EMA's Latest Guidance on AI Limits of Nitrosamine

Introduction:

Greetings! In a recent development, the European Medicines Agency (EMA) has made significant revisions to its Questions and Answers regarding nitrosamine impurities in human medicinal products, as of July 7, 2023. In this discussion, we will dive into one of the key updates – question 10 – to comprehend the limits that apply to nitrosamines in medicinal products.

Nitrosamines and ICH Guidelines:

Firstly, it's crucial to note that all nitrosamines have been classified as a "cohort of concern" under the ICH guideline M7(R2). This guideline specifically addresses DNA-reactive substances. Consequently, the conventional Threshold of Toxicological Concern (TTC) limit, set at 1.5 µg/day for nitrosamines, can no longer be applied. Instead, a Substance-Specific Acceptable Intake must be calculated for each nitrosamine.

A. Approaches for defining the AI Limit of Nitrosamine:

The following approaches can be considered to define the AI limit of Nitrosamines.

1. Less Than Lifetime (LTL) Exposure:

The concept of "less than lifetime exposure," commonly associated with mutagenic substances under ICHM7(R2), should be applied with caution. Its applicability requires consultation with the competent authority and is usually a temporary measure. It's advisable to avoid "less than lifetime exposure" whenever possible.

As per EMA, Q&A 10, the ‘less than lifetime’ (LTL) approach should not be applied in calculating the limits but can only be considered after consultation with competent authorities as a temporary measure until further measures can be implemented to reduce the contaminant at or below the limits defined above.

Treatment duration Up to 12 months: Interim limit is 13.3 x AI

Treatment duration > 12 months: Interim limit is 6.7 x AI

Further, in any case, the limit should not exceed 1.5 µg/day unless the established AI is > 1.5 µg/day or the nitrosamine concerns a category 5 according to CPCA or the nitrosamine is shown to be negative in an enhanced Ames test (EAT).

2. Advanced Cancer Products:

For products intended for advanced cancer treatment, the control of nitrosamine impurities should align with the ICH guideline Q3A or Q3B.

3. Availability of Substance-Specific Animal Carcinogenicity Data:

If such data is available, you can calculate the TD50 value (the concentration resulting in a tumor in 50% of the studied population) and extrapolate it to a concentration that results in one tumor in 100,000 studied species over their lifespan.

4. Non-availability of Carcinogenic Potential Categorization Approach (CPCA):

If substance-specific animal carcinogenicity data is unavailable, the CPCA method can be employed to establish acceptable intake.

5. EAT (Enhanced EMS Test) Results:

A negative result in a Good Laboratory Practice (GLP) compliant Enhanced Ames Test (EAT) allows for the control of nitrosamines at a limit of 1.5 micrograms per day. However, detailed information regarding the EAT can be found in the same Q&A guidance document.

6. Surrogate Nitrosamines and Mutagenicity Studies:

If a surrogate nitrosamine has robust carcinogenicity data, the TD50 value from the surrogate substance can be used to derive the acceptable intake through the Structure-Activity Relationship (SAR) and read-across approach.

Regulators often employ this approach to define acceptable intake limits. A negative result in a well-conducted in vivo mutagenicity study can allow nitrosamines to be controlled as non-mutagenic impurities, following ICH's Q3A or Q3B guidelines.

B. Approaches for defining the AI Limit of Nitrosamine when one or more than one nitrosamine is identified:

1. Calculation of the limit when a single known nitrosamine is identified:

Limit (ppm) = AI of Nitrosamine(ng/day)/maximum daily dose (mg) of a product

2. Calculation of limit when more than one nitrosamine is identified in the same product:

Two approaches are considered acceptable:

Option 1: The total daily intake of all identified N-nitrosamines not to exceed the AI of the most potent Nitrosamine identified:

Example:

NDMA and NDEA are detected at or above 10% of their respective AI in a finished product with a maximum daily dose of 300 mg.

AI Limit for NDEA (Most potent): 26.5 ng/day / 300 mg/day = 0.088 ppm or 88 ppb

Spec for Total Nitrosamines (NDMA + NDEA): Shall not exceed 88ppb

Spec for individual Nitrosamines: Not applicable

Option 2:

When dealing with multiple nitrosamines, Option 2 offers both a fixed and flexible approach:

Option-2 (Fixed approach): The total risk level calculated for all identified Nitrosamines not to exceed 1 in 100,000:

The limit for each Nitrosamine should be set at a % of its AI limit such that the sum of the % AI limits for each specified nitrosamine does not exceed 100%.

So, there is a fixed limit (in ppm/ppb) for individual nitrosamines

There is no limit for total Nitrosamines under a fixed approach.

Example:

NDMA and NDEA are both detected at or above 10% of their respective AI) in a finished product with a maximum daily dose of 300 mg.

Let us use the ratio of 20% NDEA to 80% NDMA (i.e. 20%+80% =100%) as an example only

AI limit for NDEA: 26.5 ng/day / 300 mg/day = 0.088 ppm or 88 ppb

AI limit for NDMA: 96.0 ng/day / 300 mg/day = 0.32 ppm or 320 ppb

Spec for NDEA under option2 (fixed): = 20% of 88ppb = 17.6ppb

Spec for NDMA under option2 (fixed): = 80% of 320ppb = 256ppb

Spec for Total Nitrosamine: Not applicable

Option-2 (Flexible approach): The total risk level calculated for all identified Nitrosamines not to exceed 1 in 100,000:

AI limit in ppm/ppb for each Nitrosamine should be specified

The limit for total Nitrosamines should also be specified, which is NMT 100%

For each batch, the amount of each Nitrosamine present (in ppm/ppb) should be converted to a % of its respective AI limit (below formula can be used...).

Individual Nitrosamine found in ppb

% AI limits of individual nitrosamine = ---------------------------------------------------------- x 100

AI limit of individual Nitrosamine in ppb

Then the sum of % AI limits of each specified Nitrosamines should be calculated, which shall not exceed 100%.

Example (Option 2 Flexible approach):

NDMA and NDEA are detected at or above 10% of their respective AI in a finished product with a maximum daily dose of 300 mg.

Calculate the AI limit for individual Nitrosamines:

AI limit for NDEA: 26.5 ng/day / 300 mg/day = 0.088 ppm or 88 ppb

AI limit for NDMA: 96.0 ng/day / 300 mg/day = 0.32 ppm or 320 ppb

Then calculate the sum of % AI limits of each nitrosamine, which shall not exceed 100%

NDEA found ppb NDMA found in ppb

Total % AI limit = ---------------------------- x 100 + ----------------------------- x 100

AI Limit (88ppb) AI Limit (320ppb)

Case-1:

20ppb 90 ppb

% value = --------- x 100 + ------------ x 100

88ppb 320ppb

% value = 22.7% + 28.1% = 50.8%

Case-2:

44pb 160 ppb

% value = --------- x 100 + ------------ x 100

88ppb 320ppb

% value = 50% + 50% = 100%

Case-3:

100ppb 64ppb

% value = --------- x 100 + ------------ x 100

88ppb 320ppb

% value = 113.6% + 20% = 133.6%

Conclusion: Case 1 and 2 meets the option 2 (flexible approach). However, case 3 exceeds the 100% risk and hence does not meet option 2 (flexible approach).

Conclusion:

EMA's revised guidance on nitrosamine impurities brings clarity to setting limits and controlling these potentially harmful substances in medicinal products. By understanding these updates and applying the appropriate approaches, pharmaceutical manufacturers can ensure compliance and patient safety in their drug development processes.