LONDON, Aug 15 (Reuters) - Siga Technologies' ( SIGA )

antiviral drug tecovirimat helped the very sickest mpox patients

in a trial in Democratic Republic of Congo recover more quickly

than those given a placebo, the company said, indicating the

treatment could have a role in controlling the disease now

spreading in parts of Africa.

Topline results from the trial, released on Thursday, showed

that the drug, branded TPOXX, helped those treated within seven

days or with severe disease - classed as having 100 or more skin

lesions - make "meaningful improvement". However, the majority

of patients in the trial did not recover more quickly than those

given a placebo, which meant that the drug failed in the main

goal of the study.

"To describe these results as mixed is not a negative

result," said Jay Varma, Siga's ( SIGA ) chief medical officer. "It's

simply a pathway to get more data to be studied."

Mpox, a viral infection, was declared an emergency this week

by the World Health Organization after it spread from Democratic

Republic of Congo to neighbouring countries.

There have been more than 17,000 suspected mpox cases in

Africa this year and more than 500 deaths, according to data

from the Africa Centres for Disease Control and Prevention,

mainly among children in Congo.

The trial of TPOXX, originally developed and licensed for

smallpox, began in 2022 during a previous mpox outbreak that the

WHO declared a global health emergency.

Due to the emergency, the trial accepted any patients who

wanted to take part when they presented with symptoms at

hospitals in Tunda and Kole, in central Congo - regardless of

underlying conditions or time since symptom onset. That

complicated the results, as antivirals are best given as soon as

possible after patients fall ill, Siga ( SIGA ) said.

Participants were also hospitalized throughout to ensure

data could be collected accurately as well as to give them

reliable access to food, the company said. That level of care

also helped many people, including in the placebo arm, recover

more quickly than previously seen in observational mpox studies

in Congo.

The study included 295 patients who received a 14-day course

of tecovirimat, and 302 who received a placebo. Around 75% of

the participants were children, who are known to be at higher

risk of complications from mpox.

Varma said it was important that the drug remained available

under compassionate use protocols for the sickest patients.

A number of other mpox trials in the United States and

Europe are testing outcomes among different patient groups,

including more people with HIV, who are at higher risk from

mpox.

Tecovirimat is not currently available in Congo outside

clinical trials, although the WHO and some countries have small

stockpiles.

The PALM 007 trial was co-led by Congo's National Institute

for Biomedical Research (INRB) and the United States National

Institutes of Health, and detailed results are expected soon.