The ideal drug would exhibit pure action at a single site. Such pinpoint precision would work as if a single gene were switched off. Rosetta Inpharmatics is pursuing technology aimed at helping drug designers determine if their compounds have such precision.

The approach uses cDNAs from yeast knock-out mutants and from drug-treated yeasts to make comparisons of gene expression. Writing in Nature Medicine, the company showed that the degree of overlap of patterns of gene expression may predict side effects or suggest alternate therapeutic targets.