Method Development and Validation for Pyrogallol Content Quantification by HPLC in Trimetazidine Dihydrochloride

Trimetazidine dihydrochloride (TD) is an anti-ischemic drug that is used to effectively treat angina pectoris symptoms. During the manufacture of TD from gallic acid a process related impurity, pyrogallol, is produced. Up to the present time, no appropriate method has been proposed for the detection and analysis of pyrogallol in the TD at the level of threshold of toxicological concern. Therefore, in this investigation, a reliable and reproducible HPLC method was developed for the detection and analysis of pyrogallol in the TD. The method was validated in full compliance with the recommendations of the International Harmonization Council. Regression analysis indicated a correlation coefficient value of 0.9990 for pyrogallol between 6.3 ppm and 31.5 ppm. The LOD was 1.89 ppm and LOQ was 6.3 ppm for pyrogallol. Good recovery (accuracy) was observed in the range of 98.34% to 118.54 % with an RSD value (precision) of 0.150%. Pyrogallol analysis in batches TD material has demonstrated the good performance of the method. The process is therefore useful in the identification and evaluation of pyrogallol content in drug substance of TD.

Threshold of Toxicological Concern—An Update for Non-Genotoxic Carcinogens

The Threshold of Toxicological Concern (TTC) concept can be applied to organic compounds with the known chemical structure to derive a threshold for exposure, below which a toxic effect on human health by the compound is not expected. The TTC concept distinguishes between carcinogens that may act as genotoxic and non-genotoxic compounds. A positive prediction of a genotoxic mode of action, either by structural alerts or experimental data, leads to the application of the threshold value for genotoxic compounds. Non-genotoxic substances are assigned to the TTC value of their respective Cramer class, even though it is recognized that they could test positive in a rodent cancer bioassay. This study investigated the applicability of the Cramer classes specifically to provide adequate protection for non-genotoxic carcinogens. For this purpose, benchmark dose levels based on tumor incidence were compared with no observed effect levels (NOELs) derived from non-, pre- or neoplastic lesions. One key aspect was the categorization of compounds as non-genotoxic carcinogens. The recently finished CEFIC LRI project B18 classified the carcinogens of the Carcinogenicity Potency DataBase (CPDB) as either non-genotoxic or genotoxic compounds based on experimental or in silico data. A detailed consistency check resulted in a dataset of 137 non-genotoxic organic compounds. For these 137 compounds, NOEL values were derived from high quality animal studies with oral exposure and chronic duration using well-known repositories, such as RepDose, ToxRef, and COSMOS DB. Further, an effective tumor dose (ETD10) was calculated and compared with the lower confidence limit on benchmark dose levels (BMDL10) derived by model averaging. Comparative analysis of NOEL/EDT10/BMDL10 values showed that potentially bioaccumulative compounds in humans, as well as steroids, which both belong to the exclusion categories, occur predominantly in the region of the fifth percentiles of the distributions. Excluding these 25 compounds resulted in significantly higher but comparable fifth percentile chronic NOEL and BMDL10 values, while the fifth percentile EDT10 value was slightly higher but not statistically significant. The comparison of the obtained distributions of NOELs with the existing Cramer classes and their derived TTC values supports the application of Cramer class thresholds to all non-genotoxic compounds, such as non-genotoxic carcinogens.

Genotoxic impurities in pharmaceutical products – regulatory, toxicological and pharmaceutical considerations

This article provides an overview of the most important aspects around the detecting and reporting of genotoxic impurities in the pharmaceutical industry. It focuses on relevant regulatory, toxicological, and pharmaceutical considerations. In this regard, the concept of Threshold of Toxicological Concern is explained and the most common genotoxic impurities are described. Furthermore, toxicological methods for genotoxic impurities screening are presented. Finally, the article emphasises several issues regarding further development.

Development of a New Threshold of Toxicological Concern Database of Non-cancer Toxicity Endpoints for Industrial Chemicals

In cases where chemical-specific toxicity data are absent or limited, the threshold of toxicological concern (TTC) offers an alternative to assess human exposure below which “there would be no appreciable risk to human health.” The application of TTC to non-cancer systemic endpoints has been pursued for decades using a chemical classification and Point of Departure (POD). This study presents a new POD dataset of oral subacute/subchronic toxicity studies in rats for 656 industrial chemicals retrieved from the Hazard Evaluation Support System (HESS) Integrated Platform, which contains hundreds of reliable repeated-dose toxicity test data of industrial chemicals under the Chemical Substances of Control Law in Japan. The HESS TTC dataset was found to have less duplication with substances in other reported TTC datasets. Each chemical was classified into a Cramer Class, with 68, 3, and 29% of these 656 chemicals distributed in Classes III, II, and I, respectively. For each Cramer Class, a provisional Tolerable Daily Intake (TDI) was derived from the 5th percentile of the lognormal distribution of PODs. The TDIs were 1.9 and 30 μg/kg bw/day for Classes III and I, respectively. The TDI for Cramer Class II could not be determined due to insufficient sample size. This work complements previous studies of the TTC approach and increases the confidence of the thresholds for non-cancer endpoints by including unique chemical structures. This new TTC dataset is publicly available and can be merged with existing databases to improve the TTC approach.

Application of the Threshold of Toxicological Concern (TTC) in Food Safety: Challenges and Opportunities

The safety assessment of chemicals added or found in food has traditionally made use of data from in vivo studies performed on experimental animals. The nature and amount of data required to carry out a risk assessment is generally stipulated either in the different food legislations or in sectoral guidance documents. However, there are still cases where no or only limited experimental data are available or not specified by law, for example for contaminants or for some minor metabolites from active substances in plant protection products. For such cases, the Threshold of Toxicological Concern (TTC) can be applied. This review explores the use of the TTC approach in food safety in the European Union, in relation to the different food sectors, legal requirements and future opportunities.