(T1330-02-09) Evaluating Static and Dynamic Interactions between Preservative and Tubing during Filling of Parenteral Liquid Formulations

Purpose: The purpose of this research is to establish a lab-scale model for predicting tubing compatibility with parenteral liquid formulation containing preservative during static and dynamic interactions. Preservatives are essential for ensuring the integrity of liquid formulations, particularly those used in multi-dose applications, by providing microbial stability.¹ Maintaining preservative levels throughout the manufacturing process is crucial, as it ensures the integrity of the drug product while in-use. However, interactions between the formulation and contact materials during manufacturing and storage can significantly impact both the preservative's effectiveness and the formulation’s stability. For example, silicone tubing is widely used for its flexibility and chemical resistance but poses challenges in maintaining preservative concentrations due to the migration of preservative molecules into the tubing, followed by diffusion and evaporation.^1,2 This loss is exacerbated with smaller tubing diameter due to larger surface area-to-volume ratios. While thermoplastic elastomer (TPE) tubing can prevent such losses due to its low permeability, its rigidity may cause variability in subvisible particulates during peristaltic pumping.³ This is of particular concern because parenteral liquid formulations must be essentially free of visible particles and must comply with regulatory guidelines regarding the tolerance limits for subvisible particles.⁴ Therefore, it is crucial to not only assess material compatibility but also the behavior of the tubing under manufacturing conditions with associated physical stressors (e.g. pumping shear, hold duration, etc.). In this study, a framework was developed through lab-scale peristaltic pumping model to determine filling parameters in manufacturing through evaluation of pumping shear stress on the tubing and its resulting effect on subvisible particulates.

Methods: Static incubation with tubing: In both clinical and commercial manufacturing settings, products are commonly filled using silicone tubing with an diameter as small as 1.6 mm. In this study both TPE and silicone tubing with 1.6 mm diameter were evaluated. Solutions mimicking generic parenteral formulations containing benzyl alcohol were utilized. Tubing was cut into specified lengths, rinsed with MilliQ water, dried, and sterilized by autoclaving. The tubing was then filled with the solution, ensuring absence of air gaps, and the ends were sealed with hemostats. The filled tubing was stored at room temperature until the end of the incubation periods. Samples were collected at 0, 40-, 360- and 1440-minutes post-incubation. After each incubation period, the entire volume was extracted and stored at 2-8°C until analysis. An RP-UPLC method was employed to quantify the preservative content at all time points. Dynamic interaction with tubing: Sections of TPE and silicone tubing were assessed to determine the effect of peristaltic pumping on subvisible particles. First, an optimum surrogate fluid was identified. The surrogate (placebo buffer containing preservative), along with two controls (WFI and a generic mAb parenteral formulation containing preservative) were used for the screening. The solutions were recirculated for up to 3-cycles and samples collected after 1^st and 3^rd recirculation at 500 rpm using a Flexicon PD12I peristaltic pump. The collected samples were evaluated for sub-visible particulates through microflow imaging and preservative content was quantified through RP-UPLC. The confirmatory arm of the study was conducted for select worst-case conditions to further evaluate tubing longevity.

Results: Dependence of preservative recovery on contact time and tubing material: Preservative loss was observed to be time-dependent at a surface area-to-volume ratio of 25 cm^-1 (Figure 1). Silicone tubing exhibited a more pronounced loss, while both types of TPE tubing demonstrated significantly higher preservative recovery. Evaluating subvisible particulate dependence on tubing material during pumping: It was first determined that surrogates yielded equivalent levels of subvisible particulates when exposed to same pumping stress conditions as formulations containing active pharmaceutical ingredients. It was then determined that the type of tubing material corresponded with the number of subvisible particulates generated, particularly in the 2-10 µm size range (Figure 2). Furthermore, across both types of tubing material tested, preservative recovery was sustained when the liquid was kept in circulation, i.e., under continuous pumping. Impact of Pumping Duration and Speed on Tubing Longevity: The process of filling DP vials can take several hours, influenced by the number of vials filled per minute, dosing volumes, and inevitable process interruptions, leading to prolonged exposure to pumping stress. It was observed that the longer duration of pumping expected during clinical and commercial manufacturing settings, along with pumping speed, had an impact on external wear through of the TPE tubing. However, no increase in subvisible particulates in the 2-10 µm range was observed during the pumping duration (Figure 3).

Conclusion: A systematic method was used to identify suitable tubing for filling drug products with preservatives. TPE tubing consistently demonstrated improved preservative retention compared to silicone at same tubing inner diameter. Moreover, while one type of TPE tubing showed a higher number of subvisible particulates, another TPE tubing was identified, that resulted in a comparable number of subvisible particulates to silicone tubing, thereby meeting the requirements for preservative recovery while minimizing particulates.

References: (1) Gottschalk, P.; Schlossbauer, P.; Schleicher, L.; Lindner, K.; Presser, I.; Wittmann, M. Interaction of Preservatives with Contact Materials during Filling and Storage of Parenteral Liquid Formulations. Eur. J. Pharm. Sci. 2025, 204, 106971. https://doi.org/10.1016/j.ejps.2024.106971.
(2) Saller, V.; Matilainen, J.; Rothkopf, C.; Serafin, D.; Bechtold- Peters, K.; Mahler, H.-C.; Friess, W. Preservative Loss from Silicone Tubing during Filling Processes. Eur. J. Pharm. Biopharm. 2017, 112, 109–118. https://doi.org/10.1016/j.ejpb.2016.11.021.
(3) Her, C.; Tanenbaum, L. M.; Bandi, S.; Randolph, T. W.; Thirumangalathu, R.; Mallela, K. M. G.; Carpenter, J. F.; Elias, Y. Effects of Tubing Type, Operating Parameters, and Surfactants on Particle Formation During Peristaltic Filling Pump Processing of a mAb Formulation. J. Pharm. Sci. 2020, 109 (4), 1439–1448. https://doi.org/10.1016/j.xphs.2020.01.009.
(4) Carpenter, J. F.; Randolph, T. W.; Jiskoot, W.; Crommelin, D. J. A.; Russell Middaugh, C.; Winter, G.; Fan, Y.-X.; Kirshner, S.; Verthelyi, D.; Kozlowski, S.; Clouse, K. A.; Swann, P. G.; Rosenberg, A.; Cherney, B. Overlooking Subvisible Particles in Therapeutic Protein Products: Gaps That May Compromise Product Quality. J. Pharm. Sci. 2009, 98 (4), 1201–1205. https://doi.org/10.1002/jps.21530.

Preservative recovery after static incubation in 1.6 mm diameter silicone and TPE tubing.

Dependence of subvisible particulate count on tubing type and pumping fluid

Tubing longevity and subvisible particulates