In vitro and in vivo experiments--what is more informative?

In-vitro experiments offer a lot of informations but if in-vitro technics would be used exclusively for drug research and screening of new substances the complete pharmacological profile would be unknown. It is always necessary to integrate knowledge of basic research into living and active animals. The fruitful co-operation between theoretical and clinical disciplines--as demonstrated by the L-DOPA story here--demonstrates how to achieve real progress in medical research and the question which type of experiments is more informative is not relevant.