Quantitative characterization of leachables sinks in biopharmaceutical downstream processing

Assessing biologic/toxicologic effects of extractables from plastic contact materials for advanced therapy manufacturing using cell painting assay and cytotoxicity screening

Plastic components are essential in the pharmaceutical industry, encompassing container closure systems, laboratory handling equipment, and single-use systems. As part of their material qualification process, studies on interactions between plastic contact materials and process solutions or drug products are conducted. The assessment of single-use systems includes their potential impact on patient safety, product quality, and process performance. This is particularly crucial in cell and gene therapy applications since interactions with the plastic contact material may result in an adverse effect on the isolated therapeutic human cells. We utilized the cell painting assay (CPA), a non-targeted method, for profiling the morphological characteristics of U2OS human osteosarcoma cells in contact with chemicals related to plastic contact materials. Specifically, we conducted a comprehensive analysis of 45 common plastic extractables, and two extracts from single-use systems. Results of the CPA are compared with a standard cytotoxicity assay, an osteogenesis differentiation assay, and in silico toxicity predictions. The findings of this feasibility study demonstrate that the device extracts and most of the tested compounds do not evoke any measurable biological changes on the cells (induction  ≤ 5%) among the 579 cell features measured at concentrations  ≤ 50 µM. CPA can serve as an important assay to reveal unique information not accessible through quantitative structure-activity relationship analysis and vice versa. The results highlight the need for a combination of in vitro and in silico methods in a comprehensive assessment of single-use equipment utilized in advanced therapy medicinal products manufacturing.

Cell and Gene Therapies: Challenges in Designing Extractables and Leachables Studies and Conducting Safety Assessments

Over the past decade, Cell and Gene Therapies (C>) have been an emerging therapeutic area with more than twenty C> drug products approved and over 1000 registered trials. The remarkable progress in these modalities brings new challenges for scientists who evaluate manufacturing and storage materials, including risk assessments for extractables and leachables (E&L). Establishing a business process to qualify materials for these applications is an important risk mitigation strategy in support of these assessments. Process validation verifying process performance and product quality requirements using qualified materials also ensures that leachables from the materials do not result in an impact to process and product. The authors provide an overview of available guidelines and publications relevant to E&L risk assessments that can be used to support ex vivo C> products, highlighting gaps and standardization needs in the areas of biocompatibility and extractables conditions. Finally, the authors present leachable testing strategies, relevant to the specific manufacturing and storage conditions of C> products, and safety assessment considerations for organic and inorganic chemical entities.

Identification of nonvolatile organic compounds (NVOCs) in biopharmaceuticals through non-target analysis and quantification using complexation-precipitation extraction

Single-use systems in biopharmaceutical manufacturing can potentially release chemical constituents (leachables) into drug products. Prior to conducting toxicological risk assessments, it is crucial to establish the qualitative and quantitative methods for these leachables. In this study, we conducted a comprehensive screening and structure elucidation of 23 leachables (nonvolatile organic compounds, NVOCs) in two antibody drugs using multiple (self-built and public) databases and mass spectral simulation. We identified 7 compounds that have not been previously reported in medical or medicinal extractables and leachables. The confidence levels for identified compounds were classified based on analytical standards, literature references, and fragment assignments. Most of the identified leachables were found to be plasticizers, antioxidants, slip agents or polymer degradants. Polysorbate (namely Tween) is commonly used as an excipient for protein stabilization in biopharmaceutical formulations, but its ionization in liquid chromatography-electrospray ionization mass spectrometry can interfere with compound quantification. To address this, we employed a complexation-precipitation extraction method to reduce polysorbate content and quantify the analytes. The developed quantitative method for target NVOCs demonstrated high sensitivity (limit of quantification: 20 or 50 μg/L), accuracy (recoveries: 77.2 to 109.5 %) and precision (RSD ≤ 8.2 %). Overall, this established method will facilitate the evaluation of NVOC safety in drug products.

Dimethylsilanediol from silicone elastomers: Analysis, release from biopharmaceutical process equipment, and clearance studies

Polysiloxanes are considered one of the most important commercial families of synthetic elastomers. They are frequently employed in biopharmaceutical manufacturing equipment as flexible single-use solutions due to superior material properties and compatibility with diverse sterilization methods. Extractables and leachables (E&L) testing is essential in qualifying such equipment, involving extraction studies to assess the potential release of compounds from plastic components for risk assessment. Silicone releases oligomeric siloxanes and small hydrolysis products, with dimethylsilanediol (DMSD) being the main hydrolysis product found in significant concentrations in aqueous process solutions. DMSD presents challenges for analysis, requiring specifically tailored analytical methods to detect it, which are commonly not applied in standard E&L screening tests. In biopharmaceutical manufacturing, it is relevant to consider the potential of DMSD to repolymerize into silicone oil when specific process parameters are altered. This may lead to interactions with drug ingredients, including proteins, resulting in the formation of aggregates. We synthesized and characterized DMSD using X-ray structure analysis and established an HPLC method with a refractive index detector to investigate the release of DMSD from commercially available silicone tubing used in drug manufacturing following autoclaving and irradiation. Subsequently, we assessed typical biopharmaceutical downstream operations for effectively removing this compound from the process stream.

Biosorption of process-equipment-related leachables (PERLs) in biomanufacturing: A quantitative approach to study partitioning of PERLs in a cell culture system

The assessment and potential risk of process equipment-related leachables (PERLs) in the production of biopharmaceuticals and cell therapeutics using single-use (SU) equipment has been discussed previously. However, potential interactions of cells with PERLs have not yet been considered. Here, we present a quantitative adsorption study of neutral, organic small-molecule leachable compounds - known for extractables & leachables (E&L) analysis of SU equipment - in aqueous suspensions of CHO and T cells. The solid-water partition coefficient K_d was obtained for all compounds that showed adsorption. The findings implied that hydrophobic interactions are dominant; however, there was no unambiguous correlation between the derived adsorption coefficient K_d and the octanol-water partition coefficient K_ow. Interestingly, a maximum affinity of both cell types to the leachable bis(2,4-di-tert-butylphenyl)phosphate, which is known to be detrimental to cell development, was observed. A comparison of both cell types revealed that they generally interact with the same compounds in most cases but to different extents. Using partition coefficients enables estimation of the concentrations of leachable compounds associated with the biomass phase and in the aqueous suspensions and could be used for risk assessment of SU systems in biopharmaceutical and cell therapy (CT) manufacturing processes.

Transformation of Biopharmaceutical Manufacturing Through Single-Use Technologies: Current State, Remaining Challenges, and Future Development

Single-use technologies have transformed conventional biopharmaceutical manufacturing, and their adoption is increasing rapidly for emerging applications like antibody-drug conjugates and cell and gene therapy products. These disruptive technologies have also had a significant impact during the coronavirus disease 2019 pandemic, helping to advance process development to enable the manufacturing of new monoclonal antibody therapies and vaccines. Single-use systems provide closed plug-and-play solutions and enable process intensification and continuous processing. Several challenges remain, providing opportunities to advance single-use sensors and their integration with single-use systems, to develop novel plastic materials, and to standardize design for interchangeability. Because the industry is changing rapidly, a holistic analysis of the current single-use technologies is required, with a summary of the latest advancements in materials science and the implementation of these technologies in end-to-end bioprocesses.

Linear Solvation Energy Relationships (LSERs) for Robust Prediction of Partition Coefficients between Low Density Polyethylene and Water Part I: Experimental Partition Coefficients and Model Calibration

When equilibrium of leaching is reached within a product's duty cycle, partition coefficients polymer/solution dictate the maximum accumulation of a leachable and thus, patient exposure by leachables. Yet, in the pharmaceutical and food industry, exposure estimates based on predictive modeling typically rely on coarse estimations of the partition coefficient, with accurate and robust models lacking. This first part of the study aimed to explore linear solvation energy relationships (LSERs) as high performing models for the prediction of partition coefficients polymer/water. For this, partition coefficients between low density polyethylene (LDPE) and aqueous buffers for 159 compounds spanning a wide range of chemical diversity, molecular weight, vapor pressure, aqueous solubility and polarity (hydrophobicity) were determined and complimentary data collected from the literature (n=159, MW: 32 to 722, logK_i,O/W: -0.72 to 8.61 and logK_i,LDPE/W: -3.35 up to 8.36). The chemical space represented by this compounds set is considered indicative for the universe of compounds potentially leaching from plastics. Based on the dataset for the LDPE material purified by solvent extraction, a LSER model for partitioning between LDPE and water was calibrated to give:logK_i,LDPE/W=-0.529+1.098E_i-1.557S_i-2.991A_i-4.617B_i+3.886V_i. The model was proven accurate and precise (n = 156, R² = 0.991, RMSE = 0.264). Further, it was demonstrated superior over a log-linear model fitted to the same data. Nonetheless, it could be shown that log-linear correlations against logK_i,O/W can be of value for the estimation of partition coefficients for nonpolar compounds exhibiting low hydrogen-bonding donor and/or acceptor propensity. For these nonpolar compounds, the log - linear model was found to be: logK_i,LDPE/W=1.18logK_i,O/W-1.33 (n = 115, R²=0.985, RMSE = 0.313). In contrast, with mono-/bipolar compounds included into the regression data set, an only weak correlation was observed (n = 156, R² = 0.930, RMSE = 0.742) rendering the log-linear model of more limited value for polar compounds. Notably, sorption of polar compounds into native (non-purified) LDPE was found to be up to 0.3 log units lower than into purified LDPE. To identify maximum (i. e. worst-case) levels of leaching in support of chemical safety risk assessments on systems attaining equilibrium before end of shelf-life, it appears adequate to utilize LSER - calculated partition coefficients (in combination with solubility data) by ignoring any kinetical information.

Linear Solvation Energy Relationships (LSERs) for Robust Prediction of Partition Coefficients between Low Desity Polyethylene and Water Part II: Model Evaluation and Benchmarking

By neglecting the kinetics of leaching, the accumulation of leachables in a clinically relevant medium in contact with plastics is principally driven by the equilibrium partition coefficient between the polymer and the medium phase. Based on experimental partition coefficients for a wide set of chemically diverse compounds between low density polyethylene (LDPE) and water, a linear solvation energy relationship (LSER) model was obtained in part I of this study, reading: logK_i,LDPE/W=-0.529+1.098E_i-1.557S_i-2.991A_i-4.617B_i+3.886V_i. The model was proven accurate and precise (n = 156, R2 = 0.991, RMSE = 0.264).) In this part II of the study, for further evaluation and benchmarking of the LSER model ∼ 33% (n = 52) of the total observations were ascribed to an independent validation set. Calculation of partition coefficients logK_i,LDPE/W for this validation set was based on experimental LSER solute descriptors. Linear regression against the corresponding experimental values yielded R2 = 0.985 and RMSE = 0.352. When using LSER solute descriptors predicted from the compound's chemical structure by means of a QSPR prediction tool, instead, R2 = 0.984 and RMSE = 0.511 were obtained. These statistics are considered indicative for extractables with no experimental LSER solute descriptors available. By comparison to LSER models from the literature, a strong correlation between the quality of experimental partition coefficients and the chemical diversity of the training set to the model's predictability was observed, the latter of particular relevance for the application domain of the model. Further, to tentatively match partitioning into LDPE to partitioning into a liquid phase, partition coefficients logK_i,LDPE/W were converted into logK_{i,LDPEamorph/W} by considering the amorphous fraction of the polymer as effective phase volume only. A LSER model now recalibrated based on the observations for logK_{i,LDPEamorph/W} exhibited the constant in the equation above to now read -0.079 instead of -0.529 which rendered the model more similar to a corresponding LSER-model for n-hexadencane/water. Based on LSER system parameters available, the sorption behavior of LDPE could be efficiently compared to the one of polydimethylsiloxane (PDMS), polyacrylate (PA) and polyoxymethylene (POM). The latter, by offering capabilities for polar interactions due to their heteroatomic building blocks, exhibit stronger sorption than LDPE to the more polar, non-hydrophobic domain of sorbates up to an logK_i,LDPE/W range of 3 to 4. Above that range, all four polymers exhibited a roughly similar sorption behavior. Overall, LSERs were found to represent an accurate and user-friendly approach for the estimation of equilibrium partition coefficients involving a polymeric phase. All intrinsic input parameters can be retrieved from a free, web-based and curated database along with the outright calculation of the partition coefficient for any given neutral compound with a known structure for a given two-phased system.

Risk analysis of leachables in cell and gene therapy using a CAR-T model process

With the rapidly emerging field of autologous therapies, Single-Use (SU) technologies are increasingly used in personalized medicine due to their manifold advantages. Although qualification of the starting material of autologous therapies such as the CAR-T process has been highlighted, little attention has been paid to the effect of leachables on cell-based therapies, even if recent studies indicate interactions of leachables with cells. To close this gap, this study presents a risk-analysis of SU-material on a CAR-T process and identifies hazards imposed by tubing materials and leachables thereof. In order to represent a CAR-T process in its entirety, two test systems, namely a lentivirus production process and primary T-cells, were used. While the effects on lentivirus production are comparable to those reported for antibody production processes in CHO cells, we found that PVC material and corresponding leachables, i.e. plasticizer, inhibit cell growth of primary T-cells to a great extent. Additionally, our results indicate that critical quality attributes are affected by the PVC material.

X-ray sterilization of biopharmaceutical manufacturing equipment-Extractables profile of a film material and copolyester Tritan™ compared to gamma irradiation

The biopharmaceutical industry gains enormous flexibility in production processes by using sterilized preassembled single‐use devices. Gamma irradiation is an established sterilization technology that may be restricted in the future by the availability of ⁶⁰Co as irradiation source and irradiation capacities. X‐ray technology is considered an alternative type of radiation for sterilizing SU equipment. In the context of extractables and leachables—one concern connected with the use of single‐use process equipment—the effect of X‐ray irradiation on the extractables profile of the materials needs to be compared to established gamma irradiation to qualify this alternative technology. An approach is presented to obtain robust and comprehensive extractables data for materials used in SU devices after sterilization either using X‐ray or gamma irradiation. A careful selection of the test items and the test design allows a one‐to‐one comparison of data obtained from a combination of orthogonal analytical techniques. The extractables of a modern SU film material and the copolyester Tritan™ are evaluated. The data presented allow a risk evaluation on the safety of this new sterilization modality for biopharmaceutical applications. It is demonstrated that the extractables profile of a polymer is not affected by the type of irradiation used for sterilization.

4-Hydroxynonenal - A Toxic Leachable from Clinically Used Administration Materials

INTRODUCTION

The migration of chemicals from processing materials into biopharmaceuticals can lead to various problems. Leachables from administration materials, with no possibility of further clearance, are of particular concern. Released chemicals can be toxic or react with formulation components, thereby impacting product safety. Therapeutic proteins, which are susceptible to chemical modifications, have highest risk to be affected.

AIM

The aim of this study was to identify a previously unknown leachable compound from clinical administration sets, which was present above the applied generic safety threshold.

METHODS

Extracts of commonly used clinical administration sets were analyzed using a recently established specific assay allowing the identification and quantification of the α,β-unsaturated aldehyde 4-hydroxynonenal (HNE) in a drug product surrogate solution. HNE was quantified after derivatization with 2,4-dinitrophenylhydrazine (DNPH) and liquid extraction of the formed hydrazone by LC-MRM analysis.

RESULTS

Potentially genotoxic HNE was a leachable compound from all tested administration sets, in parts exceeding safety thresholds for genotoxicants. The HNE-releasing polymer was identified as PVC.

CONCLUSION

Clinical administration sets should be, like manufacturing materials and container closure systems, in the focus of routine leachables studies. Manufacturers of clinical administration sets should show responsibility to avoid the presence of safety concerning chemicals, like HNE.

Identification of an Oxidizing Leachable from a Clinical Syringe Rubber Stopper

Leaching of toxic or reactive chemicals from polymeric materials can adversely affect the quality and safety of biopharmaceuticals. It was therefore the aim of the present study to analyze leachables from a disposable clinical administration syringe using a polysorbate-containing surrogate solution and to assess their chemical reactivity. Analytical methods did include (headspace) GC-MS, Fourier-transform-infrared spectroscopy, a ferrous oxidation-xylenol orange assay, and nuclear magnetic resonance analysis. In the syringe leachables solution, the carcinogenic 1,1,2,2-tetrachloroethane (TCE) was detected in concentrations above the ICH M7-derived analytical evaluation threshold. TCE was shown to be an oxidation product of dichloromethane used during sample preparation. Since TCE was only isolated from incubations with the contained rubber stopper, we hypothesized that a stopper-derived leachable acted as a reactive oxidant promoting this chemical reaction. Subsequently, the leachable was identified to be the polymerization initiator Luperox® 101. Combining different analytical approaches led to the structural elucidation of a chemical reactive oxidant, which has the potential to interact and alter drug products. We conclude that chemically reactive compounds, such as the newly identified rubber stopper leachable Luperox® 101, may be of concern and therefore should be routinely considered if a prolonged exposure of polymers with drug products can be anticipated.

Interaction of leachable model compounds and their impact on Chinese hamster ovary cell cultivation

The presence of leachables in biopharmaceutical processes using single-use technologies (SUT) is well known. For the detection and quantification of the latter, extractable studies of SUT are very common nowadays. Although a mixture of compounds is regularly found in extractable studies, research has only been carried out regarding the effect of individual compounds on cell culture and the cumulative effect of a mix of leachables has not been investigated yet. In this study, a set of leachable model compounds (LMCs) was chosen and the effect of the LMCs on a Chinese hamster ovary DG44 cell line producing an IgG antibody was investigated concerning cell growth, cell cycle distribution and productivity. It was shown that even if worst-case concentrations were used, the LMCs solely impact cell growth. Additionally, interaction studies revealed that the inhibiting effect of the mix is lower than the expected cumulative effect. A strong antagonism between the antioxidant butylated hydroxytoluene and the plasticizer Tris(2-ethylhexyl)trimellitate was found using an isobologram analysis.