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Steps Towards a Smallpox Treatment

Through the middle of the 20th century, smallpox was a disease that annually afflicted tens of millions of people around the world, killing as many as 30 percent and leaving many others with permanent blindness and disfiguring scars. But thanks to the World Health Organization's highly successful smallpox eradication program in the 1960s and 1970s, the world has been free from smallpox. The last naturally occurring case was in October 1977, and except for a few known samples in laboratory freezers, variola, the virus that causes smallpox, no longer exists.

The anthrax attacks in fall 2001, however, raised the possibility that variola might re-emerge as an agent of bioterrorism. While the old smallpox vaccine could be resurrected to help prevent the virus' spread, there are no approved antiviral drugs for treating variola infections.

In 2006, NIAID awarded a contract to SIGA Technologies Inc., to develop and clinically test the anti-variola compound, ST-246. “Poxviruses are unique in that they make two forms of their virion [infectious particle],” explains Dennis E. Hruby Ph.D., Chief Scientific Officer of SIGA. The initial form of the virus produced within a cell must mature into a second form in order to be transmissible. ST-246 targets the protein that catalyzes this conversion, says Dr. Hruby, and prevents it from functioning properly. This halts the spread of the virus within a person's body and improves an individual's prognosis, especially if given early in the course of an infection.

NIAID has supported the development of ST-246 from early discovery through Phase II development. The compound has activity against a wide range of orthopox viruses, as demonstrated in efficacy studies conducted in animal models. Clinical trials have shown ST-246 to be safe and well-tolerated in humans. In 2011, the ST-246 research program was transitioned to the Biological Advanced Research and Development Authority (BARDA) for advanced product development activities.

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Last Updated October 19, 2011