COLEY PHARMACEUTICAL GROUP FILES REGISTRATION STATEMENT FOR PROPOSED INITIAL PUBLIC OFFERING

WELLESLEY, MA - April 20, 2005 - Coley Pharmaceutical Group, Inc. today announced that the Company has filed a registration statement with the U.S. Securities and Exchange Commission relating to the proposed initial public offering of its common stock. All shares of the common stock to be sold in the offering will be offered by the Company.

Merrill Lynch & Co. is sole book runner for the offering with J.P. Morgan Securities Inc. acting as co-lead. Lazard and Leerink Swann & Company are acting as co-managers for the offering.

A registration statement relating to these securities has been filed with the Securities and Exchange Commission but has not yet become effective. These securities may not be sold nor may offers to buy be accepted prior to the time the registration statement becomes effective. This press release shall not constitute an offer to sell or a solicitation of an offer to buy, nor will there be any sale of these securities in any state or jurisdiction in which such an offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

When available, copies of the preliminary prospectus relating to the offering may be obtained from: Merrill Lynch & Co., 4 World Financial Center, New York, New York 10080 (telephone: +1.212.449.1000).

About Coley Pharmaceutical Group
Coley Pharmaceutical is an international biopharmaceutical company, headquartered in Wellesley, Massachusetts, USA, that discovers and develops TLR Therapeutics TM , a new class of investigational drug candidates that direct the human immune system to treat cancers, infectious diseases, asthma and allergy. Coley has established a pipeline of four TLR Therapeutic product candidates currently advancing through clinical development either independently or with partners, and additional product candidates in preclinical development. Coley has product development, research and license agreements with Pfizer, sanofi-aventis, Chiron, the United States Government and GlaxoSmithKline.