Tetraphase Pharmaceuticals Added to Russell 3000®, Russell 2000® and Russell Global Indexes

Tetraphase Pharmaceuticals, Inc. TTPH, a clinical-stage biopharmaceutical company developing a portfolio of potent new antibiotics designed to be effective against dangerous, drug-resistant bacteria (including multidrug-resistant (MDR) gram-negative pathogens), today announced that it was added to the Russell 3000®, Russell 2000® and Russell Global Indexes when the Russell Investment Group reconstituted its family of U.S. indexes after stock market close on June 28, 2013. Annual reconstitution of Russell's U.S. indexes captures the 4,000 largest U.S. stocks as of the end of May, ranking them by total market capitalization. Membership in the Russell 3000®, which remains in place for one year, means automatic inclusion in the large-cap Russell 1000® Index or small-cap Russell 2000® Index as well as the appropriate growth and value style indexes. Russell determines membership for its equity indexes primarily by objective, market-capitalization rankings and style attributes. The Russell 3000® also serves as the U.S. component to the Russell Global Index, which Russell launched in 2007. "Tetraphase has built meaningful value in its antibiotic franchise, and we are pleased to be included in the Russell Indexes only three months following our initial public offering," said Guy Macdonald, Tetraphase President and Chief Executive Officer. "We expect that being included in the broadly referenced Russell Indexes will add important liquidity to our stock by attracting the many index funds that reference them." About the Russell Indexes The Russell Indexes are widely used by investment managers and institutional investors for index funds and as benchmarks for both passive and active investment strategies. According to Russell Investments, approximately $4.1 trillion in assets are benchmarked to the Russell Indexes. Russell calculates more than 700,000 benchmarks daily covering approximately 98 percent of the investable market globally, more than 80 countries and 10,000 securities.