Acceleron Pharma Inc. (NASDAQ:XLRN), a clinical stage biopharmaceutical company focused on the discovery, development and commercialization of novel protein therapeutics for cancer and rare diseases, today announced the closing of its underwritten public offering of 2,760,000 shares of common stock, including 360,000 shares of common stock issued upon the exercise in full by the underwriters of their option to purchase additional shares, at a public offering price of $50.00 per share. The aggregate net proceeds to the Company, after underwriting discounts and commissions and other estimated offering expenses, were approximately $129 million. The addition of the net proceeds of this financing, including net proceeds from the exercise of the underwriters’ option, to the 2013 year-end cash balance of approximately $113 million is expected to provide the Company funding into the second half of 2017. Citigroup and Leerink Partners LLC acted as joint book-running managers for the offering. Piper Jaffray & Co. acted as lead manager and JMP Securities acted as co-manager for the offering. A registration statement relating to these securities was declared effective on January 22, 2014. Copies of the final prospectus relating to the offering may be obtained from Citigroup, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY, 11717, or by email at firstname.lastname@example.org, or by phone at 800-831-9146; or Leerink Partners LLC, Attention: Syndicate Department, One Federal Street, 37 th Floor, Boston, MA, 02110, or by email at Syndicate@Leerink.com, or by phone at 800-808-7525. This press release shall not constitute an offer to sell or the solicitation of an offer to buy, 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 the registration or qualification under the securities laws of such state or jurisdiction.