It almost always starts in a field.
A farmer's heel brushes against something coiled in the grass. There is a flash of movement, two pinpricks, and a Russell's viper slips back into the undergrowth as though nothing has happened. Something has, though. The venom is already at work, and the nearest hospital is often hours away over rough roads.
This scene plays out tens of thousands of times a year in India. Snakebite kills more than 100,000 people worldwide every year, and India accounts for nearly half of those deaths. No snake kills more people here than the Russell's viper, Daboia russelii.
For more than a century, we have had exactly one properly validated treatment for snakebite: antivenom. It works, and it has saved countless lives. But it is really a hospital treatment, in a country where the danger is out in the fields. It has to be dripped into a vein, it can set off severe allergic reactions, and it often struggles against the sheer variety of venom that different snakes, and even different populations of the same snake, produce. The person bitten in the field cannot use any of it until they reach a clinic that knows how to treat snakebite. And all the while, the venom keeps working.
It raises a simple question. Could that first treatment be a tablet instead of a vial?
Borrowed weapons
As it happens, the most promising answer was never designed for snakebite at all.
Antivenom works through antibodies: large, temperamental molecules raised in horses, ponies, and mules. The newer approach reaches for something quite different, small-molecule inhibitors, which are tiny chemical compounds that latch onto a venom toxin and block it. Two of these compounds stood out, and both came with something almost no new drug has: a thick file of human safety data. Both had already been through advanced clinical trials for completely unrelated diseases before being shelved.
One is varespladib, which shuts down phospholipase A₂ (PLA₂) toxins. The other is marimastat, which blocks snake venom metalloproteinases (SVMPs). Two forgotten drugs, dropped by the companies that made them, turned out to fit this new problem almost exactly.
And that fit is no accident. Russell's viper venom is dominated by a handful of toxin families, and the PLA₂s and metalloproteinases do much of the damage. They stop the blood from clotting and break down tissue, and in the end they shut the body down. Antivenom tries to neutralise the whole venom at once. These small molecules are more targeted: they go after the specific toxins doing the harm.
To understand how PLA₂s and SVMPs act together to amplify venom toxicity, read the companion story on toxin synergy in Russell's viper venom.
The trouble with maps
There is a catch that has dogged snakebite therapy for decades: venom is not a single, fixed substance.
A Russell's viper in Punjab can carry a venom noticeably different from one in Karnataka or West Bengal (Senji et al. 2021). This geographic variation is one big reason antivenom can work well in one region and poorly in the next. Any treatment worth pursuing has to hold up across the whole country, not just one part of it.
So we collected Russell's viper venoms from across India and tested both drugs against all of them. The results were encouraging. Varespladib reliably switched off PLA₂ activity, and marimastat neutralised the metalloproteinase damage. Either drug on its own was often effective, and where one fell short, the two together closed the gap, giving complete protection with just two repurposed compounds.
After the bite
But a clean laboratory test and a real snakebite are two very different things.
The standard test for antivenom efficacy, the one used across industry and research and even endorsed by the World Health Organization, has a hidden flaw: it quietly stacks the odds in favour of the antivenom. The venom and the treatment are mixed together beforehand at 37 °C for 30 minutes and then injected as a single dose. That is a best-case scenario no snakebite victim ever actually experiences. We wanted to ask the harder and more honest question: can these drugs still help once the venom is already loose in the body?
This is where the results became genuinely striking. In rescue experiments in mice, treatment given up to thirty minutes after the venom, once it had already started spreading, still gave complete protection in several cases. The combination of varespladib and marimastat was the standout, neutralising the venom's lethal effects well after the damage had begun. Thirty minutes is not a short delay in a mouse. Their small bodies are overwhelmed far faster than ours, so venom spreads and does its damage much more quickly. A half-hour in a mouse can therefore stand for a much longer treatment window in a person. And out in the field, that extra time is often the difference between reaching a hospital and never getting there.
A future beyond the vial
None of this replaces antivenom tomorrow. For a long time yet, it is far more likely to work alongside it. But think about what these molecules could eventually offer that a vial of antivenom cannot. A treatment you could swallow instead of having infused. One that keeps at room temperature, is far less likely to trigger a dangerous immune reaction, and is cheaper to make. And, crucially, one that works across regions rather than being defeated by local differences in venom.
Picture that farmer again. This time, a few minutes after the bite, someone puts a tablet in their hand. It buys enough time to reach the nearest hospital, and in the best case it removes the need for antivenom altogether. With snakebite, time is almost everything.
That scene is no longer science fiction. We are now hoping to work with the Indian Council of Medical Research (ICMR) to carry this preclinical work out of the lab and into the clinic.
And maybe that is the real lesson here. For more than a hundred years, snakebite treatment has rested on a single idea: raise antibodies in a horse and hope they are enough. What we are describing is a different approach altogether. Instead of trying to fight the whole snake, you disarm its weapons. Sometimes the most useful new medicine isn't new at all. It is an old, shelved drug that was simply waiting for the right problem.
Don't fight the snake, disarm its weapons.
Paper: Rudresha GV, Khochare S, Casewell NR, Preclinical evaluation of small molecule inhibitors as early intervention therapeutics against Russell's viper envenoming in India . Communications Medicine. 2025;5:226.
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