The atypical antipsychotic agents ziprasidone [correction of zisprasidone], risperdone and olanzapine as treatment for and prophylaxis against progressive multifocal leukoencephalopathy.

Progressive multifocal leukoencephalopathy (PML) is an unremitting, advancing disease of central nervous system white matter. PML is caused by infection of the JC polyoma virus, most always in patients with immunosupression due to, for example, cancer, anti-rejection transplant medications or HIV. There is no specific treatment or cure for PML, and untreated it has a median life expectancy is less than four months. Highly active antiretroviral treatment (HAART) has greatly reduced the incidence and prevalence of PML in HIV+ patients likely, however, even in the best case scenario of an HIV+ patient with PML and taking HAART, a significant mortality remains. Novel treatments for PML are needed. Recently Atwood and colleagues have found that the cellular receptor for JC virus is the serotonin 5HT2A receptor. In vitro they used the older antipsychotic medications chlorpromazine and clozapine to block the serotonin 5HT2A receptor and block JC virus cell entry. Unfortunately, however, chlorpromazine and clozapine have such significant side effects and toxicities, e.g., extrapyramidal symptoms and the possibility of bone marrow dyscrasias - that they may be problematic to use clinically. Here, we point out that some newer atypical antipsychotics such as zisprasidone, risperidone and olanzapine--medicines with much better side effect and toxicity profiles than the older antipsychotics--in vitro are significantly more potent 5HT2A receptor antagonists than chlorpromazine or clozapine by in some cases more than a factor of 10, and thus may be useful as treatment for or prophylaxis against PML.