- Written by Sally Chege, PhD, GlobalData's Analyst covering Neurology.

Lyrica (pregabalin) is one of more than twenty anti-epileptic drugs (AEDs) currently on the market. Although more commonly used as a pain medication, it is also approved for the adjunctive treatment of adult epilepsy patients experiencing refractory partial onset seizures. The path to cementing Lyrica’s clinical positioning in treating epilepsy, however, has been a tortuous one for Pfizer, with different clinical trials yielding somewhat contradictory results. The most recent of these trial results were announced on February 21, from a Phase III study comparing Lyrica with the current leading epilepsy treatment, Keppra (levetiracetam). These positive top-line results indicated that the study met its primary endpoint by demonstrating that a comparable proportion of patients on Lyrica achieved at least a 50% reduction in the 28-day seizure rate during the maintenance phase, relative to levetiracetam.

However, only three months ago, in November 2012, Pfizer announced that in a Phase III trial conducted in adult epilepsy patients with partial onset seizures, the controlled-release (CR) formulation of Lyrica failed to meet its primary endpoint when comparing the change in seizure frequency with placebo. It is worth noting that these two trials tested different formulations of the drug; while the 2012 study failure involved Lyrica CR, a once-a-day formulation, the results from the February 2013 study involved Lyrica CV capsules, which are an immediate-release formulation. Nonetheless, it is surprising that one formulation of the drug would prove ineffective compared with placebo, whereas a different formulation would show similar efficacy to the industry-leading drug. Furthermore, a recently published GlobalData report indicated that although Lyrica is an approved treatment, its share of sales reflected only a small fraction of the global epilepsy market.