The great reaction
Nobel laureate K Barry Sharpless hopes to make drug design as simple as building with Legos.india Updated: Nov 12, 2009 13:50 IST
As a boy growing up in the late 1940s, K Barry Sharpless fell under the spell of the coelacanth. The lungfish-like creature was believed to have been extinct for 6 million years until researchers pulled one out of the waters off South Africa in 1938. Sharpless fished obsessively in the rivers of his native New Jersey and never found any archeologic creature. But in the end he did find virtual coelacanths--biochemical treasures that took nature eons to produce.
Sharpless has produced some of the most important breakthroughs of chemistry in the past 30 years. Scientists long knew that some medicinal molecules come in mirror-image forms, only one of which is effective or only one of which is safe. Sharpless discovered several reactions that could produce just the useful form, an innovation that won him the 2001 Nobel Prize in chemistry. That work led to mass-production of heart pills, antibiotics and pain medicines.
Sharpless, 68, is now a professor with a large lab at the Scripps Research Institute in La Jolla, Calif. (He's named one of the seven most powerful innovators by Lemelson-MIT Program director Michael Cima.) For the past decade he's been pushing an idea called click chemistry, a term Sharpless coined before the ink on his Swedish diploma was dry. Click chemistry might have an even bigger impact than his Nobel-winning work.
Click chemistry is as much an operating philosophy as it is a recipe. Organic chemists make much of what we see--drugs, plastics, food, gasoline--by linking carbon atoms via such methods as heat, pressure, enzymes, caustic chemicals and explosions. But figuring out how to devise complex new chemicals can be a laborious and time-consuming process. It took chemists two decades to figure out how to produce the cancer drug Taxol in the lab. Before that, it had to be derived from the bark of the Pacific yew tree.
Sharpless aims to simplify medicinal chemistry by devising reliable ways to link together small chemical building blocks to form far more complex structures. If his concept works, drug design will become a bit like building with Legos. Chemists could rapidly create new drugs by linking together numerous simple building blocks, one after the other.
Sharpless and his colleague Valery Fokin demonstrated in 2002 one such reaction that can within minutes latch together smaller carbon molecules into bigger ones at room temperature by adding copper as a catalyst. The results are stable and repeatable.
Click chemistry is still mostly being used for basic research, but the method has already attracted the attention of forward- thinking drug designers. "It's become the standard way of linking two molecular pieces to make a larger structure," says David Tirrell, a professor at Caltech.
James Heath, a professor of chemistry at Caltech, is using click techniques to develop new diagnostic tests that will spot specific proteins in the blood. Current diagnostics can cost a hundred dollars per test because they use antibodies to spot proteins. Such antibodies, usually made inside animal cells, are expensive and unstable. Heath clicked together a chain of peptides that assembles only when it binds to the protein being targeted, exactly the job of an antibody. The solution is stable enough to be dried into a powder and shipped anywhere. He thinks someday the cost of diagnostics testing could drop to pennies per test.
Derek Lowe, a chemist at Vertex Pharmaceuticals ( VRTX - news - people ) who also writes a blog called In The Pipeline, is looking into similar approaches for drug discovery. The hope, he says, is that click chemistry will turn up fewer duds--compounds that look like they bind to a target in the lab but then don't work in animals. "If there is one reaction like this out there that nobody has discovered, it makes you wonder how many more there are," Lowe says.