Building drugs like Legos
Photo Credit: Gaelen Morse
By David Levin
January 22, 2026
During surgery, a blood clot can kill in minutes. That's why heparin sulfate, a powerful blood thinner, is one of the most widely used drugs in hospitals worldwide. But this life-saving medication has a strange origin story: It comes from pig intestines, and requires organs from millions of slaughtered animals each year to meet global demand.
By its nature, this process comes with risk. Drugs sourced from animals may contain molecules that aren’t uniform in their structure, causing side-effects and — in rare cases — severe immune reactions.
To get around this problem, Brandeis chemistry professor Hao Xu’s research team is searching for new ways to make chemically pure versions of drugs like heparin, a type of molecule called a complex carbohydrate, from scratch.
The major challenge of making these drugs, he notes, is ensuring that each of the molecule’s building blocks remains in a specific orientation. A complex carbohydrate is made up of a long chain of sugar molecules linked together in a precise, branching structure — so building one from the ground up requires assembling all the building blocks in exactly the right order and geometry. A single branch installed facing the wrong direction could radically alter how the molecule works in the body.
To ensure accuracy, Xu’s new method uses a new sort of metal catalyst — an ingredient that acts like a factory worker on a molecular assembly line, fastening specific building blocks together in a precise way. These sorts of reactions are already used to manufacture complex carbohydrate drugs, but most existing methods rely on exotic precious metals like rhodium or palladium. Instead, Xu’s new technique is based on iron, one of the most abundant metals on the planet.
Ultimately, he envisions making a complete toolkit of different iron catalysts, each one responsible for making a specific type of chemical bond. Used together, these tools would provide a standardized way to build any type of complex carbohydrate, eliminating the need to create a bespoke process for each new molecule. As a result, manufacturers could produce drugs more quickly affordably than current methods allow.
"Our long-term goal is to assemble complex carbohydrates just like Legos, combining any building block precisely in any sequence we want,” he says.
If successful, this approach could mark the beginning of a new era in drug production — one that doesn't depend on animals, lowers risk and makes essential medications more affordable for the public.
