Letter to the Editor pubs.acs.org/OPRD
Regulatory Expectations Towards Genotoxic Impurities in Drug Substances: DMF and ASMF Perspective
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where assessments according to this guideline are conducted, the mutagenic impurity classification and rationale for this classification should be provided. This would include the results and description of in silico (Q)SAR systems used, and as appropriate, supporting information to arrive at the overall conclusion for Class 4 and 5 impurities. When bacterial mutagenicity assays were performed on impurities, all results and the study reports should be provided for any bacterial mutagenicity-negative impurities’. Hence, it is required to declare all the compounds/impurities including potential processrelated impurities and degradants either as genotoxic impurities or Class 4 or 5 impurities while submitting the DMF or ASMF as per CTD format. The practicality comes into picture here. The Ames test procedure is laborious, time-consuming, and requires good quantities of impurities in hand. Pharmaceutical industries while filing para-IV and commercially important molecules cannot afford such time. Even if some compounds, such as phenol9 or benzoyl chloride,10 undergo Ames evaluation, they showed ambiguous results in Ames tests (both positive and negative findings). In such cases, regulatory authorities while sending DMF/ASMF deficiencies are insisting to perform the studies with respect to TTC (Threshold of Toxicological Concern) limits. In view of these limitations, in silico evaluation is the preferable option for pharmaceutical industries. DEREK for windows was found to perform best in terms of a sound sensitivity and specificity. However, there is a doubt about the fate of a compound which is initially considered as genotoxic by structural alert, shows a negative result in the Ames test. In these cases, the drug substances shall undergo evaluation as per TTC limits to check process capabilities. If the process is capable of controlling the compounds with structural alerts below 30% of the TTC limit, they can avoid Ames testing. The Question and Answers supplement11 on the CHMP Guideline on the Limits of Genotoxic Impurities clarifies and supports this approach. The question is ‘Is it acceptable to control impurities with a structural alert by assuming they will be positive (without resorting to any testing) and ensuring the level remains below the appropriate TTC value?’ The answer is ‘Yes, genotoxicity testing is not obligatory when a potential genotoxic impurity is controlled at the TTC level, unless it belongs to a class of very potent genotoxic carcinogens (N-nitroso and azoxy compounds, or a aflatoxin-like compound)’. In this context, if the process is capable of controlling these impurities below 30% of the TTC limit, the Ames test can be avoided, and it is helpful if the process is not capable of controlling genotoxins below 30% of the TTC level. Snodin considered an appropriate model for the Bocprotected amino aldehyde. No compound can be omitted based on appropriate compounds and regulators are insisting on either the study with the TTC limit or an Ames negative test. In addition, it cannot be excluded by considering 3-phenyl propanal as an appropriate model, as it is reported to have acute
ear Editor:
Genotoxic impurities in drug substances shall be handled by considering guidances,1 regulatory expectations, industry needs and process capabilities. Adequate approach shall be opted beyond the theoretical and hypothetical approaches. Snodin’s letter to the editor2 is indicating the lack of familiarity on regulatory expectations towards genotoxic impurities in drug substances and current pharma industry approaches while submitting Drug Master Files (DMF) and Active Substance Master Files (ASMF). The aim of our article3 is to establish derivatization methods by considering various functional groups and to assess process capabilities. Basically the reported ones are determination methods in drug substances rather than assay methods as claimed by Snodin. In the letter, it was stated as ‘the use of structural alerts alone and/or the uncritical adoption of in silico predictions for determining the mutagenicity status of a potential impurity has the potential in some cases to be misleading and can lead to the resource-intensive and unnecessary development of highly sensitive assay methods’. However, another Snodin article4 claims ‘If the impurity is a known compound and has a structural alert for genotoxicity, Ames-test data may be available in the public domain. Alternatively, if no published data are available and/or the compound is not known (by searching on PubChem for example), it is acceptable to assume that the compound is genotoxic in the Ames assay and control accordingly (in most cases using the default TTC limit of 1.5 μg/day), or an Ames test could be undertaken’. Hence, the statements in letter to the editor and in article (both by Snodin) are contradictory. Pharmeuropa5 states that, ‘Potentially genotoxic compounds are identified initially by chemical structure, certain structural features being associated with genotoxic activity. In general, structural alerts are considered to be meaningful, although there is not complete agreement on the structural features that should give rise to alerts’. FDA guideline6 on genotoxic impurities states that ‘If an impurity that is present at levels below the ICH qualification thresholds is identified, the impurity should be evaluated for genotoxicity and carcinogenicity based on structural activity relationship (SAR) assessments (i.e., whether there is a structural alert). This evaluation can be conducted via a review of the available literature or through a computational toxicology assessment; commonly used software includes MDL-QSAR, MC4PC, and Derek for Windows’. These are indicating the importance of in silico evaluations for the identification of genotoxic impurities. This guidance also states about the limits that ‘The appropriateness of a flexible approach should be informed by the feasibility of controlling impurity levels and the capabilities of the current process’. Hence, it is always preferable to assess process capabilities for which analytical methods shall be developed. While submitting the DMF or ASMF in the CTD (common technical document) format as per the ICH M4(R3) guideline,7 genotoxicity information is to be submitted under the section 4.2.3.3. ICH M7 guideline8 under the heading CTD states ‘for all actual and potential process related impurities and degradants © XXXX American Chemical Society
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dx.doi.org/10.1021/op500110n | Org. Process Res. Dev. XXXX, XXX, XXX−XXX
Organic Process Research & Development
Letter to the Editor
toxicology in rats.12 MIC is a hydrazine13,14 derivative, which is a proven genotoxin. Tetrafluorobenzoyl chloride shall be studied at the TTC level as benzoyl chloride has both Ames positive and negative results.10 Formaldehyde is proved to be genotoxin. The study of formaldehyde cannot be avoided by considering the formation of methyl formate. In this case the unreacted formaldehyde shall be demonstrated to ensure the complete conversion of formaldehyde in to methyl formate. Hence, in the literature a formaldehyde determination method with the TTC limit was reported.15 In the literature, 4-chloro butyryl chloride has been used with respect to acute and repeated dose toxicity and mutagenicity16 and was determined in leverircetam using the TTC limit17 which may be the outcome of the regulatory requirement. To conclude, the methods reported in our article are mainly to assess process capabilities in view of genotoxins identified by in silico evaluations. In addition, the concept is to select various functional groups to demonstrate different chemistries useful for derivatization. A literature survey also reveals the importance of derivatization using hyphenated techniques due to stability and sensitivity of genotoxic impurities.18 Even though purging is a useful methodology, these types of determination methods are required in order to assess the purged material in the final drug substance.19 Hence, the reported methods can be used for initial manufacturing development, process validations, DMF/ASMF filings, and skip testing for limited batches on need basis.
the registration of pharmaceuticals for human use; M7. Draft Consensus Guideline, 2013. (9) International Agency for Research on Cancer (IARC) Monographs Program; 1989; Vol. 71, pp 749−768. (10) Final HPV Data Summary For Benzoyl Chloride. Benzoates Panel, American Chemistry Council: 1300 Wilson Boulevard, Arlington, VA 22209, 2005 (11) European Medicines Agency, Question & Answers on the CHMP Guideline on the Limits of Genotoxic Impurities. 2009. (12) Opinion of the scientific panel on food additives, flavourings, processing aids and materials in contact with food (AFC) on a request from the commission related to flavouring group evaluation 15 (FGE.15): Aryl-substituted saturated and unsaturated primary alcohol/aldehyde/acid/ester derivatives from chemical group 22. EFSA J.. 2005, 247, 1−45. (13) Occupational Safety and health guideline for hydrazine - Potential human carcinogen; U.S. Department of Health and Human Services: OSHA Salt Lake Technical Center, Salt Lake City, UT, 1988. (14) Khan, M.; Kumar, S.; Jayasree, K.; Krishna Reddy, K. V. S. R.; Dubey, P. K. Simultaneous trace level determination of potentially genotoxic hydrazine, methylhydrazine and alkylamines in pharmaceutical substances by using indirect photometric detection. Chromatographia 2013, 76 (13−14), 801−809. (15) Nageswari, A.; Krishna Reddy, K. V. S. R.; Mukkanti, K. Low level quantitation of formaldehyde in drug substance by HPLC−UV. Chromatographia 2012, 75, 275−280. (16) OECD Environment, Health and Safety Publications Series on Testing and Assessment No. 166: Environment directorate joint meeting of the chemicals committee and the working party on chemicals, pesticides and biotechnology, ENV/JM/MONO(2012)4/PART6; 2012. (17) Gangadhar, V.; Saradhi, P.; Rajavikram, R. The Determination and Control of Genotoxic Impurities in APIs. Pharm. Technol. 2011, 35, 24−s30. (18) Wijka, A. M.; Niederländera, H. A. G.; Siebuma, A. H. G.; Vervaarta, M. A. T.; Jong, G. J. A new derivatization reagent for LC− MS/MS screening of potential genotoxic alkylation compounds. J. Pharm. Biomed. Anal. 2013, 74, 133−140. (19) Teasdale, A.; Elder, D.; Chang, S. J.; Wang, S.; Thompson, R.; Benz, N.; Flores, I. H. S. Risk assessment of genotoxic impurities in new chemical entities: Strategies to demonstrate control. Org. Process Res. Dev. 2013, 17, 221−230.
Nanduri V. V. S. S. Raman* Adapa V. S. S. Prasad*
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Research and Development, Hetero Drugs Ltd., Plot No. B. 80 & 81, APIE, Balanagar, Hyderabad - 500018, India
AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected] *E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) European Medicines Agency(EMA) and Committee for Proprietary Medicinal Products (CPMP), Guideline on the Limits of Genotoxic Impurities, CPMP/SWP/5199/02, EMEA/CHMP/QWP/ 251344/2006; Committee for Medicinal Products (CHMP), European Medicines Agency (EMEA): London, 2007. (2) Snodin, D. J. Unnecessary Development of Highly Sensitive Assays for Potentially Mutagenic Impurities (PMIs). Org. Process Res. Dev. 2014, 18, 360−361. (3) Raman, N. V.; Prasad, A. V.; Reddy, K. R. Sensitive derivatization methods for the determination of genotoxic impurities in drug substances using hyphenated techniques. J. Pharm. Biomed. Anal. 2014, 89, 276−281. (4) Snodin, D. J. Genotoxic impurities: from Structural Alerts to Qualification. Org. Process Res. Dev. 2010, 14, 960−976. (5) Potentially genotoxic impurities and European Pharmacopoeia monographs on substances for human use. Pharmeuropa 2008, 20(3), 426−427. (6) Center for Drug Evaluation and Research (CDER) Guidance for Industry, Genotoxic and Carcinogenic Impurities in Drug Substances and Products: Recommended Approaches, Draft Guidance; 2008. (7) ICH Harmonised Tripartite Guideline: Organization of the Common Technical Document for the registration of pharmaceuticals for human use, M4(R3); 2004. (8) Assessment and control of DNA reactive (mutagenic) impurities in pharmaceuticals to limit potential carcinogenic risk. ICH Harmonised Tripartite Guideline: Organization of the Common Technical Document for B
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