A harmonization effort for acceptable daily exposure application to pharmaceutical manufacturing – Operational considerations

Safety assessment of protein A and derivation of a parenteral health-based exposure limit

Protein A (PA) is a bacterial cell wall component of Staphylococcus aureus whose function is to bind to Immunoglobulin G (IgG). Given its ability to bind IgG as well as its stability and resistance to harsh acidic and basic cleaning conditions, it is commonly used in the affinity chromotography purification of biotherapeutics. This use can result in levels of PA being present in a drug product and subsequent patient exposure. Interestingly, PA was previously evaluated in clinical trials as well as supporting nonclinical studies, resulting in a database that enables the derivation of a health-based exposure limit (HBEL). Given the widespread use of PA in the pharmaceutical industry, the IQ DruSafe Impurities Safety Working Group (WG) evaluated the available information with the purpose of establishing a harmonized parenteral HBEL for PA. Based on this thorough, collaborative evaluation of nonclinical and clinical data available for PA, a parenteral HBEL of 1.2 μg/kg/dose (60 μg/dose for a 50 kg individual) is expected to be health protective for patients when it is present as an impurity in a biotherapeutic.

A simple and universal headspace GC-FID method for accurate quantitation of volatile amines in pharmaceuticals

Volatile amines are reagents commonly used in pharmaceutical manufacturing of intermediates, active pharmaceutical ingredients (APIs), and drug products as participating regents for chemical reactions and optimization of product yield. Due to their compound specific daily allowable intake, residual volatile amines are required by regulatory agencies to be monitored and controlled in pharmaceutical products intended for human consumption. However, the accurate quantification of residual volatile amines in pharmaceutical entities can often be challenging as these analytes may chemically react and/or interact with the sample matrix. Herein, we describe a simple and universal headspace gas chromatography with flame ionization detection (HS-GC-FID) method capable of separating 14 commonly used volatile amines. The chemical activity of the volatile amines with the API matrix were mitigated by using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as an additive to reduce matrix effects in conventional high-boiling diluents. The addition of DBU drastically improved the detectability and method accuracy of the residual volatile amines in an acidic API, namely, Ketoprofen®. Additionally, DBU was employed as a GC deactivation reagent to ensure interfacial adsorption of the analytes to GC components were reduced, thereby improving method precision. Method validation showed acceptable linearity, limit of detection, limit of quantitation, solution stability, precision, and robustness. Separation specificity, evaluated by observing the chromatographic resolution of the volatile amines with one-another and against a set of 23 common residual solvents, were shown to be acceptable for most peak pairs.

Setting impurity limits for endogenous substances: Recommendations for a harmonized procedure and an example using fatty acids

Endogenous substances, such as fatty, amino, and nucleic acids, are often purposefully used in parenterally pharmaceuticals, but may be present as impurities. Currently, no consensus guidance exists on setting impurity limits for these substances. Specific procedures are needed, as the amount and types of toxicity data available for endogenous substances are typically far less than those for other chemical impurities. Additionally, the parenteral route of administration of these substances is inherently non-physiological, resulting in potentially different or increased severity of toxicity. Risk Assessment Process Maps (RAPMAPs) are proposed as a model to facilitate the development of health-based exposure limits (HBELs) for endogenous substances. This yielded a framework that was applied to derive HBELs for several fatty acids commonly used in parenteral pharmaceuticals. This approach was used to derive HBELs with further vetting based on anticipated perturbations in physiological serum levels, impacts of dose-rate, and consideration of intermittent dosing. Parenteral HBELs of 100-500 mg/day were generated for several fatty acids, and a proposed class-based limit of 50 mg/day to be used in the absence of chemical-specific data. This default limit is consistent with the low toxicity of this chemical class and ICH Q3C value for Class 3 solvents.

The estimation of permitted daily exposure (PDE) values for Myroxylon balsamum (L.) Harms var. pereirae (Royle) Harms, balsamum (balsam of Peru) for regulatory toxicology purposes: application of various toxicological strategies

Myroxylon pereirae resin (MP; balsam of Peru) is a botanical balsam which is derived from a tree known as Myroxylon balsamum (L.) Harms var. pereirae (Royle) Harms, balsamum. This natural substance has a long history of medicinal use (antiseptic and for wound healing) but surprisingly there is a lack of toxicological data. The medicinal application of Peru balsam has been documented throughout a period of at least 30 years, however, due to the high risk of sensitisation and other treatment options available in the proposed indication, the medicinal use of MP in EU today is limited. The aim of this article is deriving Permitted Daily Exposure (PDE) values for MP for regulatory purposes using various toxicological strategies due to the problems with toxicological data. The results described in this article fills a gap in the literature on toxicological aspects of MP for the first time.

The utility of hERG channel inhibition data in the derivation of occupational exposure limits

Inhibition of the human ether-à-go-go (hERG) channel may lead to QT prolongation and fatal arrhythmia. While pharmaceutical drug candidates that exhibit potent hERG channel inhibition often fail early in development, many drugs with both cardiac and non-cardiac indications proceed to market. In this study, the relationship between in vitro hERG channel inhibition and published occupational exposure limit (OEL) was evaluated. A total of 23 cardiac drugs and 44 drugs with non-cardiac indications with published hERG channel IC₅₀ and published OELs were identified. There was an apparent relationship between hERG IC₅₀ potency and the OEL for cardiac and non-cardiac drugs. Twenty cardiac and non-cardiac drugs were identified that had a potent hERG IC₅₀ (≤25 μM) and a contrastingly large OEL value (≥100 μg/m³). OELs or hazard banding corresponding to ≤100 μg/m³ should be sufficiently protective of effects following occupational exposure to the majority of APIs with hERG IC₅₀ values ≤ 100 μM. It is important to consider hERG IC₅₀ values and possible cardiac effects when deriving OEL values for drugs, regardless of indication. These considerations may be particularly important early in the drug development process for establishing exposure control bands for drugs that do not yet have full clinical safety data.

Active pharmaceutical contaminants in dietary supplements: A tier-based risk assessment approach

The presence of active pharmaceutical ingredients (APIs) in adulterated or contaminated dietary supplements is a current product safety concern. Since there are limited guidelines, and no published consensus methods, we developed a tier-based framework incorporating typical lines of evidence for determining the human health risk associated with APIs in dietary supplements. Specifically, the tiered approach outlines hazard identification and decision to test for APIs in products based on criteria for likelihood of contamination or adulteration, and evaluation of manufacturer production standards. For products with detectable levels of APIs, a variety of default approaches, including the use of fraction of the therapeutic dose and the threshold of toxicological concern (TTC), as well as health-based exposure limits (HBELs) are applied. In order to demonstrate its practical use, as well as any limitations and/or special considerations, this framework was applied to five dietary supplements (currently available to the public). We found that the detected levels of APIs in some dietary supplements were above the recommended dose of the drugs, and thus, pose a significant health risk to consumers and potentially workers involved in manufacturing of these supplements. The results support the value of increased product quality surveillance and perhaps regulatory activity.

Development of a rapid GC-FID method to simultaneously determine triethylamine, diisopropylamine, and 1,1,3,3-tetramethylguanidine residues in an active pharmaceutical ingredient

A rapid GC-FID method was developed to simultaneously determine residual levels of triethylamine (TEA), 1,1,3,3-tetramethylguanidine (TMG), and diisopropylamine (DIPA) in the synthetic route of an active pharmaceutical ingredient (API). Due to the severe absorption of amines on GC stationary phases, GC columns with various stationary phases were evaluated for optimal peak shape and reproducibility. The final conditions used the Agilent CP-Volamine column to resolve the three amines in 12 min. Various inlet liners were also screened to further improve the sensitivity of the analysis. The Restek Siltek® liner was selected to achieve the desired detectability for the method. The quantitation limits were 4, 3, and 4 μg/mL for TEA, DIPA, and TMG in the presence of API, respectively. All three amines showed good linearity (r > 0.999) and recoveries (> 90%) over the concentration range of 3 to 16 μg/mL. The testing of residual amines was initially performed at the penultimate stage of the synthesis. However, this work demonstrates that TMG can act as a proton sponge to react with salicylic acid, the counter ion of the penultimate, to form a volatile component that elutes at a different retention time. Consequently, in the final method, these three amines were monitored in the final API to circumvent the matrix interference. Key parameters of the method were qualified per method validation requirements in ICH guidelines. The method was successfully applied for batch testing during development and implemented as an in-process control procedure at manufacturing sites.

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A fast and sensitive GC-FID method was developed to monitor the residue of three volatile amines in an API.

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The detection of 1,1,3,3-Tetramethylguanidine (TMG) at trace level is reported the first time.

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The method circumvented the interference of sample matrix since TMG can react with carboxylic acid in penultimate.

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The method was qualified per ICH guideline and implemented as an in-process-control procedure.

Development and evaluation of a harmonized whole body physiologically based pharmacokinetic (PBPK) model for flutamide in rats and its extrapolation to humans

By their definition, inadvertent exposure to endocrine disrupting compounds (EDCs) intervenes with the endocrine signalling system, even at low dose. On the one hand, some EDCs are used as important pharmaceutical drugs that one would not want to dismiss. On the other hand, these pharmaceutical drugs are having off-target effects and increasingly significant exposure to the general population with unwanted health implications. Flutamide, one of the top pharmaceutical products marketed all over the world for the treatment of prostate cancer, is also a pollutant. Its therapeutic action mainly depends on targeting the androgen receptors and inhibiting the androgen action that is essential for growth and survival of prostate tissue. Currently flutamide is of concern with respect to its categorization as an endocrine disruptor. In this work we have developed a physiologically based pharmacokinetic (PBPK) model of flutamide that could serve as a standard tool for its human risk assessment. First we built the model for rat (where many parameters have been measured). The rat PBPK model was extrapolated to human where the re-parameterization involved human-specific physiology, metabolic kinetics derived from in-vitro studies, and the partition coefficient same as the rat model. We have harmonized the model by integrating different sets of in-vitro, in-vivo and physiological data into a PBPK model. Then the model was used to simulate different exposure scenarios and the results were compared against the observed data. Both uncertainty and sensitivity analysis was done. Since this new whole-body PBPK model can predict flutamide concentrations not only in plasma but also in various organs, the model may have clinical applications in efficacy and safety assessment of flutamide. The model can also be used for reverse dosimetry in the context of interpreting the available biomonitoring data to estimate the degree to which the population is currently being exposed, and a tool for the pharmaceutical companies to validate the estimated Permitted Daily Exposure (PDE) for flutamide.

Topical otic drugs in a multi-purpose manufacturing facility: a guide on determination and application of permitted daily exposure (PDE)

Due to newly introduced EU GMP (Good Manufacturing Practice) guideline for Medicinal Products for Human and Veterinary use, product specific permitted daily exposure (PDE) for toxicological evaluation in multi-purpose facilities are required within a documented process for risk assessment. European Medicines Agency (EMA) guidance on setting PDE limits so far focused on systemic administration routes such as intravenous (IV), oral or inhalation. This article provides guidance on setting PDE values for risk management purposes in multi-purpose facilities for active pharmaceutical ingredients (APIs) applied as topical otic drugs to the outer ear canal. The therewith determined PDE otic, is used for the calculation of maximum safe carry-over (MSC) in manufacturing scenarios where a topical otic product is manufactured followed by another topical otic product.

The regulatory framework for preventing cross-contamination of pharmaceutical products: History and considerations for the future

Cross-contamination in multi-product pharmaceutical manufacturing facilities can impact both product safety and quality. This issue has been recognized by regulators and industry for some time, leading to publication of a number of continually evolving guidelines. This manuscript provides a historical overview of the regulatory framework for managing cross-contamination in multi-product facilities to provide context for current approaches. Early guidelines focused on the types of pharmaceuticals for which dedicated facilities and control systems were needed, and stated the requirements for cleaning validation. More recent guidelines have promoted the idea of using Acceptable Daily Exposures (ADEs) to establish cleaning limits for actives and other potentially hazardous substances. The ADE approach is considered superior to previous methods for setting cleaning limits such as using a predetermined general limit (e.g., 10 ppm or a fraction of the median lethal dose (LD50) or therapeutic dose). The ADEs can be used to drive the cleaning process and as part of the overall assessment of whether dedicated production facilities are required. While great strides have been made in using the ADE approach, work remains to update good manufacturing practices (GMPs) to ensure that the approaches are clear, consistent with the state-of-the-science, and broadly applicable yet flexible enough for adaptation to unique products and situations.

Special endpoint and product specific considerations in pharmaceutical acceptable daily exposure derivation

Recently, a guideline has been published by the European Medicines Agency (EMA) on setting safe limits, permitted daily exposures (PDE) [also called acceptable daily exposures (ADE)], for medicines manufactured in multi-product facilities. The ADE provides a safe exposure limit for inadvertent exposure of a drug due to cross-contamination in manufacturing. The ADE determination encompasses a standard risk assessment, requiring an understanding of the toxicological and pharmacological effects, the mechanism of action, drug compound class, and the dose-response as well as the pharmacokinetic properties of the compound. While the ADE concept has broad application in pharmaceutical safety there are also nuances and specific challenges associated with some toxicological endpoints or drug product categories. In this manuscript we discuss considerations for setting ADEs when the following specific adverse health endpoints may constitute the critical effect: genotoxicity, developmental and reproductive toxicity (DART), and immune system modulation (immunostimulation or immunosuppression), and for specific drug classes, including antibody drug conjugates (ADCs), emerging medicinal therapeutic compounds, and compounds with limited datasets. These are challenging toxicological scenarios that require a careful evaluation of all of the available information in order to establish a health-based safe level.

A harmonization effort for acceptable daily exposure derivation - Considerations for application of adjustment factors

Acceptable daily exposures (ADEs) are established to determine the quantity of one drug substance that can contaminate another drug product without causing harm to the patient. An important part in setting an ADE for a drug substance, after identification of the unwanted critical effect(s) of the compound (see Bercu et al., 2016, this issue), is the determination of an appropriate overall margin of safety that is need to be maintained below the dose causing a certain critical effect (i.e., the point of departure or PoD). The overall margin of safety used to protect the general patient population from critical effects is derived as the product (i.e., composite adjustment factor) of various individual factors that account for variability and uncertainty in extrapolating from the PoD to an ADE. These factors address the considerations of interindividual variability, interspecies extrapolation, LOAEL-to-NOAEL extrapolation, exposure duration adjustment, effect severity, and database completeness. The factors are considered individually, but are not necessarily independent and their interdependence should be identified, with subsequent adjustment to the composite factor, as appropriate. It is important to identify all sources of variability and uncertainty pertinent to the derivation of the ADE and ensure each is considered in the assessment, at least by one of the adjustment factors. This manuscript highlights the basis for and selection of factors that address variability and uncertainty as used in the guidance documents on setting ADEs or other related health-based limits.