The antiviral drug tecovirimat (brand name, Tpoxx) was prescribed to more than 7,100 US mpox patients in 2022 and 2023, mainly for treating rash and pain in sensitive areas, with most serious adverse events (SAEs) occurring in patients with weakened immune systems, according to a new analysis from the Centers for Disease Control and Prevention (CDC).
The authors cautioned that tecovirimat safety and effectiveness can’t be determined from the data.
Mpox is a viral illness transmitted primarily through skin-to-skin contact and, in the global outbreak caused by clade 2 virus that peaked in 2022, was diagnosed mainly in men who have sex with men. Mpox manifests as a blistering rash, pain, and swollen lymph nodes and usually resolves on its own within a few weeks but can also lead to death.
The investigators parsed data on the characteristics, clinical courses, and outcomes from the intake and outcome forms and diaries of patients from 49 states, Puerto Rico, and Washington, DC, who were prescribed tecovirimat from May 2022 to July 2023.
Amid the clade 2 outbreak, many US patients were prescribed tecovirimat, stockpiled by the US government for a potential reintroduction of smallpox, under an expanded-access Investigational New Drug (EA-IND) program.
The results were published late last week in NEJM Evidence.
Skin, anogenital region most affected
Most of the roughly 7,100 patients were prescribed a 14-day course of tecovirimat for the treatment of lesions in sensitive areas, such as the anogenital region (83.5%), and for pain (52.5%). Most patients who received tecovirimat were men with a median age of 35 years but cases were also seen in women (220 patients), pregnant women (12), and children younger than 12 years (17).
The median time from symptom onset to tecovirimat prescription was 7 days. Clinicians reported that 77.1% of mpox patients had a rash at illness onset. The skin (76.3%) and anogenital region (73.1%) were the most commonly affected areas at baseline, but lesions in the mouth (17.3%) and eyes (4.2%) were also reported.
Of the 7,181 patients with returned intake forms, 22.6% also had returned outcome forms. A total of 223 SAEs (3.1%) and 40 deaths (0.6%) were reported, mainly among those with severely weakened immune systems, and 3.9% were hospitalized. In addition to death, the most common SAEs were headache, nausea, vomiting, elevated liver enzymes, hives, fatigue, acute kidney injury, abdominal pain, dizziness, and tremor.
Children, pregnant women, and those with conditions compromising skin integrity didn’t have severe outcomes.
Half also had HIV
Many patients with HIV and low CD4 white blood cell counts (22 of 51 [43.1%]) were given multiple tecovirimat courses, some of them intravenous, and often had poor outcomes (18 of 51 [35.3%]). One severely immunocompromised patient reported hallucinations after receiving twice the recommended dose of tecovirimat.
The EA-IND data are not definitive; controlled clinical trial data are essential to elucidating if and how tecovirimat should be used.
Roughly 52% of people with returned intake forms had HIV, and 8.5% had other underlying illness; of the latter, 4.3% had severely weakened immune systems (including 277 HIV patients with low CD4 counts), 4.2% had conditions affecting skin integrity (atopic dermatitis or eczema (240 patients), psoriasis (40), cystic acne (4), and other conditions (15).
Of HIV patients with low CD4 counts, 11 had another condition that met the definition of severe immunocompromise (10 with cancer and 1 with a solid-organ transplant).
In total, 15.1% of patients (128 of 846) had received the Jynneos mpox vaccine before reported mpox exposure. The median number of lesions at intake after receipt of one dose of Jynneos was seven.
“The EA-IND data are not definitive; controlled clinical trial data are essential to elucidating if and how tecovirimat should be used,” the study authors cautioned.
