Does HIV Status Affect Tecovirimat Treatment Efficacy in Mpox Patients?

In May 2022, outbreaks of the mpox virus (formerly called monkeypox) in nonendemic countries placed the world on high alert.

Mpox is a zoonotic Orthopox virus, similar to smallpox. The most infamous mpox symptoms is a fluid-filled, blister-like rash that can be very itchy or painful.

The epidemiology of the recent mpox outbreaks was unique from prior outbreaks in that most infections occurred among men who have sex with men (MSM). Since mpox primarily spreads through skin-to-skin contact or through the bodily fluids of an infected person, such as during sex, it is unsurprising that the virus circulated in sexual communities.

However, people living with HIV (PWH) were also disproportionately affected, with 35-47% of mpox infections occurring in PWH. These outbreaks led to increased utilization of the antiviral tecovirimat.

Developed by SIGA Technologies, Inc., tecovirimat was previously approved by the US Food and Drug Administration (FDA) to treat smallpox. Tecovirimat has been reportedly well tolerated, with most treated individuals experiencing complete symptom resolution and only mild adverse reactions.

Original research published in the ACP journal Annals of Internal Medicine was the first to compare clinical presentation and treatment outcomes between PWH and people without HIV who were treated with tecovirimat for mpox virus.

The retrospective cohort study was conducted in 2 medical centers in New York City, and included 154 persons who contracted mpox and were treated with tecovirimat from June 20-August 29, 2022. An additional 42 patients who initiated tecovirimat treatment but did not have documented confirmation of mpox infection were included only in safety outcomes.

The investigators utilized case reports and electronic health records to collect demographic data on patients’ age, sex assigned at birth, gender identity, race, ethnicity, gender of sex partners, number of sex partners in the last month, HIV preexposure prophylaxis (PrEP) usage, HIV status (most recent viral load and whether CD4 count was < 0.20 × 109 cells/L), and coinfection of sexually transmitted infection (STI) (in both the 2 weeks before tecovirimat initiation and at the primary study visit). The investigators also collected data regarding mpox illness manifestations and signs of improvement after tecovirimat treatment initiation.

Of the 154 patients who tested positive for mpox and received tecovirimat, 72 were PWH and 82 were HIV-negative. All patients were assigned male sex at birth, and 1 reported female gender identity. Only 2 of all mpox patients reported exclusively female sex partners.

The PWH were generally older and more likely to be Black or Hispanic, and 14 of the 72 had a viral load greater than 1000 copies/mL or CD4 count less than 0.20 × 109 cells/L. Among the HIV-negative patients, 70% reported taking HIV PrEP.

The indications for tecovirimat treatment were similar between the PWH and HIV-negative cohorts. Nonsevere adverse events occurred in 22% of patients. Serious adverse events were reported in 4 patients, 3 of whom were PWH and 2 with CD4 counts less than 0.20 × 109 cells/L. None of the serious adverse events were determined to be due to tecovirimat.

The 2 cohorts had similar rates of hospitalization, indication for treatment, and concurrent infections. However, PWH had fewer days from symptom onset to treatment than patients without HIV (7.5 days vs 10 days). On day 1 of illness, PWH were more likely to report skin lesions, fever, and diarrhea, while HIV-negative patients were more likely to experience a prodrome and to develop additional symptoms or examination findings, such as lymphadenopathy.

Notably, there was no difference in treatment outcomes between the PWH and HIV-negative patients. While prior studies found PWH were hospitalized with mpox at higher rates than those without HIV, this research found no differences in hospitalization rates. The investigators determined all mpox patients who initiated tecovirimat treatment had comparable days to improvement and rates of persistent symptoms, regardless of their HIV status.