Biogen presents new data on its controversial Alzheimer's drug

Biogen Inc on Thursday presented new data from on its experimental Alzheimer's drug aducanumab showing that no patients in a high-risk group that were genetically predisposed to get Alzheimer's died while taking the high dose of the drug, which had been a key concern.

The company said the most common side effect from the drug was a headache.

Biogen's shares, which had been halted before the presentation, opened down, then gained 1.5 percent, in choppy trade on the New York Stock Exchange.