US FDA Relaxes Final Deadline for NDSRI Impurity Mitigation Measures for Merck, Pfizer, and Others
US FDA Extends Deadline and Provides Flexibility in Responding to NDSRI Regulations
The US Food and Drug Administration (FDA), through its Center for Drug Evaluation and Research (CDER), has adjusted the final deadline for mitigation measures and submissions related to Nitrosamine Drug Substance-Related Impurities (NDSRIs). The original deadline of August 1, 2025, has been replaced with a more flexible approach involving the submission of Progress Reports. This decision reflects the practical technical challenges faced by the pharmaceutical industry in modifying formulations and manufacturing processes, aiming to prevent disruptions in the supply of key medicines. Manufacturers can now report detailed progress and improvement plans through the 'NDSRI Update' section within their Annual Reports, instead of immediate recalls. This flexible approach by the regulatory agency balances the goal of ensuring safety with the need to guarantee patient access to essential treatments.
NDSRI Formation Mechanisms and Enhanced CPCA Guidelines
Nitrosamine Drug Substance-Related Impurities (NDSRIs) are potential carcinogens formed when secondary or tertiary amine structures within Active Pharmaceutical Ingredients (APIs) react with trace amounts of nitrites present in excipients during the manufacturing process. To supplement the toxicity data of individual compounds, the FDA has introduced the Carcinogenic Potency Categorization Approach (CPCA), reclassifying the risk levels from 1 to 5. Manufacturers must recalculate the Acceptable Intake (AI) for potential impurities based on the new criteria and redesign their processes accordingly. The use of highly sensitive analytical techniques, such as Liquid Chromatography-Mass Spectrometry (LC-MS), has become essential, increasing the short-term quality control costs for companies.
Impact of Impurity Issues on Blockbuster Drugs and Market Competition
The drugs most affected by this regulatory flexibility are Januvia (sitagliptin, a DPP-4 inhibitor) from Merck & Co., Inc. (MRK) and Chantix (varenicline, an alpha4beta2 nicotinic acetylcholine receptor partial agonist) from Pfizer Inc. (PFE). When impurities, including NTTP, were detected in sitagliptin, which generated approximately USD 5.3 billion in annual sales and was approved in 2006, the FDA temporarily raised the permissible limit to 246.7ng/day to prevent supply disruptions and potential risks to patients. In contrast, after a voluntary recall by Pfizer, the market for Chantix was quickly reshaped by generic products that met the standard of 37ng/day or less. Similarly, Januvia faces intense competition from alternative DPP-4 inhibitors like linagliptin and SGLT-2 inhibitors like Jardiance, making compliance with quality standards crucial for maintaining market share.
Increased Costs for Pharmaceutical Companies and Expanded R&D Investment for Process Improvement
Global pharmaceutical companies are significantly increasing their investment in Research and Development (R&D) to modify formulations and incorporate nitrite scavengers, such as ascorbic acid, to meet the stricter safety standards. However, changing the formulation requires conducting Bioequivalence Studies, which adds hundreds of thousands of dollars in costs and several months of additional regulatory review time. As a result, the market dominance of large Contract Development and Manufacturing Organizations (CDMOs) that have proactively invested in facilities and analytical capabilities is expected to strengthen. Conversely, small and medium-sized generic manufacturers with limited financial resources and inadequate quality control (QC) infrastructure may face increasing difficulties in complying with regulations, potentially leading to their displacement from the market.
The FDA's relaxation of the NDSRI regulation deadline provides an opportunity for companies like Merck (MRK) to mitigate the risk of short-term supply disruptions for blockbuster drugs such as Januvia (with annual sales exceeding $5 billion) and maintain their market dominance. However, in the medium to long term, it will be a factor in gauging the potential benefits for competitors in the global type 2 diabetes treatment market (valued at $6.6 billion in 2024), such as linagliptin and Jardiance, which are alternative DPP-4 inhibitors and SGLT-2 inhibitors, respectively. In particular, the increase in quality control (QC) fixed costs due to formulation changes, such as the introduction of highly sensitive analytical equipment and nitrite scavengers, will serve as a premium factor for original pharmaceutical companies and Contract Development and Manufacturing Organizations (CDMOs) with abundant R&D funding. On the other hand, small and medium-sized generic manufacturers with insufficient self-verification capabilities may face accelerated margin pressure and an increased risk of being phased out of the market due to the burden of re-conducting bioequivalence studies.
Source: FDA Drug Approvals (rss)