Health officials in the United States are advising against overusing the only medication available to treat monkeypox since even a tiny change in the virus could make the pills useless.
Tens of thousands of people with the virus have been administered Tpoxx, and this week the Food and Drug Administration modified its recommendations for the drug.
A single molecular alteration to monkeypox “may have a major influence on the antiviral activity of Tpoxx,” FDA authorities said in an online update. Regulators emphasized that doctors should be “judicious” when prescribing the treatment because viruses are continually mutating to escape infection-preventing measures, including medications.
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 reduction in Tpoxx use comes in response to weeks of criticism from HIV advocacy groups and other patient groups, who pushed the Biden administration to increase access to the antiviral medication. The use of Tpoxx against the related monkeypox virus is restricted and is regarded as experimental by federal authorities.
The Centers for Disease Control and Prevention requires doctors who want to prescribe the medication to fill out an application, certifying their patient’s need and their commitment to monitoring the patient’s progress and any negative effects. 37,000 courses of the medication have been sent to doctors by officials.
Tpoxx functions by selectively destroying a specific protein present on smallpox, monkeypox, and related viruses. The FDA stated this week that there are numerous potential ways in which monkeypox could become resistant to the treatment, according to research in labs, on animals, and in humans.