The antiviral tecovirimat, or TPOXX, appears to be safe and effective for treating monkeypox symptoms and skin lesions, a small study from the University of California, Davis suggests.
The study on tecovirimat by UC Davis researchers included patients referred to UC Davis Medical Center between June 3 and August 13, 2022.
Patients with skin lesions in multiple body parts or sensitive areas such as the face or genital region were offered oral tecovirimat treatment, which prevents the virus from leaving infected cells and stops its spread within the body.
In total, 25 patients — all males aged 27 and 76 — with confirmed monkeypox infection completed a course of tecovirimat therapy and tolerated the treatment well. Nine of the patients also had HIV.
On average, the patients had symptoms or lesions for 12 days before they started their treatment. Other common symptoms were fever, fatigue, sore throat, and chills.
According to the research letter published in JAMA Network, the patients were treated for two weeks, except for one patient who was treated for 21 days. On day 7 of tecovirimat therapy, 40% of patients had healed from their lesions. By day 21, 92% had healed and were pain-free.
The most reported adverse events on day 7 of therapy included fatigue, headache, nausea, itching, and diarrhea.
The study authors note that data have to be interpreted carefully, as it is hard to differentiate the side effects due to therapy from those caused by the infection. In addition, the study was small and did not include a control group, and the time from symptom onset to starting the antiviral therapy varied among the patients.
The US Food and Drug Administration (FDA) approved TPOXX to treat smallpox in adults and children in 2018 under the Animal Rule regulations. It allows approval of certain drugs based on studies in animal models when human efficacy studies are not ethical or feasible.
As smallpox was eradicated globally in 1980, the drug’s efficacy was established using related viruses, such as non-human primates infected with monkeypox virus and rabbits infected with rabbitpox virus. The TPOXX was also tested in healthy human volunteers to assess safety.
When it comes to monkeypox, the agency allows the use of TPOXX as a non-research expanded access investigational new drug (EA-IND) in patients with severe disease or who are more likely to get severely ill.
During the current outbreak, more than 48,000 monkeypox cases were reported globally, among which 18,101 were identified in the US. The disease disproportionately affects men who have sex with men; however, anyone can catch the virus through close, intimate contact.
Last week the Oxford University team announced launching the placebo-controlled randomized trial of tecovirimat in non-hospitalized monkeypox patients (PLATINUM). Researchers are now recruiting up to 500 people with monkeypox across the UK to participate in the trial remotely.
“Although the early data on tecovirimat are promising, only a randomized clinical trial will provide the level of evidence we need to treat patients with confidence. PLATINUM will provide that evidence,” said Sir Peter Horby, Professor of Emerging Infections and Global Health at the University of Oxford and one of the leading researchers in the trial.