Retigabine (ASTA Medica).

ASTA Medica is developing retigabine, a carbamic acid ethyl ester and a selective potassium channel opener, for the treatment of complex partial seizures. Phase II trials have commenced [249117], and a multicenter placebo-controlled dosage-finding study has begun in Europe and Australia [392702]. Retigabine is also undergoing phase II testing in Germany, Switzerland, Russia and the US for the potential treatment of epilepsy [323383]. Phase II trials have shown >50% reduction in seizure frequency in 12 of 35 patients with refractory epilepsy [373379]. Phase I clinical trials for epilepsy were successfully completed in Germany in 1995 [180371]. Single and multiple dose trials demonstrated the tolerability and favorable pharmacokinetic behavior of the compound [264306]. The compound showed good compatibility and exhibits an antisense anticonvulsive effect in various preclinical epilepsy models [250565,299344]. Side effects of mild to moderate tiredness, fatigue and nausea were observed [276123]. The spectrum of activity of retigabine resembles that of valproate, but its potency is greater and toxicity is reduced [373379]. The mechanism of action of retigabine is probably multifactorial. Research has shown that retigabine acts as a selective K+ channel opener in neuronal cells and this can be expected to contribute to its anticonvulsant effect [273670]. In addition it demonstrates potentiation of GABA transmission and possibly also weak modulation of sodium and calcium channels [299344]. Retigabine also has neuroprotective activity with potential for the treatment of stroke and neurodegenerative diseases, such as Alzheimer's disease, Huntington's disease and multiple sclerosis [249381]. In February 2000, Lehman Brothers predicted product launch could be as early as 2002 for epilepsy in the US [357788]. In February 1999, Lehman Brothers predicted that the first major launch date of the drug would be 2003, and the year of peak sales to be 2011 [319225].