The once-daily pill that promises to improve the lives of thousands of patients who suffer from the disease that debilitates the central nervous system has good chances to become the gold standard after a U.S. regulatory panel earlier this month recommended the drug for approval.

Despite raising safety concerns, the U.S. Food and Drug Administration's panel, in an unanimous vote, found the drug to be so effective as to allow it to become a first-line multiple sclerosis treatment despite side effects such as lung, heart and eye problems.

This, analysts say, raises the likelihood the FDA in September will fully back Gilenia's marketing launch that could come as early as in the third quarter of 2010 and net more than $1 billion in sales for Novartis.

The FDA panel's decision was a positive surprise and will act as a confidence booster for the Swiss pharma giant, which with the help of Gilenia may curb the sales drop it faces when its two top medicines--heart drug Diovan and cancer medicine Gleevec--lose patent protection over the next few years.

Analysts have hitherto been skeptical that Gilenia will make a deep impact, as early-stage trials raised the specter that the drug's side-effects could negate its benefits, limiting the sales and profit potential for the drug or even annihilating its chances to win approval.

But after the U.S. drug panel's verdict, the market's view is slowly changing and analysts have started to upgrade their forecasts that range between $1 billion to $3.5 billion.

"The strong endorsement [from the FDA panel] sets the stage for Novartis to shake up the multiple sclerosis market which is projected to grow to $15 billion by 2015," said Karl-Heinz Koch of brokerage Helvea. "We believe there is significant upside to our above consensus $1.4 billion sales forecast."

Analysts also welcomed Gilenia's potential to become a first-line treatment, thus hurting existing players, who are set to lose massive market share.

"The Gilenia recommendation for approval was expected, but the first line status wasn't", said Ian Hunter of Goodbody Stockbrokers. "The implication is that it is a greater setback for drugs already on the market." According to his estimates, Elan, for example, could lose some 10% of its patient base.

Other market leaders could suffer too as think tank Datamonitor expects Gilenia to become the leading multiple sclerosis therapy by 2016 and could net sales of more than $1 billion.

To date, the market for multiple sclerosis, which affects about 2.5 million people worldwide, is led by firms such as Biogen, Merck Serono, Bayer AG ( BAYN.XE), Elan and Teva Pharmaceutical Industries Ltd (TEVA.TV).

Teva and Sanofi-Aventis SA's (SAN.FR) own the market's best-selling drug Copaxone, which had more than $2.8 billion in sales in 2009. Biogen's Avonex also had more than $2 billion in annual revenue, while Bayer's Betaseron and Merck's Rebif had more than $1 billion in sales.

Most of these drugs, however, go with side-effects that could prove crippling for them once Gilenia is on the market. While many existing drugs need to be administered through a daily injection or infusion, the medicines also cause flu-like symptoms, a condition many patients dislike although it isn't dangerous.

Gilenia's pill form is believed to appeal to both patients and doctors because it's easier to administer and analysts say the lack of flu-like symptoms could even help Novartis expand the market, as many early-stage patients avoid taking some of the existing drugs because of the hampering side-effects.

"I believe the drug will be approved and will become a success because it is administered orally and is very efficacious," said Andrew Weiss, pharma analyst at Bank Vontobel. Still, he warns that Gilenia's dose related side-effects could prove a stumbling block and even delay the drugs approval. Weiss puts the approval probability at 50%, while he sees non-probabiltiy adjusted peak sales at about $2.9 billion.

Concerns about the drug's side effects have diminished after the FDA's panel decision, they but haven't fully abated--partly because the FDA asked Novartis to provide more research data and to consider lowering the drug's dosage to reduce side effects.

Fears that the drug could falter in late stage or even after approval are fueled by the fact that late-stage setbacks for multiple sclerosis drugs medicines are common.

For example, one year after the launch of multiple sclerosis drug Tysabri, Biogen and Elan had to pull off the drug from the market due to serious side effects such as brain tumors. The drug was later reintroduced but has since failed to live up to the high hopes of its producers. Also, Merck's oral multiple-sclerosis drug needed be resubmitted after the FDA rejected approval, saying Merck's filing was incomplete.

For brokerage Bernstein, these recent drug setbacks could serve to postpone Gilenia's market introduction. Also, the brokerage expects that Novartis' post- marketing efforts to highlight the drug's side effects will be strenuous. Nevertheless, the drug holds blockbuster potential and the brokerage sees sales of more than $1 billion by 2015.