Early clinical experience using tecovirimat during the 2022 mpox epidemic in Toronto underscores ongoing clinical equipoise and the need for randomized trials.

Background: Tecovirimat is an antiviral drug that was used compassionately for treating mpox in high-income settings during the 2022 global outbreak. Randomized controlled trials of its efficacy have not yet been completed.

Objectives: To describe medication adherence, tolerability and clinical outcomes of adults receiving open-label tecovirimat for mpox infection.

Methods: We conducted a prospective observational study and a retrospective case series of adults with mpox cared for at three academic hospitals in Toronto, Canada, between May and August 2022. We present a descriptive analysis of those prescribed oral tecovirimat 600 mg twice daily for 14 days for the management of severe manifestations.

Results: Of 69 consenting participants, all were cisgender men, of whom 60 (87%) identified as gay, and 6 (9%) as bisexual. Nearly half (46%) were living with HIV, with a median (IQR) CD4 count of 468 (328-678) cells/mm3, among whom plasma HIV RNA was <20 copies/mL in 29 (91%) participants. One-third (33%) of participants received tecovirimat during the course of their illness. All participants experienced a decline in number of symptoms over time, but three treated participants initially experienced worsening symptoms despite therapy. Self-reported adherence to tecovirimat was excellent and tolerability was good.

Conclusions: Our experience prescribing tecovirimat for mpox suggests it is safe and well tolerated, but the evolution of symptoms in some tecovirimat-treated patients underscores the ongoing uncertainty regarding its efficacy. In the context of considerable community demand for the drug, efforts should be made to connect mpox patients to rigorous randomized controlled trials, given this ongoing clinical equipoise.