Bifeprunox

Bifeprunox is an atypical antipsychotic drug with mixed (agonist/antagonist) receptor activity with the neurotransmitters dopamine (D2/3/4) and serotonin. Bifeprunox differs from first-generation atypical antipsychotics in that it acts as a partial D2 agonist. This property is shared by aripiprazole, a drug already marketed in Europe and the US for treatment of schizophrenia. A placebo-controlled, dose-finding phase II trial in patients with schizophrenia showed that bifeprunox was both efficacious and well tolerated. Importantly, treatment with bifeprunox did not appear to cause some of the side effects seen with other atypicals agents in routine use, such as weight gain, hyperprolactinaemia and cardiotoxicity.

In contrast to D2 receptor antagonism, partial D2 agonism is believed to decrease dopamine activity in an overactive dopamine system while simultaneously increasing dopamine activity in regions of the brain where dopaminergic activity is too low. By blocking overstimulated receptors and stimulating underactive ones, partial D2 agonists act as dopamine stabilisers. In common with aripiprazole, bifeprunox also acts as a serotonin, 5-HT1A agonist. This property may contribute to efficacy against the negative symptoms of schizophrenia and reduce the likelihood of extrapyramidal symptoms (EPS).