The U.S. Food and Drug Administration has recently approved a new drug for the treatment of smallpox, a pill stockpiled in case the virus is used as a bioweapon.
TPOXX, a small-molecule antiviral treatment, is the first therapy approved for this biosecurity use and was developed by SIGA Technologies in partnership with the Biomedical Advanced Research and Development Authority (BARDA).
The pharmaceutical company has a $472 million procurement and development contract with BARDA, as part of which 2 million courses of oral TPOXX have been delivered to the Strategic National Stockpile. In the event of a bioterrorism attack, Health and Human Services estimates that more than 1.7 million people could need treatment.
“To address the risk of bioterrorism, Congress has taken steps to enable the development and approval of countermeasures to thwart pathogens that could be employed as weapons … Today’s action reflects the FDA’s commitment to ensuring that the U.S. is prepared for any public health emergency with timely, safe and effective medical products,” said FDA Commissioner Scott Gottlieb in a written statement on Friday.
TPOXX works by preventing the smallpox virus from spreading to the rest of the body, thus containing the infection until the body’s immune system can fight off the disease. More than 700 healthy human volunteers participated in 12 clinical trials of oral TPOXX and showed no drug-related serious adverse events.
“We use the same antiviral techniques that were used for the hepatitis C therapies but apply those for biodefense,” Phil Gomez, CEO of SIGA Technologies, told Homeland Preparedness News.
There were challenges to developing TPOXX, though. The variola virus — the virus that causes smallpox — didn’t infect animal models well in the initial trials. There were also inconsistences in control groups. Eventually, SIGA was able to use a surrogate, Monkeypox, a virus in the same family as variola, to conduct experiments. The drug was also tested in vitro against seven strains of smallpox to demonstrate efficacy, Gomez said.
This drug was awarded a Material Threat Medical Countermeasure Priority Review Voucher, which serves as a “coupon” SIGA can apply toward a future drug, gaining a priority review by the FDA.
Vaccination campaigns against smallpox in the United States ended in the early 1970s, and the virus was eradicated globally by 1980. Anyone born after that time is now highly vulnerable to the disease, according to officials at HHS. Also, small amounts of the variola virus still exist in research labs in the United States and in Russia, raising concerns about access to a virus that could be used as a weapon.
In addition, BARDA is working toward the approval of an intravenous formulation of TPOXX for patients who are too young or too sick to take oral medications.