Gilenya Safety Review. Eleven deaths among people taking the multiple sclerosis drug Gilenya have caused it to lose market share since it hit the U.S. market in late-2010. According to a Bloomberg report, Gilenya’s share of the market for immunomodulatory drugs used in the treatment of MS from from 6.2 percent to 6.1 in February.

This drop marks the first time the drug has dipped in this rating since it was introduced in September 2010. Skepticism of the overall effectiveness of Gilenya in treating MS has been raised recently with reports of 11 patient deaths, specifically some of those who died after taking their first dose of the drug.

Late last year, the makers of Gilenya, Novartis, acknowledged the death of a U.S. patient who died within a day of taking it.

Chief among the side effects of Gilenya is its ability to impact heart rhythm. Though Gilenya has not been blamed for the deaths, those taking the drug at the time of their unexpected death were attributed to cardiac complications, including three deaths due to heart attack in Europe. Just more than half the 11 deaths remain “unexplained.”

In response to this recent news, the Food and Drug Administration and some other regulators worldwide have issued updated safety guidelines regarding Gilenya prescriptions.

Patient’s first dose of the drug should be administered in a physician’s presence

In the U.S., a patient’s first dose of the drug should be administered in a physician’s presence and that patient should be monitored for at least six hours after it’s taken, specifically monitoring the heart for any signs of complications.

Though Novartis has not issued much detail in the cases of the patient deaths, it is likely that people who are already being treated for heart problems like irregular heart beats, low or high blood pressure, or take beta blocker drugs may be more likely to experience complications when taking Gilenya.

The FDA, Health Canada, and the European Medicines Agency are all conducting safety reviews of Gilenya in response to the recent deaths. A total of about 30,000 people worldwide take Gilenya to treat symptoms of MS and to slow physical disability caused by the disease. Gilenya is the first approved pill drug for the treatment of multiple sclerosis.

News of Gilenya’s drop in market share for MS drugs lowered its overall expectations. Analysts cited by Bloomberg believe sales of the drug will peak in 2016 at $1.96 billion annually, a 12 percent drop from the previous forecast.

Gilenya’s presence as the only pill-form MS drug is not expected to last much longer, and that could impact future sales if the questions surrounding these and potentially more patient deaths persist. Bloomberg indicates Biogen Inc. is seeking approval of its own pill-form MS drug, BG-12.