Several new antipsychotics have been submitted to the Food and Drug
Administration (FDA) for marketing review, making the therapeutic landscape
for schizophrenia and bipolar disorder in the near future hard to predict.
One of the most recent new drug applications (NDAs) was for asenpine
sublingual tablet, developed by Organon. The drug binds with both dopamine
D2 receptor and a host of serotonin 5-HT receptors subtypes, with a
greater antagonism to all serotonin receptor subtypes except 5-HT1a
and 5-HT1b, according to Steven Potkin, M.D., of the Department of
Psychiatry and Human Behavior at the University of California, Irvine, and two
researchers from Organon in their study published in the October 2007
Journal of Clinical Psychiatry.
In this randomized, double-blind, controlled study, asenapine was compared
with placebo and risperidone in 174 patients with acute schizophrenia for six
weeks. The asenapine group saw a significantly greater reduction in mean
Positive and Negative Syndrome Scale total, negative symptom, and positive
symptom scores compared with placebo. Asenapine had a better profile than
risperidone in terms of weight gain and prolactin levels, but the authors
acknowledged that the 6 mg/day of risperidone given in this study was at the
high end of usual dosage.
In an earlier phase 3 study in 488 patients, asenapine produced a
significantly greater reduction in bipolar manic symptoms compared with
placebo after three weeks. The study results were presented at APA's 2007
annual meeting in San Diego in May.
Asenapine has a somewhat curious history. Initially developed by Organon,
it was licensed to Pfizer. In late 2006, however, Pfizer terminated the deal
and gave the molecule back when an interim assessment of the phase 3 trials of
asenapine became available. Schering-Plough acquired Organon last November,
shortly before the announcement that the FDA had accepted the new drug
application for a standard review.
Regulatory success is, however, far from certain for novel antipsychotics.
Another previously promising molecule, bifeprunox, was rejected by the FDA
last August as "unapprovable" based on the submitted clinical
data; the agency appeared to be lukewarm about the drug's efficacy compared
with other available antipsychotics in treating acute schizophrenia, according
to the announcement from Wyeth, the manufacturer. The company stated that it
would continue with the development of bifeprunox.
An NDA for paliperidone palmitate intramuscular injection, intended for
once-monthly use, was filed with the FDA in October 2007 by its makers,
Johnson and Johnson and Elan Pharmaceuticals. The oral extended-release tablet
formulation of paliperidone has been approved for acute and maintenance
treatment for schizophrenia. Paliperidone is an active metabolite of
A third new antipsychotic, iloperidone, is also waiting for the FDA to
render a judgment on its NDA, which was filed by Vanda Pharmaceuticals last
September and accepted by the agency in late November. The drug binds to a
spectrum of dopamine and serotonin receptors and, according to the company,"
provides a favorable profile on adverse symptoms such as weight gain,
extrapyramidal symptoms, akathisia, and prolactin elevation."
An abstract of "Efficacy and Tolerability of Asenapine in
Acute Schizophrenia: A Placebo- and Risperidone-Controlled Trial" is