Bioisostere is a term used in designing of drugs to signify a group, which can be utilized for replacement of another group. It includes the classical as well as non-classical isosteres involved in drug design.
They are usually to replace functional groups required for specific target binding. They display compound and garget specificity. They, however, do not provide guarantee for activity retention for each drug at each target.
Bioisosteres are also found to increase selectivity and target interactions. They are very often used to replace a group that is problematic along with retention of activity. For example a commonly used bioisostere is a pyrrole ring used to replace an amide. This activity was used on sultopride to develop DU 122290.
Sultopride is antagonistic to dopamine, whereas DU 122290 displayed increased selectivity and activity towards the receptors of dopamine at positions two and three. It has been developed as a promising antipsychotic agent. It does not show the side effects that are generally associated with the receptor of dopamine at position two.