorbitan were detected (Figure 2). Compared to the quantitation method, the characterization method provided additional resolution in the form of a fingerprint, or chromatographic profile, of each sample. Therefore, the characterization method could potentially be used to assess the variation of PS-80 composition from lot to lot.
Figure 2. Chromatographic overlay of stressed samples by characterization method. (A) Thermal stress. Inset illustrates change upon stress. (B) Base hydrolysis. POE sorbitan (left inset) and oleic acid (right insert) were generated. (C) AAPH oxidation. (D) UV/FL light exposure in (a) exposed and (b) protected samples.
Stability and potency are critical characteristics of drug development and manufacture. Excipients are valuable substances used to improve stability and potency, but sourcing and stability of the excipients themselves can be a challenge. To address this need, Catalent developed a two-method solution to evaluate one such excipient (PS-80) for quantity and quality. Using HPLC and CAD, Catalent demonstrated that they could measure PS-80 concentration and distinguish between PS-80, structural-related materials, impurities and by-products of degradation. This method has multiple applications, including assessment of PS-80 as a raw material during manufacturing, PS-80 content confirmation, forced degradation studies, shelf-life studies and study of other polysorbates (e.g. PS-20).