A detailed analysis of the receptor profile of clozapine,the onlyantipsychotic used in treatment-resistant schizophrenia,2,3 in addition to well-known blockade of serotonin type 2A (5-HT2A) receptor, revealed the antagonistic properties at the serotonintype 3 receptor (5-HT3R)4 andserotonin type 6 receptor (5-HT6R).5 Although concurrent blockade of the muscarinic, histamine, and dopaminereceptors hampers procognitive properties of clozapine,1,6 its high affinity for both 5-HT3R and 5-HT6R has triggered academic and industrial research. The gene discussed is HTR3A; the disease is schizophrenia.