The two types of antagonist, competitive and noncompetitive, are distinguished by how the antagonist binds the receptor. A competitive antagonist binds at the same site as an agonist. A competitive antagonist increases the EC50 of any agonist present without decreasing the maximum response. By increasing the EC50 of the agonist, the antagonist decreases the agonist's potency.
A noncompetitive antagonist binds at an allosteric site. Such binding does not affect the EC50 value (potency) agonist, but it does diminish the response caused by the agonist.
Depending on the needs of the discovery program, one type of antagonist might be more effective than the other. Competitive antagonists, however, tend to be more common. If the drug discovery group knows the structure of a receptor's endogenous ligand, then the team often designs antagonists to resemble the natural ligand. The designed antagonist will likely the bind the same site as the endogenous ligand. OPTIONAL‐Please participate in the online discussion forum.
Interpreting dose‐response graphs Background: Dose‐response relationships are commonly encountered in drug development programs. The characteristic sigmoidal plots convey a large amount of information concisely and can be readily interpreted.