The Food and Drug Administration is warning that the overuse of an experimental antiviral drug to treat monkeypox could have unintended consequences.
The FDA said that overuse of Tpoxx, which was authorized to treat smallpox in 2018, could cause the monkeypox virus to mutate, rendering the treatment ineffective.
"Tpoxx works by inhibiting a viral protein, called VP37, that all orthopoxviruses (e.g., smallpox virus, monkeypox virus, vaccinia virus) share. However, as noted in the drug label, Tpoxx has a low barrier to viral resistance. This means small changes to the VP37 protein could have a large impact on the antiviral activity of Tpoxx," the FDA explained.
Currently, Tpoxx is considered an experimental treatment for monkeypox, and its use is tightly controlled.
The National Institute of Allergy and Infectious Diseases began running clinical trials on September 8 to determine the safety and efficacy of Tpoxx for treating a monkeypox infection.
Speaking during a webinar, Dr. Sapna Bamrah Morris, with the CDC, said that health officials "know that there's a point mutation could lead to resistance to tecovirimat, or Tpoxx, which is our primary antiviral being used."
"We don't want to discourage people to use Tpoxx when it's indicated, but we do want to think about when it's indicated," she said, according to Newsweek. "And that really is for severe immunocompromised patients, particularly right now with our risk population with those who are infected with HIV and not well controlled. Leukemics, lymphomics, generalized malignancy, solid organ transplant, the list goes on for our sort of general kind of immunocompromised patients."