FDA Approves Drug to Treat Smallpox
June 4, 2021

The US Food and Drug Administration (FDA) approved brincidofovir (Tembexa) to treat smallpox.

Although the World Health Organization declared smallpox, there have been long standing concerns that the virus that causes smallpox, the variola virus, could be used as a bioweapon.

Before its eradication in 1980, the variola virus mainly spread by direct contact among people. Symptoms typically began 10 to 14 days after infection and included fever, exhaustion, headache, and backache. A rash consisting of small, pink bumps progressed to pus-filled sores before it crusted over and scarred. Complications of smallpox included encephalitis, corneal ulcerations , and blindness.

Although naturally occurring smallpox no longer exists, concerns about potential uses of variola virus as a bioweapon has made smallpox drug development an important component of the US medical countermeasures response.

Because smallpox is eradicated, the effectiveness of brincidofovir was studied in animals infected with viruses that are closely related to the variola virus. Effectiveness was determined by measuring animals’ survival at the end of the studies. More animals treated with brincidofovir survived compared with the animals treated with placebo.

The FDA approved brincidofovir under the agency’s Animal Rule, which allows findings from adequate and well-controlled animal efficacy studies to serve as the basis of an approval when it is not feasible or ethical to conduct efficacy trials in humans.

Safety information to support approval of brincidofovir was derived from clinical trials of the drug for a non-smallpox indication, primarily from patients who received hematopoietic stem cell transplants. An increased risk of death was seen in another disease (Cytomegalovirus disease) when brincidofovir was used for a longer-than-recommended duration (longer than once a week for 2 weeks on days 1 and 8).

The most common side effects when using brincidofovir were diarrhoea, nausea, vomiting, and abdominal pain.

Brincidofovir was developed in conjunction with the U.S. Department of Health and Human Services’ Biomedical Advanced Research and Development Authority (BARDA). FDA granted approval of brincidofovir to Chimerix Inc.

Reference: https://www.fda.gov/drugs/drug-safety-and-availability/fda-approves-drug...

SOURCE: US Food and Drug Administration