Nitrosoamine impurities have been a major concern to regulators and the pharmaceutical industry since 2018 when N-nitrosodimethylamine (NDMA) was discovered in the angiotensin-II receptor blocker (ARB), valsartan. Since then, nitrosamine impurities have been detected in several medicines, such as metformin, pioglitazone, ranitidine, rifampicin, rifapanthine and other sartans. This has been followed by batch recalls of some of these medicines and the ultimate suspension of the authorisation of ranitidine in the EU and many other countries.1 In South Africa manufacturers withdrew their ranitidine-containing products from the market.2
Nitrosamines have been shown to be mutagenic and carcinogenic in animals, and hence, are anticipated to have similar effects in humans. This means that long term exposure to a nitrosamine impurity above a level that is considered safe may increase the risk of cancer. Nitrosamines are ubiquitous and have been found in processed foods, malted beer, drinking water, tobacco, cosmetics and several consumer products (balloons, dummies, packaging materials, etc.). Animal data for 228 low molecular weight nitrosamine derivatives revealed that 82 % are considered in vivo carcinogens3.
Since the report on the detection of NDMA in valsartan, regulatory authorities have published several key guidelines and communication documents for stakeholders on how to deal with the presence of nitrosamines in medicines. The EMA in 2020 published an assessment report on nitrosamine impurities in human medicinal products.4 Similarly, SAHPRA published a “Nitrosamine Communication” on 22 June 2022.5 What is notable about both documents is that they are not limited to pharmaceutical products, but include biological medicines as well. SAHPRA, like most regulatory authorities, has adopted a three-step approach on the assessment and control of nitrosamines in the API and final product, which consist of:
- Step 1: Risk assessment;
- Step 2: Confirmatory testing;
- Step 3: Application for a variation, if required.
SAHPRA has also made available templates that are to be used by applicants for the risk assessment and confirmatory testing outcomes. The templates, which can be accessed via links in the “Nitrosamine Communication” document must be completed and submitted on specific dates. For Step 1, the due date is 31st December 2023 and for Step 2, the submission date is 1st December 2024. Should the outcome of the risk assessment and confirmatory testing lead to the application of a variation due to higher levels of nitrosamines than the acceptable intake limit, then the interim investigation report (detailing the root cause, risk mitigating plan and benefit/risk assessment) must be submitted by 1st July 2025.
The risk for the formation of nitrosamines in medicines depends on three factors:
- A secondary amine functional group (-N-H)
- A nitrosating agent (nitrous acid)
- Conducive conditions (temperature, pH, concentration)
Amino acids are the building blocks of biologics and as such they have many amine functional groups. It may, therefore, appear that they should have a higher potential to form genotoxic nitrosamine impurities compared to pharmaceuticals. However, the general view is that nitrosamine risk factors for biologics are minimal. This is because of several factors, which include, but are not limited to, the following:
- The use during manufacture, of water of high quality or purity, that is free of nitrosating agents such as nitrates.
- Sophisticated purification procedures based on molecular size that reduce the potential for low molecular weight impurities such as nitrosamines.
- Storage at low temperatures (- 70 °C for the drug substance and 2 – 8 °C for the final product) that inhibit formation of nitrosamines.
- The use of excipients such as sugars, polyols, inorganic salts, surfactants, etc., that do not present a concern with respect to nitrosamine impurities. In fact, a number of the excipients employed in the formulation of biologics are antioxidants that inhibit nitrosamine formation.
Biologics are, however, not without risks. A number of biologics are conjugated to synthetically derived pharmaceuticals and some peptides are also produced by total chemical synthesis. Thus, when performing risk assessment, chemically produced starting materials, intermediates and protein drug substances should be considered to have the same potential for nitrosamine impurities as pharmaceutical products. In addition, elastomeric stoppers of vials and prefilled syringes, which are common container closer systems for biologics, are also well-known potential sources of nitrosamines.6
In conclusion, biological medicines have a much lower potential of being contaminated with nitrosamine impurities than pharmaceuticals. Consequently, it is unlikely that a nitrosamine risk assessment and confirmatory testing exercise of a biological product would lead to a variation application because the acceptable intake limit has been exceeded. Finally, it should be noted that not a single batch of any biological medicine has been recalled from the market due to an unacceptable nitrosamine concentration.
- European Medicines Agency. Suspension of ranitidine medicines in the EU. 30 April 2020. https://www.ema.europa.eu/en/news/suspension-ranitidine-medicines-eu.
2. South African Health Products Regulatory Authority. Update on recall and quarantine of ranitidine containing medicines. 29 October 2016. https://www.sahpra.org.za/wp-content/uploads/2020/01/SAHPRA_Final-Media_Release_Update_on_Ranitidine_containing_Medicines_31-Oct-2019-final-3.pdf
3. Horne S, Vera MD, Nagavelli LR, Sayeed VA, Heckman L, Johnson D, Berger D, Yip YY, Krahn CL, Sizukusa LO, Rocha NFM, Bream RN, Ludwig J, Keire DA, Condran G. Regulatory Experiences with Root Causes and Risk Factors for Nitrosamine Impurities in Pharmaceuticals. J Pharm Sci. 2023 May;112(5):1166-1182. doi: 10.1016/j.xphs.2022.12.022. Epub 2023 Jan 1. PMID: 36599405.
4. Nitrosamine impurities in human medicinal products, June 2020 EMA/369136/2020 Committee for Medicinal Products for Human Use (CHMP), Procedure under Article 5(3) of Regulation EC (No) 726/2004.
5. South African Health Products Regulatory Authority. Communication to industry on nitrosamine review for new applications and registered products including biological.https://www.sahpra.org.za/document/communication-to-industry-on-nitrosamine-review-for-new-applications-and-registered-products-including-biologicals/
6. Are nitrosamines a concern for biologic manufacturers? 30 March 2023. https://www.europeanpharmaceuticalreview.com/wp-content/uploads/HN-HS-GLO-Nitrosamines-Article-3-1.pdf