DUBLIN, Ireland, Oct. 3, 2013 (GLOBE NEWSWIRE) -- Prothena Corporation plc. (Nasdaq:PRTA), a clinical stage biotechnology company focused on the discovery and development of novel antibodies for the potential treatment of a broad range of diseases, announced that it has priced an underwritten public offering of 5,910,000 of its ordinary shares at a price of $22.00 per ordinary share, before underwriting discounts and commissions. Of these ordinary shares, Prothena is offering 3,500,000 ordinary shares and Janssen Pharmaceutical, a wholly owned subsidiary of Johnson & Johnson, as selling shareholder, is offering 2,410,000 ordinary shares. In addition, the underwriters have been granted a 30-day option to purchase up to an additional 886,500 ordinary shares. If the option is exercised in full, Prothena will issue and sell an additional 677,079 ordinary shares and Janssen Pharmaceutical will sell an additional 209,421 ordinary shares, which represents all of Janssen's shareholdings in Prothena.

Net proceeds to Prothena from the ordinary shares to be sold by Prothena in the offering are expected to be $70.8 million, after deducting the underwriting discount and estimated offering expenses, but excluding any exercise of the underwriters' option to purchase additional ordinary shares. Prothena will not receive any proceeds from the sale of ordinary shares by Janssen Pharmaceutical. The offering is expected to close on or about October 8, 2013, subject to customary closing conditions.

BofA Merrill Lynch, Credit Suisse and RBC Capital Markets are acting as joint book-running managers and Wedbush PacGrow Life Sciences and Roth Capital Partners are acting as co-managers for the offering.

A registration statement on Form S-1 relating to these securities has been filed with the Securities and Exchange Commission and declared effective. The offering of these securities will be made only by means of a written prospectus forming part of the effective registration statement relating to these securities. Copies of the prospectus for this offering may be obtained, when available, by contacting BofA Merrill Lynch, 222 Broadway, New York, NY 10038, Attn: Prospectus Department, email: dg.prospectus_requests@baml.com, or Credit Suisse Securities (USA) LLC, One Madison Avenue, New York, NY 10010; Tel: 1-800-221-1037; Attn: Credit Suisse Prospectus Department, email: newyork.prospectus@credit-suisse.com, or RBC Capital Markets, LLC, 3 World Financial Center, 200 Vesey Street, 8th Floor, New York, NY 10281-8098; Attention: Equity Syndicate; Tel: 877-822-4089; Fax: 212-428-6260.

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 other 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 other jurisdiction.
CONTACT: Investors: Tran Nguyen, CFO         650-837-8535, IR@prothena.com         Media: Anita Kawatra         646-256-5116, anita.kawatra@prothena.com