Researchers at the University of Maryland and Texas A&M University-Kingsville have identified a new way to neutralize rattlesnake venom, using naturally occurring blood proteins from the western diamondback rattlesnake (Crotalus atrox). In controlled experiments, the protein mixtures protected mice from lethal doses of venom with far less material than the commercial antivenom used for comparison.
The study, posted on bioRxiv in April, remains at an early stage and has not been tested in humans. The team investigated FETUA proteins, a family of four proteins found in rattlesnakes that can neutralize venom components. Sean Carroll and Fiona Ukken of the University of Maryland worked with collaborators on the research. Carroll described the basic result on a Proceedings of the National Academy of Sciences podcast: “We were startled to discover that we could block lethality with certain combinations, but not with individual proteins.”
The experimental mixtures included FETUA-2, FETUA-3 and FETUA-5, which target different venom components. The effective combination varied by snake venom: FETUA-2 and FETUA-3 were sufficient in the reported mixture for western diamondback venom, while eastern diamondback venom required FETUA-5 as well. In the mouse experiments, the selected mixture had a median effective dose (ED50) of 5.6 mg/kg, compared with 52.6 mg/kg for CroFab. These figures measure experimental potency by weight; they are not a dose comparison that can be directly applied to treatment in people.
How the Protein Mix Works
FETUA proteins bind to and neutralize venom components, particularly metalloproteinases associated with tissue damage and hemorrhage. Combining proteins can broaden the range of targets, but the precise mixture matters because different snake species have different venom metalloproteinases. “Depending on the kind of venom you have, you might have to use a certain combination of these FETUA proteins,” Carroll said on the PNAS podcast.
The researchers mixed venom and proteins before administering them to the mice, testing immediate neutralization rather than treatment after a bite. Each group of five mice received venom at three times the median lethal dose, and researchers monitored survival for 48 hours. The design shows protection under controlled laboratory conditions. It does not establish whether the proteins would work if treatment were delayed or how they would behave in a human body.
Potency Compared to Existing Antivenoms
In the reported comparison, the experimental FETUA mixture was about ten times more potent by weight than CroFab and roughly three times more potent than complete serum from Crotalus atrox. Carroll summed up the comparison on the PNAS podcast: “We found it was about 10 times more potent, on a weight basis.” These results are preclinical proof of concept, not evidence of clinical effectiveness or regulatory approval.
The research also points to possible activity beyond rattlesnakes. The PNAS account describes complete protection against lethality in an experiment using venom from a Malayan pit viper, a lineage said to have diverged from rattlesnakes about 30-35 million years ago. Other tests reported impressive protection against some venoms, including those of Crotalus adamanteus and Echis carinatus sochureki, but the mixture did not prevent death from Bitis arietans venom. The differing outcomes show why a single formulation may not work equally well across species.
The proteins target a toxin family Carroll described as restricted to vipers. That makes the approach a potential targeted or modular strategy, not a universal antivenom. It cannot be assumed to neutralize elapid venoms, such as those of cobras or taipans, whose toxins and effects differ. The study’s cross-species results also do not establish protection against all medically impressive snakes.
Challenges Before Human Use
Several hurdles remain before a FETUA-based therapy could be used in people. Snake venoms contain many toxic proteins from different families, while the current approach targets metalloproteinases and leaves other components, such as neurotoxins and phospholipases, unaddressed. A broader antivenom could require a combination of molecules with different targets and mechanisms.
Further studies would need to examine treatment after envenomation, dosing, distribution in the body, immune reactions, manufacturing and safety. The work has not established human safety or efficacy, and FETUA proteins are not an approved antivenom. U.S. pit-viper bites are currently treated in medical settings with antivenoms such as CroFab or Anavip. The World Health Organization estimates that snakebites cause up to 5.4 million injuries and more than 80,000 deaths worldwide each year, with hundreds of thousands of people left permanently disabled.
Efforts to harness natural resistance mechanisms extend beyond this study. Similar strategies have been explored in other fields, including environment restoration through invasive-species removal, as seen in the return of clear waters to Pyrenean lakes after fish eradication. Both cases show how studying nature can inform approaches to complex biological challenges.
