US warns monkeypox could mutate to resist antiviral drug

WASHINGTON (AP) — United States 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 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.

Meanwhile, the Centers for Disease Control and Prevention on Thursday said Tpoxx should no longer be given to otherwise healthy adults who are not suffering severe symptoms.

“For most patients with healthy immune systems, supportive care and pain control may be enough,” agency officials said in a statement.

The moves to scale back Tpoxx's use follow 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.

Doctors wishing to prescribe the drug must submit an application to the Centers for Disease Control and Prevention, documenting their patient's needs and agreeing to track their results and any side effects. Officials have shipped 37,000 courses of the drug to physicians.

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