Controlling Novichok Nerve Agents after the Skripal and Navalny Incidents


By Dr. Stefano Costanzi, Professor of Chemistry, American University, USA and Dr. Gregory D. Koblentz, Director of Biodefense Graduate Programs, George Mason University, USA.

Since Novichok nerve agents came to public attention following a high-profile assassination attempt in 2018, the international chemical weapons nonproliferation regime has taken important, but incomplete, steps to reduce the risk of these chemical weapons proliferating. The Chemical Weapons Convention has added some Novichok agents to its list of chemicals subject to declaration and verification and the Australia Group has included some Novichok precursors to its list of dual-use chemicals that should be subject to export controls. However, gaps in coverage of Novichok agents and precursors by the chemical weapon nonproliferation regime remain in a way that can be exploited by proliferators. We recommend adopting a family-based approach to controlling Novichok agents and precursors and leveraging advances in cheminformatics to facilitate implementation of this more comprehensive approach to nonproliferation and export controls.

Novichok agents are a class of nerve agents developed by the Soviet Union beginning in the 1970s. In recent years, these once obscure agents have become notorious due to their use in the assassination attempts of Sergey Skripal in 2018 and Alexei Navalny in 2020. The chemical structures of Novichoks, also called A-series agents, were publicly revealed in the 2009 book State Secrets by Vil Mirzayanov, an analytical chemist formerly involved in the Soviet chemical weapons program. Of note, these structures are different from those of the better known, canonical nerve agents of the G series, such as sarin or soman, and the V series, such as VX or VR. Because of these differences, Novichoks and precursors for their synthesis ended up not being included in lists of chemicals that support chemical weapons disarmament and nonproliferation frameworks. In fact, Mirzayanov suggests in his book that, as the Chemical Weapons Convention (CWC), was under negotiation, one of the motives behind the development of the Novichok agents was the intention to the obligations of the forthcoming treaty.

The Chemical Weapons Convention Schedules and the Australia Group Chemical Weapons Precursors List

The CWC is an international disarmament and nonproliferation treaty that poses a complete ban on chemical weapons. It entered into force in 1997 and enjoys almost universal membership. To support its verification regime, the CWC uses a tiered system composed of three schedules. Going from Schedule 1 to Schedule 3, the schedules contain chemicals that, beyond their chemical-weapon-related role, have increasingly legitimate commercial applications. Nerve agents of the G and V series are listed in Schedule 1. Conversely, as mentioned above, Novichoks were not included in the original schedules. It must be emphasized that this does not mean that Novichok agents were not banned by the treaty. Article II of the treaty codifies the general purpose criterion, according to which any toxic chemical intentionally used or intended to be used against humans or animals to cause “death, temporary incapacitation or permanent harm” is to be considered a chemical weapon. However, listing chemicals of concerns in the CWC schedules indeed strengthens the treaty’s declaration requirements and verification regime.

Beyond the CWC, other international mechanisms are in place to support chemical weapons nonproliferation. Among them is the Australia Group (AG), a multilateral informal arrangement of 42 participant countries plus the European Union, established in 1985 to harmonize export control legislation to prevent the proliferation of chemical and biological weapons. The Australia Group has developed the AG Chemical Weapons Precursors list that enumerates specific dual-use chemicals to which all participants agree to apply their export licensing measures.

Aftermath of the Salisbury Incident

The attempted assassination of Sergey Skripal triggers amendments to the CWC Schedules and the AG Chemical Weapons Precursors List

Following the attempted assassination of Sergey Skripal and his daughter Yulia in 2018, two proposals seeking to add Novichoks to Schedule 1 were submitted to the OPCW. One was jointly submitted by the United States, Canada, and the Netherlands. The other was submitted by Russia.

Following a long negotiation process, the Conference of States Parties approved the adoption of both proposals, leading to the first amendment of the CWC schedules since the treaty’s entrance into force in 1997. This historical amendment, which entered into force in June 2020, provided comprehensive coverage for a portion of the nerve agents of the Novichok class. However, it provided minimal coverage to another portion of the Novichok agents. In particular, the new CWC Schedule 1 entries 1A13 and 1A14 identify two large families of Novichok agents, namely fluorophosphonates and fluorophosphates with amidine branches.

This family-based approach to listing chemical warfare agents is very powerful, since it covers a very large number of related chemicals without the need to enumerate them individually.

Conversely, the new CWC Schedule 1 entry 1A15 exclusively identifies a single Novichok agent, namely a fluorophosphonate agent with a guanidine branch. The emphasis on Novichoks bearing amidines rather than guanidine was due to the fact that the agent used in the attempted assassination of the Skripals was allegedly an amidine-bearing Novichok known as A-234. No precursors for the synthesis of Novichok agents were added to the CWC schedules.

However, in February 2020, the AG added to Chemical Weapons Precursors list 22 individually enumerated chemicals that are precursors for the synthesis of a limited subset of the Novichok agents added to CWC Schedule 1. As explained below, the AG Chemical Weapons Precursors list does not feature any families of chemicals in it.

The Navalny incident underscores the need to further revise the CWC schedules and AG Chemical Weapons Precursors list

The attempted assassination of Navalny in 2020 highlighted the gap left open by the weak coverage of guanidine-bearing Novichok agents, as it became evident that a Novichok agent not covered by CWC Schedule 1 was used to perpetrate the attack. Although the agent used for Navalny’s attempted assassination has not been publicly revealed, from the report issued by the OPCW following the analysis of the victim’s biomedical sample by designated laboratories, it is possible to infer that the agent in question is likely to be a fluorophosphate bearing a guanidine branch.

The CWC schedules should be further amended to provide Novichok agents that have guanidine branches the same degree of coverage given to their counterparts bearing amidine branches. This can be accomplished by adding to CWC Schedule 1 two more families of agents fashioned in the same way as those identified by entries CWC 1A13 and CWC 1A14. It is also worth considering whether it would be feasible to add the Novichok precursors featured in the AG precursors list to the CWC schedules, possibly expanding the schedules with a family-based approach, which would provide wider coverage. Adding Novichok precursors to the CWC schedules will make it more difficult for proliferators to produce or acquire these chemicals, since the CWC has a wider membership than the AG and the inclusion of families of chemicals on the CWC schedules enables a more comprehensive coverage of the precursors. It must be noted that, given that they typically are dual-use chemicals, adding precursors to control lists is something that requires careful consideration. Beyond their role in the synthesis of chemical-warfare agents, these chemicals are likely to have legitimate uses as well. Hence, thorough feasibility studies must be conducted to the ensure that the addition of these dual-use chemicals to the control lists bolsters chemical security without imposing an excessive burden on the chemical industry.

Regarding the AG, the Chemical Weapons Precursors list features only individually enumerated chemicals rather than families of chemicals because frontline officers who do not have sufficient training in chemistry are unable to interpret them and to infer whether a chemical under scrutiny falls within their scope. However, the adoption of cheminformatics tools, like the one that the Costanzi Research Group at American University and the Stimson Center are currently prototyping, promises to fill this gap by equipping frontline officers with a capability to automatically query lists of controlled chemicals and interdict those of concern. Such tools would allow the AG to include families of chemicals in the Chemical Weapons Precursors list. The addition of families of Novichok precursors to this list could serve as a test case for potentially expanding the same approach for other chemical warfare agent precursors on the AG list.


The ability of the CWC and AG to adapt to the new challenge posed by these fourth-generation nerve agents demonstrates the resilience of the chemical weapon nonproliferation regime. However, further measures need to be implemented to reduce the opportunities for proliferators to develop and use Novichok nerve agents. Embracing a family-based approach to listing chemicals of proliferation concern would strengthen the nonproliferation regime and the adoption of technologies such as cheminformatics can facilitate the transition to this new approach to containing the threat posed by chemical weapons.

** For more information on the current gaps in the CWC and AG coverage of Novichok agents and precursors and recommendations for how to close those gaps, please see Stefano Costanzi and Gregory D. Koblentz, “Strengthening Controls on Novichoks: A Family-Based Approach to Covering A-Series Agents and Precursors Under the Chemical-Weapons Nonproliferation Regime,” The Nonproliferation Review, Vol. 28, No. 1-3 (2021): 95-113.

About the Authors:

Dr. Stefano Costanzi is a Professor of Chemistry at American University, in Washington DC, with an educational background in both the chemical sciences and international affairs. His current teaching and research interests mainly focus on the countering of chemical weapons. He is particularly interested in the analysis of gaps in current policies and practices that allow the proliferation of chemical weapons and in the conceptualization and development of solutions and tools to narrow them, based on a blend of chemistry, information technology, and science-based policy. Moreover, Dr. Costanzi is interested in modeling the interactions of chemicals with living organisms, through computational chemistry techniques.

Gregory D. Koblentz is an Associate Professor and Director of the Biodefense Graduate Program at George Mason University’s Schar School of Policy and Government. Dr. Koblentz is also an Associate Faculty at the Center for Security Policy Studies at George Mason and a member of the Scientist Working Group on Biological and Chemical and Security at the Center for Arms Control and Non-Proliferation in Washington, DC. In 2016, he briefed the United Nations Security Council on the impact of emerging technologies on the threat posed by non-state actors armed with weapons of mass destruction. Dr. Koblentz is the author ofLiving Weapons: Biological Warfare and International Security (Cornell University Press, 2009) and co-author of Editing Biosecurity: Needs and Strategies for Governing Genome Editing (George Mason University and Stanford University, 2018). He has published widely on issues related to biodefense, dual-use research, and the proliferation of nuclear, biological, and chemical weapons. He received a PhD in political science from the Massachusetts Institute of Technology and a MPP from the John F. Kennedy School of Government at Harvard University.

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