US regulators have issued a green light for Biogen Idec's multiple sclerosis (MS) pill Tecfidera, which industry observers expect will become the king of oral therapies for the disease.

Specifically, the US Food and Drug Administration has approved the drug as a first-line oral treatment for people with relapsing forms of MS. 

Tecfidera's (dimethyl fumarate) arrival on the market has been hotly anticipated ever since data from Phase III trials first came to light, showing not only impressive efficacy in reducing disease activity but also a seemingly solid safety profile, which could set is apart from it key rival, Novartis' MS pill Gilenya (fingolimod).

Gilenya was approved in the US in September 2010 and thereby became the first oral therapy for the disease to hit the market, but safety issues - particularly with regards to its potential cardiovascular effects - have since muted its performance.

According to Biogen, the strong efficacy and favourable safety profile of its medicine in the convenience of a pill "will have a significant positive impact on the way people live with this chronic disease,” and "will raise expectations for what people living with MS can achieve with their therapy".

In one Phase III study (DEFINE), Tecfidera (formerly known as BG-12) significantly reduced the proportion of MS patients who relapsed by 49% and 12-week confirmed disability progression by 38% compared to placebo at two years, highlighting its potential.

Tecfidera's approval will certainly give Biogen's existing MS franchise in the US - which already includes the blockbusters Avonex (interferon beta-1a), injected once a week, and Tysabri (natalizumab), administered as an intravenous infusion once every four weeks - a massive boost, with analysts polled by Bloomberg forecasting sales of $3.25 billion for the drug in just four years.

Biogen said its plans to launch the drug in the US "in the coming days". As stipulated by the FDA, before starting treatment, and annually thereafter, patients' white blood cell counts must be assessed because Tecfidera was found to decrease lymphocyte levels in some patients during trials.

Things are also looking good for the drug across the pond, where the European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) issued a thumbs up for approval earlier this month. Tecfidera is also under review in Australia, Canada and Switzerland.

Shares in Biogen had risen more than 3% in late afternoon trading (Wednesday) on the Nasdaq, as investors welcomed the news.