Snakebites: combining existing drugs could help prevent major injuries in rural areas

Combining existing drugs could prevent life-changing injuries from snakebites across the globe, as findings by scientists at the Centre for Snakebite Research and Interventions (CSRI) at the Liverpool School of Tropical Medicine (LSTM) hope this could pave the way for new and affordable treatments for what they call a “neglected tropical disease”.

According to the World Health Organisation (WHO), the disease known as “snakebite envenoming”, caused by the toxins in the bite of a venomous snake, is “potentially life threatening”.

Between 4.5 million and 5.4 million people get bitten by snakes across the world annually, WHO data shows, with between 1.8 million and 2.7 million developing an illness, and between 81,000 and 138,000 dying from complications.

The first line of treatment is having antivenom administered intravenously in hospitals, but it is not effective against tissue damage caused by snake bites as necrosis kills the flesh and cannot be reversed, leading to permanent injury and amputation.

Researchers at CSRI said previous studies have also shown that it takes snakebite victims an average of five to nine hours to reach hospitals from rural settings, so the team explored existing small molecule drugs that could be given to the patient immediately following a bite.

They repurposed cancer drug marimastat, varespladib, which acts as an anti-inflammatory agent, and 2,3-dimercapto-1-propanesulfonic acid – known as DMPS – which is used in cases of heavy metal poisoning and through using human skin cells and mice, different combinations of the three drugs were found to protect against tissue damage from venom found in a number of snake species in North and Central America, west Africa, east Africa, south-east Asia and the Middle East.

Professor Nicholas Casewell, head of CSRI at LSTM, said the findings, published in Nature Communications, are “exciting” as they “show that combinations of drugs that have already been shown to be safe in human clinical trials can prevent local tissue damage caused by different snake species. This is important because cytotoxic snake venoms cause hundreds of thousands of cases of morbidity each year across the world."

He added: “Identifying new, affordable and safer treatments for snakebite is a priority to mitigate the devastating impact caused by this neglected tropical disease.”

Lead researcher Dr Steven Hall said: “Snakebite affects millions of people yearly with upwards of 400,000 being permanently injured as a result, which is why this study is so promising.

“We successfully showed that combining two drugs that target just two different snake venom toxin families can almost completely inhibit the skin necrotising activity of a wide range of geographically distinct snake species with differing venom profiles. Even more impressive is the fact that this reduction in necrosis remained significant even when the drugs were administered up to an hour after the envenoming event in vivo”.