German drugmaker Boehringer Ingelheim won a green light in the USA late last week to sell pramipexole, its dopamine agonist, for the treatment of moderate to severe primary restless legs syndrome.

Pamipexole, sold as Mirapex in the USA and already used to treat parkinson’s disease, is only the second drug to secure US approval for restless legs syndrome after GlaxoSmithKline’s Requip (ropinirole), which was launched there for the condition in May.

Launch of the new drugs is expected to lead to an explosion in the market to treat restless legs from around $200 million at present to more than $1 billion by 2015, according to market analysis firm Decision Resources. Requip is scheduled to lose patent protection in 2008

Restless legs syndrome is a neurological disorder characterised by an uncontrollable urge to move the legs, usually accompanied by pain. It affects up to 10% of the adult population. It is an important new indication for pramipexole; European approval in April helped add momentum to the drug’s sales, which advanced 33% to 260 million euros in the first half of the year.

Schwarz Pharma, soon to become part of UCB, also has a drug for restless legs syndrome in the pipeline, Neupro (rotigotine), and first results of Phase III trials are expected in the first quarter of 2007. Other players include XenoPort with gabapentin prodrug XP-13512 (Phase III) and Serono with safinamide.