Enlarge / The structure of the human factor VIII.University of Washington

Rational drug design seems so promising.

Identify a drug that has a desired effect.

This is usually done either by screening a library of possible drugs or even of random chemicals, or by actively searching for a molecule hypothesized to be active against a cellular target of interest.

Optimizing can be done by tweaking a drug s interaction with its target: changing its shape, size, or electric charge so that it fits better.

If all those work out, the modified drug may eventually be tested in humans.

The text above is a summary, you can read full article here.