AR-A 2 is a selective 5-HT1B receptor antagonist, with a high affinity to guinea pig cortex 5HT1B/1D and recombinant guinea pig 5-HT1B receptors (Ki: 0.24 and 0.47 nM) and with 10-fold lower affinity to guinea pig 5-HT1D receptor (Ki: 5 nM).
Bifeprunox is a potent partial agonist of dopamine D2-like and 5-HT1A receptor (pEC50: 6.37 for hippocampus 5-HT1A; pKis: 7.19 and 8.83 for cortex 5-HT1A and striatum D2). It is an antipsychotic for the research of schizophrenia.