Biogen resurrects Alzheimer's drug, stock soars

Possible good news for those suffering from Alzheimer's and for family members taking care of them.

Biotech company Biogen announced Tuesday it is planning to seek regulatory approval for an experimental treatment that it said at high doses improved cognition and function such as memory, orientation and language.

This is a startling reversal on a drug that at first seemed to be so unsuccessful that Biogen stopped two studies....but after looking at data from more patients, Biogen said it realized the treatment did have a positive impact on those testing out the drug.

That development set the stock on fire. Shares of Biogen soared nearly 40 percent on Tuesday, the one-day rally was so powerful the stock erased all of its losses for the year.

But getting regulatory approval for the drug is not a certainty. One analyst warns Biogen will have a hard time convincing regulators to give the green light.

It's important to note -there is currently no approved treatment for reversing the effects of Alzheimer's.