The chemical probe - scopes, limitations and challenges.

Drug design needs high-quality chemical probes for target validation, but the demands on chemical probes are largely different than those on drugs. Whereas therapeutic value and safety are main criteria for a drug evaluation, the chemical probe is influencing a biological target in a well-characterized way. Affinity, efficacy, selectivity and versatility in different read-outs are main criteria for chemical probes to test biochemical hypothesis and verify targets for new therapeutic approaches.