Mast Therapeutics, Inc. (NYSEMKT:MSTX) Files An 8-K Regulation FD Disclosure

Item7.01

As previously announced, on January6, 2017, Mast Therapeutics,
Inc. (Mast or the Company), Victoria Merger Corp., a Delaware
corporation and a wholly-owned subsidiary of Mast (Merger Sub),
and Savara Inc., a privately-held Delaware corporation focused on
the development and commercialization of novel therapies for the
treatment serious or life-threatening rare respiratory diseases
(Savara), entered into an Agreement and Plan of Merger and
Reorganization (the Merger Agreement), to which, among other
things, subject to approval of the stockholders of Mast and
Savara and the satisfaction or waiver of the other conditions set
forth in the Merger Agreement, Merger Sub will merge with and
into Savara, with Savara becoming a wholly-owned subsidiary of
the Company (the Merger).

The information furnished in Exhibit 99.1 to this report, which
relates to Savara and its development programs, may be presented
from time to time by Savara at various meetings with securities
market participants. Mast has not independently verified the
material in this presentation. The presentation shall not be
deemed filed for any purpose, including for the purposes of
Section18 of the Securities Exchange Act of 1934, as amended (the
Exchange Act), or otherwise subject to the liabilities of that
Section.

The information in this Item 7.01, including Exhibit 99.1, shall
not be deemed incorporated by reference into any filing under the
Securities Act of 1933, as amended, or the Exchange Act,
regardless of any general incorporation language in the filing.

By furnishing the information in this Item7.01 of this Current
Report on Form 8-K, including Exhibit 99.1, the Company makes no
admission as to the materiality of such information. The
information contained herein is intended to be considered in the
context of the Companys filings with the Securities and Exchange
Commission (SEC) and other public announcements that the Company
makes, by press release or otherwise, from time to time. The
Company undertakes no duty or obligation to publicly update or
revise the information contained in this report, although it may
do so from time to time as its management believes is
appropriate. Any such updating may be made through the filing of
other reports or documents with the SEC, through press releases
or through other public disclosure.

Additional Information about the Merger and Where to Find
It

In connection with the Merger, the Company has filed relevant
materials with the SEC, including a registration statement on
Form S-4 that contains a prospectus, proxy statement and
information statement. Investors and security holders of the
Company and Savara are urged to read these materials because they
contain important information about the Company, Savara and the
Merger. The proxy statement/prospectus/information statement and
any other documents filed by the Company with the SEC may be
obtained free of charge at the SEC web site at www.sec.gov. In
addition, investors and security holders may obtain free copies
of the documents filed with the SEC by the Company by directing a
written request to: Mast Therapeutics, Inc., 3611 Valley Centre
Drive, Suite 500, San Diego, CA 92130, Attention: Investor
Relations. Investors and security holders are urged to read the
proxy statement/prospectus/information statement and the other
relevant materials before making any voting or investment
decision with respect to the Merger.

This communication shall not constitute an offer to sell or
the solicitation of an offer to sell or the solicitation of an
offer to buy any securities, nor shall there be any sale of
securities in any jurisdiction in which such offer, solicitation
or sale would be unlawful prior to registration or qualification
under the securities laws of any such jurisdiction. No offering
of securities shall be made except by means of a prospectus
meeting the requirements of Section10 of the Securities Act of
1933, as amended.

Participants in the Solicitation

The Company and its directors and executive officers and Savara
and its directors and executive officers may be deemed to be
participants in the solicitation of proxies from the stockholders
of the Company in connection with the proposed transaction.
Information regarding the special interests of these directors
and executive officers in the merger is included in the proxy
statement/prospectus/information statement referred to above.
Additional information regarding the directors and executive
officers of the Company is also included in the Companys Annual
Report on Form 10-K for the year ended December31, 2016 which is
available free of charge at the SEC web site (www.sec.gov)
and from the Company, Attn: Investor Relations, at the address
described above.

-2-

Reference is made to the Exhibit Index included with this Current
Report on Form 8-K.

-3-

About Mast Therapeutics, Inc. (NYSEMKT:MSTX)

Mast Therapeutics, Inc. is a biopharmaceutical company. The Company develops clinical-stage therapies for serious or life-threatening diseases with unmet needs. The Company focuses on developing new therapies for sickle cell disease, a chronic and genetic disorder classified as a rare, or orphan, disease in the United States of America and European Union, and for heart failure, a condition with an unmet need for treatment options. The Company’s segment is engaged in the business of developing therapies for serious or life-threatening diseases. The Company focuses on its Molecular Adhesion and Sealant Technology (MAST) platform, to develop MST-188 (vepoloxamer) Injection, its lead product candidate. The Company also develops AIR001, a sodium nitrite solution for intermittent inhalation through nebulizer. The Company’s AIR001 is in Phase II clinical development for the treatment of patients with HFpEF.

Mast Therapeutics, Inc. (NYSEMKT:MSTX) Recent Trading Information

Mast Therapeutics, Inc. (NYSEMKT:MSTX) closed its last trading session up +0.006 at 0.137 with 10,354,392 shares trading hands.