Ironwood Pharmaceuticals, Inc. (NASDAQ: IRWD) today announced that it has commenced a $150 million underwritten public offering of its Class A common stock. All of the shares are being offered by Ironwood. Ironwood will grant the underwriters a 30-day option to purchase additional shares equal to up to 15% of the number of shares of Class A common stock sold in the offering. Ironwood intends to use the net proceeds from this offering to support the commercialization of LINZESS ® (linaclotide) in the U.S. and to fund linaclotide and other development opportunities to advance its strategy to grow a leading gastrointestinal company, in addition to general corporate purposes. J.P. Morgan and BofA Merrill Lynch are acting as joint bookrunning managers and as representatives of the underwriters for the offering. A preliminary prospectus supplement related to the offering will be filed with the Securities and Exchange Commission (SEC) and will be available on the SEC’s website located at www.sec.gov. Copies of the preliminary prospectus supplement and the accompanying prospectus relating to this offering may be obtained from the offices of: J.P. Morgan, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, New York 11717 (telephone number: 866-803-9204) or from BofA Merrill Lynch, 222 Broadway, New York, New York 10038, Attention: Prospectus Department or by emailing email@example.com. 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 final terms of the offering will be disclosed in a final prospectus supplement filed with the SEC. The securities described above are being offered by Ironwood pursuant to an automatically effective shelf registration statement that was previously filed with the SEC. The press release shall not constitute an offer to sell, or the solicitation of an offer to buy, any of the securities, nor shall there be any sale of these securities, in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.