Acceptable Intakes (AIs) for 11 Small molecule N-nitrosamines (NAs)

Low levels of N-nitrosamines (NAs) were detected in pharmaceuticals and, as a result, health authorities (HAs) have published acceptable intakes (AIs) in pharmaceuticals to limit potential carcinogenic risk. The rationales behind the AIs have not been provided to understand the process for selecting a TD₅₀ or read-across analog. In this manuscript we evaluated the toxicity data for eleven common NAs in a comprehensive and transparent process consistent with ICH M7. This evaluation included substances which had datasets that were robust, limited but sufficient, and substances with insufficient experimental animal carcinogenicity data. In the case of robust or limited but sufficient carcinogenicity information, AIs were calculated based on published or derived TD₅₀s from the most sensitive organ site. In the case of insufficient carcinogenicity information, available carcinogenicity data and structure activity relationships (SARs) were applied to categorical-based AIs of 1500 ng/day, 150 ng/day or 18 ng/day; however additional data (such as biological or additional computational modelling) could inform an alternative AI. This approach advances the methodology used to derive AIs for NAs.

Extending (Q)SARs to incorporate proprietary knowledge for regulatory purposes: is aromatic N-oxide a structural alert for predicting DNA-reactive mutagenicity?

(Quantitative) structure-activity relationship or (Q)SAR predictions of DNA-reactive mutagenicity are important to support both the design of new chemicals and the assessment of impurities, degradants, metabolites, extractables and leachables, as well as existing chemicals. Aromatic N-oxides represent a class of compounds that are often considered alerting for mutagenicity yet the scientific rationale of this structural alert is not clear and has been questioned. Because aromatic N-oxide-containing compounds may be encountered as impurities, degradants and metabolites, it is important to accurately predict mutagenicity of this chemical class. This article analysed a series of publicly available aromatic N-oxide data in search of supporting information. The article also used a previously developed structure-activity relationship (SAR) fingerprint methodology where a series of aromatic N-oxide substructures was generated and matched against public and proprietary databases, including pharmaceutical data. An assessment of the number of mutagenic and non-mutagenic compounds matching each substructure across all sources was used to understand whether the general class or any specific subclasses appear to lead to mutagenicity. This analysis resulted in a downgrade of the general aromatic N-oxide alert. However, it was determined there were enough public and proprietary data to assign the quindioxin and related chemicals as well as benzo[c][1,2,5]oxadiazole 1-oxide subclasses as alerts. The overall results of this analysis were incorporated into Leadscope's expert-rule-based model to enhance its predictive accuracy.

Regulatory risk assessments: Is there a need to reduce uncertainty and enhance robustness? Update on propylparaben in relation to its EU regulatory status

Over 10 years ago, propylparaben (propyl- p-hydroxybenzoate; PP) was withdrawn as a permitted food preservative in the EU based entirely on findings reported in a single dietary study in juvenile rats claiming to show adverse effects on male reproductive parameters [Oishi S. Effects of propyl paraben on the male reproductive system. Food Chem Toxicol 2002; 40(12): 1807 -1813]. Subsequent data reviews have cast serious doubt on the validity of the Oishi results, mainly in relation to aberrant concurrent-control values, and in two further comprehensive studies using neonatal and juvenile rats there were no adverse effects in males at oral doses up to 1000 mg/kg/day. By contrast, juvenile animal toxicity data on the two paraben preservatives currently permitted in the EU as food additives (methylparaben and ethylparaben) are non-robust and rudimentary. Although PP is a permitted preservative in cosmetics its use pattern is highly restricted based mainly on the results of a screening study in the rat using butylparaben as test material, and not taking into account the more recent data on PP. The European Medicines Agency has determined a permitted daily exposure of 2 mg/kg for PP, which applies to both adult and paediatric patients, based on an oral no-observed-adverse-effect level of 100 mg/kg/day in females, treatment-related changes suggestive of an estrogenic effect being noted at 1000 mg/kg/day. The weight of evidence strongly supports a toxicological re-evaluation of PP regarding its use in foodstuffs and cosmetics in the EU, with a view to reinstatement as a food additive, consistent with its status in other major jurisdictions.

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.

Acceptance criteria for levels of hydrazine in substances for pharmaceutical use and analytical methods for its determination

This report includes a brief review of the toxicology of hydrazine and the strategies used to set acceptance criteria. A preliminary examination of a number of approaches to determine hydrazine in pharmaceutical substances susceptible to its presence either as residue from the synthesis or from decomposition are described.

Alternatives models in carcinogenicity testing--a European perspective

Transgenic mouse strains offer the prospect of significant benefits in the in vivo assessment of carcinogenic potential. The European Regulatory Authorities have been supportive of their inclusion as one of the second-test options in the International Conference on Harmonization of Technical Requirements for the Registration of Pharmaceuticals for Human use (ICH). However, there is a concern regarding premature systematic use of these models. At present, the information from the International Life Sciences Institute (ILSI) project suggests that the transgenic models under study are similarly sensitive to genotoxic pharmaceuticals. There are apparently some false negatives and false positives. For regulatory purposes, it is not yet possible to differentiate the models with respect to hazard identification and risk assessment. The evaluation of the models has reached an interesting but, at certain points, equivocal stage. Based on the weight of evidence gathered thus far, regulatory authorities cannot neglect the outcome of such studies but need to be cautious in their interpretation of data from such models, and the application in risk assessment procedures.