A long-lasting version of Pfizer's Lyrica has failed in a late-stage trial which evaluated the drug in adults with partial onset seizures caused by epilepsy.

The drugs giant announced top-line results of a Phase III study evaluating both the 165mg and the 330mg doses of Lyrica (pregabalin) controlled-release formulation. The results indicated that the drug did not meet its primary endpoint comparing the change in seizure frequency to placebo, although both doses were well-tolerated.

Steven Romano, head of the medicines development group for the global primary care business unit at Pfizer, said that "while the study showed an observed improvement, it did not show a statistically significant difference in seizure frequency, which we believe may have been due to a higher-than-expected placebo response". He added that  "Lyrica immediate-release has a proven success record in patients with epilepsy and we look forward to understanding further the potential role of a once-a-day pregabalin formulation".

The trial is one of three Phase III studies of the pregabalin CR formulation looking at its potential use as a once-a-day therapy. The other two studies are evaluating the drug in fibromyalgia and post-herpetic neuralgia.

Since its first approval from the Food and Drug Administration in 2004, Lyrica has been approved for five indications in the USA, of which four are in pain. It is Pfizer's best-selling drug, with third-quarter sales reaching $1.04 billion (+8%).