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.

Assessing the utility of common arguments used in expert review of in silico predictions as part of ICH M7 assessments.

Expert review of two predictions, made by complementary (quantitative) structure-activity relationship models, to an overall conclusion is a key component of using in silico tools to assess the mutagenic potential of impurities as part of the ICH M7 guideline. In lieu of a specified protocol, numerous publications have presented best practise guides, often indicating the occurrence of common prediction scenarios and the evidence required to resolve them. A semi-automated expert review tool has been implemented in Lhasa Limited's Nexus platform following collation of these common arguments and assignment to the associated prediction scenarios made by Derek Nexus and Sarah Nexus. Using datasets primarily donated by pharmaceutical companies, an automated analysis of the frequency these prediction scenarios occur, and the likelihood of the associated arguments assigning the correct resolution, could then be conducted. This article highlights that a relatively small number of common arguments may be used to accurately resolve many prediction scenarios to a single conclusion. The use of a standardised method of argumentation and assessment of evidence for a given impurity is proposed to improve the efficiency and consistency of expert review as part of an ICH M7 submission.

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.

Framework for sensitization assessment of extractables and leachables in pharmaceuticals.

During the toxicological assessment of extractables and leachables in drug products, localized hazards such as irritation or sensitization may be identified. Typically, because of the low concentration at which leachables occur in pharmaceuticals, irritation is of minimal concern; therefore, this manuscript focuses on sensitization potential. The primary objective of performing a leachable sensitization assessment is protection against Type IV induction of sensitization, rather than prevention of an elicitation response, as it is not possible to account for the immunological state of every individual. Sensitizers have a wide range of potencies and those which induce sensitization upon exposure at a low concentration (i.e. strong, or extreme sensitizers) pose the highest risk to patients and should be the focus of the risk assessment. The Extractables and Leachables Safety Information Exchange (ELSIE) consortium has reviewed the status of dermal, respiratory, and systemic risk assessment in cosmetic and pharmaceutical industries, and proposes a framework to evaluate the safety of known or potential dermal sensitizers in pharmaceuticals. Due to the lack of specific regulatory guidance on this topic, the science-driven risk-based approach proposed by ELSIE encourages consistency in the toxicological assessment of extractables and leachables to maintain high product quality and ensure patient safety.

Practical and Science-Based Strategy for Establishing Acceptable Intakes for Drug Product N-Nitrosamine Impurities.

The potential for N-nitrosamine impurities in pharmaceutical products presents a challenge for the quality management of medicinal products. N-Nitrosamines are considered cohort-of-concern compounds due to the potent carcinogenicity of many of the structurally simple chemicals within this structural class. In the past 2 years, a number of drug products containing certain active pharmaceutical ingredients have been withdrawn or recalled from the market due to the presence of carcinogenic low-molecular-weight N,N-dialkylnitrosamine impurities. Regulatory authorities have issued guidance to market authorization holders to review all commercial drug substances/products for the potential risk of N-nitrosamine impurities, and in cases where a significant risk of N-nitrosamine impurity is identified, analytical confirmatory testing is required. A key factor to consider prior to analytical testing is the estimation of the daily acceptable intake (AI) of the N-nitrosamine impurity. A significant proportion of N-nitrosamine drug product impurities are unique/complex structures for which the development of low-level analytical methods is challenging. Moreover, these unique/complex impurities may be less potent carcinogens compared to simple nitrosamines. In the present work, our objective was to derive AIs for a large number of complex N-nitrosamines without carcinogenicity data that were identified as potential low-level impurities. The impurities were first cataloged and grouped according to common structural features, with a total of 13 groups defined with distinct structural features. Subsequently, carcinogenicity data were reviewed for structurally related N-nitrosamines relevant to each of the 13 structural groups and group AIs were derived conservatively based on the most potent N-nitrosamine within each group. The 13 structural group AIs were used as the basis for assigning AIs to each of the structurally related complex N-nitrosamine impurities. The AIs of several N-nitrosamine groups were found to be considerably higher than those for the simple N,N-dialkylnitrosamines, which translates to commensurately higher analytical method detection limits.

Development of Duration-Based Non-Mutagenic Thresholds of Toxicological Concern (TTCs) Relevant to Parenteral Extractables and Leachables (E&Ls).

The threshold of toxicological concern (TTC), i.e., the dose of a compound lacking sufficient experimental toxicity data that is unlikely to result in an adverse health effect in humans, is important for evaluating extractables and leachables (E&Ls) as it guides analytical testing and minimizes the use of animal studies. The Extractables and Leachables Safety Information Exchange (ELSIE) consortium, which consists of member companies that span biotechnology, pharmaceutical, and medical device industries, brought together subject matter expert toxicologists to derive TTC values for organic, non-mutagenic E&L substances when administered parenterally. A total of 488 E&L compounds from the ELSIE database were analyzed and parenteral point of departure (PPOD) estimates were derived for 252 compounds. The PPOD estimates were adjusted to extrapolate to subacute, subchronic, and chronic durations of nonclinical exposure and the lower fifth percentiles were calculated. An additional 100-fold adjustment factor to account for nonclinical species and human variability was subsequently applied to derive the parenteral TTC values for E&Ls. The resulting parenteral TTC values are 35, 110, and 180 µg/day for human exposures of >10 years to lifetime, >1-10 years, and ≤1 year, respectively. These parenteral TTCs are expected to be conservative for E&Ls that are considered non-mutagenic per ICH M7(R1) guidelines.

Calculating qualified non-mutagenic impurity levels: Harmonization of approaches.

The presence of impurities in drugs is unavoidable. As impurities offer no direct benefit to the patient, it is critical that impurities do not compromise patient safety. Current guidelines on the derivation of acceptable impurity levels leave aspects of calculations open for interpretation, resulting in inconsistencies across industry and regulators. To understand current impurity qualification practices from a safety standpoint, regulatory expectations and the safety risk that impurities pose, the IQ DruSafe Impurities Working Group (WG) conducted a pharmaceutical industry-wide survey. Survey results highlighted areas that could benefit from harmonization, including nonclinical species/sex selection and the application of adjustment factors (i.e., body surface area). Recommendations for alignment on these topics is included in this publication. Additionally, the WG collated repeat-dose toxicity information for 181 starting materials and intermediates, reflective of pharmaceutical impurities, to understand the toxicological risks they generally pose in relation to the drug substance (DS) and the assumptions surrounding the calculation of qualified impurity levels. An evaluation of this dataset and the survey were used to harmonize how to calculate a safe limit for an impurity based on toxicology testing of the impurity when present within the DS.

Deriving Compound-Specific Exposure Limits for Chemicals Used in Pharmaceutical Synthesis: Challenges in Expert Decision-Making Exemplified Through a Case Study-Based Workshop.

A workshop entitled "Deriving Compound-Specific Exposure Limits for Chemicals Used in Pharmaceutical Synthesis" was held at the 2018 Genetic Toxicology Association annual meeting. The objectives of the workshop were to provide an educational forum and use case studies and live multiple-choice polling to establish the degree of similarity/diversity in approach/opinion of the industry experts and other delegates present for some of the more challenging decision points that need to be considered when developing a compound-specific exposure limit (ie, acceptable intake or permissible or permitted daily exposure). Herein we summarize the relevant background and case study information for each decision point topic presented as well as highlight significant polling responses and discussion points. A common observation throughout was the requirement for expert judgment to be applied at each of the decision points presented which often results in different reasoning being applied by the risk assessor when deriving a compound-specific exposure limit. This supports the value of precompetitive cross-industry collaborations to develop compound-specific limits and harmonize the methodology applied, thus reducing the associated uncertainty inherent in the application of isolated expert judgment in this context. An overview of relevant precompetitive cross-industry collaborations working to achieve this goal is described.

Considerations when deriving compound-specific limits for extractables and leachables from pharmaceutical products: Four case studies.

Leachables from pharmaceutical container closure systems are a subset of impurities that present in drug products and may pose a risk to patients or compromise product quality. Extractable studies can identify potential leachables, and extractables and leachables (E&Ls) should be evaluated during development of the impurity control strategy. Currently, there is a lack of specific regulatory guidance on how to risk assess E&Ls; this may lead to inconsistency across the industry. This manuscript is a cross-industry Extractables and Leachables Safety Information Exchange (ELSIE) consortium collaboration and follow-up to Broschard et al. (2016), which aims to provide further clarity and detail on the conduct of E&L risk assessments. Where sufficient data are available, a health-based exposure limit termed Permitted Daily Exposure (PDE) may be calculated and to exemplify this, case studies of four common E&Ls are described herein, namely bisphenol-A, butylated hydroxytoluene, Irgafos® 168, and Irganox® 1010. Relevant discussion points are further explored, including the value of extractable data, how to perform route-to-route extrapolations and considerations around degradation products. By presenting PDEs for common E&L substances, the aim is to encourage consistency and harmony in approaches for deriving compound-specific limits.

Skin sensitization in silico protocol.

The assessment of skin sensitization has evolved over the past few years to include in vitro assessments of key events along the adverse outcome pathway and opportunistically capitalize on the strengths of in silico methods to support a weight of evidence assessment without conducting a test in animals. While in silico methods vary greatly in their purpose and format; there is a need to standardize the underlying principles on which such models are developed and to make transparent the implications for the uncertainty in the overall assessment. In this contribution, the relationship between skin sensitization relevant effects, mechanisms, and endpoints are built into a hazard assessment framework. Based on the relevance of the mechanisms and effects as well as the strengths and limitations of the experimental systems used to identify them, rules and principles are defined for deriving skin sensitization in silico assessments. Further, the assignments of reliability and confidence scores that reflect the overall strength of the assessment are discussed. This skin sensitization protocol supports the implementation and acceptance of in silico approaches for the prediction of skin sensitization.

Calculation of a permitted daily exposure value for the solvent 2-methyltetrahydrofuran.

In response to increasing concerns around the potential environmental impact of industrial chemicals, the pharmaceutical industry is seeking alternatives for traditional solvents used during the manufacturing process. Taking into consideration the principles of green chemistry, 2-methyltetrahydrofuran (2-MeTHF) is proposed as a suitable replacement for the structurally similar solvent tetrahydrofuran (THF). 2-MeTHF is derived from renewable sources and is more easily recovered thereby facilitating its reuse. However, 2-MeTHF is currently not included in the International Conference on Harmonisation (ICH) Q3C residual solvent guidelines and there is no Permitted Daily Exposure (PDE) limit proposed below which there would be negligible safety concerns for patients exposed to it as a residual impurity in a drug product. To enable the calculation of a PDE, a GLP compliant 3-month repeat-dose oral toxicity study in rats with a 1-month recovery period was conducted with doses of 2-MeTHF of 0, 80, 250, 500 and 1000 mg/kg/day. Administration of doses of up to 1000 mg/kg/day was tolerated. Based upon minimal observed effects on the liver at ≥500 mg/kg/day, the NOAEL in this study was considered to be 250 mg/kg/day. Inclusion of this NOAEL, and a safety factor of 250 a PDE of 50 mg/day was derived to support the safe use of 2-MeTHF in the pharmaceutical industry.