Tecovirimat for treating mild monkeypox: new studies open in the UK and US

Simon Collins, HIV i-Base

On 23 August 2022, the PLATIMUM study was launched in the UK to look at using tecovirimat to treat monkeypox (MPX). [1]

This study plans to randomise 500 people (1:1) with mild MPX to either tecovirimat or matching placebo. Follow-up is for 28 days.

Participants need a referral from their doctor, but no further clinic visits are needed. This means that anyone who is self-isolating can still take part. The referral email is simple and only takes a few minutes (

Although tecovirimat interacts with some HIV medications (darunavir, rilpivirine and maraviroc) these are either not cliniclly important or can be easily managed.

Other drugs with potential interactions include: bupropion. repaglinide, voriconazole, midazolam, atorvastatin, tacrolimus, methadone, flurbiprofen, erectile drugs (sildenafil, tadalafil, vardenafil) and proton pump inhibitors (lansoprazole, omeprazole, rabeprazole).

Anyone with severe MPX, especially if hospitalised, should have named-patient access to tecovirimat without needing to join a placebo-controlled study.

Further participant information and the study protocol are available online.

In the US, the phase 3 STOMP study is randomising 530 adults and children with MPX (2:1) to either tecovirimat or placebo. It asks people to send photographs of their symptoms as part of the ongoing monitoring. [2, 3]


Several studies have already reported anecdotal evidence on potential benefits of tecovirimat to treat MPX, also supported in animal studies for smallpox. [4, 5, 6, 7, 8, 9]

This includes, as we went to press, a review of open-label use of tecovirimat in 549 participants in the US, reported in MMWR. Data is included for about 350 people. [9]

This makes results from a randomised study essential in order to be able to inform future access and use. This is a very study to refer people to – only a standard email – but the referral is needed.

Results should similarly be compiled from open-label use, although these will be more limited.

The PLATINUM study is also linked to a similar study in Canada. [10]


  1. The PLATINUM study website.
  2. Study of Tecovirimat for Human Monkeypox Virus (STOMP)?
  3. A5418:Study Of Tecovirimat For Human Monkeypox Virus (STOMP)
  4. Seven cases of monkeypox virus in the UK from 2018 to 2021. HTB (1 June 2022).
  5. Desai AN et al. Compassionate use of tecovirimat for the treatment of monkeypox infection. JAMA. doi:10.1001/jama.2022.15336. (22 August
  6. Thornhill JP et al for the SHARE-net clinical group. Monkeypox virus infection in humans across 16 countries — April–June 2022. NEJM, doi: DOI:
    1056/NEJMoa2207323. (21 July 2022).
  7. Lucer J et al. Monkeypox virus–associated severe proctitis treated with oral tecovirimat: a report of two cases. Letter. Annals Internal Medicine. (18 August 2022).
  8. Grosenbach DW et al. Oral tecovirimat for the treatment of smallpox. N Engl J Med 2018;379:44-53.
  9. O’Laughlin K et al. Clinical use of tecovirimat (Tpoxx) for treatment of monkeypox under an investigational new drug protocol — United States, May–August 2022. MMWR Morb Mortal Wkly Rep. ePub: 9 September 2022. DOI:
  10. Tecovirimat in non-hospitalized patients with monkeypox. (PLATINUM-CAN).

This page was updated on 11 September to includ US and Canadian studies.

Links to other websites are current at date of posting but not maintained.