Getting to the Bottom of Genotoxic Impurities in APIs
By Francis Finot, CEO, GeneEvolution and partner of SEQENS’LAB
Addressing genotoxic impurities in the creation of Active Pharmaceutical Ingredients (APIs) is perhaps the biggest challenge of Contract Development & Manufacturing Organizations (CDMOs) everywhere. Yet reducing these impurities should be their key goal, helping to not only ensure the safety of patients treated with the final drug products, but also to ensure faster approvals and a less likely chance of seeing costly product recalls.
The real impact of genotoxic impurities are everywhere. Take for instance the news that the heartburn drug, Zantac and generic versions of it were recalled from store shelves because of the level of carcinogens found in them. Or, the news that generic versions of the popular blood pressure medication valsartan were recalled by the FDA and The European Medicines Agency (EMA) because of high levels of the carcinogen NDMA.
Because of these situations, it’s critical to better identify and understand the physical, structural and behavioral attributes of genotoxic impurities in APIs in order to identify the potential cause of variations in the finished product during drug development.
So what exactly are genotoxic impurities? They are chemical substances found in a confined amount of a sample which differ from the chemical composition of the material or compound of interest. Impurities are either naturally occurring or formed during the synthesis of a chemical compound. They are essentially reactive compounds that can induce genetic mutations and cancer when they react with DNA. Genotoxic impurities are not always a bad thing, and can sometimes be useful in chemical synthesis.
What may be surprising is that it is virtually impossible to have a molecular substance that is 100 percent pure and free of impurities. The goal for most manufacturers is to exceed 99 percent.
Raw Materials Impurities
Since raw materials most often have some level of impurity, it’s important to properly vet suppliers to ensure the highest levels of quality. Many CDMOs perform tests on various raw materials to determine the levels of impurities before they are purchased or before manufacturing begins. This can be accomplished by getting a sample and performing a test to make sure it meets the requirements.
Impurities in Process Manufacturing
Another place where impurities can come from is in the process itself. One way to look at it is, when you take “A” and “B” to make “C,” the molecules undergo a chemical reaction. Although the majority of molecules will orient themselves to create “C,” sometimes they create “D.” This is an example of process impurities, and most firms strive for 70 percent of the desired compound if not higher.
Evaluating risk Through Root Cause Analysis
During root cause analysis to evaluate the impact of an impurity on drug quality and safety, the origin of the compound can determine which guidelines to follow in the final evaluation of the drug impurity. Relevant guidelines include ICH Q3A (Impurities in New Drug Substances), ICH Q3B (Impurities in New Drug Products), ICH Q3C (Impurities: Guideline for Residual Solvents), and ICH M7 (Assessment and control of DNA reactive impurities in pharmaceuticals to limit potential carcinogenic risk).
According to ICH guidelines, if there are impurities in the range of .15 or higher, or compounds that are less than 98 percent pure, you need to identify the impurities and evaluate them for potential toxicity.
Yet it’s almost impossible to eliminate all genotoxic impurities during API synthesis. Our scientists are always on the lookout for structural alerts but there’s really no answer as to why one compound is genotoxic and another is not.
Identifying and controlling these impurities is also extremely challenging because they have highly reactive, diverse properties, and must be controlled at levels much lower than what is typically found in traditional impurities.
So, at what level does a CDMO decide to move ahead with the API? It really boils down to deciding if the presence of some toxins– at the detected concentrations – would pose an unacceptable risk to the patient, or if it would seriously compromise the quality or efficacy of the drug product. Many times, the presence of the compound may not pose any safety, quality or efficacy issues for the drug product, so in that case, proper documentation of the impurity (its identity, concentration, toxicological evaluation and quality impact) may be sufficient.
Regulatory Guidelines for Genotoxicity
Most CDMOs follow guidelines set forth from industry regulatory bodies, such as the International Conference of Harmonization (ICH), as well as the FDA and the EMA. These guidelines provide a practical framework for identifying, categorizing and qualifying genotoxic impurities to limit potential carcinogenic risk.
According to the ICH guidelines, when genotoxic impurities are identified, an appropriate control strategy leveraging process understanding and/or analytical controls should be developed to ensure that the mutagenic impurity is at or below the acceptable cancer risk level. The impurity assessment is a two-stage process:
- Actual impurities that have been identified should be considered for their mutagenic potential.
- An assessment of potential impurities likely to be present in the final drug substance is carried out to determine if further evaluation of their mutagenic potential is required.
Current Innovations from GeneEvolution
The most up-to-date thinking is that when a new impurity from a degradation product appears, this impurity should be characterized by its molecular structure, following by an in silico evaluation, and a review of the dossier expert, and if a doubt still remains, the impurity should be synthetized and evaluated in an Ames test, the gold standard test to detect mutagenic potential (ICH M7 guideline). Recently GenEvolution, a Seqens’ partner in the Seqens labs in Porcheville, France, set up a new method for quick response. The NanoAmes method provides a relevant response using only 35 µg (micrograms) of the test item/impurity on the 5 OECD tester strains in the absence or presence of metabolic activation. The traditional test requires 500 mg per assay or 35 mg if miniaturized. Without any chemical characterization, just testing the unknown collected peak from analysis process as a sample in a NanoAmes study, provides the crucial response to question, is it mutagen or not mutagen?
Genotoxic impurities are a fact of life in API manufacturing and CDMOs must work diligently to identify them at the source, while deploying sound processes to eliminate them. Through careful regulatory management and conscientious API manufacturers, product recalls and even more dire consequences of genotoxicity impurities can be eliminated.
If you’re interested in learning more about how we approach genotoxic impurities, check our other articles on our blog. We’d be happy to talk with you if you are interested in additional information or have a potential project to discuss. You can reach us here.