Human leukocyte antigen-A1 predicts a good therapeutic response to clozapine with a low risk of agranulocytosis in patients with schizophrenia

Several studies indicate an association between human leukocyte antigens (H LA) and clozapine-induced agranulocytosis. The authors have previously repo rted a significantly increased frequency of HLA-A1 among patients with schi zophrenia who do not respond to conventional drugs, but do respond to cloza pine treatment. In this study, the authors addressed the question of whethe r the same association is found in patients developing granulocytopenia or agranulocytosis. The frequency of the HLA-A1 allele in patients with clozap ine-induced agranulocytosis or granulocytopenia was low (11.5%), whereas HL A-A1 was associated with a good therapeutic response to clozapine at an all ele frequency of 58%. The frequency of HLA-A1 is 20% in the Finnish populat ion. These results suggest that HLA-A1 may predict a good therapeutic outco me and a low risk of agranulocytosis and, thus, enable defining a subgroup of patients with schizophrenia in whom clozapine treatment could be started early to stop the disease from progressing.