Establishment of Acceptable Intakes, framework

The EMA has taken significant steps towards establishing a framework for evaluating the risks associated with nitrosamine contamination in pharmaceutical products. Two scenarios are outlined in the EMA/409815/2020 Rev.16.

Scenario A: Substance-Specific Animal Carcinogenicity Data Available
When N-nitrosamines are identified, and sufficient substance-specific animal carcinogenicity data is available, the EMA recommends calculating the TD50 as per the (ICH) M7(R1) guideline.

Scenario B: Insufficient Substance-Specific Data Available
In cases where N-nitrosamines are identified, but there is a lack of substance-specific data to calculate the TD50 and derive a substance-specific limit for lifetime exposure, an alternative approach is required. The specific details and criteria can be found in the figure below:

What is your opinion on this framework, and how can it be a new tool in the discussion surrounding nitrosamines?


I think it’s really good to have clarity around the testing strategies required and the ability to use the structural features in the CPCA - it’s wonderful to see all of the SAR work that I and others have done over the past couple of years bear fruit in this way. I look forward to seeing it in practice, and a dramatic reduction in the number of nitrosamines that need control to 18 ng/day.

I assume that, while this has come out under an EMA banner, health authorities have worked collectively on this - it will be important now to see whether other authorities accept limits proposed under this framework.


Thanks @David and others who has really put forward this enormous significant work on Nitrosamines SAR.
My reverence to you all!
Any insights, in similar lines, any other Health authority would accept this CPCA.



Here I would like to put an asterisc on the outcome after in-vivo assays (e.g.: TGR). The guideline indicates that if + Option 1 or 3 are recommended.

However, I am still optimistic that also after further evidence and tests, it will be possible to say that if you are controlling mutagenicity, you are controlling carcinogenicity and there is a relation behind. Therefore, the possibility to use PDEs and relative potency comparison.

Now with the new guideline, we can now put resources into the nitrosamines that are expected to be positive and not so many in nitrosamines that were expected to be out of the cohort on concern.


My workflow may be complex.


Is there an additional branch needed from negative Ames to surrogate use? Some of the surrogates have TD50s that correspond to AIs above 1500 ng/day, which would allow the use of higher limits if needed.


I believe there has been a collective effort from the entire community. There has been involvement from everyone who is directly or indirectly connected to the matter. This review (EMA/409815/2020 Rev.16) is merely a consequence of the work that has been carried out collaboratively.
However, of course, I cannot overlook your valuable contributions through the articles you have published, @David

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It may indeed be complex @Yosukemino , but you have captured the essence of the strategies to be adopted.

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But we need to see what is the ongoing work at USFDA and when the Agency publishes the similar recommendation or proposes the flowchart / decision tree to derive AI for NDSRIs for NDA/ANDAs.
is there any update or anticipated updates from USFDA ?

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Hi, @David

Thank you for your good suggestion. I did not think a negative Ames result might be available when ready to apply the read-across method. But available ames test results in public may increase due to EMA Q&A rev.16 in the future. And data sharing project by Lhasa will encourage it. The opportunity of applying the read-across method to compounds with ames negative may increase.

Thanks @Yosukemino for yet again another visualization. Small Query- In above picture from B4 to B2, if in vivo mutagenicity study available and found positive- Do we need to really again go to Enhanced Ames test?

Thank you for pointing it out, @Pradpharma. Yes, you are right. I improved my workflow.


Dear All,

I just want to ask if some one has applied the below approach of “Molarity based AI limit” for read across and successful in regulatory compliance

“When a read-across exercise is performed with low molecular weight nitrosamines for a weight- based AI (Acceptable Intake) limit extrapolation for a larger compound, the derived limit permits even fewer molecules of the larger compound. Hence a molarity-based limit may provide a more relevant comparison (Cross & Ponting, 2021).”