Mast Therapeutics Completes Acquisition Of Aires Pharmaceuticals, Inc.

SAN DIEGO, Feb. 27, 2014 /PRNewswire/ -- Mast Therapeutics, Inc. (NYSE MKT: MSTX) today announced that it has completed its acquisition of Aires Pharmaceuticals, Inc. Aires' lead product candidate, AIR001, is an intermittently nebulized formulation of nitrite that has orphan drug designation in the U.S. and European Union for the treatment of pulmonary arterial hypertension.

"The addition of AIR001 provides us with not only an exciting phase 2 asset in the area of pulmonary disease, but also an ideal complement to our lead product, MST-188," said Brian M. Culley, Chief Executive Officer. "With MST-188 in an ongoing pivotal trial for sickle cell disease and a phase 2 trial expected to initiate this quarter in acute limb ischemia, the addition of another phase 2-ready asset further enhances our pipeline, providing us with diversity across specialized indications as well as cohesion in addressing significant unmet medical needs. In addition, as previously reported, although our estimated costs for AIR001 will change as we refine our development strategy over the next few months, we currently anticipate that our first year of development of AIR001 will be covered by Aires' net cash at closing of $2.6 million."

Under the terms of the all-stock transaction, which was completed on February 27, 2014, Aires became a wholly-owned subsidiary of Mast Therapeutics in exchange for a total of 5.2 million shares of Mast common stock, representing approximately 5% of Mast's outstanding common stock. Approximately 80% of the shares comprising the merger consideration are being held back for a period of six months to satisfy any indemnification obligations of the former Aires' stockholders under the merger agreement. There are no milestone obligations payable by Mast.

About AIR001
AIR001 (sodium nitrite) inhalation solution, also known as Aironite®, is an intermittently nebulized formulation of nitrite, which can be converted to nitric oxide independent of nitric oxide synthase activity. Nitrite mediated nitric oxide formation has several beneficial effects, including dilation of blood vessels and reduction of inflammation and undesirable cell growth. AIR001 has been granted orphan drug designation by the U.S. Food and Drug Administration and the European Commission for the treatment of pulmonary arterial hypertension.

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 with significant unmet needs. MST-188 is a cytoprotective, hemorheologic, anti-inflammatory and anti-thrombotic agent that has potential utility in diseases or conditions characterized by microcirculatory insufficiency (endothelial dysfunction and/or impaired blood flow).

The Company is enrolling subjects in EPIC, a pivotal phase 3 study of MST-188 in sickle cell disease. In the first quarter of 2014, the Company plans to initiate a phase 2, clinical proof of concept study in acute limb ischemia that will evaluate whether MST-188 improves the effectiveness of existing thrombolytic agents. The Company is also evaluating development options for MST-188 in heart failure. More information can be found on the Company's web site at www.masttherapeutics.com. (Twitter: @MastThera)

Mast Therapeutics™ and the corporate logo are trademarks of Mast Therapeutics, Inc. Aironite® is a trademark of Aires Pharmaceuticals, Inc.

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 relating to the Company's development plans for AIR001, as well as the cost and timing of activities related to those plans, and the Company's development plans for MST-188 in acute limb ischemia and heart failure, including the timing of initiation of any clinical studies. 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: the uncertainty of outcomes in ongoing and future studies of any investigational drug, including MST-188 and AIR001, and the risk that they 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 institutional review boards or the FDA or other regulatory agencies to require additional nonclinical or clinical studies prior to initiation of any planned phase 2 clinical study of MST-188 or AIR001; 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 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 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 and regulatory activities for MST-188 and AIR001, and that such third parties may fail to perform as expected; the Company's ability to obtain additional funding on a timely basis or on acceptable terms, or at all; 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 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 to 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. 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 when made. 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.