The biological toxin ricin is one of the threats that elicits concern from both military chemical, biological, radiological and nuclear (CBRN) defence specialists, as well as civil-sector public health and counterterrorism officials. Ricin is a highly toxic protein that naturally occurs in the beans of the castor bean plant (Ricinus communis), also known for (ricin-free) castor oil. This molecule is a potent cytotoxin which causes harm by inhibiting the human body’s ability to synthesise proteins. Since the body is always synthesising proteins to make new cells, the failure to synthesise proteins leads to death.

Three factors combine to cause the public concern over this substance. First, the castor bean plant is easily cultivated in a wide variety of climates and conditions. Many people raise them, they grow wild in places, and growing a few castor bean plants is generally something that doesn’t raise suspicions. Second, unlike most biological and chemical threats, the actual production process is not inherently difficult. The process is dangerous but not difficult and an undergraduate chemistry student, or someone who can carefully follow instructions, could extract ricin from the beans with relatively unsophisticated equipment. Third, ricin is extremely toxic, often lethal, by injection or ingestion, with no easy method to treat the total breakdown of the human body caused by this toxin.

These concerns are borne out by a number of incidents wherein ricin was used or threatened in terrorist acts.  It has been used as an assassination weapon, most notably in the 1978 assassination of the Bulgarian defector Georgi Markov. A plot in Cologne, Germany to use ricin in an attack was foiled by German police in 2018. Dozens of other incidents, some involving mere threats not actual material, have been investigated.  It is also well-documented that ricin was manufactured as part of several historic national-level biological weapons programmes, although it is harder (but not impossible) to administer it as a wide-area respiratory threat as it is a non-volatile solid. [See here for more on biological weapon limitations.]

A ricin antidote emerges

Up to now, part of the threat profile of ricin has been the lack of effective treatment. Various research efforts have creaked along in the US and UK. Some labs have worked on vaccines, but this presumes a target vulnerable population that can be protected in advance, and so far the vaccines have had short periods of effective protection. But a French government-funded effort has jumped the queue. It is rare for a new product development to get this somewhat cynical correspondent to pay serious attention. The French firm Fabentech, based in Lyon, has announced that they have received Marketing Authorisation from the French government for a new medication, Ricimed. This new drug is an antidote to ricin, representing a major watershed moment.

Ricimed contains ‘polyclonal antibodies’ to directly inactivate the ricin molecules. Antibodies can work by a number of different mechanisms. In the case of ricin, it is a long and complicated protein molecule. Ricimed works by binding to the ricin protein in certain spots, like a key machined to fit a particular lock. In this case, the ricin protein is taken out of action and cannot inhibit protein synthesis. While this has been done in the lab over 40 years ago with a monoclonal antibody, Fabentech has managed to navigate a theoretical approach into an actual medicine usable in humans. In their case, they derive the drug from horses, a time-honoured manufacturing approach for antitoxins, antivenoms, and immunoglobulins.

According to Fabentech’s press releases, this effort was heavily underwritten by the French government, with some support from the European Union. The French Ministry of Defence, France’s Direction Générale de l’Armement, and the French military health system are credited with financial support for the project. Social media posts from Fabentech also credit the EU’s HERA and HERAInvest programmes and the European Investment Bank.

So far, this is a France-only product. The next hurdles will be regulatory approvals and authorisations elsewhere, including the USA. It should be noted that this is the sort of product that would elicit great interest in the US military, but also elsewhere. The market potential could theoretically be great.

From an operational standpoint, ricin poisonings are rare and relatively unpredictable, but the existence of a viable medical treatment means that poisonings can be definitively treated. This may involve adding the drug to emergency preparedness stockpiles, which exist in Europe and the USA, that could be pre-positioned for major events. Given the rate of action of ricin, it is likely that there’s a window of time for administering the drug to have a beneficial effect. In other words, it would not be necessary to administer it immediately. Additionally, unlike, say, the nerve agent antidote atropine, which is a poison in its own right, ricin antibodies have low potential for harm in scenarios where ricin is possible but not yet proven.