Proteins are key players in the biological processes that determine whether a person is sick or well. So not surprisingly, they form the basis for some of today's most important and effective drugs. But in some ways, these large, complex biomolecules are far from being the perfect drugs: they're chewed up in the stomach if taken by mouth, and many of them break down even when injected-severely limiting which proteins can be used. Now a number of biotech companies are reporting progress in designing smaller, more stable molecules that mimic the therapeutic action of proteins, opening the door to completely new drugs, and to the possibility of replacing some painful injections with equally effective pills.

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