The treatment options for multiple sclerosis (MS) are, sadly, limited. All existing medications — from interferons like Merck’s Rebif to Teva’s immunomodulator Copaxone to Biogen’s monoclonal antibody-based Tysabri — require regular injections. So it comes as welcome news to MS sufferers that federal regulators have approved the first oral treatment for the disease, Gilenya, manufactured by the Swiss drug maker Novartis.

The thumbs-up from the US Food and Drug Administration was highly anticipated after an advisory panel voted unanimously in June in favor of the drug for treating relapsing MS. The announcement also comes less than two weeks after regulators in Russia approved the pill.

Being the first with a oral MS treatment could prove to be a big advantage for Novartis, with some analysts predicting sales of up to $3.5 billion. But Merck could be close behind. In the past two months, both Russia and Australia approved Merck’s cladribine tablets; and, in July, the FDA granted Merck’s application priority review status after the regulator had rejected a previous submission last year. A final decision on cladribine is expected toward the end of the year.

Gilenya’s success, however, is by no means guaranteed. Many observers — and competitors — have issued cautionary statements about the drug’s mixed profile of side effects. Biogen, for instance, wrote in a press release: “The long-term safety profile of Gilenya has yet to be established, and there is limited data for it in patients with certain common comorbidities.”

In a Community Corner article in the March 2010 issue of Nature Medicine, Hans Link from the Karolinska Institute in Stockholm, Sweden also warned of serious viral infections and cancer, while Roland Martin from the University Medical Center-Eppendorf in Hamburg, Germany raised the prospect of reduced blood cell counts, brain inflammation and heart problems

Another novel treatment option under development for MS are immuno-tolerizing vaccines. For more on that research, you can read my feature story from July.