Parylene C Coating Efficacy Studies: Enhancing Biocompatibility of 3D Printed Polyurethane Parts for Biopharmaceutical and CGT Applications.

Additive manufacturing, particularly Vat photopolymerization, presents a promising technique for producing complex, tailor-made structures, making it an attractive option for generating single-use components used in biopharmaceutical manufacturing equipment or cell culture devices. However, the potential leaching of cytotoxic compounds from Vat photopolymer resins poses a significant concern, especially regarding cell growth and viability in cell culture applications. This study explores the potential of parylene C coating to enhance the inertness of a polyurethane-based photopolymer resin, aiming to prevent cytotoxicity and improve biocompatibility. The study includes an analysis of extractables from the resin and photoinitiator to evaluate the resin's composition and to define selected marker compounds for investigating the coating efficiency. The time-dependent accumulation of relevant extractable compounds over a 70-day period are assessed to address the long-term use of the coated components. The impact of irradiation on the material and the coating was evaluated, along with an accelerated aging study to address the long-term performance of the coating. Biocompatibility in terms of in vitro cell growth studies is evaluated using Chinese hamster ovary cells, a standard cell line in biopharmaceutical manufacturing. Results demonstrate that parylene C coating significantly reduces the release of cytotoxic compounds, such as the photoinitiator diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO). Although accelerated aging indicates a reduction in the barrier properties of the coating over time, the parylene C coating still effectively slows the release of extractables and significantly improves cell compatibility of the 3D printed parts. The findings suggest that parylene C-coated components can be safely integrated into biopharmaceutical manufacturing processes, with recommendations to minimize storage times between coating application and use to ensure optimal performance.

In Silico Assessment of Biomolecule Reactivity with Leachables.

Leachables in pharmaceutical products may react with biomolecule active pharmaceutical ingredients (APIs), for example, monoclonal antibodies (mAb), peptides, and ribonucleic acids (RNA), potentially compromising product safety and efficacy or impacting quality attributes. This investigation explored a series of in silico models to screen extractables and leachables to assess their possible reactivity with biomolecules. These in silico models were applied to collections of known leachables to identify functional and structural chemical classes likely to be flagged by these in silico approaches. Flagged leachable functional classes included antimicrobials, colorants, and film-forming agents, whereas specific chemical classes included epoxides, acrylates, and quinones. In addition, a dataset of 22 leachables with experimental data indicating their interaction with insulin glargine was used to evaluate whether one or more in silico methods are fit-for-purpose as a preliminary screen for assessing this biomolecule reactivity. Analysis of the data showed that the sensitivity of an in silico screen using multiple methodologies was 80%-90% and the specificity was 58%-92%. A workflow supporting the use of in silico methods in this field is proposed based on both the results from this assessment and best practices in the field of computational modeling and quality risk management.

Characterizing Extractables and Leachables Chemical Space to Support In Silico Toxicological Hazard Assessments.

This article describes the development of a representative dataset of extractables and leachables (E&L) from the combined Extractables and Leachables Safety Information Exchange (ELSIE) Consortium and the Product Quality Research Institute (PQRI) published datasets, representing a total of 783 chemicals. A chemical structure-based clustering of the combined dataset identified 142 distinct chemical classes with two or more chemicals across the combined dataset. The majority of these classes (105 chemical classes out of 142) contained chemicals from both datasets, whereas 8 classes contained only chemicals from the ELSIE dataset and 29 classes contain only chemicals from the PQRI dataset. This evaluation also identified classes containing chemicals that were flagged as potentially mutagenic as well as potent (strong or extreme) dermal sensitizers by in silico tools. The prevalence of alerting structures in the E&L datasets was approximately 9% (69 examples) for mutagens and 3% (25 examples) for potent sensitizers. This analysis showed that most (80%; 20 of 25) E&L predicted to be strong or extreme dermal sensitizers were also flagged as potential mutagens. Only two chemical classes, each containing three chemicals (alkyl bromides and isothiocyanates), were uniquely identified in the PQRI dataset and contained chemicals predicted to be potential mutagens and/or potent dermal sensitizers.

A Case Study Demonstrating the Importance of Glass Vial Selection for Parenteral Pharmaceutical Products.

There are many factors to consider when selecting a container closure system for parenteral drug products to maintain their quality, efficacy, and safety. One aspect to consider for products stored in glass vials is the glass type. Although the glass vials in which most parenteral products are stored are classified as Type I by the United States Pharmacopoeia, Chapter <660>, not all glass vials that meet the glass performance characteristics of Type I are equivalent. In the study presented here, Type I glass vials from three suppliers of three different Type I glass vials (standard, delamination control, and coated) were investigated to evaluate the impact that each Type I glass vial had on the stability of a drug product under development. To evaluate this impact, a three-phase study was conducted in which the compatibility between the drug product and each vial was assessed through the measurement of the critical quality attributes of the product, extractable and leachable inorganic elements were analyzed for each vial, and finally a stability study under accelerated conditions was conducted for the drug product in the most compatible vial based on the aforementioned experiments. Results from this study demonstrated that there are, in fact, significant differences in glass vials regardless of their classification as Type I. In the study conducted here, delamination control Type I glass vials were found to be superior to both Standard Type I and coated Type I vials for the drug product under investigation.

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.

Identification and quantification of medical device extractables and leachables via non-target analysis (NTA); Analytical uncertainty.

Leachables are substances that are leached from a medical device during its clinical use and are important due to the patient health-related effects they may have. Thus, medical devices are profiled for leachables (and/or extractables as probable leachables) to assess their potential impact on patient health and safety. This profiling is accomplished by screening extracts or leachates of the medical device for released organic substances via non-targeted analysis (NTA) employing chromatographic methods coupled with mass spectrometric detection. Chromatographic mass spectral response factors (RFs) for extractables and leachables vary significantly from compound to compound, complicating the quantitation of these compounds and the application of assessment strategies such as the Analytical Evaluation Threshold (AET). The analytical uncertainty resulting from response factor variation can be expressed in terms of an uncertainty factor (UF), which estimates the magnitude of response factor variation. This manuscript discusses the concept and impact of analytical uncertainty and provides best practice recommendations for the calculation and use of the uncertainty factor, UF.

Evaluation of a Novel LC-MS/MS Based Analytical Method for the Risk Assessment of Nitrosamines in Pharmaceutical Products and Packaging Materials.

The detection of nitrosamine impurities, particularly small dialkyl types, which are frequently known to be potent mutagenic carcinogens, in some Sartan group active pharmaceutical ingredients (APIs) and finished drug products caused global regulatory organizations to have concerns. Accordingly, Registration Holders/Applicants, API manufacturers, and their raw material suppliers are required to check the presence of nitrosamines in their products and carry out risk assessments using the quality risk management principles specified in the ICH Q9 guide. In this context, a new LC-MS/MS method has been developed and validated for the simultaneous determination of NDMA, NDEA, NMBA, NDIPA, NEIPA, NDBA, and MeNP nitrosamine compounds in API and finished products as well as in primary packaging materials, one of the risk sources. This validated method was applied to check the nitrosamine content may occur from canister, blister, printed aluminum foil, nasal spray, and eye drop packaging materials as part of the Extractables & Leachables studies arising from interactions between the product and the primary packaging. For the determination and quality control of nitrosamines in sartan group pharmaceutical products and packaging materials, the developed LC-MS/MS analytical method offers highly reliable, fast, high accuracy, good sensitivity and simultaneous detection even at low concentrations.

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.

Modeling the Migration Behavior of Extractables from Mono- and Multilayer Polyolefin Films to Mathematically Predict the Concentration of Leachable Impurities in Pharmaceutical Drug Products. Part 1: Experimental Details and Modeling Experimental Results.

An important step in the development of a pharmaceutical drug product is to demonstrate acceptable levels of leachable impurities during the shelf-life and therapeutic use of the drug product. If the diffusion and partition coefficients are known, the concentration profile of a leachable impurity in the drug product can be predicted theoretically at a given temperature and time. With this objective in mind, kinetic experiments were performed to study the migration of low- to high-molecular-weight organic compounds from mono- and multilayer polyolefin films. Migration curves at different temperatures were generated for each compound when these films were brought in contact with aqueous solutions with varying pH or with another plastic film made from a different polyolefin material. "Best fit" migration curves and the corresponding diffusion and partition coefficients (about 300 pieces) were obtained by using numerical software developed by FABES. The results obtained show that, in general, the correlation between the calculated diffusion and partition coefficients and temperature, between 30°C and 85°C, obeys the Arrhenius and Van't Hoff equations. In this temperature range, the diffusion and partition coefficients can be used to model and predict migration of the investigated compounds from the same pharmaceutical packaging materials. A comparison of these coefficient values with other polyolefin films also provides insights into the chemistry of the mono- and multilayers and the impact it has on the migration behavior of the compounds. In a consecutive paper, an approach to overestimate the diffusion and partition coefficients to account for the variability in experimental data is explained and finally, the use of these overestimated parameters to predict the concentrations for other compounds leaching from the multilayer films into aqueous drug product formulations is discussed.

Modeling the Migration Behavior of Extractables from Mono- and Multilayer Polyolefin Films to Mathematically Predict the Concentration of Leachable Impurities in Pharmaceutical Drug Products. Part 2: Conservative Diffusion and Partition Coefficient Determinations.

In the development of a pharmaceutical drug product packaging, an important step is to demonstrate acceptable levels of leachable impurities migrating from the packaging material into the drug product during its shelf life and therapeutic use. Such migration processes can be quantified either by analytical methods (which is often challenging and labor intensive) or (in many cases) through theoretical modeling, which is a reliable, quick, and cost-effective method to forecast the level of leachable impurities in the packaged drug when the diffusion and partition coefficients are known. In the previous part, it was shown how these parameters can be determined experimentally, and subsequent theoretical fitting of the results for a series of low- and high-molecular-weight organic compounds (known leachables) in a series of polyolefin materials was performed. One of the interpretations of these results is that a theoretical calculation can be made only for organic compounds and materials whose diffusion/partition/solubility coefficients were determined experimentally and theoretical fitting was achieved. However, in practice, there will be situations in which other leachable compounds may have to be investigated. In such cases, strictly speaking, it would be necessary to perform the whole experimental and fitting procedure for the new compound before a proper theoretical modeling is possible. But this would make the theoretical calculation of a leaching process from a pharmaceutical packaging material a cumbersome and cost intensive procedure. To address this problem, the pools of diffusion and partition coefficients were used to develop an approach that allows the estimation, without any additional experimentation, of so-called "conservative" diffusion and partition coefficients for a much wider range of potential leachables in the polyolefin pharmaceutical packaging materials and aqueous solutions investigated previously.

Efficiency of ultrafiltration/diafiltration in removing organic and elemental process equipment related leachables from biological therapeutics.

In the production of biological therapeutics such as monoclonal antibodies (mAbs), ultrafiltration and diafiltration (UF/DF) are widely regarded as effective downstream processing steps capable of removing process equipment related leachables (PERLs) introduced upstream of the UF/DF step. However, clearance data available in the literature are limited to species with low partition coefficients (log P) such as buffer ions, hydrophilic organic compounds, and some metal ions. Additional data for a wide range of PERLs including hydrophobic compounds and elemental impurities are needed to establish meaningful, comprehensive safety risk assessments. Herein, we report the results from studies investigating the clearance of seven different organic PERLs representing a wide range of characteristics (i.e., log P (-0.3 to 18)), and four model elements with different chemical properties spiked into a mAb formulation at 10 ppm and analyzed during clearance using gas chromatography-mass spectrometry (GC-MS), liquid chromatography-photodiode-array-mass spectrometry (LC-PDA-MS), and inductively coupled plasma mass spectrometry (ICP-MS). The clearance data showed ideal clearance and sieving of spiked organic PERLs with log P < 4, partial clearance of PERLs with 4 < log P < 9, and poor clearance of highly hydrophobic PERLs (log P > 9) after nine diafiltration volumes (DVs). Supplemental clearance studies on seven additional PERLs present at much lower concentration levels (0.1-1.5 ppm) in the mAb formulation upstream of UF/DF and three PERLs associated with the tangential flow filtration (TFF) equipment also demonstrated the similar correlations between log P and % clearance. For model elements, the findings suggest that UF/DF in general provides ideal clearance for elements. Evidence showed that the UF/DF process does not only help mitigate leachables risk from PERLs introduced upstream of UF/DF, but also from the TFF operation itself as all three TFF-related PERLs were effectively cleared. Overall, the UF/DF clearance presented in this work demonstrated whereas highly hydrophobic PERLs and elements that exist as charged species, particularly transition metal ions, may not be as effectively cleared and thus warrant further risk assessment; hydrophilic and some hydrophobic PERLs (log P < 4) are indeed well-cleared and thus present a lower overall safety risk.

Challenges Associated with Biological Safety Assessments for Drug-Device Combination Products.

Biological safety assessments for drug-device combination products involve evaluation of the drug container closure and the device constituent part. When the device constituent part is the drug delivery system as well as the drug container closure system, both device and drug-based packaging standards have been deemed applicable. Approaches used for the biological safety assessment of medical devices differ from those used for pharmaceutical packaging/delivery systems. One area of difference is the extent to which chemical characterization with toxicological assessment is used either in addition to, or in place of, biological in vivo or in vitro tests. Differences also exist in the way nonclinical studies are used to evaluate the safety of medical devices or drug delivery systems. The lack of alignment in standards and guidance has resulted in confusion over what combination of tests and methods of evaluation constitute a biological safety assessment that will meet regulatory expectations for a drug-device combination product. The intent of this article is to discuss the challenges created when the packaging or delivery system is also a device constituent part of a drug-device combination product. Suggestions are offered regarding approaches that may be useful for conducting suitable biological safety assessments for drug-device combination products.

Characterization of Silicone from Closed System Transfer Devices and its Migration into Pharmaceutical Drug Products.

Closed System Transfer Devices (CSTDs) are increasingly used in healthcare settings to facilitate compounding of hazardous drugs but increasingly also therapeutic proteins. However, their use may significantly impact the quality of the sterile product. For example, contamination of the product solution may occur by leaching of silicone or particulates from the CSTDs. It was therefore the aim of the present study to identify and quantify the types of silicone oil in a panel of typically used CSTDs. Particles found after simulated CSTD compounding processes were evaluated using Light Obscuration and Micro-Flow Imaging and were confirmed to be silicone oil particles. The number of particulates shed from CTSDs was in single cases exceeding pharmacopeial limits for a final parenteral product. Using X-ray microtomography, lubrication was shown to be primarily applied at connecting parts of the CSTD. Quantitative and qualitative analysis by Fourier transform infrared spectroscopy (FTIR) revealed a total released amount between 0.8 and 16 mg per CSTD of polydimethylsiloxane or polymethyltrifluoropropylsiloxane per CSTD. While pronounced differences in total silicone content between CSTDs were observed, it did not fully correlate with particle contamination in the test solutions, potentially due to variations in CSTD design. The impact of typical surfactants in biological formulations on silicone migration into product was additionally evaluated. We conclude that CSTDs may compromise final product quality, as (different types of) silicone oil may be released from these devices and contaminate the administered product.

Corrigendum: Analytical approaches for the evaluation of data deficient simulated leachable compounds in ENDS products: a case study.

[This corrects the article DOI: 10.3389/fchem.2023.1212744.].

Accurate or Protective: What is the Goal of Non-targeted Extractables and Leachables Quantitation and Identification?

Leachables are quantified and identified to enable their quantitative toxicological safety risk assessment (qTSRA). The leachable's reported concentration and identity must meet certain quality expectations to be suitable for qTSRA. In this Correspondence, the author considers accuracy and protectiveness as competing key quality attributes and suggests that protectiveness is the proper quality attribute for qTSRA as qTSRA is based on the foundation that a leachable's potential adverse effect on patient health and safety must not be under-estimated. Considering this conclusion, means of making concentration estimates and proposed identities protective are discussed.

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.

Sensitization Assessment of Extractables and Leachables in Pharmaceuticals: ELSIE Database Analysis.

Quality by design is the foundation of the risk management framework for extractables and leachables (E&Ls) recommended by the Extractables and Leachables Safety Information Exchange (ELSIE). Following these principles during the selection of materials for pharmaceutical product development minimizes the presence of highly toxic substances and decreases the health risk of potential leachables in the drug product. Therefore, in the context of the broad arena of chemicals, it is important to distinguish E&Ls as a subset of chemicals and evaluate this relevant chemical space to derive appropriate analytical and safety thresholds. When considering the health hazards posed by E&Ls, one area presenting a challenge is understanding the sensitization potential and whether it poses a risk to patients. A dataset of E&Ls compiled by ELSIE (n=466) was analysed to determine the prevalence and potency of skin sensitizers in this chemical subset and explore a scientifically justified approach to the sensitization assessment of potential leachables in parenteral drug products. Approximately half of the compounds (56%, 259/466) had sensitization data recorded in the ELSIE database and of these, 20% (52/259) are potential skin sensitizers. Only 3% (8/259) of the E&L dataset with sensitization data were considered potent (strong or extreme) sensitizers following in silico analysis and expert review, illustrating that potent sensitizers are not routinely observed as leachables in pharmaceutical products. Our analysis highlights that in silico potency prediction and expert review are key tools during the sensitization assessment process for E&Ls. The results confirm where material selection is anticipated to mitigate the risk of presence of strong and/or extreme sensitizers (e.g., extractable testing via ISO 10993-10), and that implementing thresholds per ICH M7 and/or Masuda-Herrera et al. provides a reasonably conservative approach for establishing the analytical testing and safety thresholds.

Harmonisation of read-across methodology for drug substance extractables and leachables (E&Ls).

Health-based exposure limits (HBELs) are derived for leachables from polymeric components that interact with the drug substance which exceed a safety concern threshold (SCT). However, given the nature of leachables, there is not always chemical-specific toxicology data. Read-across methodology specific to extractables and leachables (E&Ls) was developed based on survey data collected from 11 pharmaceutical companies and methodology used in other industries. One additional challenge for E&L read-across is most toxicology data is from the oral route of administration, whereas the parenteral route is very common for the leachable HBEL derivation. A conservative framework was developed to estimate oral bioavailability and the corresponding oral to parenteral extrapolation factor using physical chemical data. When this conservative framework was tested against 73 compounds with oral bioavailability data, it was found that the predicted bioavailability based on physico-chemical properties was conservatively greater than or equal to the experimental bioavailability 79% of the time. In conclusion, an E&L read-across methodology has been developed to provide a consistent, health protective framework for deriving HBELs when toxicology data is limited.

Analytical approaches for the evaluation of data deficient simulated leachable compounds in ENDS products: a case study.

Leachable investigations are routinely undertaken across a range of sectors (e.g., pharmaceuticals, medical devices, etc.) to determine whether chemicals from a container closure system transfer into a product under normal conditions of use. For Electronic Nicotine Delivery Systems (ENDS) the container closure system includes all materials in contact with the e-liquid that is aerosolized and subsequently inhaled by the user. Currently, there is no guidance for conducting leachable studies for ENDS products, however, there are relevant guidance documents for orally inhaled drug products that can be applied to an ENDS container closure system. We present a case study of the analytical investigation of two leachable compounds identified in simulated leachable studies using aged JUULpods filled with unflavored e-liquid (PG/VG/nicotine/benzoic acid). Both compounds had limited toxicological information and were considered data deficient. A qualitative analysis of the aerosol collected from aged commercial JUULpods (Virginia Tobacco and Menthol), using a similar analytical method (LC-MS/MS) used in the simulated leachable studies, showed no trace or detectable levels of either leachable compound. Therefore, this qualitative analysis did not provide semi-quantitative values for the data-deficient leachable compounds necessary to support toxicological risk assessment. Further, no commercial authentic standards or reasonable synthetic route were available due to the molecular size and structural complexity of the compounds. Instead, method limits were established using an alternative approach to standard ICH guidelines. The experimentally determined method limit of quantitation, using spiked samples of simulated leachable e-liquid, provided conservative semi-quantitative values for each data deficient leachable compound in the aerosol that enabled a transfer efficiency from e-liquid to aerosol to be estimated. The transfer efficiency of each leachable compound was experimentally determined to be less than 2% based on the limit of quantitation, which then could be used to define a relevant exposure limit for the toxicological risk assessment. This work details a novel analytical approach for determining the transfer efficiency of data deficient leachable compounds from ENDS container closure systems into the ENDS aerosol to support toxicological health risk assessments.

Predicting partitioning from low density polyethylene to blood and adipose tissue by linear solvation energy relationship models.

The variety of polymers utilized in medical devices demands for testing of extractables and leachables according to ISO 10993-18:2020 in combination with ISO 10993-1:2018. The extraction of the materials involves the use of organic solvents as well as aqueous buffers to cover a wide range of polarity and pH-values, respectively. To estimate patient exposure to chemicals leaching from a polymer in direct body contact, simulating solvents are applied to best mimic the solubilization and partitioning behavior of the related tissue or body fluid. Here we apply linear solvation energy relationship (LSER) models to predict blood/water and adipose tissue/water partition coefficients. We suggest this predictive approach to project levels of potential leachables, design extraction experiments, and to identify the optimal composition of simulating extraction solvents. We compare our predictions to LSER predictions for commonly applied surrogates like ethanol/water mixtures, butanol, and octanol as well as olive oil, butanone, 1,4-dioxane for blood and adipose tissue, respectively. We therefore selected a set of 26 experimentally determined blood/water partition coefficients and 33 adipose tissue/water partition coefficients, where we demonstrate that based on the root mean squared error rmse the LSER approach performs better than surrogates like octanol or butanol and equally well as 60:40 ethanol/water for blood. For adipose tissue/water partitioning, the experimentally determined octanol/water partition coefficient performs best but the rmse is at the same range as our LSER approach based on experimentally determined descriptors. Further, we applied our approach for 248 extractables where we calculated blood/low density polyethylene (LDPE) and adipose tissue/LDPE partition coefficients. By this approach, we successfully identified chemicals of potential interest to a toxicological evaluation based on the total risk score.