"We wanted to take a very complex process, chemical synthesis, and make it simple," said Burke, a Howard Hughes Medical Institute Early Career Scientist. "Simplicity enables automation, which, in turn, can broadly enable discovery and bring the substantial power of making molecules to nonspecialists."
The researchers described the technology in a paper featured on the cover of the March 13 issue of Science.
"Small molecules" are a specific class of complex, compact chemical structures found throughout nature. They are very important in medicine - most medications available now are small molecules - as well as in biology as probes to uncover the inner workings of cells and tissues. Small molecules also are key elements in technologies like solar cells and LEDs.
However, small molecules are notoriously difficult to make in a lab. Traditionally, a highly trained chemist spends years trying to figure out how to make each one before its function can even be explored, a slowdown that hinders development of small-molecule-based medications and technologies.
"Up to now, the bottleneck has been synthesis," Burke said. "There are many areas where progress is being slowed, and many molecules that pharmaceutical companies aren't even working on, because the barrier to synthesis is so high."
The main question that Burke's group seeks to answer: How do you take something very complex and make it as simple as possible?
The group's strategy has been to break down the complex molecules into smaller building blocks that can be easily assembled. The chemical building blocks all have the same connector piece and can be stitched together with one simple reaction, the way that a child's interconnecting plastic blocks can have different shapes but all snap together. Many of the building blocks Burke's lab has developed are available commercially.
To automate the building-block assembly, Burke's group devised a simple catch-and-release method that adds one building block at a time, rinsing the excess away before adding the next one. They demonstrated that their machine could build 14 different classes of small molecules, including ones with difficult-to-manufacture ring structures, all using the same automated building-block assembly.
"Dr. Burke's research has yielded a significant advance that helps make complex small molecule synthesis more efficient, flexible and accessible," said Miles Fabian of the National Institutes of Health's National Institute of General Medical Sciences, which partially funded the research. "It is exciting to think about the impact that continued advances in these directions will have on synthetic chemistry and life science research."
The automated synthesis technology has been licensed to REVOLUTION Medicines, Inc., a company that Burke co-founded that focuses on creating new medicines based on small molecules found in nature. The company initially is focusing on anti-fungal medications, an area where Burke's research has already made strides.
"It is expected that the technology will similarly create new opportunities in other therapeutic areas as well, as the industrialization of the technology will help refine and broaden its scope and scalability," Burke said.
"Perhaps most exciting, this work has opened up an actionable roadmap to a general and automated way to make most small molecules. If that goal can be realized, it will help shift the bottleneck from synthesis to function and bring the power of making small molecules to nonspecialists."