Biotechnology company Dendreon Corp. said Thursday it agreed to sell about 9.9 million of its common shares to institutional investors for gross proceeds of $45 million, before deducting offering fees and expenses.

The total proceeds imply a per-share offering price of about $4.54, representing a 15 percent discount to the stock's Wednesday closing price of $5.35.

Credit Suisse Securities (USA) LLC and Lazard Capital Markets LLC acted as joint lead placement agents for the offering, which is expected to close on Nov. 21, subject to customary closing conditions.

The company currently has about 71.9 million shares outstanding.

Shares tumbled 69 cents, or 12.9 percent, to $4.68 in morning trading on the Nasdaq, where the stock has ranged between $3.68 and $6.22 over the past year.