Stocks of Biogen Inc. traded 40% higher on Wednesday after the United States Food and Drug Administration (FDA) indicated it believed the company's Alzheimer's treatment was sufficiently safe and effective.

In a document released today, the FDA said the drug was found effective enough in a large trial to support approval, and will now be put through an independent review.

Biogen's shares jumped 40% at 10:39 pm ET, selling for $345.9500.