Less than a month after streamlining the process to endorse the lone treatment for monkeypox, the FDA is now urging doctors to be “judicious” in their prescribing of Siga’s tecovirimat (Tpoxx).
Why the shift in guidance?
According to the CDC, the rapidly evolving monkeypox virus is only one mutation away from rendering Tpoxx ineffective. Recent studies of monkeypox reveal that it has “several genetic pathways” to evade Typoxx, which has a “low barrier to viral resistance,” the CDC said.
Officials recently released the new guidance online and the label for the antiviral treatment has been adjusted accordingly.
The guidance comes days after the U.S. launched a phase 3 trial evaluating the effectiveness of Tpoxx. As part of the effort to attract more than 500 participants, the National Institute of Allergy and Infectious Diseases (NIAID) urged clinicians to access Tpoxx for patients with monkeypox through a “compassionate use” request.
“We currently lack efficacy data that would help us understand how well this drug may mitigate painful monkeypox symptoms and prevent serious outcomes,” NIAID director Anthony Fauci, M.D., said in a release. “This clinical trial was designed to answer those important questions.”
Tpoxx won approval in 2018 as the first treatment for smallpox. Earlier this year, the FDA authorized its use for monkeypox. The drug comes in pill form and is taken over a span of 14 days. It is recommended for those who have a severe case of the virus, including rashes and lesions.
Another antiviral option is likely on its way in Chimerix’s Tembexa, which was approved for smallpox last year.
The monkeypox and smallpox viruses are closely related. In the U.S., Bavarian Nordic’s vaccine Jynneos was blessed in 2019 to prevent infection from both viruses.