Joel P. Bercu

Leachables in pharmaceutical products may react with biomolecule Active Pharmaceutical Ingredients (APIs) e.g., mAb, peptide, RNA, potentially compromising product safety, 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, while 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 concluded that the sensitivity of an in silico screen using multiple methodologies was 80-90% and specificity 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 modelling and quality risk management.

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.

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 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 PPODs estimates were adjusted to extrapolate to subacute, subchronic, and chronic durations of nonclinical exposure and the lower 5th 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.