Ironwood Pharmaceuticals Announces Partial Exercise of Underwriters' Option in Public Offering of Common Stock

Ironwood Pharmaceuticals, Inc. (NASDAQ: IRWD) today announced that the underwriters of its previously announced public offering of shares of Class A common stock have partially exercised their option to purchase an additional 704,948 shares at a public offering price of $13.00 per share. These shares were purchased pursuant to the underwriters’ option to purchase up to 1,575,000 additional shares in the offering. As a result, the Company has issued a total of 11.2 million shares in the offering and has received aggregate net proceeds, after underwriting discounts and commissions and other estimated offering expenses, of approximately $137.7 million. The initial offering of 10,500,000 shares closed on May 24, 2013. The closing for the additional 704,948 shares closed on June 4, 2013.

J.P. Morgan and BofA Merrill Lynch served as joint bookrunning managers and as representatives of the underwriters for the offering. Morgan Stanley served as bookrunning manager for the offering. Cowen and Company, Ladenburg Thalmann & Co. Inc. and Mizuho Securities served as co-managers for the offering. A copy of the final prospectus supplement related to the offering has been filed with the Securities and Exchange Commission (SEC) and is available on the SEC’s website located at www.sec.gov. Copies of the final 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 dg.prospectus_requests@baml.com.

The securities described above are being offered by Ironwood pursuant to an automatically effective shelf registration statement that was previously filed with the SEC. This 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.

About Ironwood Pharmaceuticals

Ironwood Pharmaceuticals (NASDAQ: IRWD) is committed to the art and science of making medicines, from discovery through commercialization. We’re focused on three goals: transforming knowledge into medicines that make a difference for patients, creating value that will inspire the continued support of our fellow shareholders, and building a team that passionately pursues excellence. Our first product, linaclotide, is approved in the United States and Europe. Our pipeline priorities include exploring further opportunities for linaclotide, leveraging our deep expertise in functional gastrointestinal disorders, and advancing programs in other areas such as allergic conditions, cardiovascular disease, central nervous system disorders and other conditions defined by patient symptoms. Ironwood was founded in 1998 and is headquartered in Cambridge, Mass.

This press release contains forward looking statements. Investors are cautioned not to place undue reliance on these forward-looking statements, including, but not limited to, statements relating to Ironwood’s expectations regarding the use of proceeds. Each forward-looking statement is subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied in such statement. Applicable risks and uncertainties include, but are not limited to, the risk that Ironwood uses the proceeds from this offering for purposes other than those set forth in the offering prospectus. Applicable risks also include those that are included in Ironwood’s Quarterly Report on Form 10-Q for the three months ended March 31, 2013, in addition to the risk factors that are included from time to time in Ironwood’s Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, and any subsequent SEC filings, including the prospectus supplement related to the offering to be filed with the SEC. Ironwood undertakes no obligation to update these forward-looking statements to reflect events or circumstances occurring after this press release. These forward-looking statements speak only as of the date of this press release. All forward-looking statements are qualified in their entirety by this cautionary statement.