Tetraphase Pharmaceuticals Added to the Russell Microcap® Index

Tetraphase Pharmaceuticals, Inc. (NASDAQ:TTPH), a clinical stage biopharmaceutical company developing novel antibiotics to treat life-threatening multidrug-resistant (MDR) infections, today announced that it was added to the Russell Microcap® Index when the Russell Investment Group reconstituted its family of U.S. indexes effective June 27, 2016.

Membership in the Russell Microcap Index, which remains in place for one year, means automatic inclusion in the appropriate growth and value style indexes. FTSE Russell determines membership for its Russell indexes primarily by objective, market-capitalization rankings and style attributes.

About Tetraphase Pharmaceuticals, Inc.Tetraphase is a clinical-stage 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 multidrug-resistant (MDR) bacteria highlighted as urgent public health threats by the CDC. Tetraphase has created more than 3,000 novel tetracycline analogs using its proprietary technology platform. Tetraphase's pipeline includes eravacycline, its lead antibiotic candidate in phase 3 clinical trials, as well as two additional antibiotic candidates, TP-271 and TP-6076. Please visit www.tphase.com for more company information.

Investor Contacts:
Tetraphase Pharmaceuticals
Teri Dahlman
617-600-7040
[e-mail]

Argot Partners
Maeve Conneighton
212-600-1902
[e-mail]

Media Contact:
Sam Brown Inc.
Mike Beyer
312-961-2502
[e-mail]