This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pharmacology, Subject name: Pharmacology
A drug that binds to a receptor at a site distinct from the active site and reduces the affinity of the receptor for the endogenous ligand is a: 
Select and explain. 
A. Competitive antagonist, B. Paial antagonist, C. Inverse agonist, D. Allosteric antagonist
D: Allosteric antagonist
Answer: D: Allosteric antagonist 
Explanation: A drug that binds to a receptor at a site distinct from the active site (allosteric or non-agonist site) and reduces the affinity of the receptor for the endogenous ligand is termed as allosteric inhibitor. Allosteric inhibition is a form of non-competitive antagonism (Allosteric antagonism). Allosteric Modulator: An allosteric modulator is a drug that binds to a receptor at a site distinct from the active site and induces a conformational change in the receptor, which alters the affinity of the receptor for the endogenous ligand. Positive allosteric modulators increase the affinity, whilst negative allosteric modulators decrease the affinity. Ref: Katzung 14th edition Pgno: 24