GuwahatiHeparin, a commonly used blood thinner, can be repurposed as an inexpensive antidote for cobra venom, scientists at the University of Sydney and Liverpool School of Tropical Medicine have found.
Cobras kill thousands of people annually worldwide and several thousand more are maimed by venom-induced necrosis โ the death of body tissue and cells โ which can lead to amputation.
Based on a 2017 study, the World Health Organisation said about 45,900 people die from snakebites in India every year. The Indian cobra is one of the top four species of venomous snakes contributing to this figure.
โCurrent antivenom treatment is expensive and does not effectively treat the necrosis of the flesh where the bite occurs. Our discovery could drastically reduce the terrible injuries from necrosis caused by cobra bites โ and it might also slow the venom, which could improve survival rates,โ Greg Neely, a corresponding author of the study from the Charles Perkins Centre and Faculty of Science at the University of Sydney, said.
Stopping necrosis
Using specific gene-editing technology to identify ways to block cobra venom, the team, comprising scientists based in Australia, Canada, Costa Rica, and the United Kingdom, adapted heparin and related drugs and showed they could stop the necrosis caused by cobra bites.
The research has been published in the latest issue of the journal Science Translational Medicine.
โHeparin is inexpensive, ubiquitous, and a part of the WHOโs list of essential medicines. After successful human trials, it could be rolled out relatively quickly to become a cheap, safe, and effective drug for treating cobra bites,โ Tian Du, a research scholar from the University of Sydney and an author of the study, said.
The team used a bacterial defence system to find the human genes cobra venom needs to cause necrosis that kills the flesh around the bite. One of the required venom targets is enzymes needed to produce the related molecules heparan and heparin, which many human and animal cells grow.
Heparan is on the cell surface and heparin is released during an immune response. Their similar structure means the venom can bind to both. The team used this detail to develop an antidote to stop necrosis in human cells and mice.
Decoy antidote
Unlike current antivenoms for cobra bites, the heparinoid drugs act as a โdecoyโ antidote. By flooding the bite site with โdecoyโ heparin sulphate or related heparinoid molecules, the antidote can bind to and neutralise the toxins within the venom that cause tissue damage.
โSnakebites remain the deadliest of the neglected tropical diseases, with the burden landing overwhelmingly on rural communities in low- and middle-income countries. Our findings are exciting because current antivenoms are largely ineffective against severe local envenoming, leading to loss of limb function, amputation, and lifelong disability,โ Nicholas Casewell, the head of the Centre for Snakebite Research and Interventions at Liverpool School of Tropical Medicine, said. He is one of the authors of the study.
Snakebites kill up to 138,000 people a year, with 400,000 more experiencing long-term injuries due to the bite. While the number affected by cobras is unclear, in some parts of India and Africa cobra species account for most snakebite incidents.
