Gates Package — page 1003

measure the reaction. With high-throughput screening, companies can now test millions of compounds in a matter of weeks, a task that would take a normal team of humans years to complete. Many of the major pharmaceutical companies have collected millions of compounds; if each collection is a library, then high-throughput screening is the fast, methodological way to search through every book on the shelf for just the right word. And even if there isn't a good match--if there isn't an existing compound that looks as if it might make a good treatment--that's helpful information. The faster we can rule out the compounds we already have, the faster we can move on to making new molecules. Regardless of the method involved, once a promising compound is identified, the scientific teams will analyze it to determine whether it's worth further exploration. If it is, a different team--the medicinal chemists--will try to optimize the compound in a process that's a bit like squeezing a balloon. They might tweak it in one way to make it more potent, but then discover that the higher potency also made it more toxic. Once we've found a promising candidate in the exploratory phase, we'll spend a year or two in the preclinical phase, studying whether our candidate is safe and whether it actually triggers the expected response in animals. Finding the right test subject is not as easy as it sounds, because animals don't always respond to a drug the way that humans will. Researchers have a saying: "Rats lie, monkeys exaggerate, and ferrets are weasels." If all goes well in the preclinical phase, we'll move into the riskiest and most expensive part of the process: clinical trials in humans. ***