Tetraphase Pharmaceuticals to Present Data at the 38th Annual Meeting of the Surgical Infection Society

WATERTOWN, Mass., April 19, 2018 -- Tetraphase Pharmaceuticals, Inc. (NASDAQ:TTPH), a biopharmaceutical company focused on developing and commercializing novel antibiotics to treat life-threatening multidrug-resistant (MDR) infections, today announced two data presentations at the 38^th Annual Meeting of the Surgical Infection Society (SIS), taking place April 22-25, at the Four Seasons in Westlake Village, CA. Presentations will include information about the Company’s lead drug candidate, eravacycline, which is in development for the treatment of complicated intra-abdominal infections (cIAI).

“Data presented at SIS’s Annual Meeting demonstrate eravacycline’s potent in vitro activity from a total of 7,815 single-patient clinical isolates collected during a four-year period from U.S. hospitals,” said Guy Macdonald, President and Chief Executive Officer of Tetraphase Pharmaceuticals. “Eravacycline was two- to four-fold more active than tigecycline against most of the Gram-negative and Gram-positive clinical isolates including multidrug-resistant strains, supporting our belief that eravacycline offers a clear advantage in institutions where Gram-negative resistance is a problem.”

Mr. Macdonald added, “In another presentation, we examined the outcomes of the length of therapy in patients receiving eravacycline and meropenem for cIAI. Findings showed that a shorter course of treatment with eravacycline is associated with outcomes similar to those of a longer course of therapy, suggesting that the current treatment prescribing paradigm of antibiotics may have room to evolve.”

The details for the data presentations at SIS are as follows:

Poster Title:  Length of therapy during a phase 3 study of eravacycline and meropenem for complicated intra-abdominal infection
Date and time: Wednesday, April 25 from 3:30 – 5:30 p.m. PT
Location: Ballroom A
Poster number: ACS-MO10
Session information: Moderated Oral ePoster Session I - Session II - Ballroom A, Ballroom E, Ventura & Sherwood

Poster Title:  Surveillance of the in vitro activity of eravacycline and comparators against clinical isolates from the U.S. from 2013-2016
Date and time: Wednesday, April 25 from 3:30 – 5:30 p.m. PT
Location: Sherwood
Poster number: Global-MO11
Session information: Moderated Oral ePoster Session I - Session II - Ballroom A, Ballroom E, Ventura & Sherwood

Full abstracts can be found on the SIS website at www.sisna.org.

About Tetraphase Pharmaceuticals, Inc.
Tetraphase is a biopharmaceutical company using its proprietary chemistry technology to create novel antibiotics for serious and life-threatening bacterial infections, including those caused by many of the MDR bacteria highlighted as urgent public health threats by the Centers for Disease and Control. The Company has created more than 3,000 novel tetracycline analogs using its proprietary technology platform. Tetraphase's pipeline includes three antibiotic clinical candidates: eravacycline, which has completed phase 3 clinical trials and is under review for potential approval in complicated intra-abdominal infections by the U.S. Food and Drug Administration and the European Medicines Agency, and TP-271 and TP-6076, which are in phase 1 clinical trials. Eravacycline is an investigational product only and has not been approved for commercialization. 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, 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: whether the Company's regulatory submission will receive approval from the United States Food and Drug Administration or equivalent foreign regulatory agencies; whether, if any clinical candidate, including eravacycline obtains approval, it will be used in the hospital setting to treat patients or otherwise successfully distributed and marketed; and other factors discussed in the "Risk Factors" section of our Annual Report for the year ended December 31, 2017 on Form 10-K, filed with the Securities and Exchange Commission on March 6, 2018. In addition, the forward-looking statements included in this press release represent our views as of April 19, 2018. 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.

Investor Contacts:
Tetraphase Pharmaceuticals                                                                      
Jennifer Viera
[email protected]
617-600-7040