Promising drug against Mpox fails in trials as virus spreads in Africa

How mpox continues Although the disease may be spreading in Central Africa, a promising antiviral drug to treat the infection failed to relieve patients' symptoms when tested in the Democratic Republic of Congo, the epicenter of the outbreak.

In the trial, the drug tecovirimat, also known as TPOXX, did not relieve the characteristic blistering rash seen in people with Mpox, formerly known as monkeypox. In an unusual move, the U.S. National Institute of Allergy and Infectious Diseases (NIAID), which sponsored the study, announced the initial results earlier this month before the full results were peer-reviewed and published in a scientific journal.

Lori Dodd, chief of NIAID's Clinical Trials and Statistics Division, told WIRED that the agency reported the initial findings “due to the urgent need for scientific evidence to support the use of tecovirimat to treat Mpox.” That urgency was heightened by the World Health Organization's August 14 designation of the Mpox outbreak in Central Africa as a global health emergency, the second such declaration in two years.

The results are disappointing, especially as Central African countries struggle to contain transmission of Mpox. Since the beginning of the year, a total of 20,720 confirmed or suspected cases of Mpox and 582 deaths have been recorded in 13 African countries, according to an August 25 report by the Africa Centers for Disease Control and Prevention.

On Monday, the World Health Organization launched a six-month strategic plan to contain the outbreak. The plan, estimated to cost $135 million, includes increased surveillance measures and improved access to testing and vaccines. “The Mpox outbreaks in the Democratic Republic of Congo and neighboring countries can be controlled and stopped,” Tedros Adhanom Ghebreyesus, WHO Director-General, said in a statement.

There are approved vaccines to prevent Mpox, but no drugs to treat the disease. Tecovirimat was approved by the U.S. Food and Drug Administration in 2018 to treat smallpox, a related virus, and ongoing trials of the drug to treat Mpox began in 2022 amid a global outbreak of the disease. The drug is also available in the U.S. for Mpox through an expanded access program that allows a doctor to treat a patient with an investigational drug outside of a clinical trial. In the U.K. and Europe, TPOXX was approved for Mpox under exceptional circumstances, without comprehensive data on its effectiveness.

In the trial in the Democratic Republic of Congo, nearly 600 participants were randomly assigned to receive tecovirimat or a placebo and were hospitalized for at least 14 days where they were closely monitored. All participants received supportive care, which included nutrition, hydration and treatment of any secondary infections. Although the drug was deemed safe, it did not heal patients' lesions any better than the placebo.

Most notably, mortality was lower and patients' lesions healed faster than expected, regardless of whether they received tecovirimat or a placebo. The study's overall mortality of 1.7 percent among participants, regardless of whether they received the drug or not, was much lower than the Mpox mortality of 3.6 percent or more reported for all cases in the Democratic Republic of Congo.