Shares in US drug maker Cleveland BioLabs rose as much as 18%, as rumours spread that its radiation sickness medication could be called upon should the situation at Japan’s damaged nuclear reactors deteriorate.

The company’s CBLB502 drug is still undergoing clinical trials and has not yet received full approval from the US Food and Drug Administration, but could be called upon in an emergency situation.

The treatment is formulated from a protein that could reduce damage from radiation by activating cells’ protective mechanisms.

The US Government has supported the development of the medication with funding.

Cleveland BioLabs CEO Dr Michael Fonstein told, “There is, in principle, emergency use permitted where certain agencies can authorise use of the drug even without full approval by the FDA. For our drugs, there is a specific avenue to handle this problem.”