Let’s try CPCA Scoring!! If you want to post cases, the following PDF may be available to convert and custom. And images of compounds may be available in the visualization thread. And you can request the scoring, and then someone may help you.
Example of CPCA Scoring.pdf (71.4 KB)
I’m not sure I can respond to all requests correctly. I’m looking forward to your participation!! 
Thank you very much Yosukemino
Yes, it is for acyclic N-nitroso groups and wanted re-confirm the same.
Please tell us how this structure’s alpha hydrogen is +1.
Hi, @Dinkar
Thank you for asking me. The compound has two alfa-hydrogens on both sides. The alfa-hydrogen score of (2,2) is +1.
Dear Sir,
I appreciate your prompt reply.
I still have the same query: how is Q & A quote +1 if there is 2+2 alfa hydrogen in the structure?
Thank you once more for your assistance and advice.
Thank you for asking, @Dinkar. As we discussed in the Q&A thread, the score is determined from knowledge of SAR. The structure (2,2) is easiliy affected by CYP activation compared to (1, 2) and (1,3) due to the steric hindrance. And I guess this scoring system is validated with data in LCDB.
So I am not sure why the structure (2,2) is score+1 but I guess it’s reasonable.
Dear Sir,
Many thanks for your prompt response, which is valuable and helpful to us.
Regards,
Dr. Dinkar Gagare
I calculated the score of N-nitroso-vonoprazan. Strict AI should be set for the compound. What do you think about it, guys?
I add the example of NTTP(7-nitroso-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4]triazolo-[4,3- a]pyrazine) @David posted.
The AI of NTTP and NNV(nitroso-varenicline) are both calculated from the AI of NTHP by the read-across method. Though NTTP has the activating feature, NNV has no activating feature. But the score of NNV is 2, the same as that of NTTP. It’s interesting.
The score of NNV: ((2,2) for H-count = 1, In a 7-membered ring = 1, Total2, limit 100 ng/day).
NNV，按照CAPA评分方法计算，确实是2分，对应的可接受摄入量为100ng/天，这与附录中的37ng/天是相矛盾的，不知道FDA是否会同意放宽到100ng/天。
NNV is actually complex to assign, because of its fused bicyclic system - the nitrosamine is both in a 6- and 7-membered ring, and in this case, per the guidance, the smaller ring takes precedence - so I would say it gets 3 points: 6-membered ring and (2,2) for hydrogen count, i.e. a limit of 400!
However with a compound-specific AI in the guidance, I assume that takes precedence, otherwise there’s a full order of magnitude to play with.
Dear @David,
Thank you for pointing it out. Yes, you are right. The feature score for only the smallest matching
ring should be applied.
The score of NNV: ((2,2) for H-count = 1, In a 6-membered ring = 2, Total3, limit 400 ng/day).
And the current AI of 37 ng/day represents less than 10% of the AI of 400 ng/day. When CPCA becomes available on NNV, it means that varenicline is free from control for NNV. And the surrogate compound of NTHP for NNV looks controversial due to the size of the ring and the position of sp2 carbon. I anticipate the update of the AI list in the future.
Dear Sir, I feel sorry that i am reviving this old topic but is new for me. I am posting this CPCA score to be reviewed by you because I have not found any AI for N-nitroso-ritalinamide. This impurity is related to the Methylphenidate. Which it has already two reported impurities, the N-nitroso-ritalinic acid and the N-nitroso-methylphenidate. Thanks for your help.
Hi,
You can use the below link for CPAC calculation.
The result for above mentioned structure as below:
Calculate Potency Score
The count of hydrogen atoms on each α-carbon [1, 2] and corresponding α-Hydrogen Score is 3
Ring related is found, Individual Deactivating Feature Score is +2
Score: 5
Potency Category 4 : AI = 1500 ng/day
Thank you so much for the precise observation above the category. I will use the link that you suggested 
Thank you so much for your kind help!
