Potential impurities in drug substances: Compound-specific toxicology limits for 20 synthetic reagents and by-products, and a class-specific toxicology limit for alkyl bromides.

This paper provides compound-specific toxicology limits for 20 widely used synthetic reagents and common by-products that are potential impurities in drug substances. In addition, a 15 µg/day class-specific limit was developed for monofunctional alkyl bromides, aligning this with the class-specific limit previously defined for monofunctional alkyl chlorides. Both the compound- and class-specific toxicology limits assume a lifetime chronic exposure for the general population (including sensitive subpopulations) by all routes of exposure for pharmaceuticals. Inhalation-specific toxicology limits were also derived for acrolein, formaldehyde, and methyl bromide because of their localized toxicity via that route. Mode of action was an important consideration for a compound-specific toxicology limit. Acceptable intake (AI) calculations for certain mutagenic carcinogens assumed a linear dose-response for tumor induction, and permissible daily exposure (PDE) determination assumed a non-linear dose-response. Several compounds evaluated have been previously incorrectly assumed to be mutagenic, or to be mutagenic carcinogens, but the evidence reported here for such compounds indicates a lack of mutagenicity, and a non-mutagenic mode of action for tumor induction. For non-mutagens with insufficient data to develop a toxicology limit, the ICH Q3A qualification thresholds are recommended. The compound- and class-specific toxicology limits described here may be adjusted for an individual drug substance based on treatment duration, dosing schedule, severity of the disease and therapeutic indication.

Control and analysis of hydrazine, hydrazides and hydrazones--genotoxic impurities in active pharmaceutical ingredients (APIs) and drug products.

This is the latest of a series of reviews focused on the analysis of genotoxic impurities. This review summarises the analytical approaches reported in the literature relating to hydrazine, hydrazines, hydrazides and hydrazones. It is intended to provide guidance for analysts needing to develop procedures to control such impurities, particularly where this is due to concerns relating to their potential genotoxicity. Of particular note is the wide variety of techniques employed, both chromatographic and spectroscopic, with most involving derivatisation. Such a wide variety of options allow the analyst a real choice in terms of selecting the most appropriate technique specific to their requirements. Several generic methodologies, covering the three main analytical approaches; i.e. HPLC (high performance liquid chromatography), GC (gas chromatography) and IC (ion chromatography), are also described.

Analytical approaches for the detection of epoxides and hydroperoxides in active pharmaceutical ingredients, drug products and herbals.

This review summarizes the analytical approaches reported in the literature relating to epoxide and hydroperoxide impurities. It is intended that it should provide guidance for analysts faced by the need to control such impurities, particularly where this is due to concerns relating to their potential genotoxicity. An extensive search of the literature relating to this class of impurities revealed a large number of references relating to analysis of epoxides/hydroperoxides associated with herbal remedies. Given the general applicability of the analytical methodology and due to the widespread use of herbal products the authors decided to include herbal medicines in this review. The review also reflects on the very different approaches taken in terms of the assessment/control of genotoxic impurities for such herbal remedies to that required for pharmaceutical products.

Control and analysis of alkyl and benzyl halides and other related reactive organohalides as potential genotoxic impurities in active pharmaceutical ingredients (APIs).

This paper continues the review of the relevant scientific literature associated with the control and analysis of potential genotoxic impurities (PGIs) in active pharmaceutical ingredients (APIs). The initial review [D.P. Elder, A. Teasdale, A.M. Lipczynski, J. Pharm. Biomed. Anal. 46 (2008) 1-8.] focused on the specific class of sulfonate esters but in this instance reference is made to the analysis of alkyl and benzyl halides and other related reactive organohalide alkylating agents. Such reactive materials are commonly employed in pharmaceutical research and development as raw materials, reagents and intermediates in the chemical synthesis of new drug substances. Consequently a great deal of attention and effort is extended by the innovative and ethical pharmaceutical industry to ensure that appropriate and practicable control strategies are established during drug development to ensure residues of such agents, as potential impurities in new drug substances, are either eliminated or minimized to such an extent so as to not present a significant safety risk to volunteers and patients in clinical trials and beyond. The reliable trace analysis of such reactive organohalides is central to such control strategies and invariably involves a state-of-the-art combination of high-resolution separation science techniques coupled to sensitive and selective modes of detection. This article reports on the most recent developments in the regulatory environment, overall strategies for the control of alkylating agents and the latest developments in analysis culminating in a literature review of analytical approaches. The literature is sub-categorized by separation technique (gas chromatography (GC), high-performance liquid chromatography (HPLC), thin layer chromatography (TLC) and capillary zone electrophoresis (CZE)) and further tabulated by API type and impurity with brief method details and references. As part of this exercise, a selection of relevant pharmacopoeial monographs was also reviewed. The continued reliance on relatively non-specific and insensitive TLC methodologies in several monographs was noteworthy.

Control and analysis of alkyl esters of alkyl and aryl sulfonic acids in novel active pharmaceutical ingredients (APIs).

This article reviews current regulatory guidelines and relevant scientific literature pertaining to the control and analysis of potential genotoxic impurities (PGIs) in new active pharmaceutical ingredients (APIs) with specific reference to a certain sub-class of PGIs, namely alkyl esters of alkyl and aryl sulfonic acids. Sulfonic acids are very important in pharmaceutical R&D employed both as counter-ions in the formation of acid-addition salts and also as reagents and catalysts in the synthesis of new drug substances. The article reviews the evolution of analytical methodology from early studies in the mid 1970s through development of direct injection GC and HPLC methods to liquid-liquid/solid phase extraction and headspace based techniques coupled to HPLC and GC methodologies employing UV and MS detection to new derivatisation-based techniques. The paper also reflects on the significant challenges in developing robust analytical methodology capable of the trace determination of sulfonate esters, the challenges in transferring methodology from R&D to QC labs and on the cost of inappropriate limits for genotox impurities. In so doing, the authors seek to inform the debate that the control of genotoxic impurities should be driven primarily by safety and risk/benefit considerations rather than by state-of-the-art analytical and process chemistry capabilities that drive controls to levels 'as low as practicable' regardless of the risk/safety requirements.