Python Blood Contains an Appetite Suppressant That Could Rival Ozempic

Scientists at the University of Colorado Boulder and Stanford University have discovered a molecule in python blood called pTOS that suppresses appetite and causes weight loss in mice without the nausea, muscle loss, or digestive problems associated with GLP-1 drugs like Ozempic and Wegovy. The researchers have founded a startup to pursue commercialization.

From Snake Blood to Weight Loss

Burmese pythons can swallow prey weighing up to 100% of their body weight, then go months or even years without eating, all while maintaining healthy hearts and muscle mass. Their metabolism spikes 4,000-fold after a meal to aid digestion.

The research team identified 208 metabolites that surge in python blood after eating. One molecule, para-tyramine-O-sulfate (pTOS), increased by 1,000-fold. When administered to obese laboratory mice, pTOS acted on the hypothalamus, the brain's appetite center, and produced remarkable results.

The Results in Mice

Obese mice given pTOS ate significantly less than control mice. After 28 days, they had lost 9% of their body weight. The mice showed no changes in water intake, energy expenditure, or movement. Crucially, pTOS did not slow stomach emptying, the mechanism that causes GLP-1 drugs to produce nausea, and caused no muscle loss.

How It's Different from Ozempic

GLP-1 drugs (Ozempic, Wegovy) mimic a gut hormone and work partly by slowing stomach emptying, which causes feelings of fullness but also nausea and digestive distress. About half of patients stop taking them within a year. pTOS works entirely through the brain, targeting the hypothalamus directly. It is produced by gut bacteria in pythons and is found at low levels in human urine.

Senior author Leslie Leinwand said: "We've basically discovered an appetite suppressant that works in mice without some of the side effects that GLP-1 drugs have."

Next Steps

The team has formed Arkana Therapeutics to work toward chemically synthesized analogs of pTOS. Some metabolites identified in the study surged by 500–800%. "We're not stopping with just this one metabolite," Leinwand said. "There's a lot more to be learned."

The study was published in Nature Metabolism on March 19, 2026.