Tetraphase Pharmaceuticals Announces Corporate Reorganization Aimed at Maximizing XERAVA™ (Eravacycline) Commercial Opportunity

Company to Eliminate Internal Research Function and Explore Pipeline
Out-licensing Opportunities to Focus the Company’s Resources on XERAVA™
Commercial Success

Workforce and R&D Expense Reduction Expected to Result in Annualized
Savings of Approximately $8 Million

Larry Edwards Named President and Chief Executive Officer; Guy
Macdonald to Remain on Board of Directors

WATERTOWN, Mass.–(BUSINESS WIRE)–$TTPH #antibioticresistance—Tetraphase
Pharmaceuticals, Inc. (NASDAQ:TTPH), (“Tetraphase” or “the Company”)
today announced a corporate reorganization in order to maximize the
commercial opportunity for XERAVA™ (eravacycline), the Company’s novel
tetracycline antibacterial indicated for the treatment of complicated
intra-abdominal infections (cIAI) in patients 18 years of age and older.
This reorganization will include elimination of the Company’s internal
research function and an exploration of out-licensing opportunities for
the Company’s pipeline of innovative early-stage antibiotics and
oncology product candidates. As part of the reorganization, Larry
Edwards, who currently serves as Chief Operating Officer, will succeed
Guy Macdonald as President and Chief Executive Officer following a
transition period that will last through August 1, 2019. Mr. Edwards
will join the Tetraphase Board of Directors (“the Board”) in August, and
Mr. Macdonald will remain a director and, in addition, serve as a
consultant to the Company into December 2019.

“XERAVA is a critically important new addition to the hospital
antibiotic armamentarium, and we firmly believe that by implementing
this reorganization we can concentrate our efforts and resources
entirely on ensuring its commercial success,” said Mr. Macdonald.
“Despite the urgent public health crisis stemming from a need for newer,
more effective antibiotics, the process of launching one requires a long
runway and unwavering perseverance. The Board and I believe that Larry,
with his extensive experience launching novel antibiotics, is the right
person to lead Tetraphase through the XERAVA launch period, and that a
singularly focused organization is central to the success of our
mission.”

“The changes we are undertaking are intended to enable Tetraphase to
focus all of its resources on the commercial success of XERAVA, and I am
honored to lead this effort going forward,” said Mr. Edwards. “As a
result of the efforts of our field force, we are seeing a strong uptake
for XERAVA in the US, where we continue to see double digit monthly
growth in sales of cartons with a mean growth of 40% per month over the
last three months. Currently, in the second quarter of 2019 we are
tracking to double our net sales as compared to the first quarter and
continuing to observe increased formulary uptake. Tetraphase owes its
many innovations, including the discovery of XERAVA, TP-271, TP-6076 and
TP-2846, to its foundational chemistry platform, making the decision to
eliminate our research group particularly difficult. We look forward to
exploring opportunities for additional value creation through the
out-licensing of our innovative early-stage antibiotics and oncology
portfolio. We wish the best for those affected by this reorganization
and will endeavor to make their transitions to other opportunities as
smooth as possible.”

In addition to the promotion of Mr. Edwards, Maria Stahl, Senior Vice
President and General Counsel of Tetraphase, has been promoted to Chief
Business Officer. In this new role, her responsibilities will include
overseeing other corporate functions, including finance, business
development and investor relations. The reorganization will also include
the departure of Tetraphase’s Chief Medical Officer, Larry Tsai, M.D.
and Chief Scientific Officer, Jacques Dumas, Ph.D. Dr. Tsai has been an
outstanding contributor to Tetraphase’s development programs. Dr. Tsai
is resigning his position effective June 24, 2019. Dr. Dumas’ position
is being eliminated effective July 19, 2019. Dr. Dumas is expected to
enter into a consulting relationship with the Company in order to
support the out licensing of TP-2846, the Company’s novel drug candidate
for acute myeloid leukemia. Dr. Dumas leadership was critical in the
development effort leading to TP-2846. Elimination of the Company’s
research function and certain corporate support functions will result in
a reduction in force of approximately 20%, or 24 employees. The Company
expects that the reorganization and other cost-saving efforts will
result in an approximate $8.2 million reduction in net cash required for
operating activities on an annualized basis. Tetraphase estimates that
the reorganization will be substantially completed by the third quarter
of 2019 and that the Company will incur approximately $2.4 million of
pre-tax charges for severance and other costs, primarily during the
second and third quarters of 2019.

About XERAVA™

XERAVA (eravacycline for injection) is a tetracycline class
antibacterial indicated for the treatment of complicated intra-abdominal
infections (cIAI) in patients 18 years of age and older. XERAVA was
investigated for the treatment of cIAI as part of the Company’s IGNITE (Investigating
Gram-Negative Infections Treated with Eravacycline)
Phase 3 program. In the first pivotal Phase 3 trial in patients with
cIAI, twice-daily intravenous (IV) XERAVA met the primary endpoint by
demonstrating statistical non-inferiority of clinical response compared
to ertapenem and was well-tolerated. In the second Phase 3 clinical
trial in patients with cIAI, twice-daily IV XERAVA met the primary
endpoint by demonstrating statistical non-inferiority of clinical
response compared to meropenem and was well-tolerated. In both trials,
XERAVA achieved high cure rates in patients with Gram-negative
pathogens, including resistant isolates.

Important Safety Information

XERAVA is contraindicated for use in patients with known
hypersensitivity to eravacycline, tetracycline-class antibacterial
drugs, or to any of the excipients. Life-threatening hypersensitivity
(anaphylactic) reactions have been reported with XERAVA.

The use of XERAVA during tooth development (last half of pregnancy,
infancy and childhood to the age of eight years) may cause permanent
discoloration of the teeth (yellow-gray-brown) and enamel hypoplasia.

The use of XERAVA during the second and third trimester of pregnancy,
infancy and childhood up to the age of eight years may cause reversible
inhibition of bone growth.

Clostridium difficile associated diarrhea (CDAD) has been
reported with use of nearly all antibacterial agents and may range in
severity from mild diarrhea to fatal colitis.

The most common adverse reactions observed in clinical trials (incidence
≥3%) were infusion site reactions (7.7%), nausea (6.5%), and vomiting
(3.7%).

XERAVA is structurally similar to tetracycline-class antibacterial drugs
and may have similar adverse reactions. Adverse reactions including
photosensitivity, pseudotumor cerebri, and anti-anabolic action which
has led to increased BUN, azotemia, acidosis, hyperphosphatemia,
pancreatitis, and abnormal liver function tests, have been reported for
other tetracycline-class antibacterial drugs, and may occur with XERAVA.
Discontinue XERAVA if any of these adverse reactions are suspected.

To report SUSPECTED ADVERSE REACTIONS, contact Tetraphase
Pharmaceuticals Inc., at 1-833-7-XERAVA (1-833-793-7282) or FDA at
1-800-FDA-1088 or www.fda.gov/medwatch.

Please see full Prescribing Information for XERAVA at www.XERAVA.com.

About Tetraphase Pharmaceuticals, Inc.

Tetraphase Pharmaceuticals, Inc., is a biopharmaceutical company using
its proprietary chemistry technology to create novel tetracyclines for
serious and life-threatening conditions, including infections caused by
many of the multidrug-resistant bacteria highlighted as urgent public
health threats by the World Health Organization and the Centers for
Disease Control and Prevention. The Company has created more than 3,000
novel tetracycline compounds using its proprietary technology platform.
Tetraphase’s lead product XERAVA™ is approved for the treatment of
complicated intra-abdominal infections by the U.S. Food and Drug
Administration and the European Medicines Agency. Please visit www.tphase.com
for more company information.

Forward-Looking Statements

Any statements in this press release about our future expectations,
plans and prospects, including statements regarding our strategy, future
operations, prospects, plans and objectives, including the anticipated
benefits of the restructuring, and other statements containing the words
“anticipates,” “believes,” “expects,” “plans,” “will” and similar
expressions, constitute forward-looking statements within the meaning of
The Private Securities Litigation Reform Act of 1995. Actual results may
differ materially from those indicated by such forward-looking
statements as a result of various important factors, including our cash
resources and the expected revenue from sales of XERAVA will be
sufficient to fund our operations in the future; whether the
restructuring and the focus on our commercial operations will result in
the reduced expenses and other benefits that we anticipate; and other
clinical, regulatory and commercial risk factors discussed in the “Risk
Factors” section of our quarterly report on Form 10-Q for the period
ended March 31, 2019, filed with the Securities and Exchange Commission
on May 8, 2019. In addition, the forward-looking statements included in
this press release represent our views as of June 12, 2019. We
anticipate that subsequent events and developments will cause our views
to change. However, while we may elect to update these forward-looking
statements at some point in the future, we specifically disclaim any
obligation to do so.

Contacts

Investor and Media Contact:
Argot Partners
Maeve
Conneighton
212-600-1902
[email protected]