Melinta or La Jolla; the results of discussions with Melinta and/or La Jolla; the impact of actions of other parties with respect to any discussions and the potential consummation of the proposed transaction with AcelRx, or the potential transactions with Melinta or La Jolla; the outcome of any legal proceedings that could be instituted against Tetraphase or its directors related to the discussions or the AcelRx Merger Agreement, the Revised Melinta Proposal or the proposal from La Jolla; changes in the proposal from Melinta; the risk that the transactions contemplated by the AcelRx Merger Agreement, the Revised Melinta Proposal or the La Jolla proposal, as the case may be, may not be completed in a timely manner, or at all, which may adversely affect Tetraphase’s business and the price of its common stock; the failure to satisfy all of the closing conditions of the transactions contemplated by the AcelRx Merger Agreement or the definitive agreements for the Revised Melinta Proposal or the La Jolla proposal, as the case may be, including the approval of the AcelRx Merger Agreement by Tetraphase’s stockholders or a tender offer satisfying the minimum condition; the occurrence of any event, change or other circumstance that could give rise to the termination of the AcelRx Merger Agreement or the definitive agreements for the Revised Melinta Proposal or the La Jolla proposal, as the case may be; the effect of the announcement or pendency of the transactions contemplated by the AcelRx Merger Agreement, the Revised Melinta Proposal or the La Jolla proposal on Tetraphase’s business, operating results, and relationships with customers, suppliers, competitors and others; risks that the transactions contemplated by the AcelRx Merger Agreement, the Revised Melinta Proposal or the La Jolla proposal may disrupt Tetraphase’s current plans and business operations; risks related to the diverting of management’s attention from Tetraphase’s ongoing business operations; the outcome of any legal proceedings that may be instituted against Tetraphase related to the AcelRx Merger Agreement, the Revised Melinta Proposal and/or the La Jolla proposal, or the transactions contemplated by the AcelRx Merger Agreement, the Revised Melinta Proposal or the La Jolla proposal; risks relating to Tetraphase’s ability to successfully commercialize Xerava; concerns with or threats of, or the consequences of, pandemics, contagious diseases or health epidemics, including COVID-19; general economic and market conditions and the risk factors set forth under the caption “Risk Factors” in Tetraphase’s Quarterly Report on Form 10-Q for the period ended March 31, 2020 filed with the SEC on May 7, 2020 and in any other subsequent filings made by Tetraphase with the SEC. Any forward-looking statements contained in this Form 8-K speak only as of the date hereof, and Tetraphase specifically disclaims any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise.

About Tetraphase Pharmaceuticals, Inc. (NASDAQ:TTPH)

Tetraphase Pharmaceuticals, Inc. (Tetraphase) is a clinical-stage biopharmaceutical company. The Company uses its chemistry technology to create antibiotics for multidrug-resistant infections. It is developing its lead product candidate, eravacycline, a fully synthetic tetracycline derivative, as a spectrum intravenous (IV) and oral antibiotic for use as a first-line empiric monotherapy for the treatment of multidrug-resistant infections. It has developed eravacycline using its chemistry technology. The Company’s TP-271 is a fully synthetic spectrum preclinical compound that the Company developed for respiratory diseases caused by bacterial biothreat pathogens. The Company created TP-271 using its chemistry technology. In its development program for TP-271, the Company has conducted a number of in vitro, toxicology and animal studies to evaluate the efficacy of TP-271 against biothreat pathogens. It also develops TP-6076 for multidrug-resistant Gram- negative infections.