SB269652 is an allosteric modulator of D2 dopamine receptors. SB269652 binds to an allosteric site th at is distinct from the orthosteric bound by typical D2 antagonists and is only revealed in D2 receptor dimers. SB269652 is bitopic, binding to an orthosteric site one one partner in the dimer and the allosteric site in the other. Engagement of this secondary pocket at the extracellular end of TM2 and TM7 is a new mechanism of modulating binding of a ligand to the orthosteric site of a second protomer by a G-protein coupled receptor.