bluebird bio, Inc. (Nasdaq: BLUE) today announced that it has commenced an underwritten public offering of $400 million of its common stock. bluebird bio also intends to grant the underwriters a 30-day option to purchase up to an additional fifteen percent (15%) of the shares of common stock offered in the public offering. All of the shares in the proposed offering are to be sold by bluebird bio.

Goldman Sachs & Co. LLC, BofA Securities and Cowen are acting as joint book-running managers of the proposed offering. The offering is subject to market and other conditions, and there can be no assurance as to whether or when the offering may be completed, or as to the actual size or terms of the offering.

The shares are being offered by bluebird bio pursuant to an automatically effective shelf registration statement that was previously filed with the Securities and Exchange Commission (SEC).