Forest Laboratories and Gedeon Richter have announced the preliminary top-line results of the Phase II clinical trial of cariprazine, an investigational antipsychotic agent for the treatment of bipolar depression.

Due to the tolerability results of the trial, the companies are planning to conduct additional Phase II dose-response trials to evaluate a wider range of doses.

The Phase II trial was an eight-week, double-blind, randomised study, which was designed to evaluate the tolerability, safety and efficacy of once-daily dose of cariprazine in patients with bipolar depression.

The patients were randomised into one of the following three treatment arms – high-dose cariprazine, low-dose cariprazine or a placebo.

The study findings showed that there was no statistically significant difference between the drug-treated and placebo-treated groups, but over the course of the trial a clinically relevant treatment effect was observed in the high-dose treatment arm when compared with the placebo.

Approximately 9% of patients in the high-dose study arm discontinued the drug due to adverse events compared with 3% in the placebo arm.

The trial, which was conducted at US clinical sites, enrolled 233 patients between ages 18 and 65 years.