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ALMOST a century ago, a chance discovery revolutionised medicine. Alexander Fleming left a petri dish of bacteria out while he went on a two-week holiday. On his return, he found that the dish had been contaminated by a fungus that produced an antibacterial substance. He named it penicillin, and it has since saved millions of lives.

Even in the modern world, drug discovery still essentially relies on chance. Pharmaceutical companies often screen thousands of compounds trying to find one with the desired effect.

The dream, though, is to make drug development a much faster and more rational process. …