US warns monkeypox could mutate to resist antiviral drug

WASHINGTON (AP) — U.S. health officials are warning against overuse of the lone drug available to treat monkeypox, saying that even a small mutation in the virus could render the pills ineffective.

The Food and Drug Administration updated its guidance this week for Tpoxx, which has been prescribed to tens of thousands of patients afflicted with the virus.

In an online update, FDA officials cautioned that a single molecular change to monkeypox “could have a large impact on the antiviral activity of Tpoxx.” Since viruses are constantly evolving to overcome obstacles to infection, including drugs, regulators stressed that doctors should be “judicious” in prescribing the medication.

The call to scale back Tpoxx’s use follows weeks of criticism from HIV advocates and other patient groups who have urged the Biden administration to make the antiviral drug more widely available. Tpoxx is approved for the related smallpox virus, and its use against monkeypox is considered experimental and tightly controlled by federal officials.