Practical Implementation of the Control of Elemental Impurities: EMA’s new Guideline Draft

Posted on

One and a half year after its publication, the ICH Q3D guideline still raises many questions. The EMA has recently published a guideline draft aiming at clarifying the practical implementation of ICH Q3D. Read more here about what is expected in a marketing authorisation application or in an application for a CEP with regard to risk assessment and the control of elemental impurities in APIs and medicinal products.,15429,15332,S-WKS_n.html

The “ICH Q3D Guideline for Elemental Impurities” was published in December 2014 as Step 4 document and released in August 2015 under No EMA/CHMP/ICH/353369/2013 as EMA’s Scientific Guideline. The guideline came into effect in June 2016 for all medicinal products currently underlying a marketing authorisation procedure (new applications).

In the meantime, it became clear that implementing in practice the requirements of this guideline has been so complex and led to some marketing authorisation procedures being delayed. The ICH has already reacted to the situation and published 7 training modules on its website. Moreover, a concept paper announces a question & answer document.

On 12 July 2016, the draft of an EMA’s guideline entitled “Implementation strategy of ICH Q3D guideline” (EMA/404489/2016) was published. The purpose of the document is to provide support for implementing ICH Q3D in the European context.

The draft comprises three chapters addressing the most important elements in relation with the implementation of the ICH Q3D requirements. The chapter “1. Different approaches to Risk Management” starts describing the two fundamental approaches to the performance of a risk assessment and the justification for a control strategy with regard to elemental impurities:

Drug Product Approach
Here, batches of the finished product are scanned by means of analytical (validated!) procedures to develop a risk-based control strategy. If – with this approach – the omission of a routine testing has to be justified, the authority expects a detailed and valid justification though, and not just analytical data from a few batches.

Component Approach
The guideline draft clearly gives its preference to this approach. The respective contribution of the different components of a medicinal product is considered with respect to the potential total impurity profile and compared to the PDE value from the risk assessment. All potential sources of impurity, for example from production equipment or from excipients of natural (mined) origin have to be considered in this assessment. This particularly applies to outsourced APIs; here, all pieces of information available from Active Substance Master Files (ASMFs) or Certificates of Suitability (CEPs) have to be used. Substances with a Ph.Eur. monograph should always comply with the elemental impurities limits of the corresponding monograph.

The chapter “2. Particulars for Intentionally Added Element(s)” deals with the common practice in many organic syntheses to add elements to increase the specificity of the chemical reaction and the yield. It is particularly critical when the last step of an API synthesis just before the end product uses a metal catalyst. In such a case, the authority expects a convincing evidence that the catalyst is purged to levels consistently below the control threshold (<30% of the PDE) by means of appropriate methods. All details about the API synthesis including the fate of the metals intentionally added have to be consistently described and documented in the marketing authorisation application or in the application for a CEP. If the routine testing of an elemental impurity is needed, the API manufacturer may determine a specification. This information will be required by the medicinal product manufacturer for his overall risk assessment.

The chapter “3. ASMF/CEP: dossier expectations and assessment strategy” explains who has to submit the risk assessment necessary for an ASMF or a CEP and how the dossier will be processed by the assessor of the regulatory authority. Basically, two scenarios are possible:

1. The API manufacturer submits a summary of a risk assessment/management for elemental impurities
Such information flows in the overall risk assessment of the medicinal product manufacturer and is assessed by the quality assessor/ CEP assessor within the marketing authorisation procedure. All data and documents used for the risk assessment should also be available for a GMP inspection.

2. The API manufacturer doesn’t perform any risk assessment/ management.
The regulatory authority basically expects a detailed description of the API synthesis including data on all metal catalysts used. This as well as the analytical routine controls on elemental impurities performed by the API manufacturer will also be assessed by the quality assessor/ CEP assessor. Nevertheless, the assessor won’t make a final conclusion in the ASMF or CEP assessment report with regard to the compliance with ICH Q3D. This will be done within the marketing authorisation procedure for the medicinal product.

The guideline draft can be commented on until 12 August 2016.

///////////ICH Q3D, Control of Elemental Impurities,  EMA, control of elemental impurities in APIs

APIs from Legitimate and Reliable Sources

Posted on

APIs from Legitimate and Reliable Sources

1. Introduction

Counterfeit and sub-standard APIs are increasingly present. Not only are they a fact of non-compliance but also they form a serious and increasing risk for patient safety. Various initiatives have been taken such as the founding of the FDA Counterfeit Drug Task Force, the European Commission’s current “Public consultation in preparation of a legal proposal to combat counterfeit medicines for human use” and the WHO Program “IMPACT” (International Medical Products Anti-Counterfeiting Taskforce).

API =Active pharmaceutical ingredient (synonym: drug substance)

Counterfeit API =Active pharmaceutical ingredient for which source and/or quality are falsely represented on the label, on the certificate of analysis or otherwise

Rogue API =API that is counterfeit or severely, deliberately non-compliant.

This writeup focuses on the interaction between the API manufacturer and the medicinal product manufacturer and provides possible measures that may be taken by both partners in order to ensure only non-rogue APIs are used in the manufacture of medicinal products. The proposed measures are considered as elements out of a whole puzzle. A risk-based approach should be applied to determine the necessity and value of the individual proposals, alone or in combination. The document does not address in detail the vendor qualification process as it is taken for granted that APIs are only purchased from suppliers that have been thorough checked

API manufacturer= Active pharmaceutical ingredient manufacturer

Medicinal product manufacturer= formulation manufacturer

Supply Chain

A supply chain is actually a complex and dynamicsupply and demand network. A supply chain is a system of organizations, people, activities, information, and resources involved in moving a product or service from supplier to customer.

2. Supply Chain:

Agents, Brokers, Distributors, Repackers, Relabelers As a general principle, the shorter the supply chain, the more secure it will be. This is reflected in the EU GMP Guidelines, Part 1 (5.26) specifying that starting materials (APIs, excipients) should be purchased, where possible, directly from the producer.

In addition to the length of the supply chain, any changes on the original container – e.g. by repackaging, relabeling – should be considered as an additional risk for alteration and should therefore, whenever possible, be avoided.

There is no doubt that the entire supply chain needs to be assessed from a quality perspective, covered by an effective supplier qualification program and the same principles as described in the following sections for the direct supply form API manufacturer to drug product manufacturer should be applied. This already starts at the point of selecting the contractor for transportation of the API (see also ICH Q7, 10.23).

3. On Site Visits / Audits



A thorough knowledge of the supplier is a key element. Therefore, a close and stable relationship between the manufacturer of the API and the drug product manufacturer should be achieved by using various means of contact. A regular exchange between 3/8 sourcing- and purchasing people and the supplier contributes to strengthening this relationship, especially if the contact also includes regular visits on site. Site visits should not be restricted to the manufacturing site alone; intermediaries in the supply chain should be covered as well. It should be ensured that representatives of the purchasing department have a good GMP- and regulatory awareness and technical understanding so that these visits are as beneficial as possible, also in relation to compliance.

Audits=Auditing refers to a systematic and independent examination of books, accounts, documents and vouchers of an organization to ascertain how far the statements present a true and fair view of the concern.

3.2. Audits

An audit is considered the most effective way of verifying concrete and compliant manufacturing incl. distribution of APIs. However, apart from the fact that an audit is very time-consuming it only provides a snapshot of the situation and there is no 100% guarantee that evidence for any occurring counterfeiting activities may be identified. Nonetheless, there are various elements in a quality audit that may increase that probability and that respectively may confirm the reliability of the manufacturer.

Counterfeiting activities= To counterfeit means to imitate something. Counterfeit products are fake replicas of the real product. Counterfeit products are often produced with the intent to take advantage of the superior value of the imitated product

3.2.1 General

Whenever possible, the audit should be executed when an actual production campaign is ongoing.

Requests for changing the agenda at short notice during the audit, e.g. revisiting areas on another time or day, may be a useful approach to confirm the consistency of operations on site.

Warehouse=A warehouse is a commercial building for storage of goods. Warehouses are used by manufacturers, importers, exporters, wholesalers,transport businesses, customs, etc

3.2.2 Warehouse

The walk-through in the warehouse supports the verification of the materials management capability with respect to claimed annual production of the API and storage capacity.

Checking for the presence of intermediates or APIs in the warehouse that have been purchased and could be subject for relabeling or of APIs intended to undergo a reprocessing may lead to the identification of different sources of materials than claimed. The list of approved vendors should also be reviewed for this purpose.

The review of the materials management system and material movements (booking in/out) of concerned API starting materials, intermediates and the final API is another possible source of information in the warehouse. However, confidentiality with respect to other customers’ names needs to be respected.

Production=the action of making or manufacturing from components or raw materials, or the process of being so manufactured.

3.2.3 Production

The walk-through in production should cover the verification of the necessary equipment and necessary utilities by cross-checking with the production instruction and/or process flow chart.

Document Review=Document review (also known as doc review) is the process whereby each party to a case sorts through and analyzes the documents and data they possess (and later the documents and data supplied by their opponents through discovery) to determine which are sensitive or otherwise relevant to the case

3.2.4 Document Review

The review of master production instructions as well as analytical methods and specifications for raw materials, intermediates and the API as well as of executed documents/raw data and cross-checks with the regulatory document (e.g. DMF, CMC section, CEP dossier) is an important element in verifying regulatory compliance.

One can also verify the availability of production records and/or analytical raw data as well as retained samples (where applicable) of raw material, intermediates and API batches for specific batches that were either identified from the review of the stock cards/materials management system, product quality review or from supplied batches.

The timely and sequential correlation of equipment use logbooks in production and QC laboratory, production batch records (incl. electronic raw data), cleaning records and analytical raw data (incl. date/time on equipment printouts such as balances, chromatographic systems etc.) is a good indicator for on site production.

The review of the documentation related to seals (specifications – testing/approval according to specifications – reconciliation documentation – authorized persons identified and documented…) may be added.

A spot wise review of analytical raw data from stability studies (not only the summary table) as well as of the logbook of the stability chambers (e.g. date of sample in/out) and the check for physical availability of the stability samples should be included.

The adequate involvement of the drug product manufacturer in case of changes that can impact the quality and/or regulatory compliance of the API may be verified by the reviewing the history of changes and individual change request cases related to the production and testing of the API (incl. intermediates, raw materials),

4. Supporting Documentation

The availability of certain documents that are regularly available and up-dated, where applicable, may be considered as one efficient element in the continuous supplier monitoring process.

Inspections=Inspections are usually non-destructive. Inspections may be a visual inspection or involve sensing technologies such as ultrasonic testing, accomplished with a direct physical presence or remotely such as a remote visual inspection, and manually or automatically

4.1 Inspections,

Inspection history As part of the initial evaluation of a potential API supplier the GMP inspection history, with respect to inspecting regulatory body, inspection date, inspected areas (as far as this information is / is made available) and the inspection results should be reviewed. A regular up-date of the inspection history as part of the supplier monitoring and requalification process should be performed. On the other hand, as these inspections are not mandatory for APIs e.g. used in medicinal products for the EU, the non-availability of an inspection history may not lead to the conclusion that this API supplier is less reliable. 5/8

GMP=Good manufacturing practices (GMP) are the practices required in order to conform to the guidelines recommended by agencies that control authorization and licensing for manufacture and sale of food, drug products, and active pharmaceutical products. These guidelines provide minimum requirements that a pharmaceutical or a food product manufacturer must meet to assure that the products are of high quality and do not pose any risk to the consumer or public.

4.2 GMP certificates

GMP certificates of the API manufacturer, where available (see 4.1), should be provided, ideally as authentic copies.

Certificate of Analysis=A Certificate of Analysis is a document issued by Quality Assurance that confirms that a regulated product meets its product specification. They commonly contain the actual results obtained from testing performed as part of quality control of an individual batch of a product.

4.3 Certificate of Analysis

A thorough review of Certificate of Analysis, against regulatory documents (e.g. DMF, CMC section, CEP dossier) and in-house specification respectively, and with respect to GMP compliance (ICH Q7, 11.14) should be performed as part of incoming release testing of APIs. Suppliers involved in counterfeiting could apply improper documentation practices. In case of agents, brokers etc. being involved in the supply chain it is recommended to insist on a certificate of analysis issued by the original manufacturer of the API (see also 2.). Where a new certificate of analysis is prepared by agent, broker, distributor, there should be a reference to the name and address of the original manufacturer and a copy of the original batch Certificate should be attached, as specifically required by ICH Q7 11.43, 44

4.4 Certificate of Compliance,

Compliance Commitment A certificate of compliance issued by the API manufacturer, either as a separate document or as part of the certificate of analysis, which certifies that a specific batch has been manufactured according to ICH Q7 GMP requirements and in line with the applicable Registration Documents can provide additional assurance related to the awareness of the manufacturer on the quality and regulatory expectations of the customers.

4.5 On-going stability program

A GMP compliant manufacturer has an on-going stability program for its APIs (ICH Q7, 11.5). At least one batch of the API manufactured per year is added to the stability program and tested at least annually. A regular up-date of the program provided by the API manufacturer, not necessarily including stability data, gives additional assurance for actual and compliant systems.

4.6 Product Quality Review

The major objective of the Product Quality Review (ICH Q7, 2.5) is to evaluate the compliance status of the manufacture (process, packaging, labelling and tests) and to identify areas of improvement based on the evaluation of key data. It includes a review of critical in-process controls and critical API test results, of batches that failed to meet specification, of changes carried out, of the stability monitoring program, of quality-related returns/complaints/recalls and of the adequacy of corrective actions. Due to the comprehensive information included, the Product Quality Review provides a good overview of the manufacture of a certain API.

The document should be reviewed during an audit or as a minimum an approved executive summary should be made available by the API manufacturer.

4.7 Quality Agreement

The quality agreement as a tool to clearly define the GMP responsibilities strengthens the awareness of liabilities of both partners. The extent and level of detail of the agreement may vary and can depend on the material supplied, e.g. generic API versus exclusively synthesized API, but it should at least address – name of the product – mutually agreed specification (if not covered by supply agreement) – manufacturing site – applicable cGMP standards, e.g. ICH Q7 – compliance with the DMF or with other registration documentation – GMP audits related to the API (e.g. 3rd party auditing) – documents to be provided by the manufacturer, e.g. certificate of analysis, certificate of compliance, inclusion of copies of respective master documents may be addressed – arrangements for transportation and transport packaging (see 5.), e.g. description and degree of tampering proof seal to be used, inclusion of a copy of the master drum label may be considered – deviation handling – handling of and response to complaints – change management: involvement of the customer with respect to notification and approval – list of approved signatories may be included

5 Packaging:

labeling, tamper-proof sealing If the API manufacturer provides examples/templates of master labels, which he uses to label the containers, this supports the drug product manufacturer in identifying any manipulation on the material on its way from the manufacturer to the recipient.

The use of tamper-resistant packaging closure by the manufacturer provides additional assurance that the material was not adulterated on its way from the manufacturer to the drug product manufacturer. A manufacturer-specific design of the seal is recommended to be used; the use of unique seals may be considered. The communication of the type of seal, by the manufacturer to the user, completes the information chain.

Material Inspection = Critical appraisal involving examination, measurement, testing, gauging, and comparison of materials or items. An inspection determines if the material or item is in proper quantity and condition, and if it conforms to the applicable or specified requirements. Inspection is generally divided into three categories: (1) Receiving inspection, (2) In-process inspection, and (3) Final inspection. In quality control (which is guided by the principle that “Quality cannot be inspected into a product”) the role of inspection is to verify and validate the variance data; it does not involve separating the good from the bad.

Sampling= Sampling is the process of selecting units (e.g., people, organizations) from a population of interest so that by studying the sample we may fairly generalize our results back to the population from which they were chosen.

6. Material Inspection, Sampling, Analysis, Impurity Profile

At the point of receipt the first relevant action is to carefully perform the visual inspection of all the containers of the API. Attention shall be paid to the integrity and type of the sealing as well as to the special attributes added by the manufacturer (see above 4.7, 5.) such as label design, seal number and design.

The applied sampling regime related to the number of containers sampled, number of samples taken per container, analysis of individual and/or pooled samples as well as the extent of analysis, varying from identity test to full analysis may influence the probability of identifying counterfeiting, provided it may be identified by analytical means.

A risk-based approach, considering the qualification status of the supplier, may be chosen to define the extent of sampling and testing, considering the requirements for drug product manufacturers (e.g. Annex 8 to EU GMP Guidelines). 7/8 The impurity profile is normally dependent on the production process and origin of the API. The comparison of the impurity profile of a current batch with either previous batches or data provided by the manufacturer (e.g. as part of the regulatory submission) may help in order to identify changes related to modifications in the production process and may indicate whether the API might originate from a different manufacturer than the supposed one.

It is recommended to check the current (im)purity profile and compare it with former quality in regular intervals, at least once a year


I , Dr A.M.Crasto is writing this blog to share the knowledge/views, after reading Scientific Journals/Articles/News Articles/Wikipedia. My views/comments are based on the results /conclusions by the authors(researchers). I do mention either the link or reference of the article(s) in my blog and hope those interested can read for details. I am briefly summarising the remarks or conclusions of the authors (researchers). If one believe that their intellectual property right /copyright is infringed by any content on this blog, please contact or leave message at below email address It will be removed ASAP


The new Elemental Impurities Database for Excipients – ECA offers a meeting at no costs

Posted on Updated on

A step-wise integrated risk-based approach to determine a control strategy for according to ICH Q3D has to consider data from all kinds of potential sources for elemental impurities in particular from excipients. Read more about the newly created Elemental Impurities Database as a valuable support for performing risk assessments for drug products.

The new ICH Q3D Guideline on Elemental Impurities strongly advocates the use of risk assessments in order to define a final control strategy. Specific challenges appear when risks associated with production equipment, packaging material and excipients have to be determined, and quantified. In particular the contribution of elemental impurities from excipients is not easy to assess due to their big variety and the lack of information from excipient vendors.

Quite recently a pharma consortium started an initiative which aims to collect and share data from pharmaceutical excipients by establishing a database. This Elemental Impurities (EI) Database provides information required for performing a comprehensive risk assessment of a drug product with respect to elemental impurities. Interested companies can contribute to this database by providing information about excipients and may also benefit from this database by taking out information needed for their risk assessments.

The “Impurities Workshop” from 14-16 June 2016 in Heidelberg, Germany provides a comprehensive and practical oriented review of impurities analysis and characterisation in drug substances and drug products. Part III of the workshop on 16 June 2016 is specifically dedicated to Elemental Impurites. In the subsequent post-Conference Workshop on 17 June 2016 the above mentioned EI Database will be explained. The following questions will be discussed:

  • What is the procedure of providing data for the Database?
  • How can information be obtained from the Database?
  • What has to be considered in terms of confidentiality when data will be received or submitted to the Database?

This post-Conference Workshop is free of charge. It ideally complements the previous parts of the “Impurities Workshop” and can be booked in combination with either Part III or all Parts of the “Impurities Workshop”. As we expect a high interest in this post-Conference Workshop participants joining the “Impurities Workshop” (one day or all three days) will be registered first


Genotoxic impurities: the new ICH M7 addendum to calculation of compound-specific acceptable intakes

Posted on

Genotoxic impurities: the new ICH M7 addendum to calculation of compound-specific acceptable intakes

The draft for a guideline ICH M7(R1) published recently supplements the ICH-M7 guideline published last year. Read more about the calculation of compound-specific acceptable intakes of genotoxic impurities.

The final document of the ICH-Guideline M7 was published in June 2014. It describes the procedure for evaluating the genotoxic potential of impurities in medicinal products (see also our news Final ICH M7 Guideline on Genotoxic Impurities published dated 23 July 2014).

An important approach to the risk characterisation of impurities is the TTC concept (TTC = threshold of toxicological concern). According to this approach the exposure to a mutagenic impurity having the concentration of 1.5 µg per adult person per day is considered to be associated with a negligible risk. It can be used as default evaluation approach to most pharmaceuticals for long-term treatment (> 10 years) and where no carcinogenicity data are available (classes 2 and 3). According to ICH M7 the TTC concept should not be used where sufficient carcinogenicity data exist. Instead the data should be used to calculate or derive compound-specific acceptable intakes.

Now the ICH published an addendum to Guideline M7 with the title “Application of the principles of the ICH M7 Guideline to calculation of compound-specific acceptable intakes” (“Addendum to ICH M7”; short name “M7(R1)”).

This addendum describes the basis for calculating the acceptable intakes for 15 substances in total that are common and widespread in pharmaceutical manufacturing. These substances are known to have mutagenic/carcinogenic potential (ICH M7(R1) contains comprehensive references on the toxicology of these substances). The calculations of the AI (acceptable intake) or PDE (permitted daily exposure) values are partly based on a linear extrapolation from the TD50 values as well as on toxicological data on the non-linear dose-response curve of the relevant substances.

ICH M7(R1) has the status of a draft consensus guideline (step 2 document). The draft guideline was published on the EMA “Scientific Guidelines” site as step 2b document on 4 August 2015 for consultation (deadline for comments: 3 February 2016)


Elemental impurities – A database to facilitate the risk assessment of active ingredients and excipients

Posted on

One of the main demands of the Guideline ICH Q3D is to carry out risk assessments on metallic impurities. A database with analytical data provides a valuable support. Learn more about the data sharing using the new elemental impurities database.—A-database-to-facilitate-the-risk-assessment-of-active-ingredients-and-excipients_9263,9300,S-QSB_n.html

Released in December 2014, the ICH Q3D Guideline on Elemental Impurities contains extensive specifications for the control of a total of 24 elements (21 metals, 3 metalloids) that can be present as impurities in pharmaceutical products. Main sources can be

  • Active ingredients
  • Excipients (including water)
  • Processing auxiliaries and catalysts
  • Production equipment
  • Container and closure systems

The Guideline ICH Q3D calls for a risk assessment with regard to the presence of metallic impurities in various dosage forms, taking into account the respective limit values. The main factors of influence are to be included (see fishbone diagram on p. 6 of the Guideline). The risks identified in a comprehensive analysis have then to be categorized in a meaningful and justifiable manner.

The data for the content of metallic impurities, e.g. in excipients (for this purpose there is a study conducted by the FDA) or of migratable impurities in container / closure systems (there exists a Literature review in the PDA journal of pharmaceutical science and technology) is rather thin. And the sources of information can only be found through extensive research. The greatest treasure of information is located in the databases of several pharmaceutical and API manufacturers which have carried out analytical studies already.

To merge these data and information and to make them available to all interested companies in the form of a database, representatives of eight major companies have joined forces to an “Elemental Impurities Pharma Consortium”. This group was formed in October 2013, after a Conference on “Elemental Impurities” conducted by the Joint Pharmaceutical Analysis Group (JPAG).

The database that is currently established under the auspices of the EI Pharma Consortium, now comprises analytical data on elemental impurities from over 100 different materials (pharmaceutical excipients, dyes, etc.), which were provided by other companies. These data are anonymized, so that interested users of the database can not recognize the specific origin of the information.

The benefit for the user increases to the same extent as the database grows, which basically means for the companies that have to implement one of the main requirements of the ICH Q3 Guideline – to carry out a risk assessment. The timeframe for this is tight: for medicinal products still to be approved the provisions of ICH Q3D need to be fulfilled by June 2016. Already approved products have to comply from December 2017 (see also our news “Industry Coalition” gives practical advice for the control of elemental impurities in active substances and excipients).

Note : At the Impurities Forum from 16-18 June 2015 in Prague you will receive more information about this topic. Andrew Teasdale, one of the initiators of the Consortium, will report about the database and the possibilities to use it.



Risk Assessment of Potentially Genotoxic Impurities within the Framework of Quality by Design

Posted on



A strategy for the risk assessment of potentially genotoxic impurities is described that utilizes Quality by Design in an effort to furnish greater process and analytical understanding, ultimately leading to a determination of impurity criticality. By identifying the risks and parameters that most influence those risks, an enhancement of both product and process control is attained that mitigates the potential impact of these impurities. This approach calls for the use of toxicological testing where necessary, chemical fate arguments when possible, multivariate analyses to develop design space, and use of spiking data to support specifications. Strong analytical support, especially with the development of low-level detection methods, is critical. We believe that this strategy not only aids in the development of a robust API process but also delivers on the identification and subsequent mitigation of risks to a class of impurities that are of high interest in the field.

Risk Assessment of Potentially Genotoxic Impurities within the Framework of Quality by Design

Adam R. Looker, Michael P. Ryan, Bobbianna J. Neubert-Langille and Redouan Naji
Org. Process Res. Dev., 2010, 14 (4), pp 1032–1036
pp 1032–1036
Publication Date (Web): April 7, 2010 (Communication)
DOI: 10.1021/op900338g

Prediction of Drug Degradation Pathways leading to Structural Alerts for Potential Genotoxic Impurities

Posted on


An in-depth analysis of the web-based CambridgeSoft Pharmaceutical Drug Degradation Database, Pharma D3, was conducted in two phases in an attempt to generate some general rules for the prediction of alerting structures for genotoxicity that may arise as a result of degradation. The first phase involved interrogation of the database to determine the nature and frequency of alerting structures present in the degradants. This analysis revealed five functional groups, which account for approximately 70% of the alerting structures found in the degradants within the database: (1) aldehydes; (2) α,β unsaturated carbonyls; (3) aromatic amines, hydroxylamine and its derived esters; (4) epoxides; and (5) polyaromatic hydrocarbons. The second phase of the analysis involved categorizing the major chemical reactions responsible for the generation of the five most prevalent alerting structures. This two-step approach led, in turn, to a proposal for the prediction of functional groups that may have a propensity to degrade to alerting structures not necessarily present in the parent molecule.

Prediction of Drug Degradation Pathways leading to Structural Alerts for Potential Genotoxic Impurities

Stephen P. Raillard, Joel Bercu, Steven W. Baertschi and Christopher M. Riley
Org. Process Res. Dev., 2010, 14 (4), pp 1015–1020
Publication Date (Web): April 21, 2010 (Article)
DOI: 10.1021/op100007q