NEW YORK -(Dow Jones)- Biogen Idec Inc. (BIIB) disclosed four more cases of a rare brain infection in multiple sclerosis patients on Tysabri, which it sells with Elan Corp. (ELN), bringing the total number of cases to 35.

Tysabri is considered a highly effective therapy for MS, (so, just imagine if it wasn’t.. duh) and its growth is important to the future of both Elan and Biogen. But its sales have been slower than originally hoped amid concerns about the risk of PML that led to its 18- month market withdrawal beginning in 2005.

“The overall rate is about the same,” said Biogen spokeswoman Naomi Aoki. “It remains consistent with what is outlined in our label.” – this is the label that says “can cause death”, right? I see.

The last update came from the FDA, which cited 31 cases as of Jan. 21, in a recent safety update noting that MS patients using the drug had increased risk of getting PML as the number of infusions of the medicine increase.

Despite the risk, the agency said the benefits of the medicine continue to outweigh the risks. Which is absolutely true, If the patients are suicidal.

The most recent update translates to about 1.56 cases per 1,000 patients on the drug for between two and three years.

By contrast, the incidence is about 0.54 case per 1,000 patients in those using it for one to two years, and it is almost non-existent in patients using it for less than a year.

The number of cases is important because if the infection rate climbs too high, sales of the drug may drop.

Tysabri’s withdrawal from the market occurred after three patients developed PML. The infection re-emerged in mid-2008, and Biogen provided regular updates about the cases until mid-2009. The company is now providing monthly updates.

But i now know how Tysabri “helps” MS – people DON’T die from the MS, they die from the “cure”.

Eat your heart out, Darwin. Evolution? HAH.