Mast Therapeutics Announces Closing Of Underwritten Public Offering

SAN DIEGO, Nov. 13, 2014 /PRNewswire/ -- Mast Therapeutics, Inc. (NYSE MKT: MSTX), a clinical-stage biopharmaceutical company, today announced the closing of its previously announced underwritten public offering of equity securities. Gross proceeds from the offering were $21 million and the Company estimates net proceeds from the offering will be approximately $20 million, after deducting underwriting discounts and commissions and estimated offering expenses. The Company intends to use the net proceeds primarily to fund its clinical development programs, including EPIC, the Company's ongoing pivotal Phase 3 study of MST-188 in sickle cell disease, and for working capital and general corporate purposes.

The Company sold 30,941,102 Series A units at a purchase price per unit of $0.48. Each Series A unit consisted of one share of common stock and one-half (0.5) of a warrant. Each whole warrant is exercisable for one share of common stock at an initial exercise price of $0.75 per share. As a component of the offering and in lieu of Series A units that include common stock, the Company also sold 13,081,428 Series B units at a purchase price per unit of $0.47. Series B units were offered only to those purchasers whose purchase of additional Series A units in the offering would otherwise have resulted in the purchaser beneficially owning more than 4.99% of the Company's outstanding common stock following the completion of the offering. Each Series B unit consisted of one pre-funded warrant to purchase one share of common stock at an initial exercise price of $0.01 per share and one-half (0.5) of a warrant. Each whole warrant is exercisable for one share of common stock at an initial exercise price of $0.75 per share.

Cowen and Company, LLC acted as sole book-running manager. Canaccord Genuity Inc. acted as lead manager and Laidlaw & Company (UK) Ltd. and Merriman Capital, Inc. acted as co-managers for the offering.

The offering was made pursuant to a shelf registration statement previously filed with the Securities and Exchange Commission and declared effective on May 1, 2012. Copies of the final prospectus relating to the offering may be obtained by contacting: Cowen and Company, c/o Broadridge Financial Services, 1155 Long Island Avenue, Edgewood, NY, 11717, Attn: Prospectus Department, or by calling (631) 274-2806. Copies also are available on the Commission's website at www.sec.gov.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy any of the Company's securities. No offer, solicitation or sale shall be made in any state or other jurisdiction in which such offer, solicitation or sale is unlawful.

About Mast Therapeutics
Mast Therapeutics, Inc. is a publicly traded biopharmaceutical company headquartered in San Diego, California. The Company is leveraging the MAST (Molecular Adhesion and Sealant Technology) platform, derived from over two decades of clinical, nonclinical and manufacturing experience with purified and non-purified poloxamers, to develop MST-188, its lead product candidate, for serious or life-threatening diseases and conditions typically characterized by impaired microvascular blood flow and damaged cell membranes.

Forward Looking Statements
Mast Therapeutics cautions you that statements included in this press release that are not a description of historical facts are forward-looking statements that are based on the Company's current expectations and assumptions. Such forward-looking statements include, but are not limited to, statements regarding estimated net proceeds from the offering and the intended use of such proceeds. Among the factors that could cause or contribute to material differences between the Company's actual results and the expectations indicated by the forward-looking statements are risks and uncertainties that include, but are not limited to: actual expenses related to the offering; the uncertainty of outcomes in ongoing and future studies of the Company's product candidates and the risk that its product candidates, including MST-188, may not demonstrate adequate safety, efficacy or tolerability in one or more such studies, including EPIC; delays in the commencement or completion of clinical studies, including as a result of difficulties in obtaining regulatory agency agreement on clinical development plans or clinical study design, opening trial sites, enrolling study subjects, manufacturing sufficient quantities of clinical trial material, being subject to a "clinical hold," and/or suspension or termination of a clinical study, including due to patient safety concerns or lack of funding; the potential for the Company to delay, reduce or discontinue current and/or planned development activities, including clinical studies, partner its product candidates at inopportune times or pursue less expensive but higher-risk and/or lower return development paths if it is unable to raise sufficient additional capital as needed; the potential for institutional review boards or the FDA or other regulatory agencies to require additional nonclinical or clinical studies prior to initiation of a planned clinical study of a product candidate; the risk that, even if clinical studies are successful, the FDA or other regulatory agencies may determine they are not sufficient to support a new drug application; the potential that, even if clinical studies of a product candidate in one indication are successful, clinical studies in another indication may not be successful; the Company's reliance on contract research organizations (CROs), contract manufacturing organizations (CMOs), and other third parties to assist in the conduct of important aspects of development of its product candidates, including clinical studies, manufacturing, and regulatory activities for its product candidates, and that such third parties may fail to perform as expected; the risk that, even if the Company successfully develops a product candidate in one or more indications, it may not realize commercial success with its products and may never generate revenue sufficient to achieve profitability; the risk that the Company is not able to adequately protect its intellectual property rights relating to the MAST platform and MST-188 or AIR001 and prevent competitors from duplicating or developing equivalent versions of its product candidates; and other risks and uncertainties more fully described in the Company's press releases and periodic filings with the Securities and Exchange Commission, including the preliminary prospectus supplement related to the offering. The Company's public filings with the Securities and Exchange Commission are available at www.sec.gov.

You are cautioned not to place undue reliance on forward-looking statements, which speak only as of the date hereof. Mast Therapeutics does not intend to revise or update any forward-looking statement set forth in this press release to reflect events or circumstances arising after the date hereof, except as may be required by law.